PRELIMINARY ENGINEERING REPORT AND UTILITY PLAN NEW WASTEWATER TREATMENT FACILITY TOWN OF MEAD FOR A FOR THE

Transcription

1 PRELIMINARY ENGINEERING REPORT AND UTILITY PLAN FOR A NEW WASTEWATER TREATMENT FACILITY FOR THE TOWN OF MEAD REVISED NOVEMBER 6, 2006

2 PRELIMINARY ENGINEERING REPORT AND UTILITY PLAN FOR A NEW WASTEWATER TREATMENT FACILITY FOR THE TOWN OF MEAD, COLORADO JVA, Inc Spruce Street Boulder, CO phone: fax: JVA Project No. 1372c Revised November 6, 2006

3 TABLE OF CONTENTS Table of Contents... i Acronyms... ii List of Figures... ii List of Tables...iii Appendices...iii Section 1 - Executive Summary... 1 Section 1.1 Background... 1 Section 1.2 Project Description... 2 Section 2 - Introduction... 4 Section 3 - Analysis of Existing Facilities... 6 Section 3.1 Wastewater Treatment Facilities... 6 Section 3.2 Wastewater Effluent Limitations... 7 Section 3.3 Infrastructure Sizing and Staging... 8 Section 3.4 Infiltration and Inflow... 8 Section 3.5 Industrial Pretreatment Program... 9 Section 4 - Service Area, Population Projections, Wastewater Flow and Loads Section 4.1 Service Area Description Section 4.2 Population Projections Section 4.3 Wastewater Flow Rates: Historical and Projected Section 4.4 Wastewater Organic Loads: Historical and Projected Section 5 - Preliminary Effluent Limitations Section 6 - Water Quality Characterization Section 6.1 Water Quality of Receiving Water Section 6.2 TMDLs and/or Wasteload Allocation Section 6.3 Watershed Issues Section 7 - Site Location Analysis Section 7.1 Process for Selecting Proposed Site Location Section 7.2 Site Location Selection Section 8 - Treatment Alternative Analysis Section 8.1 Oxidation Ditch Section 8.2 Earth Basin Extended Aeration Section 8.3 Sequencing Batch Reactors Section 8.4 Treatment Alternatives Cost Summary Section 8.5 Comparison of Treatment Alternatives Section 9 - Consolidation Analysis Section 9.1 Background Section 9.2 Consolidation Analysis Section 10 - Selected Wastewater Alternative Section 10.1 Selected Wastewater Alternative Components Section 10.2 Proposed Wastewater Treatment Process Section 10.3 Staging or Phasing Town of Mead Wastewater Treatment Facility Preliminary Engineering Report and Utility Plan i

4 Section 10.4 Wastewater Reuse Section 10.5 Wetlands Section 10.6 Odor Control Considerations Section 10.7 Air Quality Permit Section 10.8 Stormwater Management Plan Section 10.9 Collection System Section Environmental Components Section 11 - Floodplain/Hazards Analysis Section 12 - Soils Report Section 13 - Legal Control Of Site Section 14 - Institutional Arrangements Section 15 - Management Capability Section 15.1 Management Structure and Agreements Section 16 - Financial Capability Section 16.1 Financial Management Plan and User Charge Summary Section 16.2 Revolving Loan Section 17 - Schedule Section 18 - Discharge Across Private Property References BOD 5 : Biochemical Oxygen Demand (5 day) CDPHE: Colorado Department of Public Health and Environment DMR: Daily Monitoring Reports gpd: Gallons per day gpm: Gallons per minute I-25: Interstate 25 ISDS: Individual sewage disposal systems NFRWQPA: North Front Range Water Quality Planning Association MGD: Million gallons per day SVSD: Saint Vrain Sanitation District TKN: Total Kjeldahl Nitrogen TSS: Total Suspended Solids WWTF: Wastewater Treatment Facility ACRONYMS Figure 1: Existing Wastewater System and 208 Boundary Figure 2: Existing Mead WWTF Treatment Schematic Figure 3: WWTF Location Alternatives Figure 4: Alternative Figure 5: Consolidation with SVSD WWTF Alternative Figure 6: Proposed Mead WWTF Process Schematic Figure 7: Conceptual Site Plan LIST OF FIGURES Preliminary Engineering Report and Utility Plan ii

5 LIST OF TABLES Table 1: Compliance Schedule Ammonia Limits Table 2: Population Projections, Wastewater Flows, and Load Table 3A: Preliminary Effluent Limit Summary Table 3B: Potential Effluent Limits based on New Total Ammonia Criteria Table 4: In-stream Standards for Stream Segment COSPSV06 Table 5: Summary of the Top 5 Wastewater Alternatives (2005 WW Study) Table 6: Wastewater Alternative 20 year Present Worth Cost Analysis Table 7: Treatment Alternatives Comparison Matrix Table 8A: Town Treatment and SVSD Consolidation - Plant Investment Fee Comparison Table 8B: Town Treatment and SVSD Consolidation Capital Cost Comparison Table 9: Summary of Management Agencies Table 10: Wastewater Rates per 1000 gallons Table 11: Projected O&M Budget Table 12: Projected Annual Revenue Based on User Fees Table 13: Historic Wastewater Tap Fee Summary Table 14: Project Capital Costs, Anticipated Loan Amounts, and EIG Impact Appendix A: CDPHE Site Application Appendix B: CDPHE and NFRWQPA report checklists Appendix C: Existing Mead WWTF Layouts Appendix D: IGA Agreement Appendix E: Preliminary Effluent Limits and Compliance Schedule Appendix F: Map of Watershed Boundary and Receiving Waters Appendix G: Property Deed Appendix H: Wastewater Treatment Alternative Itemized Costs Appendix I: Consolidation Information Appendix J: Smith Environmental Environment Assessment Report Appendix K: Environmental Assessment Agency Contact Letters Appendix L: Ground Engineering Soils Report Appendix M: Town Ordinance for Sewer User Fees and Wastewater Rate Study Appendix N: Low Density Area Map and Planning and Zoning Information Map Appendix O: Public Hearing Information Appendix P: Sewerline Map Appendix Q: East I-25 Service Plan Owner Map APPENDICES Preliminary Engineering Report and Utility Plan iii

