Flood Mitigation and Prevention

Transcription

1 PROPERTY OF THE UNITED STATES GOVERNMENT COPYING, DISSEMINATION, OR DISTRIBUTION OF THIS REPORT TO UNAUTHORIZED PERSONS IS PROHIBITED Do not remove this notice Properly destroy documents when no longer needed Flood Mitigation and Prevention Draft Study GSA INTERNAL REVENUE SERVICE DEPARTMENT OF JUSTICE DEPARTMENT OF COMMERCE OLD POST OFFICE ANNEX January 23, 2007 General Services Administration National Capital Region Washington, D.C. Setty & Associates, Ltd. S&A No PROPERTY OF THE UNITED STATES GOVERNMENT FOR OFFICIAL USE ONLY Do not remove this notice Properly destroy documents when no longer needed

2 SECURITY NOTICE PROPERTY OF THE UNITED STATES GOVERNMENT COPYING, DISSEMINATION, OR DISTRIBUTION OF THIS REPORT TO UNAUTHORIZED USERS IS PROHIBITED DO NOT REMOVE THIS NOTICE PROPERLY DESTROY DOCUMENTS WHEN NO LONGER NEED

3 Draft Study January 23, 2007 INTERNAL REVENUE SERVICE DEPARTMENT OF JUSTICE DEPARTMENT OF COMMERCE OLD POST OFFICE ANNEX GSA PROPERTY OF THE UNITED STATES GOVERNMENT FOR OFFICIAL USE ONLY Do not remove this notice Properly destroy documents when no longer needed

4 TABLE OF CONTENTS Page 1. Executive Summary Overview 1.2 Results and Findings 1.3 Recommendations 2. Introduction June 2006 The Flood Event Peak Rainfall 3.2 Peak Stage / High Water Marks 3.3 Historical Flooding Events 4. Causes and Extent of Flooding Constitution Avenue: Street Flooding Evaluation 4.2 Street Level 4.3 Internal Revenue Service Building 4.4 Department of Justice Building 4.5 Department of Commerce Building 4.6 Old Post Office Annex 5. D.C. Water and Sewer Authority WASA Organizational Structure 5.2 WASA System Overview 5.3 Combined Sewer Overflows (CSO) 5.4 June 2006 Event 5.5 Possible Scenarios to Rapid Rise and Fall of Flooding on Constitution Avenue 5.6 WASA Related Questions and Answers SETTY & ASSOCIATES, LTD. TOC-i

5 6. Government Communications Protocols Department of Homeland Security 6.2 Internal Revenue Service Building 6.3 Department of Justice Building 6.4 Department of Commerce Building 6.5 Old Post Office Annex 6.6 D.C. Water and Sewer Authority Communications 6.7 D.C. Emergency Management Agency 6.8 Protocol Recommendations 7. Flood Mitigation Alternatives Introduction 7.2 Site and Exterior Modifications 7.3 Internal Revenue Service Building 7.4 Department of Justice Building 7.5 Department of Commerce Building 7.6 Old Post Office Annex Appendices: (Separate report) Appendix A: WASA System, Existing Conditions and DC-EMA Maps Appendix B: Government Correspondence/Meeting Minutes Appendix C: Photographs Internal Revenue Service Building Appendix D: Photographs Department of Justice Building Appendix E: Photographs Department of Commerce Building Appendix F: Photographs Old Post Office Annex Appendix G: Flood Event Supporting Information SETTY & ASSOCIATES, LTD. TOC-ii

6 1. EXECUTIVE SUMMARY 1.1 Overview The approach and methodology of this study focused primarily on the scope of work and alternatives presented in GSA s Flood Damage Recovery Phase II directive. Principally, the charge was to determine what happened in June, 2006, and then to identify alternatives to mitigate risk of similar future flooding, and if the building envelope is penetrated again, how to avoid catastrophic building failure. The existing conditions and physical characteristics of each building in this study (Department of Justice (DOJ), Internal Revenue Service (IRS) Headquarters, Old Post Office (OPO) Annex, and the Department of Commerce (DOC) at Ariel Rios and its surroundings within the Federal Triangle were evaluated within the context of mitigating future flood damage. Mitigation alternatives focused the following elements: Enhancing protocols between the Federal Government and the District of Columbia Water and Sewer Authority (WASA) Creating physical barriers around the buildings to block floodwaters Relocating critical building systems to points above the flood level Providing a better means to physically extract flood waters infiltrating the buildings Utilizing a pumping station and storm drain upgrades to reduce flood depths on Constitution Avenue, NW Each of these measures may be considered in whole or in part, and each of them have varying degrees of physical impact to the use, occupancy, operations, and historic fabric of each building. The impact to the existing and possible future spatial configurations will require consultation and coordination with each building s facilities group. The integration of these measures should also be evaluated within the context of future building modernization plans (not presently within the scope of this work). In addition, there are significant cost implications associated with each measure considered. The restoration measures taken to date at the IRS and DOJ buildings have only brought the buildings back to pre-flood conditions. The Federal Triangle is located in Northwest Washington, DC, within the Pennsylvania Avenue National Historic District. The buildings included in this study are prominent and historically significant structures within the Historic District. As a result, any and all proposed measures to mitigate future flood damage which impact the site, surroundings, façades, and historic fabric will require coordination with GSA s Historic Preservation Officer, a Section 106 Review, and approvals by the Advisory Council on Historic Preservation, State Historic Preservation Office, National Capital Planning Commission, and the Commission of Fine Arts. Individual building measures will be reviewed within the context of the overall planning guidelines established by these agencies for the monumental corridor. In addition, these measures would also interface with the National Capital Urban Design and Security Plan. 1.2 Results and Findings The most intense 24-hour portion of the June 2006 storm event dropped 7.01 inches of rain. The historic rainfall data indicates at least three other 24-hour rainfall totals on record that were approximately 7 inches. By comparison to standard design storm events for engineering studies, a storm event in the DC area that is believed to have a recurrence interval of 50 years (a.k.a. the 50-Year Event) would result in approximately 7.04 inches of rainfall over a 24-hour period. By comparison, the DC WASA system for street drainage is reported to try and achieve a 15-year, SETTY & ASSOCIATES, LTD. PAGE 1

7 24-hour performance standard (approximately 5.5 inches of rainfall). It is important to note that the flooding began on Constitution Avenue at 10:30 p.m. after only approximately 2.25 inches of rain had fallen in a 3-hour period. If the rain had stopped at the time of the power failure, the 2.25 inches of rain would have been considered much less than the 15-year event that the WASA sewer system should be designed to handle. According to the NOAA Precipitation Frequency Data Chart in Figure 1-1, the June 2006 event came very close to a 3-hour rainfall for only a 5- year event. The preliminary results of the analysis seem to indicate that each building was capable of handling the storm water until such time that the infrastructure in the adjacent roadways failed to accommodate the flow of storm water and overflows started to occur. This failure resulted in an extreme and rapid rise in floodwaters on Constitution Avenue, resulting in the backup of storm water into the buildings and subsequent disruption of electrical service to support pumping causing additional rise in floodwaters and further failure of interior building systems. Estimates of water infiltration volumes suggest that the Internal Revenue Service Building flooded with approximately 6 million gallons and the Department of Justice Building flooded with approximately 3.5 million gallons. This is compared to an estimated 38 million gallons of storm water in Constitution Avenue at peak stage. According to information obtained through interviews, the main flooding of the Department of Justice Building occurred between 10:00 p.m. and 1:00 a.m. An IRS building security guard report stated that the power failed at 10:32 p.m. and power resumed at 10:42 p.m., when the emergency generator started. The lights began flickering at 10:45 p.m. and at approximately 10:55 p.m. the emergency generator was overwhelmed by the flooding and failed. Video surveillance tapes provided by the Department of Justice Building show that the water level on Constitution Avenue rose most substantially between 10:00 p.m. and 10:30 p.m. It is important to note that both the Department of Justice Building and the Internal Revenue Service Building flooded, but in very different manners. The Internal Revenue Service Building had water penetration at the perimeter moats along 10th Street, Constitution Avenue, and 12th Street. Excessive hydrostatic pressure built up and caused a number of window assemblies to fail. Alternately, the Department of Justice had a 15-inch storm water sewer main fail in the basement, causing severe flooding near an adjacent electrical room. Water did not penetrate the Department of Justice Building through the moats. Both buildings had secondary flooding through electrical service duct banks, abandoned duct banks, and miscellaneous pipe penetrations. When water started entering both buildings, the electrical rooms located on the lower levels, as well as emergency power equipment, were flooded and failed. After primary power and emergency power failure, the storm water pumps could no longer operate and the buildings quickly filled with water due to the street flooding and also from the building storm water system. The Department of Commerce Building had a lesser problem with floodwater. The primary entry point of water was the steam tunnel, adjacent to the building and connected by tunnel doors. The tunnel was flooded to a depth sufficient to break through the steam tunnel doors. This occurred on both the east and west side of the structure and allowed flooding in some areas to a depth of 3 feet above the basement floor. The flooding allowed the water to enter the sub-basement as well. SETTY & ASSOCIATES, LTD. PAGE 2

8 Flooding at the Old Post Office Annex (OPO) occurred through common walls between the IRS and the OPO which contain 25 windows behind drywall partitions. These windows did not have blast assemblies installed as part of the modernization project. The water level in the two buildings was at an identical elevation and it is believed that the two buildings may have contributed to each others flooding. It is known that the IRS moat (window well) windows on the upper part of 10th Street near Pennsylvania Avenue had window failure and water intrusion. The Annex is further north on 12th Street at a higher grade level and would not have had as much opportunity to flood except through the IRS wall immediately adjacent to the Annex Court. The Annex wall did not appear to be breached, although other areas may have leaked. If the floodwater had reached a level higher than 11.0 feet, even greater damage could have resulted at this common wall location. It should also be noted that the penetrations through this wall may pose security and fire integrity issues as well. Precipitation Frequency Estimates (inches) ARI* (years) min min min min min min hr hr hr hr hr day day day day day day day NOTE - Worst-Case Rainfalls in June 2006 was 3.73 (3hr), 5.91 (6hr), 7.01 (24hr), 9.41 (48hr) and (7 day) Source - WASHINGTON REAGAN AP, VIRGINIA ( ) N W 22 feet from "Precipitation-Frequency Atlas of the United States" NOAA Atlas 14, Volume 2, Version 3 G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland, 2004, Extracted: Thu Sep Figure 1-1: NOAA Precipitation Frequency Data Server 1.3 Recommendations The recommendations for the IRS and Department of Justice buildings are numerous, starting with a single level and proceeding to a multi-level effort. Consideration will be given to the reliability of each proposed alternative, including consequences of a failure of the proposed method to adequately control floodwaters entering the buildings. Since the Department of Commerce Building and the Old Post Office Annex flooded in clearly defined ways, there are more defined alternatives available to prevent future water intrusion. The Internal Revenue Service and Department of Justice buildings by comparison have multiple alternatives which need consideration as viable to move forward. A feasibility study should be pursued to clearly assess the best available alternative. SETTY & ASSOCIATES, LTD. PAGE 3

9 MATRIX OF FLOOD MITIGATION ALTERNATIVES AREA DESCRIPTIONS LEVEL OF PROTECTION COMMENTS COST RANGE Protocols A. HIGH LEVEL DIRECT COMMUNICATION HIGH Direct communications between WASA, DCEMA, and GSA Minor Site and Exterior BETWEEN GOVERNMENT AGENCIES B. EMERGENCY ACTION PLAN FOR EACH BUILDING HIGH Minor A. UPGRADE WASA STORM WATER CAPACITY FOR A 50-YEAR WASA system designed for a 15-year event currently EVENT HIGH Large capital improvement costs TBD B. PUMPING STATION & CONVEYANCE SYSTEM MED Viable alternative requiring interagency cooperation $5 M - $10 M C. CATCH BASIN MAINTENANCE IMPROVEMENTS LOW Controlling litter may avoid system blockages $10 M D. SIDEWALK LEVEE SYSTEM HIGH Significant impact to surroundings $9 M - $15M IRS Building A. SEAL ABANDONED FEEDERS HIGH Recommended, easy to implement $20k - $50k B. WATER TIGHT FIRE PUMP ROOM HIGH Life safety equipment must remain operational $100k - $150k C. FLOOD GATES/REMOVABLE BARRIERS MED Minimizes water infiltration $200k - $500k D. GROUND WATER PUMPING STATIONS MED Extensive modifications to building infrastructure $1 M - $2 M E. RELOCATE EMERGENCY POWER EQUIPMENT HIGH Recommended $2 - $4 M F. IMPROVED STORM/BLAST WINDOWS MED Minimizes water infiltration $3 M - $5 M G. WINDOW WELL WATER-TIGHT COVERS MED Deployment difficulties $3 M - $5 M H. EARTHEN BERMS LOW Impractical $4M - $6M I. MOAT WALL EXTENSIONS MED Minimizes water infiltration $7 M - $10 M J. RELOCATE MAJOR MECHANICAL AND ELECTRICAL SYSTEMS HIGH Extensive modifications to building infrastructure $40 M - $50M DOJ Building A. STORM WATER PIPING MODIFICATIONS HIGH Recommended, easy to implement $25k B. SEAL UTILITY PENETRATIONS HIGH Recommended, easy to implement $20k - $50k C. ISOLATE ELECTRICAL ROOM HIGH Recommended, easy to implement $100k - $150k D. ISOLATE FIRE PUMP ROOM HIGH Life safety equipment must remain operational $100k - $150k E. FLOOD GATES MED Minimizes water infiltration $800k - $1.2M F. RELOCATE EMERGENCY POWER HIGH Recommended $1.5M - 2.5M G. RAISE RETAINING WALLS ON CONSTITUTION AV ENUE LOW Existing moats provided protection during event $2 M - $3 M H. RELOCATE MAJOR MECHANICAL AND ELECTRICAL HIGH Extensive modifications to building infrastructure $30M - $40M DOC Building A. STEAM TUNNEL ACCESS STUDY HIGH Recommended, easy to implement $100k - $200k B. NEW REINFORCED HEAD WALLS AND DOORS HIGH Recommended, easy to implement $250k - $500k OPO Annex B. WATERPROOF WALLS HIGH Recommended, easy to implement $200k - $400k A. INFILL WINDOWS AND WATERPROOF WALLS HIGH Recommended, easy to implement $300k - $500k Legend High = No interruption of building operations Med = Limited interruption of building operations Low = Major interruption of building operations SETTY & ASSOCIATES, LTD. PAGE 4

10 2. INTRODUCTION The Washington, DC Metropolitan Area received heavy rainfall during the period of June 25 to June 28, As a result, city streets were flooded, as well as two Metro stations and the 9th and 12th Street tunnel under the mall. Businesses were closed due to flooding and power outages. A 100-year-old American elm tree fell near the front door of the White House and the House of Representatives canceled votes scheduled for June 26 because some members could not fly into Washington, DC. A state of emergency was declared in the District of Columbia and officials have estimated the resulting storm damage in the tens of millions of dollars. The General Services Administration has contracted Setty & Associates, Ltd. to investigate the heavy rainfall that occurred in June 2006 for its impact on limited buildings in the Federal Triangle area. The focus of this study is limited to four prominent buildings, including the Department of Justice (DOJ), Internal Revenue Service (IRS) Headquarters, Old Post Office Annex (OPO), and the Department of Commerce (DOC) at Ariel Rios. The study area is bounded by Constitution Avenue, NW; Pennsylvania Avenue, NW; 13th Street, NW; and 9th Street, NW. The study includes a description of the June 2006 flood, analysis of flood severity in comparison to historical events, causes and extent of flooding within the study area, an investigation of emergency event protocols for various parties involved, and concepts for mitigating or reducing the likelihood of future flooding problems within the buildings included in the study. The study will not serve as a guideline to protect the entire Federal Triangle area from future flooding, but only as an investigation as to protecting the aforementioned buildings. Proposed modifications to the site, surroundings, façades, and interior historic fabric resulting from the recommendations contained in this report will require further research, design details, and close coordination with the GSA s Historic Preservation Officer, a Section 106 Reviews, and approvals by the State Historic Preservation Office, the National Capital Planning Commission, the Commission of Fine Arts, and the Advisory Council on Historic Preservation. The Scope of Work for this study is as follows: A. Review the operations of the District of Columbia s storm and sanitary sewer system, WASA, and its Blue Plains treatment plant to ascertain what, if any, relationship these have to the flooding conditions occurring in the foreseeable future. 1. Make any recommendations for appropriate communication protocols between GSA and the District in future events of comparable rainfall. 2. Review reports of rapid water reductions on the Constitution Avenue corridor at approximately 4:30 a.m., Monday, June 26, Review the current maximum capacity/throughput of WASA s Blue Plains treatment plant to handle combined stormwater and sanitary sewage and WASA s future plans. B. Provide study services including cost estimates for each building listed below: 1. IRS Building a. Investigate, document, and verify the modes and sequence of flooding. SETTY & ASSOCIATES, LTD. PAGE 5

11 b. Provide analysis and recommend actions the government can take to prevent similar flooding. Compile data including, but not limited to, photographs. Interview GSA building managers and agency personnel. Indicate priority of work. The A/E shall explore all alternatives including but not limited to: 1) Multi-stage ground water pumping systems with emergency power. 2) Berms / Barriers. 3) Window well watertight coverings. 4) Improved storm/blast windows. 5) Recommendations to move all the HVAC/electrical equipment to other areas utilizing the Flood Damage Report. c. All recommendations need to comply with relevant codes and governing authorities requirements; National Capital Planning Commission, Commission of Fine Arts, National Historic Preservation Guidelines, DC Department of Public Works Streetscape requirements, etc. d. Utilize information contained in the following reports: 1) Flood Damage Assessment Report for the IRS Building dated July 5, 2006, by Jacobs Facilities Inc. 2) Flood Damage Phasing Construction Assessments; draft dated August 2, Department of Justice Building a. Study the existing garage doors at basement level to act as floodgates in similar flood events. Provide recommendations to modify garage doors to behave as such. b. Study and make recommendations to make utility penetrations at the basement and foundation walls watertight, such as PEPCO electric feeders. c. Evaluate the feasibility of raising retaining walls on Constitution Avenue, raising equipment bases/footings and relocating HVAC and electric equipment from basement/sub-basement to the roof and other areas. 3. Department of Commerce Building a. Study and make recommendations to eliminate water infiltration at the doorways to the GSA steam tunnels in the basement. 4. Old Post Office Annex a. Study and provide recommendations to make the common wall between the IRS Building and the Annex watertight. SETTY & ASSOCIATES, LTD. PAGE 6

12 3. JUNE 2006 THE FLOOD EVENT 3.1 Peak Rainfall The month of June 2006 was the 5th wettest ever recorded in Washington, DC, at inches of rainfall and the wettest since August The worst case 24-hour rainfall depth was measured starting on June 25, 12:00 p.m. at 7.01 inches, which is officially second only to the 7.19 inches recorded when remnants of Hurricane Agnes passed through the region in June The worst case 2-day rainfall total accumulated to 9.41 inches by midnight on June 26 and the resulting weekly rainfall total was inches. The table below shows the worst case hourly rainfall totals including the 3-hour total (3.73 inches) and the 6-hour total (5.91 inches) for June Figure 3-1: Hourly Rainfall for the Worst Case 24-Hour Period, June 25 June 26, 2006 Chief meteorologist, Jim Lee, from the National Weather Service in Sterling, Virginia, stated that the cause of the heavy rainfall was a tropical connection that funneled an extremely wet air mass up the East Coast. The moist air was up against a stationary front that had hung over the Mid-Atlantic region for that past week. The following figure outlines some of the problems caused by the heavy rain in the District of Columbia Metropolitan Area. SETTY & ASSOCIATES, LTD. PAGE 7

13 Figure 3-2: Chaos created in the DC Metropolitan Area by the June 2006 Inundation 3.2 Peak Stage / High Water Marks Peak stage for the June 2006 event was not as historically significant as the extreme rainfall that is noted above in this study. The U.S. Army Corps of Engineers has indicated that the Potomac River peak stage was measured at 9.5 feet at the Little Falls Gauging Station in their letter to the U.S. Attorney General dated July 14, 2006, included in Appendix B. This peak stage is a little higher than the peak stage indicated on the United States Geological Service (USGS) website of 7.94 feet (76,800 cubic feet per second) on June 29, Either 9.5 feet or 7.94 feet is a low peak stage when compared to historical records for the Little Falls Stream Gauge (USGS ) as shown in Figure 3-3. The March 19, 1936, event was the worst at Little Falls, with a peak stage of (484,000 cubic feet per second). The June 2006 event, from a peak stage standpoint, would be among the smallest of the 76 storm events since 1931 that are listed in Figure 3-3. It also should be noted that the Potomac River was not at flood stage until June 29, 2006, which was three days after the heaviest rainfall occurred. In summary, it appears that the river peak stage had little to do with the flooding that occurred in the Federal Triangle in June SETTY & ASSOCIATES, LTD. PAGE 8

14 Both peak stages reported for June 2006 were also well below the Federal Emergency Management Agency (FEMA) regulatory flood stages in the Potomac and Anacostia Rivers near downtown Washington, DC. FEMA maintains detailed mapping (AE designation) for the 100-Year Event in these major rivers, and nearest the tidal basin the regulatory floodplain elevation for the Potomac River is approximately 13.2 feet. The regulatory floodplain elevation is approximately 11.0 feet nearest the District of Columbia WASA main pumping station on the Anacostia River. POTOMAC RIVER NEAR WASH, DC - USGS PEAK STREAMFLOW DATA Date Flow, cfs Stage, ft Date Flow, cfs Stage, ft April 3, , March 27, , May 14, , April 3, , April 22, , February 24, , March 15, , June 24, , (Hurricane Agnes) December 2, , October 8, , March 19, , December 28, , April 28, , September 27, , October 30, , January 3, , February 5, , October 11, , April 22, , March 16, , April 7, , February 26, , May 24, , October 12, , October 17, , April 15, , May 9, , June 15, , September 20, , April 26, , June 4, , February 16, , March 17, , February 14, , April 16, , November 7, , June 20, , April 19, , February 3, , May 20, , December 6, , May 18, , April 29, , May 31, , November 23, , October 25, , March 3, , April 24, , August 20, , March 6, , July 21, , March 30, , April 7, , January 17, , May 7, , January 21, , June 4, , December 3, , May 10, , March 22, , February 21, , March 20, , March 23, , February 21, , March 21, , March 23, , March 6, , April 24, , March 7, , September 21, , (Hurricane Isabel) February 15, , December 12, , March 9, , March 30, , March 18, , June 29, , Maximum Flow = Peak Stage = 484,000 cfs ft Figure 3-3: USGS Stream Gauge Data at Little Falls SETTY & ASSOCIATES, LTD. PAGE 9

15 This study included data collection in the field, but there were no apparent June 2006 high water marks (i.e., stains, debris, etc.) visible. Reports varied as to the depth of the flooding since it occurred in the middle of the night, however, the videotape seemed to indicate floodwaters near the top of the concrete planters along Constitution Avenue, which is approximately an elevation of 11.0 feet (3-foot depth of flooding on sidewalks). The high watermark at the intersection of Constitution Avenue and 15th Street NW was also considered. This watermark is believed to indicate a worst case flooding near the Federal Triangle of approximately 38 inches above the sidewalk elevation (11.2 feet) on February 12, The actual flood depth and condition on Constitution Avenue was obtained from the watermark as shown in Photo Historical Flooding Events There are many historic storm events resulting from either a peak stage in the Potomac River or flooding in city streets due to excessive local rainfall. Some of these are described below for further comparison to the June 2006 event. Photo 3-1: 1881 High Water Mark on Constitution Avenue The old pump house at the intersection of Constitution Avenue and 15th Street NW is marked 38 inches above the sidewalk elevation (approximately 8.0 feet) and is labeled February 12, History documents that during the flood of 1881, raw sewage, which had inundated the swamp at Potomac Flats, mixed with the floodwaters and reached to within three blocks of the White House in this area. The 1881 flood prompted Congress to fund the dredging of Potomac Flats, creating what is now known as Potomac Park. On June 2, 1889, a 2-day rainfall of 4.4 inches caused a peak stage in the Potomac River of 19.5 feet, which is a crest elevation 12.5 feet above flood stage. This is still the unofficial record and the photograph below shows where flooding along Pennsylvania Avenue between 9th and 10th Streets was between 1 and 4 feet in depth. Photo 3-2: Pennsylvania Avenue in the June 1889 Flood (Library of Congress) SETTY & ASSOCIATES, LTD. PAGE 10

16 On August 12, 1928, a 1-day rainfall record totaling 7.31 inches occurred from a hurricane passing just to the southeast. On October 17, 1942, floodwaters reached to the steps of the Jefferson Memorial after a 5-day rainfall total of 6.27 inches. Heavier rainfall of 10 to 15 inches fell to the west of the District of Columbia, causing the Potomac River to crest at 17.7 feet which is still the official peak stage record for Washington, DC. Photo 3-3: 1942 Floodwaters around the Jefferson Memorial (NOAA Library) Hurricane Camille passed nearest the District of Columbia area in August 20, 1969, however the worst flooding occurred just prior to the hurricane on July 22, This peak rainfall event dropped 3.29 inches of rainfall in one hour (4.38 inches total rainfall), causing localized flash flooding throughout the District of Columbia. The June 2006 event is reported in this study to have dropped 3.16 inches in approximately one hour, which is very similar over a short duration of time. Photo 3-4: Search & Rescue during the 1969 Flash Flood (Washington Post) SETTY & ASSOCIATES, LTD. PAGE 11

17 The remnants of Hurricane Agnes passed through three years later on June 21, 1972, when Agnes dropped a total of 7.19 inches in a 24-hour period. On November 27, 1993, flash flooding occurred when 6 inches of nearly continuous rainfall fell across the city in a 12-hour period. Floods from January 20 to 23, 1996, were a result of a combination of up to 2 inches of snowmelt and up to 3 inches of rain. The river crested at feet near Wisconsin Avenue. At Great Falls, 15 miles upstream, the Potomac River raised a reported 8.5 feet in 48 hours. Photos 3-5 & 3-6: Rapid Rise of Floodwaters in January 1996 at Great Falls (National Park Service) More recently, the eye of Hurricane Floyd passed just southeast of the District of Columbia late in the evening on September 16, Up to 6 inches of rain fell across the District of Columbia, with 4.57 inches measured at Reagan National Airport. Two years later, flash flooding on August 11, 2001, dropped an estimated 7 inches of rain in one day in Northwest DC, but only 2 inches in Southeast DC. The 2001 cloudburst caused a reported $6 million in damage to 50 governmental buildings and more than 3,000 homes in the Metropolitan Area as storm drain systems were overwhelmed. In some parts of the District of Columbia, between 5 and 7 inches of rain fell in less than three hours, following heavy rainfall from the preceding day. On September 23, 2003, heavy rain fell on ground previously saturated by Hurricane Isabel, which had struck a few days before on September 18, Numerous roads began flooding during rush hour, including Constitution Avenue, and rainfall totals were approximately 3 inches for the event. The June 2006 event has similarities to many of these historic events and will be considered in future years as another flash flooding event resulting from heavy rainfall in short durations. The resulting flooding and overwhelmed storm drainage systems can be expected to continue in the Federal Triangle area in the future. Photo 3-7: Street Flooding during a Flash Flood August 2001 (WJLA) SETTY & ASSOCIATES, LTD. PAGE 12

18 4. CAUSES AND EXTENT OF FLOODING 4.1 Constitution Avenue: Street Flooding Evaluation In evaluating the design event necessary to protect GSA buildings in the Federal Triangle, the maximum rainfall, peak stage in the Potomac River, street topography, and the storm and combined sewer systems in Washington, DC, must be considered. Using this information, the following conclusions were reached as the basis of the flood mitigation alternatives study. Maximum Rainfall The National Atmospheric and Oceanic Administration (NOAA) National Weather Service (NWS) Precipitation Frequency Data Server was utilized in comparing the June 2006 rainfall totals with reported design rainfall events. This data represents the latest statistical analysis of rainfall at the Reagan National Airport, last updated in September Highlighted in red are rainfall depths that most closely resemble the measured June 2006 rainfall over 3-hour, 6-hour, 24-hour, 48-hour, and 7-day lengths of time. Highlighted in yellow is the range of recurrence intervals associated with the June 2006 event, which was determined in this study to fall between a 50-Year and 200-Year Event depending on the duration of time evaluated. In comparison, the DC WASA system for street drainage is reported to achieve an estimated 15-Year, 24-Hour performance standard (approximately 5.5 inches of rainfall). For the purposes of this study, alternatives for the June 2006 actual event are described instead of applying design events reported in the table below. This is because the June 2006 event falls within the range of design events that are considered reasonable and appropriate to evaluating flood protection alternatives in the Federal Triangle area. Precipitation Frequency Estimates (inches) ARI* (years) min min min min min min hr hr hr hr hr day day day day day day day NOTE - Worst-Case Rainfalls in June 2006 was 3.73 (3hr), 5.91 (6hr), 7.01 (24hr), 9.41 (48hr) and (7 day) Source - WASHINGTON REAGAN AP, VIRGINIA ( ) N W 22 feet from "Precipitation-Frequency Atlas of the United States" NOAA Atlas 14, Volume 2, Version 3 G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland, 2004, Extracted: Thu Sep Figure 4-1: NOAA Precipitation Frequency Data Server SETTY & ASSOCIATES, LTD. PAGE 13

19 Peak Stage For the purposes of this study, the estimated high water mark of 11.2 feet from February 12, 1881, is used since it is very similar to the 11.0 feet indicated in the videotapes for June Other historic events indicate that a flood stage of 11.0 feet has occurred along Pennsylvania Avenue and Constitution Avenue on other occasions. The use of 11.2 feet provides a baseline in this study for the June 2006 event instead of applying design peak stages in the Potomac River (such as the FEMA 100-Year Flood Stage of 13.2 feet). The use of a lower flood stage for this study is reasonable because: High water events in the Potomac River typically provide a few days of lead time and the Corps of Engineers will continue to use sandbags to protect against inflows through Potomac Park in this area; and The Corps of Engineers has plans described in the letter they provided to develop a more permanent flood protection system in Potomac Park to protect against high flood stages in the Potomac River of 13.2 feet. This approach to using the 11.2 foot flood stage is considered reasonable and appropriate to evaluating flood protection alternatives in the Federal Triangle area. Peak Volume / City Topography City topographic mapping of Washington, DC, at 1-foot contour intervals was also used for the study. The mapping shows a low section of Constitution Avenue in front of the IRS and DOJ buildings at elevation 8.0 feet street centerline. This creates a bowl in the city street system which will fill up with water during a flood event, unless the underlying storm drain and combined sewer systems have enough capacity to keep up with the rainfall. Other low lying areas indicated on the topographic mapping reviewed include the Tidal Basin (Potomac Park) and 3rd Street in front of the U.S Capital. It appears from the topographic mapping that storm water can break out from Constitution Avenue onto 3rd Street at an approximate elevation of 12.0 feet and onto 17th Street NW at an approximate elevation of 14.0 feet. City topographic mapping was also used to determine the total water accumulation volume on Constitution Avenue. For the worst case flooding which occurred in February 1881 and appears to have in some ways reoccurred in the June 2006 event, both accumulated approximately 38 million gallons of water in the streets (at elevation 11.0 feet) as shown in Photos 4-1 and 4-2. TABLE 4-1: WATER ACCUMULATION ON CONSTITUTION AVENUE Elev. Area Water Accumulation Water Accumulation System (ft) (sq.ft.) (cubic feet) (gallons) Notes bottom street gutter elevation 8 110,800 27, ,196 street centerline elevation 9 1,446, ,408 6,031,932 flooding <18" deep in streets 10 2,135,092 2,597,262 19,427,520 building flooding begins 11 2,871,866 5,100,741 38,153,543 approx. peak stage for June 2006 SETTY & ASSOCIATES, LTD. PAGE 14