6 SECTION 1.1 BACKGROUND SECTION 1 - EXECUTIVE SUMMARY The Town of Mead is located in Weld County approximately 35 miles north of Denver along Interstate 25 (I-25). Similar to many other Colorado communities, the Town has experienced past growth and foresees significant future development. At the present time, the majority of the proposed growth is residential, but the Town s location in the I-25 corridor indicates future business and commercial developments as well. The Town owns and operates two earthen basin aerated wastewater treatment facilities (WWTF). The main Town treatment facility, the existing Mead WWTF, is located about one-half mile east of downtown Mead. The existing Mead WWTF is permitted to discharge up to 0.14 million gallons per day (MGD) and 333 lbs per day of 5-day biochemical oxygen demand (BOD 5 ). Current flows and loads are approximately 0.10 MGD and 215 lbs BOD, respectively. The existing Mead WWTF was constructed in the mid 1950s originally as a two-basin facultative lagoon treatment system. The treatment system has undergone several modifications to improve effluent quality. However, the modifications have not been sufficient to completely eliminate discharge permit exceedances. At this time the Town is facing two significant issues associated with the existing Mead WWTF. First, the Town is under a compliance schedule issued by the Colorado Department of Public Health and Environment (CDPHE) that requires the existing Mead WWTF to meet ammonia discharge limits by 2009 with construction of a new wastewater facility. The existing aerated lagoon treatment system is not capable of complying with the anticipated ammonia discharge standards and will need to be replaced with a treatment process that is capable of consistently meeting the anticipated discharge limits. Secondly, the existing Mead WWTF does not have sufficient capacity to serve the growing population of the Town and its service area. To meet the future wastewater needs, the Town proposes installing a new mechanical WWTF to replace the existing aerated lagoon system. The engineer s opinion of probable cost for this project is $4.31 million, excluding the future lift station to serve the east side of I-25. It is anticipated that the $1.3 million lift station and force main will be constructed using funds from developers. The Town may be able to participate in a portion of this cost should adequate reserves be collected from new development. Additionally, the Town has offered developers the ability to prepurchase taps for capital improvements. The Town evaluated the possibility of sending its wastewater to the Saint Vrain Sanitation District (SVSD). Based on the monetary and non-monetary factors and in consideration of the fact that the Town is under a compliance schedule, the Town Board decided after a thorough review of the issues in several board meetings that the more cost-effective and expedient solution to providing wastewater service for its current and future customers was to construct the Town s own facilities, and that it would not be in the best interests of the Town to continue pursuing Preliminary Engineering Report and Utility Plan 1

7 consolidation with SVSD. However, the Town intends to continue to expand its IGA with SVSD to allow gravity sewer service to the SVSD along its present south 208 boundary, rather than this area being pumped into the Town s service area. It is important to note that the Town is not dependent on development of the areas east of I-25 to help pay for the proposed 0.5 MGD WWTF. However, since the Town Board revised its annexation ordinance in October 2006 to eliminate a requirement that landowners go through an election in order to receive approval from the public to be annexed, it is expected that an influx of annexation proposals will occur. The initial phase of this project will provide service to the existing and proposed or already platted areas in the Town or areas that are currently under development. Should areas on the east side of I-25 develop faster than currently anticipated, the plant can be easily expanded to include this growth. It is also important to note that the Town has adequate development on the books that is already annexed, zoned, and mostly platted that will pay fees to use the plants. It does not have to rely on future uncertain annexations. The Town can also completely finance the plant with existing development conditions, its own cash reserves, and its ability to obtain loans. The following utility plan presents a discussion of the proposed Mead WWTF to meet the documentation requirements of the CDPHE site application and NFRWQPA report and to provide master planning for the Town. The site application for this project is provided in Appendix A. SECTION 1.2 PROJECT DESCRIPTION The existing Mead WWTF site was not utilized for a proposed facility due to its proximity to the Town center and proposed residential areas. After an extensive site selection process, the Town purchased an acceptable 10-acre site for the proposed Mead WWTF, located approximately onehalf mile east of I-25 and 600 feet south of Weld County Road 34. Consolidation with the St. Vrain Sanitation District WWTF, located approximately 3 ½ miles southeast of the proposed Mead WWTF site and requiring approximately five miles of interceptors and force main, was also considered as a wastewater service alternative, but the Town Board determined that a Townowned treatment facility would be more economical for local residents and businesses. The proposed Mead WWTF will be designed for a capacity of 0.5 MGD to meet the projected 20-year development planning horizon for wastewater flow. The facility design will accommodate peak hourly flows of up to 2.0 MGD. Disinfected treated effluent will discharge to the same unnamed tributary of St. Vrain Creek as does the existing WWTF. Beyond the proposed Mead WWTF construction, the Town will also have to plan for several other wastewater infrastructure projects, including: decommissioning the existing Mead WWTF, sewerline construction, and a future wastewater lift station to serve the remaining 208 area. Influent wastewater from the Town service area west of I-25 and a portion of the area east of I- 25 will flow mostly by gravity through the existing collection system. The existing collection system will be extended to the proposed WWTF site. The existing Feather Ridge wastewater lift station will be decommissioned, since it will not be necessary due to the lower elevation of the Preliminary Engineering Report and Utility Plan 2