20 4.2 Street Level Photos 4-1 & 4-2: Street Flooding at Federal Triangle, June 26, Internal Revenue Service Building The IRS Building is located between Pennsylvania Avenue and Constitution Avenue, and 10th and 12th Streets and is listed in the National Register of Historic Places as part of the Pennsylvania Avenue National Historic Site. The site slopes from a high point of El /- at Pennsylvania Avenue and 12th Street and of El /- at Pennsylvania Avenue and 10th Street to a low point of El.8.0 +/- at Constitution Avenue. The existing first floor is at El.11.63, the basement is at El.(-)1.37 and the sub-basement is El.(-) The building consists of four quadrants and Courtyards A through D, and the Old Post Office Annex. The service entrance, loading dock, and parking garage ramp are located in Courtyard A and are accessible from 12th Street. Courtyards B, C and D are interior. The childcare playground is located in Courtyard C. The annex and quadrant C adjoin the Old Post Office Pavilion. Moats are located around the perimeter of the building as well as the interior courts. The primary cause of flooding at the IRS Building resulted from water infiltration at the building perimeter moats along 10th Street, Constitution Avenue and 12th Street. The total amount of water accumulation attributable to rainfall on the building and site represented only 8 percent of the total water volume that flooded the structure, clearly indicating that flooding from the exterior was the major contribution to the problem. (Refer to Table 4-2 for total water accumulations in the basement and sub-basement of the IRS Building and Table 4-3 for a tabulation of all water that fell on the roof of the building from the point when flooding began). Storm water overflowed the moat gratings approximately 1-foot above grade level, overwhelmed the drainage system, and filled the moats. Excessive hydrostatic pressure was placed on the original double hung steel frame windows and the recently installed operable interior blast window assemblies. A number of the window assemblies failed under the excessive pressure, allowing water to flow into the basement and sub-basement levels. The existing steel frame windows were not air/water tight and the blast window systems were not designed to be waterproof assemblies. The windows were designed only to mitigate flying glass shards following an explosive event. The damage assessment of these windows indicates that the laminated cases absorbed the hydrostatic load placed on them, the glass fractured within the frame, and the load was transferred to the frame with the resultant deformation of the assembly. This level of damage is consistent with the performance criteria for GSA s Level C criteria, however, the deformation and damage of the assembly obviously allowed for the infiltration of SETTY & ASSOCIATES, LTD. PAGE 15

21 water. Figure 4-3 designates the locations of the window wells where water entered the building, with the darker blue arrows indicating heavier water infiltration. As documented in the July 2006 Flood Damage Assessment Report, prepared by Jacobs Facilities Inc., the majority of the window damage was observed along the 10th Street perimeter, some damage was observed along Constitution Avenue, and no damage was observed at the southwest façade at 12th Street. Figure 4-2 illustrates how the water infiltrated through the window wells of the IRS Building. Figure 4-2: Final Water Levels in the IRS Building SETTY & ASSOCIATES, LTD. PAGE 16

22 Figure 4-3: Points of Water Infiltration into the IRS Building SETTY & ASSOCIATES, LTD. PAGE 17

23 The conditions at the interior courtyard moats were quite different than the exterior moats. No window damage or significant water infiltration was observed at the interior locations. This supports the conclusion that the building storm water drainage system and specifically the moat drains were handling the rainfall until such time that the power and pumps failed. Two conditions in service Courtyard A present points of potential water infiltration into the building during an extreme flooding event. The first condition is the parking garage ramp to the basement and the second condition is the entrance at stairwell No The high point of the ramp is at El.9.13 and the low point at basement El.(-)1.37. The entrance at stairwell No is at mid-landing and El.9.8 +/-. Water infiltration at the exterior doors at this point would flow down the stairwell and flood the basement level and potentially the sub-basement. A secondary contribution to flooding originated from water infiltration at an electrical service duct bank along 12th Street. The duct bank was abandoned and the concrete plugs on the interior of the building appeared to have failed. Evidence at adjacent buildings suggests that the PEPCO street vaults were flooded and resulted in water infiltration through the duct banks. The total water accumulation within the IRS Building as a result of the flooding was an estimated 6.1 million gallons, indicated by Table 4-2. The sub-basement level was completely inundated under 13 feet of water and the basement was flooded to an average depth of 4 to 5 feet (see Figure 4-4). TABLE 4-2 Amount of Water accumulated in IRS building Area (sq ft) Water Depth (ft) Water Accumulation (cu. ft.) Water Accumulation (GAL) SUB BASEMENT 7, , ,657 BASEMENT 181, ,308 5,440,264 Total 6,149,921 SETTY & ASSOCIATES, LTD. PAGE 18

24 Figure 4-4: Flood Level in Basement and Sub-basement of IRS Building For comparison, Table 4-3 shows the total amount rainfall that fell on the projected roof and courtyard area of the building between the hours of approximately 10:30 p.m. and 6:00 a.m. on June 26. Calculations show that the roof and courtyard areas, which feed into the storm drainage system, accumulated only 492 thousand gallons of water. This represents only about 8 percent of the more than 6 million gallons which flooded the basement and sub-basement areas. TABLE 4-3 Actual rainfall on IRS building projected area (Roof and Courts) Area (sq ft) Water Depth (in) Water Accumulation (ft^3) Water Accumulation (GAL) Court A 11, ,910 29,246 Court B 11, ,910 29,246 Court C 11, ,910 29,246 Court D 11, ,910 29,246 Roof 147, , ,367 Total Projected Area 194,071 Total 492,352 SETTY & ASSOCIATES, LTD. PAGE 19

25 4.4 Department of Justice Building The Department of Justice Building is located between Pennsylvania Avenue, Constitution Avenue, 9th and 10th Streets. The Building is listed in the National Register of Historic Places as part of the Pennsylvania Avenue National Historic Site. The site slopes from a high point of El /- at Pennsylvania Avenue and 10th Street and of El /- at Pennsylvania and 9th Street to a low point of El.8.0 +/- at Constitution Avenue. The existing first floor is at El.12.0, the basement is at El.(-)1.0 and the sub-basement is El.(-)15.5. The building consists of four quadrants and courtyards A through E. The service entrance and parking garage ramps are located in Courtyard A and are accessible from both 9th and 10th Streets. The Attorney General s entrance ramp is located under Courtyard E off of 10th Street and the Solicitor General s entrance ramp is located under Courtyard D off of 9th Street. The moats and basement windows along each of the building s façades are protected by 42-inch high walls from the sidewalk level. Figure 4-5: Final Water Levels in the Department of Justice Building Based on interviews and surveys, it appears as though the DOJ building pumps were initially able to handle the storm run-off into the building. Eyewitness accounts put the water level of Constitution Avenue at approximately 36 inches high at its deepest. This height reached near the top of the planters shown in the photo below. However, the water never entered the front doors and it did not overtop the moat walls (see Photo 4-4 on next page). No water accumulated in the moats and the moat drainage system operated as designed. There was a large amount of debris in the moats and the drains appeared to be clogged, but they did not flood. SETTY & ASSOCIATES, LTD. PAGE 20

26 Photo 4-3: High Water Mark - Planters Photo 4-4: High Water Mark Moat Wall The buildup of water on Constitution Avenue was eventually compounded by the water cascading down 9th and 10th Streets. At approximately 10:30 p.m., the water pressure in the main storm discharge line built up, causing the service weight gasket to blow on the main U tube fitting on the line (see Photo 4-5 and Figure 4-6). This fitting is not designed to take larger pressures and it is likely that 5-10 psi of pressure would have dislodged this seal. The seal is designed to relieve the pressure in the pipe so that water does not back up the pipe and flood other floor drains. Photo 4-5: Storm Water Main which Failed Photo 4-6: Flooded Switchgear Room Once the pipe had been compromised, the room flooded quickly. Adjacent to this room through an open passageway is the electrical switchgear room. The water quickly entered both spaces and shorted out the electricity. The water level reached 51 inches in the electrical room (see Photo 4-6). The damage was not as severe due to the fact that the equipment was already on a 36-inch platform, which afforded some protection. When the power shorted out, the pumps stopped working initially until the emergency power started. However, the emergency power is supplied by generators which are all located on the basement level. These generators were soon overwhelmed by the floodwaters and ceased operation. Reports stated that the emergency power ran the four sets of building sump pumps for approximately 15 minutes before the generators were inundated and became inoperable. After emergency power was lost, the rain continued for almost three hours with no means of pumping the water out of the building. At this point, water was entering in the building from the Attorney General s and Solicitor General s ramps, overwhelming the trench drains. SETTY & ASSOCIATES, LTD. PAGE 21

27 Figure 4-6: Primary Means of Basement Flooding, Department of Justice Building A secondary cause of flooding resulted from water infiltration at an Attorney General s Ramp at 10th Street and the Solicitor General s Ramp at 9th Street (see photos 4-7 and 4-8). Additional water flowed into the parking level from the ramps at Courtyard A, overwhelming the trench drains at the base of the ramps (see photos 4-9 and 4-10 on next page). It was also noted that the existing gratings do not span the entire width of the ramps and heavy rainfall tends to flow to the side curbs, overshooting the gratings. Photo 4-7: Attorney General s Ramp - Flooded Photo 4-8: Ramp Doors - Exterior SETTY & ASSOCIATES, LTD. PAGE 22

28 Photo 4-9: Flooded Courtyard and Tunnel Photo 4-10: Garage Trench Drains Water was also entering the basement through the PEPCO feeders in the electrical room, which was also the case at the IRS Building (see photo 4-11). As the water level rose on Constitution Avenue, this duct bank started to channel the water into the electrical room. The rate of water entry is not known but eyewitness accounts said that water was flowing through the duct bank. Photo 4-11: PEPCO Feeders Photo 4-12: IRS Moats and PEPCO Feeders Water entered the sub-basement mainly through a trap door which is used for moving equipment in and out of the sub-basement. The trap door is located in the loading dock, where the water reached nearly 30 inches in depth at its peak (see photos 4-13 and 4-14). Photo 4-13: Flooded Subbasement Photo 4-14: Sub-basement Trap Door Access SETTY & ASSOCIATES, LTD. PAGE 23

29 Department of Justice Building security staff provided video from security cameras to the project team for the 30 minute period between 10:00 p.m. and 10:30 p.m. on the night of the event. The video tracked rising water to extreme levels along Constitution Avenue, 9th and 10th Streets. Within a very short 15 minute period, water rose to the planter rims and the top main entrance steps. The exterior and interior doors to the Attorney General s and Solicitor General s ramps were breached shortly thereafter. Figure 4-7 offers a perspective of how much rain fell between 10:00 p.m. and 10:30 p.m., when primary power was lost, and how much rain fell after the power was lost. The most significant periods of precipitation occurred between the hours of 9:00 p.m. and 11:00 p.m. and 1:00 a.m. and 2:00 a.m., when over an inch of rain per hour was falling. The heaviest rainfall occurred between the hours of 10:00 p.m. and 11:00 p.m., when two inches of rain accumulated within the hour. It was also during this period of the heaviest rainfall that initial water infiltration into the buildings occurred and continued once the initial barriers were breached. Figure 4-7: Rainfall per hour during the flood event before and after power was lost. SETTY & ASSOCIATES, LTD. PAGE 24

30 At the peak of the flood, the total amount of water accumulated in the Department of Justice Building, as shown in Table 4-4, was nearly 3.5 million gallons. The sub-basement was completely inundated under approximately 14.5 feet of water, resulting in the loss of all equipment located there. Much of the central basement and parking garage area that flooded accumulated water levels between 1 and 2 feet deep. The areas located along the south wall of the building had water levels typically only 2 inches deep. The exceptions were the electrical vault and generator room directly next to the U trap that caused this area to flood with 3 feet of water. Also, the basement loading area located next to the sub-basement flooded with nearly 3 feet of water, and several rooms along the east wall of the basement saw just over 4 feet of water. Figures 4-8 and 4-9 illustrate the known and probable entry points of water into the building and the final water depths recorded within the basement and sub-basement areas. TABLE 4-4 Amount of Water accumulated in DOJ Building Location Area (sq. ft) Water Depth (ft.) Water Accumulation (cu. ft.) Water Accumulation (GAL.) Sub-Basement Area # Area # Area # Area # Area # Area # Area # Total 3,434,056 Table 4-5 shows the total amount of water that fell on the Department of Justice Building between the hours of approximately 10:30 p.m. on June 25 and 6:00 a.m. on June 26. Calculations show that the roof and courtyard areas, which feed storm water into the drainage system, accumulated roughly 838,000 gallons of rain water. This represents about 25 percent of the nearly 3.5 million gallons which flooded the basement area. Thus, the Department of Justice Building was flooded by a larger percentage of water that hit the building projected area than the IRS Building. The logical explanation for this discrepancy is the fact that the window wells were penetrated at the IRS Building but were not at the DOJ Building. Also, floodwaters at the DOJ Building entered primarily through a pipe which collects storm water from the roof and courtyards and expels it to the sewer system. SETTY & ASSOCIATES, LTD. PAGE 25

31 Figure 4-8: Points of Water Infiltration, Department of Justice SETTY & ASSOCIATES, LTD. PAGE 26

32 TABLE 4-5 Actual rainfall on DOJ building projected area (Roof and Courts) Location Area (sq. ft) Water Depth (in.) Water Accumulation (cu. ft) Water Accumulation (GAL.) Court A 43, , ,269 Court B 8, ,819 21,090 Court C ,776 Court D 10, ,455 25,844 Court E 10, ,426 25,628 Roof 257, , ,741 Total Projected Area 330,453 Total 838,348 Figure 4-9: Final Water Depths, Department of Justice Because Courtyard A also flooded during the June 2006 event (see Photos 4-15 and 4-16), an investigation was performed on the building storm drainage system to check the capacity. It was found that Courtyard A is served by two main rainwater drain pipes which run below the courtyard and serve to prevent rainwater from backing up in the area and causing a flood. The sizes of these drain pipes are 10 inches each. According to the 2003 International Plumbing SETTY & ASSOCIATES, LTD. PAGE 27

33 Code, the maximum capacity for storm drains of this size, assuming a 1 percent slope, is 20,700 square feet of coverage each. However, the area of each half of Courtyard A is approximately 21,930 square feet. Therefore, using the design criteria of a 100-year rain event that yields 4 inches of rain per hour, these drains are undersized by approximately 6 percent, indicating that flooding of the courtyard area could occur in a future, more severe event. Yet, the rainfall which occurred on June 25 and June 26 did not meet the 100-year design criteria since the maximum one-hour rainfall amount was only 2 inches. Thus, for this event, the storm drain system for Courtyard A should have been sufficient to handle the load. Again, the building was compromised by the storm water pumps failing. Photo 4-15: Flooded Courtyard Photo 4-16: Courtyard High Water Mark The total capacity for all eight Department of Justice Building rainwater drains combined, the locations and sizes of which are indicated by Figure 4-10 and Table 4-6, is 319,800 square feet of rainwater collection space according to the 2003 International Plumbing Code. The total rainwater collection area for the Department of Justice Building, including the roof and all courtyard areas, is 330,453 square feet. In the event of a rainfall which yields 4 inches of rain in one hour, the storm drainage system for the building would need to operate at about 3 percent beyond current capacity, indicating that the system is slightly undersized for a 100-year event. However, the event which occurred on June 25 and June 26 yielded only 2 inches of rain in one hour, putting the system under a load of only about 50 percent of capacity. Therefore, the drainage system was capable of handling this particular load. It was not, however, designed to accommodate the impacts from adjacent street flooding and the backup of storm drain systems. SETTY & ASSOCIATES, LTD. PAGE 28

34 Figure 4-10: Rainwater Drain Pipe Locations TABLE 4-6: Total Capacity for all DOJ Building Rainwater Drains Building RW Drains Drain Size (in.) Max Storm Drain Capacity (sq. ft) A B C D E F G H Building Capacity 319,800 Actual Building Area 330,453 Spare Capacity -3% SETTY & ASSOCIATES, LTD. PAGE 29

35 4.5 Department of Commerce Building The Commerce Building is located between 14th and 15th Streets NW with Pennsylvania Avenue to its north and Constitution Avenue to the south. Photo 4-17: Commerce Building, 1401 Constitution Ave NW, Washington, DC The existing structure of the Commerce Building dates from the 1930 s with several renovations and maintenance projects having taken place since then. The original foundation of pile clusters, thick concrete slab, and retaining walls is in good condition and does not show any serious signs of cracking or water infiltration. Where ground water seeps through the floor in the sub-basement level, it is collected into a deep sump and then pumped up to the basement ejector sump pumps. Another constant source of water inflow into the building is the steam condensate return which is prevented from returning into the central system. The condensate return flows into the storm sump in the Basement Main Compressor Room and is ejected by the existing pumps. These two sources of continuous water flow into the building are manageable by the present ejector pumping system but remain a constant maintenance responsibility. SETTY & ASSOCIATES, LTD. PAGE 30

36 Photo 4-18: Commerce Building, 1401 Constitution Ave NW, Washington, DC As reported, the recent flooding incident was caused by floodwater bursting through the steam tunnel doors. It was also reported that there was no floodwater inflow from the 15th Street drive ramps/loading docks into the basement and no inflow from Constitution Avenue, 14th Street or from Pennsylvania Avenue or E Street to the north. In addition, there was no flooding reported coming in from the courtyards. The flooding that occurred in June 2006 originated only from the steam tunnels to the east and west sides of the building. The steam tunnels had filled with storm water completely and the pressure forced the tunnel doors open. The water entered the basement level (where the tunnel doors opened) and flooded the area to a depth of at least 3 feet. The water then ran down through various openings and flooded the sub-basement. SETTY & ASSOCIATES, LTD. PAGE 31

37 4.6 Old Post Office Annex The existing structure of the Old Post Office Annex was constructed after the construction of the IRS Building. It is believed that structural support of the Annex utilizes the IRS exterior wall only to a minor extent, having its own steel column, concrete footing, and steel deck concrete floor slab systems. The columns running parallel with construction which are run at the exterior of the rear of the IRS Building shows angle bracing for a portion of the structural system to be cantilevered. Existing IRS footings were unburied along the wall of the Annex and supplemental footing was added above the floor level of the Annex. The existing and new footing extend approximately 4 feet into the Annex s lowest level floor. The sub-basement of the IRS does not share any of the common wall between the Annex and the IRS basement and it does not appear that water penetrated the footing system as a point of entry. The lowest floor level of the Annex is not at grade but approximately 10-0 feet below grade with a floor to floor height of approximately 20-0 to the first floor level. This lower level has natural light due to the open court floor plan of the first floor and does not feel like a basement. The floor level is approximately 1-6 below the IRS basement finished floors and had a floor water level of some five to six feet above the finished floor. A sloped and depressed former theater area was filled with water to an additional depth of approximately 8-0. The main lower level floor area had floor drains in the Men s, Women s and Handicapped toilets but not in the Theatre area or any other locations. In the toilet rooms, the water level was above the water closets and sinks. No determination could be made as to whether these fixtures had a direct effect on the flooding due to back-ups. The theater depression (at its lowest level) showed some reaction to the unusually high ground water pressure as the construction point at the retaining wall/floor slab showed some back wash and opening. The Theater area held water much longer than the main and lower level. It was not clear whether the water was eventually pumped out, evaporated or swept out through this construction point since no floor drains are located in this area. As noted, the IRS building was in existence prior to the design and construction of the Old Post Office Annex. The shared wall between the buildings is constructed of several different materials including brick and concrete masonry unit, poured-in-place construction concrete, limestone, and concrete block. The wall also has approximately 25 metal frame single pane windows with a rough opening of 32.5 square feet each. Most windows on the Annex side are hidden behind drywall partitions. Due to the demolition and reconstruction of the IRS basement, most windows are currently viewable from the IRS side of the wall. Evidence of floodwater lines still exist on many of these windows. Some window panes are broken out, allowing floodwater to freely interchange between the two building entries. It is understood that the IRS Building provides the Old Post Office Annex Building with hot water for heating and domestic use, water and electrical power. It does not provide steam, chilled water, or other services or utilities. The drainage system of the storm or sanitary sewer is not widely known or is perhaps unknown. Utilities and services provided to the Annex pass through the common wall. Additionally, fresh, ventilated, and exhaust air ducts pass through this wall for the benefit of the IRS Building. Other penetrations such as roof drains and downspouts from gutters appear to be present and may also penetrate the joint wall. However, most of these penetrations appear to be minor and only a few pipe and conduit pipe sleeves were observed. SETTY & ASSOCIATES, LTD. PAGE 32

38 5. DC WATER AND SEWER AUTHORITY (WASA) Based on the results of this study, it appears that the primary reason for flooding of the Federal Triangle area in June 2006 was the inadequate capacity in the city s storm drainage and combined sewer systems to handle the large rainfall and storm runoff, especially along Constitution Avenue. This section of the report looks more closely at the system and the agency responsible for maintenance of the system in the District of Columbia Metropolitan Area, the DC Water and Sewer Authority (WASA). A meeting was held with WASA s Chief Engineer, Assistant General Manager and Director of Engineering and Technical Services to discuss the June 2006 event, WASA s Blue Plains operations, and WASA s future capital improvements. These representatives of WASA are highly placed within the WASA organizational structure (see Figure 5-1). The minutes of this meeting are in Appendix B. Additionally, the intent of the meeting was to gain a better understanding of WASA operations and protocols to enhance inter-governmental communications in times of emergency. Many topics were discussed with WASA but two important pieces of information were brought to light. Firstly, WASA indicated that they try and achieve a 15-year storm event performance in the combined sewer and drainage systems, but very few parts of the system that they have taken over maintenance for in DC meet this design guideline. In other words, the WASA storm water system in the vicinity of the Federal Triangle is probably not capable of handling a 15-year storm event. Upgrading the storm water system to handle a 50-year event would help to mitigate certain storm events and may have helped during the June 2006 event. Upgrading the system would take several years and be very costly. There are currently no WASA plans to upgrade their infrastructure to handle a 50-year event. Secondly, WASA has two main pump stations, one near the Anacostia River and one near the Potomac River. Neither pump station has backup power, but WASA only confirmed a power outage at the 12th Street Tunnel pump station, which they indicated drains away from the Federal Triangle to the south. The locations of both main pumping stations are indicated on the WASA System Map in Appendix A. According to WASA, if there is a power outage at their main pump stations the system automatically allows the storm water to be dumped into either the Potomac or Anacostia Rivers directly without treatment. There may be a small backup in the system depending on the river height but the system is designed for overflow into the rivers 5.1 WASA Organizational Structure WASA is a semi-autonomous regional entity created by the U.S. Government and the District of Columbia government in 1996, which serves several counties and cities in Virginia, Maryland, and Washington, DC, primarily as a public water and wastewater utility provider. They have close ties with the DC Department of Public Works for a large portion of their system, but are also separate with federal funding approved directly by the U.S. Congress. WASA operations are led by a General Manager who reports to an 11-member Board of Directors. The board includes six members representing the District of Columbia, two members representing Prince George s County, two members representing Montgomery County, and one member representing Fairfax County. Additional staff and their organizational structure are shown in Figure 5-1. Coordination for this study included significant efforts to attain information SETTY & ASSOCIATES, LTD. PAGE 33

39 from the WASA Chief Engineer (Deputy General Manager), John T. Dunn, and his staff for use in this study. Figure 5-1: WASA Organizational Structure SETTY & ASSOCIATES, LTD. PAGE 34

40 5.2 WASA System Overview The WASA wastewater collection system covers 725 square miles and serves an estimated 2 million people. The system includes approximately 1,800 miles of sanitary and combined sewer lines and nine wastewater pumping stations. The system is predominantly separated sanitary and storm sewer, but combined sewers serving both the sanitary flow and the storm water flow are prevalent in the District of Columbia Metropolitan Area and in older portions of the service area, including along Constitution Avenue in the area of this study. WASA also operates the Blue Plains Advanced Wastewater Treatment Plant (AWTP), the largest facility of its type in the United States with a permitted average daily capacity of 370 million gallons per day (MGD) and a peak wet weather capacity of 847 million gallons per day. The Blue Plains facility treats all storm and sewer water from Washington, DC, conveyed through the combined sewer system. Also, much of the wastewater from municipalities in Maryland and Virginia, who choose to purchase treatment services from WASA, is funneled to Blue Plains. The MS-4 permit is held by the District of Columbia and WASA operates the Blue Plains plant only. WASA indicated that the combined sewer main in Constitution Avenue drains in both directions. There is a 460 MGD pump station to the west near the Potomac River. There is also a 200 MGD pump station (with plans to increase capacity to 240 MGD) near the Anacostia River. There is also a separated storm drain system in Constitution Avenue which drains directly to the Tidal Basin. Two maps showing the overall WASA system to the Blue Plains Wastewater Treatment Plant and some details of the pipe sizes for the separated storm drain along Constitution Avenue are included in Appendix A (map pockets). The Tiber Creek Sewer Interceptor handles all combined sewage flows along Constitution Avenue, and is sized on average as 12 x12 cross section. It drains east along Constitution Avenue and then southeast towards the WASA main pumping station, which pushes sewage flows under the Anacostia River through 60-inch siphons and has a 200 MGD capacity. The sewer main then drains south to the Blue Plains Wastewater Treatment Plant along the Anacostia River. The Tiber Creek Sewer Interceptor also loops back to the west, where it connects to a 460 MGD pump station on the banks of the Potomac River, which then drains south to the Blue Plains Wastewater Treatment Plant. The Constitution Avenue storm drain was created when a bulkhead was installed near the intersection of 9th Street NW to separate flows from the combined sewer system. Street drainage systems are connected to the storm drain, and then drain west through a culvert that increases in size from a 5-0 span (rise unknown) to a 9-0 x 6-9 culvert in front of the White House. The storm drain then runs south to the Tidal Basin in Potomac Park, where the size decreases to a 6-0 x 4-9 before discharging to a submerged outlet pipe. A new tide gate was installed in 2003 (Tideflex by Red Valve) to prevent backflow into the pipe system from the Potomac River. From a maintenance standpoint, WASA inspects and cleans catch basins and pump stations on an annual schedule with additional cleaning in response to customer requests on their 24-hour emergency hotline, (202) However, WASA indicated that piping systems underneath the street network in Washington, DC are rarely inspected or cleaned. SETTY & ASSOCIATES, LTD. PAGE 35

41 5.3 Combined Sewer Overflows (CSO) Combined Sewer Overflow (CSO) is a significant policy issue for WASA in managing the system in the Metropolitan DC Area and demands some discussion in this report. During storm events when the capacity of the combined sewer system is unable to convey the mixture of wastewater and storm water to the treatment plant, CSO will occur. WASA has 53 CSO outfalls listed in their National Pollutant Discharge Elimination System (NPDES) storm water permit that was issued by the EPA to WASA. These CSO outfalls discharge a mixture of storm and sewage flows that can create a significant environmental and health concern related to heavy flooding events in Washington, DC. In December 2004, WASA reached an agreement in a suit filed by the federal government to implement a very extensive program of CSO Abatement that will dramatically reduce the overflows from the District s combined sewer system to help protect the Anacostia, Potomac, and Rock Creek/Piney Branch waterways. The agreement calls for WASA to implement a plan over a 20-year period for a variety of capital improvements throughout the District. The CSO Abatement Program over the past decade has made an effort to reduce CSO discharges and maximize in-pipe storage of sewer overflows. To date, overflows are down an estimated 24 percent due mostly to the replacement of tide gates to reduce backflow, installation of 12 inflatable dams that hold back sewer overflows, construction of separated storm drain systems, plant/pumping stations upgrades, and the construction of a sewer monitoring and control system. WASA is now completing $140 million in additional projects that are projected to further reduce overflows by an additional 40 percent, mostly through the construction of tunnels along the banks of the Potomac and Anacostia Rivers to store CSO until the downstream system to the plant can receive the flow; however, this will not improve the capacity of the storm water system. It should be noted that the WASA capital improvement plan (CIP) shows very little funding for the construction of improvements to the separated storm drainage systems in Washington, DC, which is the only way to avoid treating storm water runoff at the plant by improving the capacity of the separated storm drainage system. WASA has modeled only 5 percent of the DC sewer infrastructure at a cost of nearly $15 million. A complete model of the system will most likely need to be completed in order for the system upgrades to be implemented and funded. WASA s intent to complete the modeling of the remaining 95 percent of the system is still under consideration. Various portions of WASA s capital improvement plan are included in Appendix G. 5.4 June 2006 Event There was a very sudden rise and rapid reduction of the floodwaters on Constitution Avenue over a 30-minute period as reported by Government personnel. Our rough calculations using the high watermarks and the DC topographical maps indicate approximately 38 million of gallons of water entered Constitution Avenue in 30 minutes. This represents an average rate of flow of billion gallons per day (or 1,179 cubic feet per second), which is greater than the combined capacity of the entire WASA system at Blue Plains and most certainly greater than the capacity of the drainage system in Constitution Avenue. Coordination with WASA as to the hydraulic gradients and peak flood stages anticipated in their system has been attempted, but after several requests no modeling information was provided by WASA for this study. During the WASA coordination meetings, it was evident that very limited information is available to quickly understand the capacity of a portion of the WASA system, SETTY & ASSOCIATES, LTD. PAGE 36

42 except in areas where recent detailed hydraulic modeling has been completed. Given the lack of information provided by WASA, basic hydraulic observations were developed as described below to support the site alternatives in this study that follows in this report. The peak stage of flooding on Constitution Avenue was 11.2 feet outside the Department of Justice, the head loss in the Constitution Avenue storm drain can be based on the peak stage in the tidal basin at around 1:00 a.m. on June 26, The exact peak stage in the Potomac River (and tidal basin) is unknown, but has been reported by the Corps of Engineers to be 9.5 feet (equal to 1.7 feet of head pressure) at the Little Falls Gauging Station. The USGS website stated the peak stage three days later was 7.94 feet (equal to at least 3.26 feet of head pressure in the system). It should also be noted that the combined sewer system is separate from the storm drainage system in Constitution Avenue and would likely have contributed to the flooding although there is no clear way to determine which pipe caused the backups. 5.5 Possible Scenarios to Rapid Rise and Fall of Flood Waters on Constitution Avenue Although the exact cause of the flooding of Constitution Avenue is not known, several possible scenarios or combinations thereof could have contributed to it. These scenarios were discussed with WASA during the meeting but no definitive causes were supported. In rare situations such as the recent flooding of the Shockoe Creek Watershed in Richmond, Virginia, from Hurricane Gaston in 2004, a sudden rise of this magnitude can occur mostly due to overtaxed piping systems. In the case of Constitution Avenue in June 2006, the exact cause of the sudden rise and fall of storm water remains unknown. Scenario One WASA Main Pumping Station The main pumping stations could have stopped operating causing the water to backup rapidly in the storm water system and then into the streets. The pumping stations could have lost power; there were PEPCO outages across the city that night. It was determined there was no standby power for these pump stations. The rapid decline in the water off of Constitution Avenue also lends itself to pumps re-energizing and thereby draining the area rapidly. During discussions with WASA, it was discovered that the main pumping stations were operational continuously on June 25 and June 26, The 12th Street tunnel pump station did lose power and was not pumping during the event peak as it does not have standby power. Furthermore, if the main pumping stations did not operate, combined storm and sewer flow would reportedly discharge directly into the Potomac and Anacostia Rivers at the WASA pumping stations due to overtopping. Scenario Two WASA System Blockage On June 24 and 25, 2006, the National Barbeque Battle took place on Pennsylvania Avenue. This is an annual event occurring between 9th and 14th streets on Pennsylvania Avenue. The large volume of litter created by the event, if not removed properly, could have contributed to diminished capacity in the storm system. This event was discussed with WASA and they said that cleaning of catch basins is the responsibility of WASA and is done regularly but the impact on the storm water system is likely to be minimal. Generally, there are excessive amounts of litter in the WASA system from all parts of DC. The introduction of litter into the system is extremely difficult to assess as to overall impact. SETTY & ASSOCIATES, LTD. PAGE 37