8 proposed site. The remainder of the service area east of I-25 will be served through a wastewater lift station that will be constructed in the future when needed. The sequencing batch reactor (SBR) has been determined to be the preferred treatment option for the proposed Mead WWTF. SBRs are a proven wastewater treatment system used to reliably and effectively treat wastewater to the ammonia levels as required by the CDPHE compliance schedule. The SBR controls will be programmed as needed to handle anticipated daily and seasonal flow and load variations as required to meet treatment standards. The SBR treatment process will also have flexibility to meet anticipated future permit requirements. The schematic of the proposed Mead wastewater facility process train is illustrated in Figure 6. The raw wastewater influent will first enter a splitter box, then to the headworks facility where a mechanical bar screen will remove, wash, and compact large solids. Following the screening process the wastewater will flow to a grit removal system, and finally to an influent flow meter. After the headworks the wastewater will flow to the SBR treatment facility. The treated wastewater then flows to a flow equalization basin to normalize flows through the disinfection system and the receiving waterbody. Waste activated sludge will be treated utilizing an aerobic digester, and sludge will be hauled offsite and land applied. Figure 7 presents the proposed site plan with the preliminary process layout for the Mead WWTF. The Town has been planning for this WWTF for several years and has gradually increased tap fees from $3,000 to $7,000 for a single residential tap. A rate study was completed in 2004 and has positioned the Town to recover the necessary O&M funds for operation of the new WWTF plus establishment of a repair and replacement fund for the existing WWTF and collection system. Details of the Town s financial plan can be found in Section 16. Preliminary Engineering Report and Utility Plan 3

9 SECTION 2 - INTRODUCTION The Town of Mead is located in Weld County just north of Longmont and approximately 35 miles north of Denver, Colorado. The Town has two exits off I-25 allowing easy access. The original Town core is situated about one mile west of I-25. The Town was founded in 1906 as a rural farm-to-market center and railroad stop along the Great Western Railroad for the sugar beet industry, and up to the 1980s had gradually grown to a population of about 350. The Town s population grew by about 100 additional people during the 1980s, and then to about 2,000 residents in the 1990s, when growth factors such as easy access to I-25 increased the demand for exurban housing (as Mead was then perceived as being in such a market at the time), and population migration out of Boulder County induced the approval and rapid build-out of several subdivisions that decade. Between 2001 and 2003 there was relatively little growth, perhaps only 100 more residents, as subdivisions in the pipeline were finished. Since 2003, several new subdivisions have been started that comprise roughly 1,000 lots, and over 300 building permits within the sewer service area have been issued as of July There are several annexations that have been approved that will bring approximately 2,000 more homes into the community where construction has not yet started. In addition, the community is now receiving numerous development inquiries and proposals, and the Town expects that this trend will continue and intensify. Most proposals are for residential projects at this time, although there is potential for substantial large-scale commercial developments along the I-25 and SH 66 corridors, and smaller-scale commercial development along Town arterials and collector streets. The Town has an industrial park and a business park, both adjacent to I-25, plus an ailing traditional downtown that it desires to revitalize. At this time the Town is facing two significant issues associated with the existing Mead Fairbairn wastewater treatment facility (WWTF). First, the Town is under a compliance schedule issued by the CDPHE that requires the existing Mead WWTF to meet ammonia discharge limits by The discharge limits are discussed in Section 3.2. The existing aerated lagoon treatment system at the existing Mead WWTF is not capable of complying with the anticipated ammonia discharge standards and will need to be replaced with a treatment process that will consistently meet the anticipated discharge limits. Secondly, the existing Mead WWTF does not have sufficient capacity to serve the growing population of the Town and its service area. To meet the future wastewater needs, the Town proposes installing a new mechanical WWTF to replace the existing aerated lagoon system. This site application and engineering report was developed to provide the necessary information for the CDPHE to approve the site application for the proposed Mead WWTF. Additional information is provided to satisfy the approval criteria of the North Front Range Water Quality Planning Association (NFRWQPA). The site application form is provided in Appendix A. The CDPHE and NFRWQPA report checklists are provided at the end of this report, in Appendix B Preliminary Engineering Report and Utility Plan 4

10 with cross-references to relevant page or section numbers. Supplemental material, including preliminary effluent limits (PELs) and other referenced information are also provided in subsequent appendices as identified in this report. Upon dissolution of the Mead Sanitation District on January 1, 1993, the Town of Mead assumed ownership and control of the wastewater treatment facilities serving the Town. The Town of Mead has been designated as both a wastewater Management Agency and an Operating Agency in the NFRWQPA Areawide Water Quality Management Plan 2005 Update (WQMP). The WQMP is a planning document mandated by Section 208 of the Clean Water Act, which requires designation of wastewater treatment management agencies, and provides that such agencies may only obtain wastewater discharge permits which are not in conflict with the WQMP plan. Section 208, in conjunction with Section 201 of the Clean Water Act, also provides for designation of service areas for wastewater treatment facilities and facility operators within the adopted regional plan. Figure 1 illustrates the Town of Mead wastewater system, including the 208 Service Area, as designated in the WQMP. The Town currently owns and operates two WWTFs. The primary facility is the Town of Mead WWTF located east of downtown Mead on Fairbairn Avenue. The other facility is the Lake Thomas WWTF located east of I-25 on WCR 32. Both facilities are aerated lagoon WWTFs. The Lake Thomas WWTF treats only one small condominium complex, while the Town of Mead WWTF treats the remainder of the Town s wastewater. The existing Mead WWTF is the main focus of this plan. The Lake Thomas WWTF has potential for private developer use or could be decommissioned once the new WWTF is placed in service. Figures of the existing WWTFs can be found in Appendix C. The Town of Mead s WWTFs will be further discussed in the Analysis of Existing Facilities section. The existing Mead WWTF is an aerated lagoon treatment facility, with an advanced integrated pond system (AIPS) modification for influent BOD removal in an anaerobic cell. The WWTF is permitted for 0.14 MGD and 333 lbs of BOD 5. The existing Mead WWTF currently treats an average day flow slightly above 0.1 MGD. Unfortunately, the existing Mead WWTF has not been operating optimally and has exceeded effluent permit limits on several occasions. Between June 2002 and May 2004, the existing Mead WWTF experienced: five effluent BOD 5, four BOD 5 percent removal, two effluent BOD 5, one influent TSS, one effluent TSS, and one fecal coliform exceedances. These exceedances have been attributed, in part, to high solids content in the lagoon cells, as a result of algae formation. These recent treatment issues have raised concerns about the ability of the existing Mead WWTF to treat future flows and loads with the existing processes. In addition to the poor treatment performance of the existing Mead WWTF, the Town operations and engineering staff has indicated concern over the validity and accuracy of the influent flow metering and historic sampling that has been completed to date. Influent and effluent flow meters were replaced in 2005, but the impact of the high service lift station, which intermittently discharges up to 750 gallons per minute (gpm), is still skewing the influent flow data. Preliminary Engineering Report and Utility Plan 5

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12 SECTION 3 - ANALYSIS OF EXISTING FACILITIES SECTION 3.1 WASTEWATER TREATMENT FACILITIES The two WWTFs owned and operated by the Town are discussed below. Figures of the existing WWTFs can be found in Appendix C. EXISTING MEAD WWTF: The existing Mead WWTF was constructed in the mid 1950s as a two-basin facultative lagoon treatment system by the former Mead Sanitation District. After the dissolution of the Mead Sanitation District in 1993, the Town took over ownership and operation of the existing Mead WWTF. The existing Mead WWTF underwent improvements in 1992 and 1993 that converted the existing two-basin facultative lagoon into an aerated lagoon system. The 1992/93 WWTF improvements included: 1) placing an earthen berm across Lagoon No. 2 thereby creating a third lagoon (Lagoon No. 3), 2) converting Lagoon Numbers 1 and 2 into aerated lagoons by installing surface aerators, 3) addition of a chlorine contact chamber and sodium hypo-chlorite feed equipment, and 4) installing flow recording devices on plant influent and effluent. In the 1990s, an engineering study determined the detention time of Lagoon No. 1 facilitated algae growth that resulted in algae-oriented effluent TSS exceedances. The study also determined that Lagoon No. 1 had excessive sludge buildup. In 1995, the existing Mead WWTF operations were modified to bypass Lagoon No. 1, thereby allowing the basin to dry for sludge removal. Concurrently, improvements to Lagoon No. 2 were made to reduce plant detention time and to allow the plant to operate more efficiently. Improvements included the installation of two curtains in Lagoon No. 2 to create three treatment cells and a bypass line of the polishing cell (Lagoon No. 3). In July 1996, Lagoon No. 1 was cleaned and 1.1 million gallons of biosolids were removed. The existing Mead WWTF has undergone several smaller system improvements since the mid s. In 1998, a new influent headwork structure was constructed. In 2000, four new 4,500- gallon chlorine contact vaults were added. The chlorine contact tanks are sized for a 30-minute detention at the peak flow rate of 180,000 gallons per day. Currently, the existing Mead WWTF provides treatment utilizing a three-cell advanced integrated pond system (AIPS) including an anaerobic fermentation cell, aeration cell, and settling cell. The existing Mead WWTF is permitted for 0.14 MGD and 333 lbs of BOD 5. All three cells are located within the old Lagoon No. 2. A schematic of the existing Mead WWTF process follows in Figure 2. LAKE THOMAS WWTF: The Lake Thomas WWTF is an aerated lagoon that was constructed in 1989 to serve the Country View Day Care Center. The Town acquired the WWTF in 2000 as Preliminary Engineering Report and Utility Plan 6

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14 part of an annexation and redevelopment of the day care center, which was converted to the Lake Ridge Condominium complex. At present time, the Lake Ridge Condominium complex is the only development served by the Lake Thomas WWTF. In December 2001, the Lake Thomas WWTF underwent improvements, including: 1) new inlet and outlet structures, 2) a new chlorine contact chamber, 3) rehabilitation of the lagoon banks, and 4) sludge removal. The Lake Thomas WWTF provides treatment utilizing a two-cell aerated lagoon system with an aeration cell and a settling cell. The Lake Thomas WWTF has a design capacity of 12,000 gallons per day (gpd). Currently the Lake Ridge Condominium complex only has about 4 residents. Of the total 29 units, approximately 25 units have been vacant for several years due to failed marketing of the complex. Consequently, the Lake Thomas WWTF has been receiving minimal flow and loading from the Lake Ridge Condominiums. The Lake Thomas WWTF has not discharged into Lake Thomas since the day care facility was closed in late SECTION 3.2 WASTEWATER EFFLUENT LIMITATIONS The existing Mead WWTF is discharging under the State of Colorado Discharge Permit Number CO that is effective until December 31, The permitted hydraulic and organic loading is based on an average monthly flow of 140,000 gpd and 333 pounds of BOD per day. The Lake Thomas WWTF discharges under Permit Number CO that is effective until November 30, The permitted hydraulic and organic loading is based on a maximum flow of 12,000 gpd and 24 pounds of BOD per day. In conjunction with the January 1, 2005 discharge permits, the CDPHE issued a compliance schedule to the Town. The compliance schedule requires the s to consistently meet ammonia discharge limits by late A copy of the compliance schedule is included in Appendix E. The compliance schedule limits are seen in Table 1. Preliminary effluent limits (PELs) for the lagoon system were initially provided by the CDPHE for the future ammonia limits in the compliance schedule. The preliminary effluent limits for the proposed mechanical treatment facility are discussed in Section 5 and Appendix E. Table 1: Compliance Schedule Ammonia Limits, Total Ammonia (as N), mg/l Month 30 day average Daily Maximum January February March April May June July August September October November December Preliminary Engineering Report and Utility Plan 7