43 The rapid rise could have been a blockage and the rapid fall could have been a release of the blockage in the system. Also, portions of the storm water may have been able to make it through the blockage. WASA reported no large system blockages during the event, but has not provided any inspection reports to date. Scenario Three Tide Gates WASA installed new tide gates in 2003, including the tidal basin storm line (Tideflex by Red Valve). These valves will open and close automatically with no human intervention and function based on the pressure in the storm line. These particular gates also do not allow any backflow of the Potomac River into the storm water system under Constitution Avenue. It is possible that the gates did not open due to excessive back pressure from the Potomac water level or inadequate pressure from the storm sewer. Based on rough estimates of head losses for the WASA pipe system and tide flex valve as well as the water level difference between the high water level and the Tidal Basin, it is estimated that approximately 4 feet of head would have had to have been overcome to force the floodwater through the system and into the basin. The graph in Figure 5-2 shows the head loss ratings for various sizes of Tideflex Valves, the same model installed in the discharge line a few hundred feet before the pipe terminates at the Tidal Basin. Figure 5-3 illustrates the storm water discharge system that collects storm water from the area around Constitution Avenue and passes it through approximately 5,000 feet of pipe before dumping it into the Tidal Basin. Using this information, an estimated head loss for the valve was obtained. Finally, Table 5-1 indicates where the assumed losses are in the system and identifies how a total required head of 4 feet was derived as an initial estimate. It is recommended that a detailed study and flow model should be used to attain the actual hydraulic gradients and head loss in the system. Figure 5-2: Tideflex Manufacturer Provided Data SETTY & ASSOCIATES, LTD. PAGE 38

44 Figure 5-3: WASA Storm Drain System TABLE 5-1 Anticipated System Losses for June 2006 Peak Stage Head Loss Component (ft) Comments Tide Flex Valve 0.55 Assumed 9,000 gpm flow through a 48 tide gate WASA Structure Losses 2.0 Due to junction/minor losses in WASA structures WASA Pipe Losses 1.45 Due to friction and various losses in 5000 feet of pipe Total WASA Related Questions and Answers Original WASA GSA to WASA, 4-December-2006 GSA commissioned a study by Setty & Associates, an independent consultant, to review all aspects of the flooding of the Federal Triangle on June 25, The scope of this study included all buildings in the Federal Triangle affected by the floodwaters so that a comprehensive plan can be developed to mitigate/prevent future occurrences. The scope included: 1. Investigating and documenting the modes and sequencing of flooding at each building; including 1111 Constitution Avenue. SETTY & ASSOCIATES, LTD. PAGE 39

45 2. Review the operations of the Blue Plains treatment plant and any relationship to the flooding of the Federal Triangle. This will also include an analysis of the dual storm and sewer systems in the DC infrastructure. 3. Provide recommendations, with associated costs, to prevent water infiltration into these buildings in the event of similar flooding conditions occurring in the near future. Our consultant is in the final stages of writing the report surrounding the flood events of late June here in DC. To complete the work and avoid a report which indicates two branches of government cannot communicate, I would appreciate your staff looking to answer the following questions: 1- We have been led to believe the DC WASA system for street drainage meets a 15-year storm event performance for combined sewer and storm drainage. Is this the current standard? 2- What is the ability of the WASA system to respond to flooding events in terms of pumping or discharge capacity per hour to drain surface runoff? 3- What automated systems exist to bypass the Blue Plains treatment plant in flood events? 4- If automated systems do exist, did they perform as designed during the June 2006 flood event? 5- What manual procedures are available to override the WASA system to increase its capacity to handle storm runoff? 6- Describe how the automated and manual systems worked during the June 2006 Flood Event. 7- It has been reported that the flooding on Constitution Avenue occurred on June 25 th at 10:30pm after only approximately 2.25 inches of rain had fallen in a 3-hour period. Yet the capacity of the WASA system should have been able to handle the amount of rainfall that had occurred at the time that the water rose. What do you believe caused this to occur? 8- It has been reported that the flood waters (estimated at 38 million gallons) receded very quickly starting at 4:30am on June 26 th. Does WASA have any record of what occurred just precedent to 4:30am and have any explanation where the flood water went? 9- To what extent does the March 2005 USA DC & WASA consent decree reduce the capacity of the WASA combined sewer and storm drainage system serving the Federal Triangle area to process effluent through the Blue Plains treatment plant and surface runoff directly into the Potomac and Anacostia River? 10- Is there anything that WASA believes GSA can do to assist in WASA's storm-sewer drainage system within the Federal Triangle? SETTY & ASSOCIATES, LTD. PAGE 40

46 5.6.2 Answer Interpretation Matrix Question 1- We have been led to believe the DC WASA system for street drainage meets a 15-year storm event performance for combined sewer and storm drainage. Is this the current standard? 2- What is the ability of the WASA system to respond to flooding events in terms of pumping or discharge capacity per hour to drain surface runoff? 3- What automated systems exist to bypass the Blue Plains treatment plant in flood events? 4- If automated systems do exist, did they perform as designed during the June 2006 flood event? WASA response What was discussed at the October meeting between you staff and consultants was the fact that District has a 15-year return storm as the design standard for the system. Also it was noted that there are elements of the system, much of it constructed by the federal government since the middle of the 19th century, that do not meet this standard. Although WASA maintains the existing separate stormwater system, it has not assumed responsibility for the design and reconstruction of this District-owned asset, nor is it accountable for compliance with the District's MS4 Permit issued by USEPA. The capacity of the Blue Plains Advanced Wastewater Treatment Plant (BPAWTP) and its internal pumping stations system are not factors in localized urban flooding in the District. The BPAWTP is the largest advanced wastewater treatment plant in the world, providing 370 million gallons per day (MGD) of treatment capacity to two million consumers in Washington, D.C., and surrounding jurisdictions in Maryland and Virginia. The plant is rated at 370 MGD dry weather flow but, during wet weather events, the flow to the BPAWTP is limited to 511 MGD of full treatment, and an additional 336 MGD of partial treatment in order to maintain the plant's biological treatment operations. No specific answer The separate stormwater system (approximately 2/3 of the District s area) discharges by gravity to the receiving streams and rivers with the exception of sections of the system that discharge to stormwater pumps located at O Street and Main Street Pump Stations located on the Anacostia River in the vicinity of the new baseball stadium. These pumps are intended to improve the hydraulic gradient for the separate storm sewers in the area, but in the event of the failure of these pumps, the wet well overflows directly to the river by gravity. In this situation the capacity of the sewers discharging to these wet wells SETTY & ASSOCIATES, LTD. PAGE 41

47 5- What manual procedures are available to override the WASA system to increase its capacity to handle storm runoff? 6- Describe how the automated and manual systems worked during the June 2006 Flood Event. 7- It has been reported that the flooding on Constitution Avenue occurred on June 25 th at 10:30pm after only approximately 2.25 inches of rain had fallen in a 3-hour period. Yet the capacity of the WASA system should have been able to handle the amount of rainfall that had occurred at the time that the water rose. What do you believe caused this to occur? 8- It has been reported that the flood waters (estimated at 38 million gallons) receded very quickly starting at 4:30am on June 26 th. Does WASA have any record of what occurred just precedent to 4:30am and have any explanation where the flood water went? would be diminished, but these pumps did not fail during the June storm event. During the storm periods in question these pumps operated normally and, as such, maximized the carrying capacity of the sewers feeding the station wet wells. Therefore, the separate stormwater sewer s ability to move rain out of the Federal Triangle was not impacted by WASA s pumping operations at Main & O. No specific answer given. Partially answered - Although WASA is not responsible for the performance of the stormwater management system we have, under an informal agreement with DDOT, assumed certain responsibilities for maintenance of stormwater pumping stations used to control flooding at certain roadway underpasses in the District. These unmanned pumping stations are tied directly to the electric power grid that serves the District. If the power to these stations is curtailed during a storm event there is no mitigating action that can be taken in the short-term until the power is restored. Normally these stations automatically return to service once power is restored, however, if they fail to do so WASA personnel will investigate the problem and take corrective action. No specific answer given. No specific answer - There is no record of any applicable water levels during the 10:30-4:30 time frame in question, however, there is no indication that gates were not operating as designed during this storm event. Please also note that the June 25 to 26 storm was a very rare event and was reported as a 200-year storm by the National Weather Service, greatly exceeding any reasonable design standard. SETTY & ASSOCIATES, LTD. PAGE 42

48 9- To what extent does the March 2005 USA DC & WASA consent decree reduce the capacity of the WASA combined sewer and storm drainage system serving the Federal Triangle area to process effluent through the Blue Plains treatment plant and surface runoff directly into the Potomac and Anacostia River? 10- Is there anything that WASA believes GSA can do to assist in WASA's storm-sewer drainage system within the Federal Triangle? No specific answer given. No specific answer given. SETTY & ASSOCIATES, LTD. PAGE 43

49 6. GOVERNMENT COMMUNICATIONS PROTOCOLS 6.1 Department of Homeland Security GSA building managers are notified of emergency events from the Department of Homeland Security. The Department of Homeland Security (DHS) call center, also known as the Megacenter, monitors situations involving governmental facilities and has the capability to call over 1,000 entities quickly in the event of an emergency. The Megacenter operates a Notification Matrix, which requires input from each agency as to personnel to be contacted for different situations that can be anticipated. Predominantly, the Megacenter monitors intrusion alerts and fire alarm notification in specific buildings, but they have capabilities for other types of monitoring as necessary for homeland security. Currently, the Megacenter has contact capabilities through the RICCS system (see paragraph 6.7, DC Emergency Management Agency protocols). GSA NCR is notified by the DHS Megacenter of emergency incidents. The Megacenter does not have a flood triggering event. Building evacuation is listed as an action to be taken but it is not the same hazard. Also, there is no direct communication between WASA and the Megacenter at present related to combined sewer overflows. GSA has a Regional Emergency Coordinator and he is the primary point of contact with the DHS Megacenter. Starting in July 2006, GSA obtained the capabilities to receive notification of emergency incidents from the Regional Incident Communication and Coordination System (RICCS) in Washington, DC. The RICCS is hosted by the DC Emergency Management Agency. 6.2 Internal Revenue Service Building The Internal Revenue Service Building is maintained by IAP World Services. IAP World Services is an independent contractor dedicated to the maintenance of the IRS Building. IAP World Services maintains the building during the hours of 6:00 a.m. to 6:00 p.m., Monday through Friday. During these hours, IAP advises IRS Building Management, who then contacts GSA to advise of building events. It is currently understood that IAP World Services was not on site the weekend of the event. IRS physical security monitors the building at all other times and advises the IRS Building Management of building wide issues. On the night of the event, IRS building security reacted to the power failure at 10:32 p.m. and contacted the IRS Building Manager. IRS Building Management then advised GSA of the failures. 6.3 Department of Justice Building The Department of Justice Building is maintained by Justice Building Services (JBS). JBS is a federal contractor dedicated to the maintenance of the Justice Building and reports to both DOJ personnel and GSA. JBS keeps a 24-hour presence in the building and there is a 24/7 emergency number/pager which is always carried by the JBS building engineer who is on call. There is a list of emergency contacts in the JBS office for easy access in the event of an emergency. It has been determined from our interviews, that when an event occurs, the pager is called and the JBS engineer either handles the situation or reports it to his superiors. From that point, if further direction is required it is reported to DOJ staff and then to GSA. On the night of the flood, all systems that were in place for an event seemed to operate properly. The JBS building engineer, SETTY & ASSOCIATES, LTD. PAGE 44

50 when confronted with the flooding, immediately called his supervisor who arrived on the scene within two hours of the call (approximately 1:00 a.m.). From that point, GSA and DOJ were notified of the situation through the building engineers. DC agencies did not notify GSA of any street flooding and it is also unclear if DOJ security notified JBS of the street flooding. 6.4 Department of Commerce Building The Department of Commerce does not presently have any protocols between GSA, DHS, or NOAA in the event of a flood occurrence. Notification of a problem is identified only if security personnel on site notice or are made aware of a problem. 6.5 Old Post Office Annex The Old Post Office Annex does not presently have any protocols between GSA, DHS, or NOAA in the event of a flood occurrence. Notification of a problem is identified only if security personnel on site notice or are made aware of a problem. 6.6 D.C. Water and Sewer Authority (WASA) Communications Currently, WASA does not have protocols that involve contacting customers when the WASA combined sewer system overflows. In the most extreme flood events, they do participate with the DC Emergency Management Agency in staffing the city s Emergency Operations Center (EOC) and providing flood fighting and response efforts. Customers are, however, contacted regarding construction projects which might interfere with public utility service for a period of time when they are scheduled to occur. Meeting minutes with the WASA Chief Engineer as well as records of conversation with other WASA representatives regarding the June 2006 event are included in Appendix B. 6.7 DC Emergency Management Agency The District of Columbia Emergency Management Agency's (DCEMA) Operations Division manages the Emergency Operations Center (EOC) to handle emergency situations occurring in the District. The EOC is the city's main operational control and communications facility during an emergency, disaster or special event. The center monitors the Metropolitan Police Department (MPD) and the District of Columbia Fire and Emergency Medical Services emergency communications systems, and is linked via teletype to the National Weather Service, the Washington Area Warning System (WAWAS) and the National Warning System (NAWAS). The EOC primarily serves four functions. First, the EOC serves as an executive facility for major local and national emergencies, disasters, and special events. Second, it collects, analyzes, records, and disseminates essential information during local emergencies and special events. Third, it provides a communications interface with District and federal agencies, including the District of Columbia National Guard, the Military District of Washington, the Federal Emergency Management Agency (FEMA), other members of the Metropolitan Washington Council of Governments (COG), and the Virginia and Maryland State Emergency Operations Centers. Finally, it provides staff for operation of the EOC to direct emergency operations and to assure maximum availability of resources during general emergency conditions or special events. SETTY & ASSOCIATES, LTD. PAGE 45

51 Personnel from District, federal, and private agencies report to the center and serve as liaison staff to the director of the Emergency Management Agency to resolve any problems that may surface in an emergency situation. Recently, the DC Emergency Management Agency began hosting the new Regional Incident Communication and Coordination System (RICCS) to provide 24-hour, seven day a week communications capability. Eventually, the RICCS system is intended to be capable of arranging a teleconference amongst regional leaders in the event of an emergency within 30 minutes. Most involved agency heads should be capable of initiating a conference call when deemed necessary. The current understanding suggests that the RICCS is also used in an emergency to signal activation of the Emergency Operations Center. On the evening of June 25 into the morning of June 26, the EOC was activated at 1:00 a.m. by DC Emergency Management Agency Director, Barbara Childs-Pair, in response to the torrential downpours occurring in the city. There was also a coordination meeting held by DCEMA on Friday, June 23, 2006, to discuss preparations for the event. Agencies reporting to the EOC during the emergency included the Metropolitan Police, DC Public Works, Transportation, Health and Human Services, PEPCO, Metro, Consortium of Universities, Army Corps of Engineers, DC National Guard, US Park Police, the DC Energy Office, DC Office of Property Management, Department of Consumer and Regulatory Affairs, and DC Water and Sewer Authority. During the period of the storm, the EOC monitored weather forecasts, provided traffic management, street debris removal, and identification of power outages as well as distribution of sandbags to flood prone areas. Also, according to reports from the event, text and voice alerts were sent to residents in affected areas warning of impending flooding. 6.8 Protocol Recommendations The following flowchart illustrates the recommended emergency event communication protocols between the D.C. Emergency Management Agency and GSA and also within the GSA structure. The communication should be in both directions also. As events occur at the various buildings, it should be reported up the chain of command so all other GSA building managers can react. GSA or DHS should also work closely with the DCEMA office and have representation at all DCEMA meetings and be part of the notification system. It is recommended that a direct connection between DHS and DCEMA be established, but it may also be prudent for a representative from GSA to be part of the DCEMA meetings. This is shown in the flow chart. However, there is no direct communication between GSA and WASA or DHS. GSA must use the communications channels as any other customer and call the general number. This process is slow, cumbersome, and puts the GSA building problems in line with any other residential problem in the city. It is therefore recommended that a high level communication connection be established between GSA and WASA. This channel is to be used in special situations. GSA is one of WASA s largest users and should be afforded direct access to WASA management and thereby priority treatment. SETTY & ASSOCIATES, LTD. PAGE 46