15 Under current conditions, the existing Mead WWTF is operating at approximately 70% of its permitted hydraulic capacity and about 65% of its organic capacity. However, as indicated by past discharge permit limit excursions, the existing Mead WWTF may not be capable of effectively treating higher flow rates or loads. SECTION 3.3 INFRASTRUCTURE SIZING AND STAGING LIFT STATIONS: The Town of Mead currently owns and operates two wastewater lift stations located north of downtown Mead. The Feather Ridge Lift Station is located northeast of the downtown near the Great Western Railroad. The North Creek Lift Station is located north of the downtown along Weld County Road 34 ½. The Feather Ridge Lift Station has two 750 gpm pumps with the ability to add a third pump. The North Creek Lift Station has two 200 gpm pumps. The Feather Ridge lift station will be decommissioned when the new WWTF becomes operational. The North Creek Lift Station can be abandoned once a new interceptor sewer is constructed up the North Creek drainage. This would occur when a development proposal is approved by the Town for a parcel abutting the west, north, or east side of the existing North Creek subdivision. The Town has received several development inquiries about parcels in this area in the past few years, but thus far none have submitted an application. It is expected that development in this area will occur within the next 10 years. INTERCEPTORS: The Town of Mead wastewater collection system consists of force mains that range from 4 to 10 and gravity lines that range from There is one 695-foot section of 24 gravity sewerline which connects the gravity collection system to the 10 force main. See Appendix P for a Town of Mead sewerline map. The wastewater collection system consists of approximately: 6,289 ft of 4 force main 3,860 ft of 10 force main 46,774 ft of 8 sewerline 1,100 ft of 10 sewerline 9,668 ft of 12 sewerline 402 ft of 15 sewerline 1,775 ft of 18 sewerline 695 ft of 24 sewerline SECTION 3.4 INFILTRATION AND INFLOW The Town of Mead has not completed a recent infiltration and inflow study. However, though the accuracy of the historic Mead wastewater flow data is uncertain, infiltration and inflow is not believed to be an issue since flows to the WWTF appear to be low for the given population. The Town has considered exfiltration as an explanation for the low wastewater production rate per capita. However, there is no evidence of a large leak in the wastewater collection system. Most of the sewer system in the Town is fairly new, utilizing construction materials comprised of precast concrete manholes and PVC piping. The original Town subdivision was sewered in the Preliminary Engineering Report and Utility Plan 8

16 mid-1950s, making this piping system over 50 years old. The Town performed a study of this system in 1996 (Sanitary Sewer Collection System Study, October 1996, by RBD Engineering Consultants), and as part of this study a TV camera was used to perform an internal inspection of all the sewers in this area. Eleven locations were identified to have deficiencies and included holes in the pipe, offset joints, or cracked pipe. The Town has corrected all the identified deficiencies. The Town has corrected the last deficiency by replacing the Fairbairn Avenue sewer main. This sewer was originally constructed with clay and concrete sewer pipe with brick manholes. Several locations were identified to have infiltration through manhole connections and the interior of the pipe was deteriorating. Approximately 2,500 feet of the sewer was replaced with 12-inch PVC piping, and this project was completed in October SECTION 3.5 INDUSTRIAL PRETREATMENT PROGRAM According to the U.S. EPA, the National Pretreatment Program under the General Pretreatment Regulations require that any wastewater treatment facility designed to treat over five million gallons a day of wastewater, or receives significant discharges from industrial sources, must develop a local pretreatment program conforming to EPA regulations. At this time the Town does not have a pretreatment program in place, as it treats less than 5 MGD of wastewater and does not receive a significant industrial flow. The proposed growth through the year 2026 does not take the Town over 5 MGD, nor does it introduce significant industrial sources of wastewater to the WWTF. In the future, the Town plans to implement a wastewater pretreatment program to minimize oil and grease discharges to the WWTF. However, due to concerns about potential discharges by one industrial contributor, the Town did conduct a wastewater survey of the Boulder Scientific Company in December The CDPHE Industrial Pretreatment Coordinator, Rick Koplitz, participated in the wastewater inspection. This chemical manufacturer was found to have only its domestic wastewater connected to the sewer system. Preliminary Engineering Report and Utility Plan 9