52 WEATHER STRIKES OUTAGES EVENT STREET CLOSURES SECURITY NOTIFICATION VIA RICS ALERT SYSTEM DCEMA DEPT OF HOMELAND SECURITY CORP OF ENGINEERS HEALTH SERVICES DHS MEGACENTER FPS TRANSPORTATION ENERGY OFFICE GSA EMERGENCY COORDINATOR PARK/METRO POLICE PUBLIC WORKS GSA BUILDING MANAGERS NATIONAL GUARD PEPCO GSA CONTRACTORS DC WASA PROPERTY MGMT Recommended Emergency Event Protocol Flowchart SETTY & ASSOCIATES, LTD. PAGE 47

53 7. FLOOD MITIGATION ALTERNATIVES 7.1 Introduction The site level flood mitigation alternatives afford the most protection for the entire Federal Triangle; however, these alternatives have the most significant impact to the surroundings. The site level alternatives will need to involve a variety of agencies and governmental organizations ranging from GSA, the DC government, WASA, the Corps of Engineers, and NCPC. The alternatives, which are explored in this section, will take several years to implement and shall require significant capital expenditures. A range of the anticipated expenditures has been provided but the scope of the alternatives must be studied in detail before the design can move forward. The Corps of Engineers is currently working on a project to protect against river flooding. The scope of this report was to study the June 2006 rain event. A brief description of the Corps of Engineers Potomac Park Levee follows. Corps of Engineers: Potomac Park Levee The alternatives are generally focused on addressing the peak rainfall concerns involving flash flooding on Constitution Avenue and other District of Columbia streets. In should be noted, however, that flooding related to peak stage concerns in the Potomac River could also create problems on Constitution Avenue due to the low lying elevations and anticipated flood depths along the Potomac River. While the Potomac River did not contribute directly to the June 2006 flooding, it has numerous times when the DC area has flooded in the past as described in this study. With this in mind, the U.S. Army Corps of Engineers currently has a project seeking funding for final design. The Corps project would build a levee through Potomac Park that would separate peak stages for the Potomac River at an elevation approximately 3 feet above the 100-Year Flood Stage (see the letter from the Corps in Appendix B). This would work in concert with the alternatives discussed below by eliminating the river peak stage concerns, but further design coordination between the GSA and Corps projects would be needed during design development to ensure they work in combination to achieve a reliable protection for all anticipated flooding events. 7.2 Site and Exterior Modifications There are two predominant flood mitigation alternatives being considered for the overall site as a part of this study. These concepts are described below. Building specific recommendations are provided on a building by building basis Concept 1: Sidewalk Levee System - $9M to $15M The first concept, illustrated by Figure 7-1, involves the planning, design and construction of a proposed levee system that interconnects pedestrian areas outside each GSA building in this study. The levee system will involve modifications to existing sidewalks, steps, concrete landings, landscaped areas, and moat walls to surround low lying doors and windows. The levee system would effectively separate the sewer overflows on Constitution Avenue from the building, illustrated below at a flood stage of 11.2 feet on Constitution Avenue, by providing a design elevation of 12.0 feet for the levee consistently around the building. The new sidewalk levee system would be needed along four sides of each GSA building to provide protection, since Pennsylvania Avenue at 12th Street is approximately an elevation of 15.0 feet, at 10th Street is SETTY & ASSOCIATES, LTD. PAGE 48

54 approximately 11.9 feet, and at 9th Street is approximately an elevation of 9.5 feet. With more detailed planning of this levee system, some of the moat walls around the DOJ building and some other existing conditions will already have an elevation of 12.0 feet and may work as is, meaning no improvements will be proposed in those areas during design development. Figure 7-1: Proposed Sidewalk Levee System Some other items of note are: Building code would require accessible entrances built with ramps and handrails as part of the proposed levees for all public entrances. Walls, stairs, and landscaped berms could then be incorporated into the design. The design is anticipated to replace exposed aggregate sidewalks and to be of a high aesthetic quality by using granite and other similar materials that compliment the buildings and the monumental corridor. This alternative would likely be designed to be entirely on GSA property to avoid property acquisition by GSA and significant agency coordination for utility and public infrastructure issues related to the rights-of-way; SETTY & ASSOCIATES, LTD. PAGE 49

55 This alternative would require extensive coordination with the District of Columbia, the National Park Service, the National Capital Park and Planning Commission, the Commission of Fine Arts, and the Advisory Council on Historic Preservation; If GSA moves forward with a preliminary design and a more specific cost estimate, it is recommended that a detailed site survey and field review to establish design details necessary to achieve a sidewalk levee system that completely surrounds the building at elevation 12 feet be conducted Concept 2: Storm Water Conveyance and Pumping Station - $5M to $10M The second concept, shown in Figure 7-2, involves the planning, design, and construction of conveyance improvements in the existing DC WASA separated storm drain system along Constitution Avenue. Conveyance improvements would include the following key elements: Installation of a pump station to handle the June 2006 flood conditions and other similar historic flooding conditions; Inspection, repair and debris removal for the existing separated storm drain system; and Upgrades to the existing pipes to handle pressure flows. Figure 7-2: Proposed Storm Water Conveyance System and Pumping Station SETTY & ASSOCIATES, LTD. PAGE 50

56 The resulting system would be capable of pumping against high head conditions in the tidal basin and continue to discharge storm water from Constitution Avenue during extreme flooding. Additionally, this alternative does not require modifications to the existing GSA buildings or create historic fabric issues for the buildings. Since the upgrades would become part of the DC WASA system for maintenance, it should also be noted that there is a substantial environmental benefit and cost savings related to the Combined Sewer Overflow (CSO) reduction provided by redirecting a majority of the storm water flow at Constitution Avenue into the tidal basin instead of allowing it to arrive at the Blue Plains plant for treatment. This could easily be integrated into the WASA CSO strategy and would benefit other buildings in the area not included in this study (i.e., Smithsonian, National Archives, etc.). The anticipated design flood stage for this alternative would be approximately 9.0 feet, regardless of tail water controls in the tidal basin which could be as high as elevation 13.2 feet. The system would function by pressurizing flow at the pump station location and then discharging pressurized flow to the tidal basin. Upstream of the pump station, the flow capacity could be increased in the city streets to match the capability of the pump station through the installation of larger and more efficient drainage inlets along Constitution Avenue. Issues of underground utility improvements and a new storm water pumping station as they relate to the reviewing agencies are: The proposed pump station location is anticipated at the bend in the existing storm drainage system, which occurs between the Washington Monument and the White House at 17th Street NW. The pumping station would be entirely underground, with backup power and controls that alert WASA immediately and remotely of any malfunctions so as to provide quick response capabilities. This alternative would likely be designed to be entirely within city public rights-of-way and significant agency coordination for utility and public infrastructure issues will be required. This alternative would minimize visual impacts since it is underground, but would still require coordination with the District of Columbia, the National Park Service, the National Capital Park and Planning Commission, the Commission of Fine Arts, and the Advisory Council on Historic Preservation. SETTY & ASSOCIATES, LTD. PAGE 51

57 7.3 Internal Revenue Service Building Multi-Stage Ground Water Pumping Stations - $1M to $2M Utilizing groundwater pumping stations to remove the volume of water accumulated during the June 2006 event is not feasible without other means to control water penetration. It is estimated that between 120 and 150 stations dispersed throughout the building or 15 or fewer large pumps with a new distribution system (see Figure 7-3) would be required. Alternatively, when coupled with other alternatives indicated later in this report, the standby groundwater pumping stations can be reasonably accommodated with 20+/- stations located around the building that would limit the water depth to between 6 and 8 inches. Regardless, pumping stations require gravity to fill the sumps and therefore the floors will not stay totally dry, a very shallow layer of water will remain. In order for this alternative to be feasible, basements doors would need to be undercut 2 to 3 inches to allow flow of water on the basement level towards the sub-basement. However, this may affect the fire and smoke controlling capabilities of some of the doors. With the doors undercut, corridors would act as channels to guide the flow toward the sub-basement. Part of the sub-basement may be converted to a large sump pit which will collect flood water. Additionally, any new design of the pumping system must consider that the total pump head must be able to overcome any possible high water level on Constitution Avenue. Smaller submersible or sump pumps could be provided to other sub-basement areas or any low points in the building. Redesign of the existing basement and sub-basement floor drain locations would be required. Coordination with existing structure, grade beams, and pile caps would also be necessary. A check valve would provide backflow prevention and all cleanouts would be threaded or bolted to handle increased pressures. The new pumping system would have to be capable of pumping out approximately 17,000-20,000 GPM for a similar event and should also be connected to emergency power. Figure 7-3: Proposed Ground Water Pumping System for Internal Revenue Service Building SETTY & ASSOCIATES, LTD. PAGE 52

58 7.3.2 Earthen Berms - $4M to $6M It is currently believed that placing berms between the public space and the building as a primary alternative would not be effective in mitigating the overflow. The water levels could possibly breach the berm and overflow into the moat gratings. Also, the distance between the property line and the building line varies around the perimeter of the building from approximately 19 feet at 10th Street to 34 feet at Constitution Avenue and 10 feet at 12th Street. These space constraints may make it difficult to incorporate an adequate berm system. Another alternative would be to raise the moat walls and slope the berm to the wall (see Figure 7-4). The study team is not aware of a precedent in either the Federal Triangle or the Monumental Corridor of a similar type of condition and this alternative would alter the characteristics of the site conditions around the building significantly. Considering the fact that the berm would require a retaining wall to support the fill, it is more practical to consider a more decorative stand alone moat wall. Figure 7-4: Section through Typical Moat at IRS Building Perimeter indicating Proposed Berms SETTY & ASSOCIATES, LTD. PAGE 53

59 7.3.3 Moat Wall Extensions - $7M to $10M The moat wall extension alternative proposes raising the existing moat walls at 10th Street, Constitution Avenue, and 12th Street approximately three to four feet to a level aligned with the existing granite base on the building (approximate elevation of 12.0 feet). This condition presently exists along the Pennsylvania Avenue façade and will effectively mitigate the overflow of water into the moats. The extended walls would be clad in granite. The moats consist of castin-place, reverse retaining walls running parallel to the exterior wall of the building. The sliding resistance of these walls is provided by bearing against the building, and overturning is resisted by the weight of the wall. A downward force (10-12 kips) added to the column loads and the weight of the exterior wall at each pile cap provide additional weight. The existing structural drawings portray this to be an integral assembly with reinforcement extending from the wall down into the slabs (see Figure 7-5). This alternative would not achieve a complete blocking of flow into the buildings unless the entire perimeter of the building, including the openings protected by moat walls, was addressed. This is essentially the same alternative presented as the first site level concept of a sidewalk levee system and would become a continuation of that alternative. A structural analysis of the reserve loading capacity in the existing moat walls will be necessary as a part of the more detailed design of moat wall extensions. Figure 7-5: Section through Typical Moat at IRS Building Perimeter indicating Proposed Wall Extensions SETTY & ASSOCIATES, LTD. PAGE 54

60 7.3.4 Window Well Water-tight Coverings - $3M to $5M In order to make the window wells water tight, a fixed assembly at each of the existing openings would be required. The assembly would be designed to resist the hydrostatic load imposed on the glass, frame, and anchorage system. This proposed alternative presents a number of concerns relative to the probability of condensation buildup between the new exterior lights, the original double hung window, and the existing blast resistant window assemblies. This alternative would require repair to the existing brick lintels and supporting brick masonry. A number of lintels have shown signs of deterioration and deflection. Repair of the deteriorated conditions at this level was not within the scope of the recent modernization project. In addition, all existing electrical conduit and mechanical penetrations at the existing windows would need to be relocated to provide for a watertight condition. Another alternative would be to install removable water tight flaps on the exterior of the basement windows to provide protection during a storm event. These assemblies would be installed in advance of the event by building maintenance personnel, which is a disadvantage considering the unknown timing of an event. Operable water tight shutters, which would be released automatically in the event of a flood, may also be considered as part of this alternative Improved Storm / Blast Windows - $3M to $5M Improving the blast windows involves an upgrade to the existing blast resistant window assemblies to provide a water tight condition or the addition of a waterproof storm shutter on the outside of the basement windows in the moats (see Figure 7-6). A fixed window assembly which is both blast resistant and water tight may be considered for these basement locations only. This alternative would have maintenance implications for the staff. The existing blast window assemblies were designed and tested to meet GSA s Level C criteria and not as water tight assemblies and, therefore, performed as designed. These assemblies were installed inboard of the original double hung sashes and are operable to provide building maintenance personnel the ability to clean and repair the sashes. Provisions were made within and around the blast window frame for airflow between the two window assemblies as a means of preventing condensation buildup. A number of concerns must be addressed with this alternative. The Level C performance of the interior assembly cannot be jeopardized by an upgrade and probable condensation resulting from a watertight alteration must be removed. The fact that this alternative is susceptible to human error, assurance that the window is latched properly after maintenance, must also be considered. SETTY & ASSOCIATES, LTD. PAGE 55

61 Figure 7-6: Section through Typical Blast Window at IRS Building Perimeter Flood Gates and Removable Barriers - $200k to $500k Courtyard A in the IRS Building presents a flood risk considering the location of the existing vehicle ramp entrance for parking and the entrance to the building at stairwell No In an effort to mitigate that potential risk, installing a flood gate across the entrance to service Court A is proposed with this alternative. The flood gate would be automatically activated or manually operated. The location of the proposed floodgate would be adjacent to the existing vehicle barrier (see Figure 7-7). Consideration may be given to combining both functions as a floodgate and a vehicle barrier. Other moveable floodgates and barriers could also be used as necessary to achieve a consistent level of protection around the building while also accommodating building entrances. Protection to a minimum elevation of feet is necessary around the entire building perimeter in all cases. Alternatively, removable flood gates could provide a less expensive alternative by minimizing installation time and training could be provided to on site staff for the flood fighting efforts. These removable flood gates could also provide a temporary flood protection measure as part of the ongoing design development. SETTY & ASSOCIATES, LTD. PAGE 56

62 Figure 7-7: IRS Building Service Courtyard A Entrance, Proposed Locations of Flood Gate Overview of Relocating Major Mechanical and Electrical Systems to the Upper Floors $40M to $50M The first floor is the most obvious location to use for equipment relocation in the IRS Building. However, further study will be required to determine which equipment should move to which floor, many possibilities and considerations need further study. Relocating mechanical and electrical equipment to the first floor will have a significant impact to occupiable floor area and special spaces (i.e., the childcare area) and would require re-planning of office and support spaces. Also, a restacking of the building to provide for proper and functional departmental agencies would be required. Non-critical spaces, storage, and support areas would be identified for relocation to the basement level to spaces previously used for mechanical equipment. Figure 7-8 indicates the current spaces in the basement and sub-basement occupied by mechanical and electrical equipment, providing an indication of how much space would be required on the first floor if all equipment was to be moved. This alternative must be evaluated in close coordination with IRS Facilities and in concert with the future housing plan for the building. This alternative also has historic, structural, life safety, and acoustical implications. Modifications to the building s façade to accommodate louvers will require review and approval by GSA s Historic Preservation Officer, the Advisory Council, the National Capital Planning Commission, and the Commission of Fine Arts. The existing first floor slab must be analyzed for dead and live load capacity as well as conformance with GSA s SETTY & ASSOCIATES, LTD. PAGE 57

63 current design criteria. Existing fire rated assemblies of floors and walls must be analyzed to provide for proper isolation and separation of these mechanical spaces from adjacent office spaces above and paths of egress. Noise and vibration of mechanical equipment must be addressed relative to its impact on adjacent public and office spaces on the first floor and also the floor above. A possible approach to this alternative should consider restricting the locations of new mechanical spaces to Quadrants A and C and directing the intake and exhaust requirements to the interior courtyards. The loading dock at Courtyard A is in close proximity to Courtyard C, allowing for more practical placement and serviceability of large pieces of equipment. Due to the magnitude of moving all equipment from vulnerable areas, the following sections break down equipment into stages of importance and explain the implications of moving each component to a different level in the building Investigate New Location of Emergency Backup Power Equipment - $2M to $4M (not included above) Currently a new 400 kw generator is being located in Courtyard A. The final location should be investigated to ensure that there will be no adverse effects during future flood events. Also of special importance is the location and protection of the fuel supply and pumping to ensure that the backup system will not fail due to ancillary services. At the time of this study, the final locations of all emergency equipment had not been determined. SETTY & ASSOCIATES, LTD. PAGE 58

64 Figure 7-8: IRS Basement and Sub-basement Plans Mechanical and Electrical SETTY & ASSOCIATES, LTD. PAGE 59

65 Mechanical - Relocate Central Plant Equipment to First Floor To relocate existing central plant equipment to the first floor, the equipment space required is estimated to be approximately 7,500 square feet. Proposed locations on the first floor for equipment rooms are indicated by Figure 7-9. Figure 7-9: Potential Locations for Relocated Mechanical Equipment on First Floor The proposed location for central plant equipment should be relatively close to the existing main mechanical room in the basement. This would minimize the interruption to the building operation when re-connecting to the existing utility mains, such as incoming central plant steam and condensate piping, heating hot water mains, chilled and condenser water mains, fire protection mains, etc. In addition, equipment and systems that are considered less critical should remain in the basement to minimize the equipment space required on the first floor. The final determination should be made in a feasibility and building critical system analysis. These equipment and systems should include: Steam Pressure Reducing Stations: The stations may be re-configured such that the lowest reducing valves are located above the anticipated flood level in the basement. Steam Condensate Pump Receivers: These units may be re-installed on elevated platforms above the anticipated flood level in the basement. Heating Converters: Converters may be re-installed on elevated pipe stands above the anticipated flood level in the basement. SETTY & ASSOCIATES, LTD. PAGE 60

66 Heating System Pumps: Pumps may be re-installed on elevated platforms above the anticipated flood level in the basement. Semi-instantaneous Domestic Water Heaters: Heaters may be re-installed on elevated platforms above the anticipated flood level in the basement. Drinking Water System. Architectural considerations involved with relocating the central plant equipment include adding sound insulation and absorption materials around the mechanical spaces to minimize noise transmission to nearby occupied spaces. Also, in order to maintain the integrity of the exterior façade of the building, existing outside air intake and exhaust louvers (at the basement level) and gratings (on grade) should remain and be reused. Ductwork could be added in the basement level to extend to the proposed equipment location on the first floor. Alteration of the existing historical corridors on the first floor should be minimized with limited entrances and exits to the mechanical rooms. Structural considerations include considering reinforcement of the first floor slab and supports due to the weight of the mechanical equipment, such as chillers, pumps, etc. In addition, means of mechanical vibration isolation should be employed to minimize the effect of equipment operation. A new depressed slab may be required to provide sufficient space in a new central plant. This will require more extensive floor slab modifications. A. Heating Plant Considerations High pressure steam from the GSA central plant is supplied to the building year-round through a steam main that enters from the 12th Street side of the building into Room G330 in the basement. Two steam pressure reducing stations are located in the Main Mechanical Room G109. Steam condensate is collected in duplex condensate pumps / receivers located throughout the basement. Refer to the Condensate Pump Schedule below. TABLE 7-1 CONDENSATE PUMP/RECEIVER SCHEDULE UNIT NO. LOCATION NOTE QUADRANT ROOM SCP-1 C G228 SCP-2 C G228 SCP-3 C G228 SCP-5 C G546 SCP-6 A G213 SCP-10 D G401 SCP-11 B G005 SCP-12 A G109 SCP-13/14/15 A G109 SCP-16 A G109 SCP-18 C G127 SCP-19 C G127 SCP-20/21 A G109 Sub-Basement SETTY & ASSOCIATES, LTD. PAGE 61

67 B. Cooling Plant Considerations Main Chillers (CH-1/2/3): The building cooling plant includes three chillers, located in the sub-basement level of the Main Mechanical Room G109. Each chiller is the water cooled centrifugal type, rated for 1000-ton cooling capacity. The cooling towers are located on the roof. In addition, two plate type heat exchangers provide water side economizer for the chilled water system. Supplemental Chiller (REF-1-BA) The supplemental chiller unit is water cooled with centrifugal scroll, and rated for 210-ton cooling capacity. This unit is located in Room G452 in the basement. Both the chilled water and condenser water piping for the unit are cross-connected to the building piping mains. The unit is intended to serve the Fitness Center and Snack Bar in the basement during after-hours. Commissioner Chiller (ACH-1) The commissioner s chiller unit is air cooled and reciprocating, rated for 60-ton cooling capacity and is located in Room G320 in the basement. The air cooled condenser is located remotely in the exterior moat outside of Quadrant A along 12th Street. The chiller supplies chilled water to the air handling unit in Room 3033, which serves the commissioner s suite on the third floor Mechanical - Relocate Basement Air Handling Units to First Floor A. Building Main Air Handling Units The building is served by a total of 21 main air handling units, AHU-1 through AHU-21. AHU-1 through AHU-16 and AHU-22 are located in the attic. These units serve the entire area between the fourth floor and the seventh floor, and a portion of the first floor through the third floor. AHU-17 through AHU-21 are located in the basement. These units serve the bulk of the areas between the first floor and the third floor and were damaged during the flood. Details regarding these damaged units are included in the table below. TABLE 7-2 UNIT NO LOCATION SERVING CFM NOTE QUAD ROOM FLOORS QUAD AHU-17 C G228 1,2 C C,D AHU-18 C G228 1,2 A,C A,B,C,D AHU-19 C G127 1,2 B,C,D C C,D AHU-20 C G127 1,2 D AHU-21 A G213 1,2 A A SETTY & ASSOCIATES, LTD. PAGE 62

68 Each air handling unit is the built-up type, floor mounted in the mechanical room. Each unit is medium pressure, constant volume, consisting of the following sections: Intake Section. Filter Section: With pleated type filter. Supply Air Fan: Fan is double-inlet double-width, centrifugal air foil, and belt driven. Cold Deck Cooling Coil: Chilled water coil with 3-way control valve (pneumatic, mixing). Chilled water serving the coils is supplied from the building chilled water system. Hot Deck Heating Coil: Low pressure steam heating coil with steam control valve (pneumatic). Low pressure steam serving the coils is provided from the building central steam system. Unit casing is constructed of double-wall sheet metal panels with rigid insulation between the panels. The interior casing panels are perforated. The return air fans are single-inlet single-width centrifugal air foil and belt driven. Supply air from the hot deck and the cold deck of the air handling units are routed through vertical duct chases. Dual-duct mixing boxes are provided for terminal air distribution to the spaces. B. Basement Supplemental Air Handling Units The occupied areas in the basement are generally served with individual air handling units. Information pertaining to these supplemental units is included in the table below. TABLE 7-3 UNIT NO LOCATION SERVING NOTE QUAD ROOM QUAD ROOMS AC-1BB B G302 B G002, G008, G010, G014, G024, G036 AC-1BC C G245 C G233, G241, G243 AC-1BD D G401 D G031, G039, ETC AC-2BC C G546 C G549, G554 AC-2BD D G130 D G126, G130, G132, G134, G136, G138, G415 AC-2BX X G609 X AC-3BD D G040 D G042 AC-18A A G334 A G334 HV-1BB B G110 B G104, G112, G122 HV-1BC C G527 C G529 HV-1BD D G509 D G511, G519 HV-2BB B G304 B G304 HV-3BB B G005 B G005, G025 SETTY & ASSOCIATES, LTD. PAGE 63

69 Each unit is factory packaged and floor mounted in the mechanical room. The units are medium pressure, variable air volume (VAV), and consist of the following sections: Intake Section. Filter Section: With pleated type filter. Hot Water Heating Coil: Heating hot water serving the coil is supplied from the building heating system. Chilled Water Cooling Coil: Chilled water serving the coils is supplied from the building chilled water system. Supply Air Fan: Fan is double-inlet double-width, with a centrifugal air foil, and belt driven. The return air fans have centrifugal cabinets and are belt driven. Variable frequency drives are provided for both the supply and the return air fan motors for fan speed modulation. C. Basement Heating and Ventilating Units The storage and equipment areas in the basement are generally served with individual heating and ventilating units. Each unit is factory packaged and suspended in the mechanical room. The units are also low pressure, constant volume, and consist of the following sections: Intake Section. Filter Section: With pleated filter. Hot Water Heating Coil: Heating hot water serving the coil is supplied from the building heating system. Supply Air Fan: Fan is double-inlet double-width, with a centrifugal air foil, and belt driven Electrical - Relocate Major Systems and Equipment to Upper Floors A majority of the main electrical equipment at the IRS Building is located on the lower levels where the damage was severe. Figure 7-10 illustrates the current location of major electrical systems in the IRS Building. Relocating the switchgear to the First Floor would protect it from flooding in a future event of the same or even more severe magnitude. Non-critical spaces, storage, and support areas would be identified for relocation to the basement level to rooms previously used to house the switchgears. This alternative also has structural and life safety implications to be considered. SETTY & ASSOCIATES, LTD. PAGE 64

70 Figure 7-10: Current Locations of Major Electrical Components in Basement It is proposed to move the following equipment from the basement to higher levels: i. Emergency generators, switchboard, load bank, batteries and chargers, etc., to be moved to machine room on the roof. ii. Generator, diesel engine will be provided with a day tank. Fuel will be pumped from a new storage tank (location to be determined). iii. All other electrical equipment with normal power, PEPCO feed to remain in the basement. iv. PEPCO feeder entry into the basement electrical room came through the street manholes. All PEPCO feeder entries will remain at the existing basement level. The receiving switchgear for these feeders would be moved up to the first floor. Feeder terminations into the switchgear will be at a higher level. Any wire or cable product that is suitable for wet locations and whose ends have not been exposed to water should be suitable for use or continued use in case of exposure to flooding. v. All electrical switchgear, panels, transformers, etc., should be moved to the first floor. Structural implications may also apply in moving heavy equipment to a higher floor elevation and strengthening may be required. SETTY & ASSOCIATES, LTD. PAGE 65

71 7.3.8 Seal Abandoned and Spare PEPCO Feeders into Electrical Spaces - $20k to $50k Additionally, to eliminate the possibility of water entering through the PEPCO feeder duct bank, all of the empty spare conduits should be plugged at their entry point in the basement electrical room. The other end of the continuous conduit, if located at a lower level, such as a manhole or hand hole, should also be plugged. A modular sealing device, designed for field assembly, should be used to fill all annular spaces between sleeves and raceways or cables. PEPCO manholes located around the building have feeder conduits entering into the building. Annular space sealing of these manholes should also be undertaken. Spare empty conduit layouts at lower level were also noticed and end plugging / sealing of these conduits is also necessary Water-tight Enclosure for Fire Pump Room - $100k to $150k The room containing the fire pump must remain close to the point of entry of the water service to the building per good engineering practice. Therefore, relocating this equipment to the penthouse or first floor is not feasible. Instead, the fire pump should be isolated from other spaces and housed in its own dedicated room. This room should be water-tight in order to protect the fire pump from full submersion. SETTY & ASSOCIATES, LTD. PAGE 66

72 7.4 Department of Justice Building Modify existing Garage Doors at Basement Level to act as Flood Gates - $800k to $1.2M The existing garage door assemblies at the Attorney General s and Solicitor General s ramps consist of an exterior highly detailed aluminum Art Deco door, as well as an interior bi-parting wooden door. The doors are original to the building and represent significant historic fabric. The door assemblies are located at the low points of each ramp adjacent to the storm drains. Modifying the door assemblies, strengthening the frames, hinges, and locking mechanisms as well as improving the seals would be technically feasible. This alternative would, however, require review and approval by GSA s Historic Preservation Officer, the Advisory Council on Historic Preservation, a Section 106 Review, the National Capital Planning Commission, and the Commission of Fine Arts. Considering the fact that this alternative and line of defense is at the low point of the ramp, a more effective alternative should be considered. Another alternative being proposed is locating the flood gates at the top of each ramp instead of the bottom to prevent the high water levels from reaching the low points, overwhelming the drains and breaching the doors. Adjacent curbs and walls would be raised to gate level and this alternative would also require the approvals listed above (see Figure 7-11). Figure 7-11: Proposed Flood Gates at Department of Justice Building SETTY & ASSOCIATES, LTD. PAGE 67

73 7.4.2 Raise Retaining Walls on Constitution Avenue - $2M to $3M The existing limestone moat walls along Constitution Avenue, 9th and 10th Streets are approximately 42 inches high. These walls prevented the high water levels from breaching the basement windows and flooding the basement during the recent event. As the worst case scenario for a flood event is evaluated, it is technically feasible to raise the height of the existing walls further once the loading capacity of the structural system is confirmed. This alternative would, however, require review and approval by GSA s Historic Preservation Officer, the Advisory Council on Historic Preservation, a Section 106 Review, the National Capital Planning Commission, and the Commission of Fine Arts Storm Water Piping Modifications - $25k During the June 2006 event a 15-inch storm water main failed at a U-trap lid. This is a 5 to 10 psi pressure fit seal. The piping system is not designed for pressures greater than 10 psi and the gasketed lid acts to release the pressure. Instead of using the trap cover to prevent pressure from building up, a dedicated pressure release system for the storm water piping system should be installed or backflow preventors on the storm water mains should be used. This alternative needs further study and the entire storm water dissipation design must be examined. Simply bolting and sealing up the piping will cause the storm water to backup in the piping and flood at branch lines. For example, air handling unit condensate lines may be tied into the storm system per code and would overflow in the event of a pressure buildup. The pressure release system should be on all storm water mains. It should be noted that while this alternative would eliminate a primary source of water entry, it would not completely protect the building in all cases Isolate Electrical Room - $100k to $150k The current NEC codes require all electrical rooms to be isolated from other functional spaces. Furthermore, no ductwork or piping is allowed in electrical rooms. In the Department of Justice basement, the storm water main that failed shared space with electrical equipment. These two spaces should be separated, thus eliminating a pathway for the water to reach the equipment if the storm water main was to leak again Relocate Emergency Power - $1.5M to $2.5M It is proposed to move the following equipment from basement to higher levels: a) Emergency generators, switchboard, load bank, batteries and chargers, etc., to be moved to machine room on the roof. b) Generator, diesel engine will be provided with a day tank. Fuel will be pumped from a new storage tank (location to be determined). Table 7-4 identifies the emergency power equipment to be relocated and the location where it should be moved. Figure 7-12 illustrates the location of the equipment located in the basement and sub-basement levels. SETTY & ASSOCIATES, LTD. PAGE 68