17 SECTION 4 - SERVICE AREA, POPULATION PROJECTIONS, WASTEWATER FLOW AND LOADS SECTION 4.1 SERVICE AREA DESCRIPTION The Town s 208 wastewater service area, as defined by the NFRWQPA Areawide Water Quality Management Plan 2005 Update, is shown on the attached map in Figure 1. The service area incorporates two existing WWTFs and two lift stations. Currently, all of the existing collection system and sewer customers are located on the west side of I-25. The 208 service area is approximately 23 square miles and includes areas on both sides of I-25. A portion of the 208 service area is designated as very low or low density development by the 2004 Town of Mead Comprehensive Plan (See Appendix N: Planning and Zoning Information Map). These low density areas within the 208 boundary may be served by septic systems, although it is the intent of the Town to be able to provide sewer service within its 208 boundaries in the future. However, the following considerations will need to be taken into account when considering long term treatment needs: a. The Town s septic subdivisions may ultimately be required to be municipally sewered. These development are products of past land use and density decisions and are consistent with many similar subdivisions in Weld County, several of which are also in the Town s planning area and would face the same issue. b. Future regulations may require the landowners to abandon their septic systems and connect to the Town s sewer system. The landowners would be required to fund these improvements including the purchase of taps for each resident. The Town is providing additional capacity in its sewer system to accommodate possible future failures in or regulatory changes affecting these areas. c. Low land use density on the Town s Comprehensive Plan does not necessarily mean that septics would be approved. The Town has subdivisions with 1-acre lots on septic and subdivisions with average 5-acre lots that are on municipal sewer. Thus 208 boundaries should not assume that everyone inside them are on municipal sewer. Certainly the County s approval of rural subdivisions on septic inside many towns 208 boundaries indicates that this definition of urban development is not appropriate. d. Cluster subdivisions, also known as conservation subdivisions, are another way of achieving sewer service and having average low density development at the same time. Preliminary Engineering Report and Utility Plan 10

18 e. In situations where development proposals are not immediately adjacent to previously developed properties the Town may require a subdivision developer to dry-sewer a subdivision, due to timing or temporary contiguity issues. A dry-sewer subdivision would have both sewer mains and septic tanks installed. The subdivision would utilize the septic tanks only until a municipal interceptor is constructed in the vicinity. After interceptor construction, the subdivision would abandon the septic tanks and connect to the municipal wastewater system. f. Open space and large regional parks (e.g. Sandstone Ranch in Longmont) would be examples of parcels that would not be cost-effective to provide sewer service to, or which would create timing or location issues for bringing sewer service to developable properties next to them. g. There may be areas that are not currently annexed to the Town that the Town would provide sewer service to. The Town has not yet done a study to determine what tap fees and user charges should be to such properties, but is planning to do so. The Town Board revised its annexation ordinance in October 2006 to eliminate a requirement that landowners go through an election in order to receive approval from the public to be annexed, so it is expected that an influx of annexation proposals will occur. The Town of Mead has an intergovernmental agreement (IGA) with the SVSD to provide wastewater treatment to a business park near the intersection of I-25 and Highway 66 that is in the Town s 208 service area. The IGA boundaries can also be seen on Figure 1 and a copy of the IGA agreement is provided in Appendix D. In 2004, a disparate group of property owners banded together for the purpose of proposing a new Sanitation District in the area generally east of I-25 and north of SH66, directly adjacent to the corporate boundaries of Mead in numerous spots, and with a large amount of the acreage in the Mead s 208 sewer service area (See Appendix Q). This proposed project has been called the East I-25 Sanitation District (District). Because this District proposal has subsequently received a great deal of press, the Town has prepared a brief description of the situation in consultation with its legal counsel. The Town is limited in what it can submit as a part of this site application on the topic, because the situation is in litigation. Some of the origins of this proposal have been stated to be that the Town refused to annex certain properties or that it was incapable of providing sewer service in a timely manner. This is not true. In fact, the District proponents included both property owners who have either petitioned the Town for annexation at some point, and others who have never petitioned for annexation. One annexation petition is still on file with the Town because the owner has not decided which party to work with. Additionally, some property owners withdrew annexation petitions before completing negotiations, and others lost their annexation contiguity through the actions of other parties, not because the Town refused to annex them. For whatever their motivations, the District proponents prepared a service plan that was based on the assumption of being a collection system only, with treatment to be provided by the St. Vrain Sanitation District. The service plan was presented to the Weld County Board of Commissioners for approval, which the County Board did at a public hearing in February 2005 over the Preliminary Engineering Report and Utility Plan 11

19 objections of the Town. Consequently, the Town of Mead sued both the County and the District proponents to prevent the formation of the District from occurring until a court could rule on the matter. In summary, the Town alleges that the County failed to follow state statutes and its own regulations in reviewing and approving the service plan. The Town further alleges that the District proponents presented a flawed service plan that vastly understated the cost of the project, and thus its viability, and also presented misleading, incomplete, and falsely prejudicial testimony against the Town at the County s hearing that the Town was not allowed to refute. They also drew proposed District boundaries that overlapped the Town s boundaries. The matter went to trial in May 2006, and the judge in the case has yet to rule. The case is very complicated, but the fact of the matter is that the Developer proposal is still only a proposal and nothing more. The proponents have been prohibited by the court from holding an election to form the District. Accordingly, the proposed District has no standing. They have no signed agreement with SVSD for service. At this point in time, the proposed District is a hypothetical future project that is not germane to the consideration by NFRWQPA of the Town s site application, which represents a real and present need. It is possible that litigation may be elevated to a higher court by any side once a ruling is issued and could take two to three years to resolve. Furthermore, conditions have continued to change, and if any sanitation district should be proposed or come into existence within the Town s 208 service area in the future, it would need to perform its own Engineering Report and Utility Plan to prove what would be the most cost-effective treatment entity to provide them with wastewater service. The Town does not believe that it has any obligation to do this kind of analysis for them to address this issue. SECTION 4.2 POPULATION PROJECTIONS According to the 2000 U.S. Census, the total Town population was 2,017 with 641 occupied housing units, providing a residential population density equivalent of 3.15 people per household. The Town staff believes that Census population density value is not representative of the typical sewered household since the Census number also included neighborhoods that are served by septic systems. The existing downtown area and the adjacent residential neighborhoods are believed to have a lower number of residents per household. For the purposes of this report a population density of 2.67 people per home was used to establish population and flow projections connected to the sewer system. As indicated above, of the 641 occupied housing units identified in the 2000 census, less than 348 were tied into the sewer system. The remaining households were on individual sewage disposal systems (ISDS). At this time, there is no intent to tie the ISDS households or future houses in that general location to the sewer system. Since 2000, the Town has experienced an average annual growth rate of 7.7%. In 2003 and 2004 the growth rates were as high as 15.9% and 22.3%, respectively. The Town is working with several developers and has identified approximately 500 platted lots ready to be developed over the next three to five years. In light of the anticipated growth in the Town and within the 208 service area, the Town anticipates an annual growth rate of at least 5% for the 20-year planning Preliminary Engineering Report and Utility Plan 12