74 TABLE 7-4 Priority 1 - Basement - Electrical Unit ID Type of Unit Service Location Size Comment Battery #1 Backup Battery Electrical B-133 Penthouse Battery #2 Backup Battery Electrical B-133 Penthouse Battery #3 Backup Battery Electrical B-133 Penthouse Charger #1 Battery Charger Electrical B-133 Penthouse Charger #2 Battery Charger Electrical B-133 Penthouse Charger #3 Battery Charger Electrical B-133 Penthouse LS GEN - B Life Safety Generator Electrical B-133A Penthouse GEN - B SG Generator Switchgear Electrical B-133A Penthouse GEN-B RAD Generator Radiator Electrical Court E Penthouse GEN-B LB Generator Load Bank Electrical Court E Penthouse GEN - A SG Generator Switchgear Electrical SUB - NE Penthouse GEN - A LB Generator Load Bank Electrical SUB NE Penthouse TANK Generator Fuel Supply Electrical SUB NE Not Moved LS GEN - A Life Safety Generator Electrical SUB NE Penthouse Isolate Fire Pump Room - $100k to $500k The room containing the fire pump must remain close to the point of entry of the water service to the building per good engineering practice. Therefore, relocating this equipment to the penthouse or first floor is not feasible. Instead, the fire pump should be isolated from other spaces and housed in its own dedicated room. This room should be water-tight in order to protect the fire pump from full submersion Seal or Re-seal all Utility Penetrations in Basement and Foundation Walls - $20k to $50k PEPCO feeder entry into the basement electrical room is through the street manholes and all PEPCO feeder entries will remain at the existing basement level under this alternative. Feeder terminations into the switchgear should be at a higher level. Any wire or cable product that is suitable for wet locations and whose ends have not been exposed to water will be suitable for use or continued use in case of exposure to flooding. To eliminate the possibility of water entering through the PEPCO feeder duct bank, it is proposed that all the empty spare conduits be plugged at their entry point in the basement electrical room. The other end of the continuous conduit, if located at a lower level, such as a manhole or hand hole, should also be plugged. A modular sealing device, designed for field assembly, should be used to fill all annular spaces between sleeves, raceways, or cables. PEPCO manholes located around the building have feeder conduits entering into the building. Annular space sealing of these manholes should be undertaken. Spare empty conduit layouts at lower level were also noticed and end plugging/sealing of these conduits is necessary. Each condition will be evaluated independently and recommendations made based upon the proper application and installation of penetration seals, gaskets, wall sleeves and water stops. All abandoned penetrations should be sealed permanently. SETTY & ASSOCIATES, LTD. PAGE 69

75 7.4.8 Relocate and/or Raise Equipment located in Basement and Sub-basement Levels - $30M to $40M The alternative to relocate critical equipment from the basement level to the first floor would require an evaluation of the historic merits of the available space, the structural loading capacity of the floor area, fire-rating of the floor-ceiling-wall assembly and the relocation of occupiable space elsewhere in the building to accommodate this alternative Mechanical and Plumbing Equipment Relocation Figure 7-12 identifies the locations and sizes of mechanical and electrical rooms in the basement to indicate how much space would be required to relocate all equipment. Table 7-5 and Figure 7-13 catalog and show the specific mechanical equipment located in the basement and illustrate the equipment scheduled to be moved under this alternative. The air handling units and condensing unit, which are marked as A- and CDU-, respectively, in the table, are large units which will be difficult and costly to move, making it more economical to leave them in place rather than relocate them. The compressors and condensers, however, are typically smaller units and can be costly to replace if damaged. Therefore, these units should be moved for protection from any future flood damage. The Environmental Control Units (ECU s) are large items which must remain in the computer rooms where they are currently located. These devices are already on raised platforms and were not damaged during the flood because the water level only reached approximately 2 inches where they are located. However, since they cannot be moved and because they are costly to replace, they should be raised another 12 inches from the floor level to protect them in the future. Finally, the hot water generators must be moved to the penthouse level because they are too large to relocate to the other floors. SETTY & ASSOCIATES, LTD. PAGE 70

76 Figure 7-12: Department of Justice Primary Basement Mechanical and Electrical Rooms SETTY & ASSOCIATES, LTD. PAGE 71

77 TABLE 7-5 Basement/Sub-Basement - Mechanical Unit ID Type of Unit Service Location Size Comment A Air Handling HVAC B-103A Not Moved A Air Handling HVAC B-143C Not Moved A Air Handling HVAC B-145B Not Moved A Air Handling HVAC B-144 Not Moved A-2-10 Air Handling HVAC B-348A Not Moved A Air Handling HVAC B-348B Not Moved A Air Handling HVAC B-348Q Not Moved A Air Handling HVAC B-523A Not Moved A-6-4 Air Handling HVAC B-647 Not Moved A-9-3 Air Handling HVAC B-647 Not Moved A-9-4 Air Handling HVAC B-647 Not Moved A-6-3 Air Handling HVAC B-651 Not Moved A Air Handling HVAC B-728 Not Moved CDU-1 Condensing Unit HVAC B-324G Not Moved COMP Compressor HVAC B kw Move COMP Compressor HVAC B-523A Move CP-5 Condenser Pump HVAC B-103A Move CP Condenser Pump HVAC B-143C Move CP Condenser Pump HVAC B-144 Move CP Condenser Pump HVAC B-348B Move CP-6 Condenser Pump HVAC B-08A Move 2x CP Condenser Pump HVAC B-640 Move ECU-1 Environmental Control HVAC B-109 Not Moved ECU-2 Environmental Control HVAC B-113 Not Moved ECU-3 Environmental Control HVAC B-117 Not Moved ECU-4 Environmental Control HVAC B-117 Not Moved ECU-5 Environmental Control HVAC B-117 Not Moved ECU-8 Environmental Control HVAC B-114 Not Moved ECU-9 Environmental Control HVAC B-114 Not Moved ECU-10 Environmental Control HVAC B-114 Not Moved ECU-11 Environmental Control HVAC B kW Not Moved ECU-12 Environmental Control HVAC B kW Not Moved HW GEN-1 Hot Water Generator Hot Water B-730 Penthouse HW GEN-2 Hot Water Generator Hot Water B-730 Penthouse 3x Comp Air Compressor HVAC SUB Move 2x Air Dryer Building Air Dryer HVAC SUB Move 2x Air Tank Compressed Air Tank HVAC SUB Move SETTY & ASSOCIATES, LTD. PAGE 72

78 Figure 7-13: Mechanical Equipment to be Relocated Figure 7-14 shows the location of specific plumbing equipment on the basement and sub-basement levels. Table 7-6 illustrates which pieces of equipment shown in the figure are scheduled to be moved. The only plumbing devices located in the basement which should be relocated to other floors are the Triplex Booster and the sewage ejector controller. These are both electronic devices which control the sumps and sewage ejectors. In the event of a future heavy rainfall, the sumps and sewage ejectors will need to remain operational to prevent flooding, and the controllers should be protected from damage to keep these pumps operational. Since the sub-basement is the most susceptible location for any equipment in the event of a flood, any equipment located here that does not need to remain should be relocated. The domestic water pump, booster, tempering tank, and drinking fountain chiller should be moved to the first floor since they are crucial components and will be costly to replace. The sewage ejector and sump pumps cannot be moved and must remain in their current locations. SETTY & ASSOCIATES, LTD. PAGE 73

79 Figure 7-14: Plumbing Equipment to be Relocated TABLE 7-6 Basement - Plumbing Unit ID Type of Unit Service Location Size Comment TRIPLEX Triplex Booster Sanitary B-407 Move SE CONTROL Sewage Ejector Controller Sanitary B-407 Move SEWEJECT Sewage Ejector Sanitary B-133A Not Moved SEWEJECT Sewage Ejector Sanitary B-406 Not Moved 3x Sump Sump Pump Sanitary B-229 Not Moved 3x Sump Sump Pump Sanitary B-407 Not Moved 3x Sump Sump Pump Sanitary B-640 Not Moved 2x Water Pump Domestic Water Pump Domestic Water SUB 5.6kW/ea Move DW Booster Domestic Water Booster Domestic Water SUB Move Domestic Water Tempering Move DW Tempering Tank Domestic Water SUB DF Chiller Drinking Fountain Chiller Domestic Water SUB Move FP Fire Pump Fire Protection SUB Move SEWEJECT Sewage Ejector Sanitary SUB Not Moved 3x Sump Sump Pump Sanitary SUB 5.6kW/ea Not Moved SETTY & ASSOCIATES, LTD. PAGE 74

80 Electrical Equipment Relocation Fire Alarm: Since the fire alarm control panel is located on the first floor there was no flood damage to the system. The system should remain as is, at present. Telecommunication: Incoming communications cable termination boards are located in basement Room B410. Only two inches of water accumulated in the room, consequently no damage occurred due to the low level of flooding. Cables routing into Room B410 came through basement Room B123. There was no water entry into Room B123. Some cable terminations also occur in Room B123. Annular space sealing between sleeve and raceway or cables in these two rooms and other lower level location will be necessary. All electrical switchgears, panels, transformers, etc., should be moved to the first floor. Structural implications should also be considered. Figure 7-15 illustrates the location of the equipment located in the basement and sub-basement levels. Table 7-7 identifies major normal power equipment to be relocated from basement and sub-basement levels to the first floor. Figure 7-15: Electrical Equipment to be Relocated SETTY & ASSOCIATES, LTD. PAGE 75

81 TABLE 7-7 Priority 1 - Basement - Electrical Unit ID Type of Unit Service Location Size Move to T 1 1,2,3 H.V. Transformers Electrical B st Floor NDS - 1 H.V. Switchgear Electrical B st Floor PNLS-20NDS Switchboard Electrical B-SE 1 st Floor T 2 1,2,3 H.V. Transformers Electrical B-218A 1 st Floor NDS-2 H.V. Switchgear Electrical B st Floor PNLS-26NDS Switchboard Electrical B-SW 1 st Floor T 3 1,2,3 H.V. Transformers Electrical B-250A 1 st Floor NDS-3 H.V. Switchgear Electrical B st Floor PNLS-22NDS Switchboard Electrical B-NW 1 st Floor T 4 1,2,3 H.V. Transformers Electrical B-633B 1 st Floor NDS-4 H.V. Switchgear Electrical B-633A 1 st Floor PNLS-24NDS Switchboard Electrical B-NE 1 st Floor SETTY & ASSOCIATES, LTD. PAGE 76

82 7.5 Department of Commerce Building East and West Tunnel Entry The steam tunnel on the east of the building (14th Street side) is very similar to the west side location. The basement floor on the east side is about 6 inches lower than the tunnel door threshold. The access door on this side is a steel locking door with a 1-8 wide by 5-8 high opening. This door was similarly thrown open during the storm as the water accumulated in the tunnel behind it. The steam tunnel from the west (15th Street side) intersects the building at a floor elevation approximately 30 inches above the basement level in that area. The floor varies in elevation at different locations in the basement. In general, the basement floor level appears to be about 20 feet below the adjacent street level. Both the west and east side tunnels are actually separated from the building by concrete headwalls into which the access door frames are cast. There are two large sleeves through the headwall for the steam supply and return pipes. The pipes are insulated and the sleeves are sealed to the pipes. The steam tunnel is approximately 6-6 tall by 6-6 wide, has 9 +/- thick concrete side walls, 12-inch thick concrete floor slab sloped to a shallow trench in the middle and 12-inch concrete ceiling slab peaked to a 14-inch ridge in the middle. The west side access door is a steel locking man-door with an approximate opening of 2-0 width by 6-4 height. Figure 7-16 identifies the locations of the steam tunnels within the building. SETTY & ASSOCIATES, LTD. PAGE 77

83 GENERAL SERVICES ADMINISTRATION Figure 7-16: Steam Tunnel Locations at Department of Commerce Building Steam Tunnel Water Access Study - $100k to $200k Looking into the tunnels, daylight was observed from open grates/vents or open manholes at the top of the tunnel in the distance. It can be concluded that the steam tunnels will most likely fill up with storm water when the streets flood and storm water runs over manholes and grates or if the tunnel s gravity drainage system backs up. Several considerations should be analyzed in determining design solutions to prevent future flooding from the direction of the tunnel openings. Avoiding storm water build-up inside the steam tunnels would diminish the possibility of water building up behind the access doors that open into the DOC and to other building basements in the area. This civil work condition should be analyzed elsewhere in the overall scope of flood mitigation for the entire area. SETTY & ASSOCIATES, LTD. PAGE 78

84 There are several measures that can be taken at the building line to design for prevention of flood water entry from the tunnels. The analysis of such measures is required to determine the optimum correction to the existing condition of flood vulnerability from the existing steam tunnels. Partial or complete isolation of the tunnel space from the building space will be considered: Conclusions 1. The end of the tunnel could be provided with a high curb at each access door able to prevent a partial built up of water in the tunnel from coming over the threshold and into the building. Similarly the access doors could be made smaller and raised higher on the headwall. 2. New reinforced head walls can be formed and poured by pumping concrete on the tunnel side of the access doors, completely eliminating the openings (other than sleeved and sealed steam pipes) into the building. Provisions must be made to add manholes or other exterior access ways to the portions of the tunnel close to the building line by digging down from the top or the side of the structures. 3. The existing headwalls could be demolished along with the existing doors and frames and replaced with new, reinforced concrete walls and new vault type doors and frames able to resist water pressure buildup and sudden surge to the top of the tunnels. These doors would be designed to remain watertight under prolonged flood conditions. New pipe sleeves and seals around the steam pipes are also required for this alternative. Prior to final decision, the above alternatives must be compared in detail from the function/maintenance point of view, design parameters and limitations, as well as construction cost impact. Additionally, the alternative chosen must be coordinated with other available decisions and recommendations for the wider area flood mitigation and tunnel system treatment. A. Flood Resisting Headwalls and Doors - $250k to $500k At this preliminary phase of the study, the only suggestions that can be made are the design of new flood resisting walls and doors that can isolate the tunnel environment from the building interiors as stated in Alternative 3 above. This suggested alternative will not change the existing maintenance considerations and functionality originally designed while achieving the goal of the scope of work in this study. The cost of this alternative includes complete rebuilding/replacement of the end walls as well as installing new watertight and pressure resisting access doors. There is a base replacement cost to be incurred even if no design change is undertaken. Also, the existing doors and frames would have to be replaced as they appear to have been damaged beyond repair. SETTY & ASSOCIATES, LTD. PAGE 79

85 Figure 7-17: Example of Flood Resisting Door Design Based on the alternatives above, Alternative 1 is only a partial and temporary solution that may provide some immediate protection in the short run but cannot be compared with the other permanent solutions that can offer long term protection. Alternative 2 requires additional design investigation to determine whether ease of access and maintenance flexibility comparable to existing conditions can be achieved in an economic design and construction project. SETTY & ASSOCIATES, LTD. PAGE 80

86 7.6 Old Post Office Annex Waterproofing/Damproofing/Dewatering The scope of this portion of the study is to make the common wall between the IRS Building and the Old Post Office Annex Building separate and distinct from a water tightness standpoint. This is not absolutely possible due to the fact that existing structures are being retrofitted to accomplish a goal not originally anticipated. However, technology and assumptions of minor leakage with ancillary electrical pumping can lead to a reasonable alternative. A. Preferred Alternative - $300k to $500k The best and least difficult alternative is to remove the existing window, infill the window opening with two layers on solid staggered joints concrete masonry units (CMU s). At the center of the joint around the window opening install a vinyl or metal waterstop. Both sides of the wall should be receive a cold fluid-applied waterproofing from a height of 6 inches above the window head to a horizontal application of one foot along the finished floor including an application over the exposed footing on the Annex side of the wall. B. Second Alternative - $200k to $400k The above preferred alternative may not be approved by the NCPC, Fine Arts and Historic Preservations overview review boards as the original fabric of historic IRS Building would substantially changed. This raises an interesting problem. It is not known in which direction the water entered the Old Post Office Annex Building. It is only known that it was about the same elevation as the water in the IRS Building and it flowed freely between the two buildings. The problem is that the waterproofing must be applied on the side of the water penetration (both sides) to act as a barrier. Otherwise the pressure coming from the opposite side may lift the waterproofing from the wall surface. Therefore, a less desirable alternative would be to infill behind the windows between and even with the structural columns and apply the waterproofing membrane to the interior IRS Building surface side of the wall hoping that the bonding qualities of the waterproofing strata will be sufficient to hold it in place against any future water pressure Security/Fire Integrity Security and fire safety must also be recognized as a major concern. If the windows are not infilled or backfilled and the ductwork is not security barred and fireproofed a problem continues to exist not only from water infiltration but smoke and heat penetration from a potential fire on either side of the common wall between the IRS Building and the Old Post Office Annex Building (with possible ramification to the Old Post Office Annex Building). Security also becomes a problem as the Old Post Office Annex Building is a much more open (public) access building than the IRS Building. This is not a part of the Scope of the Study and further comment will not be addressed. SETTY & ASSOCIATES, LTD. PAGE 81

87 SETTY & ASSOCIATES, LTD. PAGE 82