20 horizon. Although higher growth rates may be realized throughout portions of the 20-year planning period, an average growth rate of 5% is used for this analysis to estimate flows and loads to the proposed Mead WWTF. The 5% growth rate is also consistent with the Wastewater Rate Study the Town completed in Assuming a 5% residential growth rate, the projected 2026 Town population is approximately 7,172 people. Of the total Town population, approximately 4,581 people will be connected to the Mead wastewater system in SECTION 4.3 WASTEWATER FLOW RATES: HISTORICAL AND PROJECTED The accuracy of the historic Mead WWTF recorded flow data is highly suspect. Reviewing the historical flow data collected since 2001 indicated that the average daily flow did not increase with the addition of more taps to the sewer system. Town staff has indicated that a poorly operating recording device had likely impacted flow measurement accuracy. In addition, the upstream Feather Ridge wastewater lift station intermittently discharges up 750 gpm to the WWTF, skewing the average influent flow readings considerably. In the fall of 2005, the Town implemented updated flow measuring methods to try to rectify the flow measurement issues and to improve sampling methods. However, current flow data indicate an average day flow of MGD, resulting in an estimated flow per capita of 58.5 gpd, which is considerably lower than the industry accepted average flow per capita, which ranges between 75 gpd and 85 gpd. Due to the lack of plausible historic flow data, a per capita wastewater production rate of 75 gpd was assumed for this report. The peak hour flows were assumed to be four times greater than the average daily flow. A peaking factor of four was selected since the Town has a relatively small population and collection system and will therefore see higher peak hour flows than larger systems. The peak factor of four is also consistent with the NFRWQPA equation provided in the NFRWQPA 2000 Utility Plan Guidance. Industrial and commercial development has also been identified within the Mead service area, with development occurring over the 20-year planning period. However, at this time it is difficult to quantify the extent to which industrial/commercial development will occur. In order to address treatment needs of industrial/commercial users, the Town has elected to reserve approximately 12% of its capacity for these users. If industrial/commercial usage is higher than expected, the Town will need to address expansion earlier than anticipated. If, however, the industrial/commercial growth is slow, the excess capacity could be used for residential purposes, delaying the overall period of time to expand the facility. A summary of the population projection and resulting wastewater flows is provided in Table 2. The 20 year (2026) projected Mead residential population connected to the wastewater system would contribute approximately MGD. Assuming the 12% industrial/commercial contribution occurs during this same time frame, the plant will be at 80% of its hydraulic capacity in The proposed 0.5 MGD Mead WWTF would reach 100% capacity around 2031 under the same scenario. Preliminary Engineering Report and Utility Plan 13

21 SECTION 4.4 WASTEWATER ORGANIC LOADS: HISTORICAL AND PROJECTED The historical influent water quality data for the existing Mead WWTF is questionable due to the way in which BOD, TSS, and ammonia samples were collected. Until the fall of 2005, the influent data reported on the Daily Monitoring Reports (DMR) was developed by taking grab samples at 7 a.m., 9 a.m., 11 a.m., and 1 p.m. and combining these grabs to represent a 24-hour composite sample. The resulting information indicated a 90th percentile BOD and TSS value of 342 mg/l and 279 mg/l respectively. This data is skewed and misrepresentative of typical domestic facilities. In the fall of 2005, the Town hired a new contract operator, Ramey Environmental Compliance, Inc., (REC) to operate their WWTF and collect DMR data. Since the fall of 2005, true 24-hour composite samples using an automatic sampler have been collected at the lagoon facility, resulting in a 90th percentile BOD value of 258 mg/l and a TSS of 243 mg/l; values that are more consistent with industry standards. A BOD concentration of 258 mg/l results in a total per capita loading of 0.15 pounds per day. A typical range for BOD loading is 0.16 to 0.26 pounds per day. The recent composite flow data shows that the per capita loading rate is on the low side of normal. Given the Town's concern over the historical data collected up until the fall of 2005, and the implementation of true composite sampling in the fall of 2005, the Town's wastewater engineer and JVA have determined that it was prudent to base the design of the proposed facility on the data developed by REC. However, there are only six data points available for analysis at the time of preparation of this report. Typically, several years' worth of data is utilized to develop influent organic and solids data. For design purposes, the documented average of 258 mg/l BOD 5 will be increased 20% to obtain maximum BOD loadings giving a concentration of 310 mg/l. In 2031, at the 100% design flow rate of 0.5 MGD and a population of 5,847, the resulting BOD 5 load is 1,286 lbs/day and the per capita load is 0.22 lbs/day. In 2026, an 80% capacity flow rate of 0.4 MGD will result in a load of 1,008 lbs/day of BOD 5 based on a population of 4,581. Similarly, the average TSS concentration was increased 20% to determine a design concentration of 292 mg/l. In 2031, at the 100% design flow rate of 0.5 MGD and a population of 5,847, the resulting TSS load is 1,169 lbs/day and the per capita load is 0.2 lbs/day. In 2026, an 80% capacity flow rate of 0.4 MGD will result in a load of 916 lbs/day of TSS based on a population of 4,581. Ammonia data, since the fall of 2005, has ranged from 22.5 mg/l to 37 mg/l, and Total Kjeldahl Nitrogen (TKN) between 27 mg/l and 43 mg/l. The characterization of the Town's flow contributors includes minimal industrial or commercial usage. Future development, as identified above, includes predominantly domestic growth with some commercial growth, and minimal industrial growth. It is not anticipated that the proposed commercial/industrial growth will significantly affect the overall character of the influent to the WWTF. Based on the current and proposed growth for the service area, the influent data developed since the fall of 2005 was deemed appropriate for design purposes and has been used to develop the projected flow and load to the proposed WWTF. Utilizing the projected flows to the WWTF, and assuming the influent BOD remains at about 258 mg/l, the Town will reach 80% of its organic design capacity in Preliminary Engineering Report and Utility Plan 14

22 Table 2: Population Projections, Wastewater Flows, and Load Year Total Town Population Homes in 208 Area Home on ISDS Homes on Sewer Population on Sewer Residential WW Flow (MGD) Industrial reserved capacity (MGD) WW Flow (MGD) BOD Load (BOD lbs/d) ,703 1, , ,838 1, , ,980 1, , ,129 1, , ,285 1, , ,450 1, , ,622 1, , ,803 1, , ,994 1, , ,193 1, ,003 2, ,403 1, ,053 2, ,623 1, ,106 2, ,854 1, ,161 3, ,097 1, ,219 3, ,352 2, ,280 3, ,619 2, ,344 3, ,900 2, ,412 3, ,195 2, ,482 3, ,505 2, ,556 4, ,830 2, ,634 4, % 7,172 2, ,716 4, , ,530 2,820 1,018 1,802 4, , ,907 2,961 1,069 1,892 5, , ,302 3,109 1,122 1,986 5, , ,717 3,265 1,178 2,086 5, , % 9,153 3,428 1,237 2,190 5, ,286 Assumptions: 1. Town population growth rate of 5%. 2. Population density of 2.67 persons per household. 3. A wastewater production rate of 75 gpd per capita % of WWTF capacity reserved for Industrial / Commercial users. 5. The BOD load projects are based on a per capita loading rate of 0.22 lbs per day. Preliminary Engineering Report and Utility Plan 15

23 SECTION 5 - PRELIMINARY EFFLUENT LIMITATIONS Primary Effluent Limitations (PELs) for the proposed Mead WWTF for discharge to an unnamed tributary to St. Vrain Creek were received on July 17, A copy has been included in Appendix E. The PELs are shown in Table 3A. Table 3A: Preliminary Effluent Limit Summary Pollutants WQBEL Technology Based Limitations BOD5 (mg/l) 45 (7-day average), 30 (30-day average) BOD5 (% removal) 85 (30-day average) TSS, mechanical plant (mg/l) 45 (7-day average), 30 (30-day average) TSS, mechanical plant (% removal) 85 (30-day average) Oil and Grease (mg/l) 10 (maximum) ph (s.u.) (minimum-maximum) Other Pollutants WQBEL Fecal Coliform (#/100 ml) 400 (7-day average), 200 (30-day average) E. coli (#/100 ml) 252 (7-day average), 126 (30-day average) Total Residual Chlorine (mg/l) (daily maximum), (30-day average) Total Ammonia, January (mg/l) 12 (daily maximum), 7.1 (30-day average) Total Ammonia, February (mg/l) 11 (daily maximum), 6.6 (30-day average) Total Ammonia, March (mg/l) 9.9 (daily maximum), 4.8 (30-day average) Total Ammonia, April (mg/l) 9.8 (daily maximum), 4.5 (30-day average) Total Ammonia, May (mg/l) 9.8 (daily maximum), 4.0 (30-day average) Total Ammonia, June (mg/l) 9.7 (daily maximum), 3.4 (30-day average) Total Ammonia, July (mg/l) 14 (daily maximum), 5.2 (30-day average) Total Ammonia, August (mg/l) 23 (daily maximum), 12 (30-day average) Total Ammonia, September (mg/l) 20 (daily maximum), 9.8 (30-day average) Total Ammonia, October (mg/l) 15 (daily maximum), 7.0 (30-day average) Total Ammonia, November (mg/l) 12 (daily maximum), 6.0 (30-day average) Total Ammonia, December (mg/l) 9.9 (daily maximum), 4.9 (30-day average) The PEL issuance letter also stated that a new total ammonia criteria might be adopted in for the receiving segment, potentially effective in October of Table 3B shows the potential new ammonia water quality-based effluent limits (WQBEL) computed using the AMMTOX model. Table 3B: Potential Effluent Limits based on New Total Ammonia Criteria Month WQBEL (mg/l) January February March April May June July August September October November December 15 (daily maximum), 3.9 (30-day average) 13 (daily maximum), 3.8 (30-day average) 11 (daily maximum), 3.1 (30-day average) 11 (daily maximum), 2.9 (30-day average) 12 (daily maximum), 2.7 (30-day average) 12 (daily maximum), 2.4 (30-day average) 21 (daily maximum), 3.0 (30-day average) 35 (daily maximum), 4.1 (30-day average) 30 (daily maximum), 3.9 (30-day average) 21 (daily maximum), 3.5 (30-day average) 15 (daily maximum), 3.5 (30-day average) 11 (daily maximum), 2.3 (30-day average) Preliminary Engineering Report and Utility Plan 16