City and County of San Francisco 2030 Sewer System Master Plan TASK 400 TECHNICAL MEMORANDUM NO. 405

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1 City and County of San Francisco 2030 Sewer System Master Plan TASK 400 TECHNICAL MEMORANDUM NO. 405 REGULATORY CONSIDERATIONS FOR WET WEATHER COLLECTION SYSTEM BACKUPS FINAL DRAFT August YGNACIO VALLEY ROAD SUITE 300 WALNUT CREEK, CALIFORNIA (925) FAX (925)

2 CITY AND COUNTY OF SAN FRANCISCO SEWER SYSTEM MASTER PLAN TASK 400 TECHNICAL MEMORANDUM NO. 405 REGULATORY CONSIDERATIONS FOR WET WEATHER COLLECTION SYSTEM BACKUPS 1.0 PURPOSE SUMMARY BACKGROUND City Wastewater System Causes of Backups and Outflows Consequences Responses REGULATORY ISSUES Current NPDES Wastewater Discharge Permits Clean Water Act: EPA Region IX Investigation of Backups and Outflows State Water Code: State Sanitary Sewer System Program Property Owners Responsibilities RELATED TECHNICAL ISSUES Oil and Grease Blockages Flow Reduction Efforts APPENDIX - Definitions DRAFT - October 1, 2009 i

3 Technical Memorandum 405 REGULATORY CONSIDERATIONS FOR WET WEATHER COLLECTION SYSTEM BACKUPS 1.0 PURPOSE This technical memorandum (TM) is intended to identify regulatory and other issues related to backups in the sewer system during wet weather. More specifically, the goal is to identify whether the Clean Water Act (CWA), the State Water Code, or other legal requirements compel the City to address sewer system backups and outflows caused by wet weather flows. Outflows in this memorandum are discharges of untreated combined wastewater from sewer manholes, catch basins, sewer vents or any other location other than the permitted CSD outfalls. Backups are discharges of combined wastewater (sanitary sewage or sewage and stormwater) into buildings as a result of additional stormwater flows to the system. 2.0 SUMMARY San Francisco has a combined sewer system that collects sewage and storm water in the same network of pipes. The average daily wastewater flow in the sewers is 85 million gallons per day (mgd). During wet weather this flow can increase to as high as 575 mgd. Sewer system outflows and backups into residences and businesses can occur when the system is overloaded. The causes of these backups and outflows include the following: Localized blockage typically caused by fats, oils, and greases (FOG); roots; other foreign material; or pipe failure Hydraulic inadequacy undersized sewer or a sewer that has settled below the appropriate grade Excessive runoff an extremely large storm that overwhelms the system. The outflows that occur within the combined sewer system are generally recaptured down gradient in the system. In other words, flows may exit a manhole and flow along a street but then re-enter the sewer system through a storm drain elsewhere. Backups into residences and businesses can occur in conjunction with or separately from an outflow. Both of these create a significant nuisance and potential health risk. Current state and federal regulations do not appear to address either backups or outflows from combined sewer systems that do not reach receiving waters. The state has recently adopted General Waste Discharge Requirements (WDRs) intended to control sanitary sewer overflows. However, these WDRs are not applicable to combined sewer systems. Similarly, the NPDES permits issued to San Francisco under the Clean Water Act are DRAFT - October 1,

4 directed at protecting receiving waters - the San Francisco Bay or Pacific Ocean - and not at internal issues within the collection system such as backups and outflows. However, NPDES permits do require San Francisco to adequately operate and maintain its facilities, including its sewer system. Regardless of the lack of regulations directly pertinent to backups and outflows, this problem is a major focus of the Sewer System Master Plan because it directly affects the quality of life of the citizens of San Francisco. 3.0 BACKGROUND 3.1 City Wastewater System The City s combined sewer system includes over 900 miles of pipe. Since virtually all storm water runoff is directed into the system, flows increase by a factor of six or more in wet weather. During particularly large storms, the runoff can exceed the overall capacity of the system. In addition, localized hydraulic problems or blockages can limit flows and cause backups. More than 70 percent of the system was built 70 years ago, 15 percent was built more than 100 years ago, and some portions were built more than 150 years ago. Pipe settling and pipe deterioration have affected sewer system operations. Due to spending constraints, maintenance focuses on immediate needs over long-term preventative maintenance. The City typically makes more than 500 repairs a year on the sewer system patching breaks and restoring caved-in areas. 3.2 Causes of Backups and Outflows 1 When sewer pipes are blocked or restricted, the wastewater backs up in the pipe and may flow out through manholes or other outlets. Wastewater flows may also back up into residences or businesses via toilets and other drains. Most problems occur in wet weather but dry weather blockages are also possible. 3.3 Consequences Most outflows are relatively small and can be stopped and cleaned up quickly. Larger overflows or backups can result in property damage, odors, environmental problems, and possible public health and safety hazards. In addition, structural and aesthetic damage may result from backups. 1 See definitions in the Appendix. DRAFT - October 1,

5 3.4 Responses City crews respond to reports of backups and outflows. When possible, the crew removes the blockage and cleans up affected streets. The City s long term response is based on the PUC s Wastewater System Reliability Assessment, Baseline Facilities Report (December 2003) which includes the Sewer Replacement Priority List and prioritizes projects based on hydraulic and structurally inadequacies as well as flooding complaints. 4.0 REGULATORY ISSUES Currently no regulatory requirements appear to apply to backups and outflows from combined systems that do not result in a discharge to receiving waters (Bay or Ocean). 4.1 Current NPDES Wastewater Discharge Permits NPDES permits regulate discharges from point sources to waters of the US. An outflow or backup that does not enter either the Bay or Ocean does not appear to be regulated by the permits. NPDES permits, however, do impose requirements for operation and maintenance and San Francisco s permits have these requirements: Discharge Prohibition D. The bypass of untreated or partially treated wastewater to waters of the United States is prohibited except during wet weather and as provided for in the conditions stated in 40 CFR (m)(4) and in A.12 of the Standard Provisions and Reporting Requirements for NPDES Surface Water Discharge Permits, August Order No. R , NPDES No. CA for the Bayside Facilities "Provision C.2.a. Combined Sewer Collection System Overflow Study The combined sewer system commingles stormwater and domestic and industrial sewage. Heavy storm events can potentially result in flows that exceed the collection system capacity, at least in some areas. The Discharger shall submit a report, for planning purposes, by June 30, 2012, evaluating the potential locations of such system excursions and the primary conditions that result in such events. The report shall evaluate the feasibility and effectiveness of alternatives to minimize these events. Order No. R , NPDES No. CA for the Oceanside Facilities DRAFT - October 1,

6 4.2 Clean Water Act: EPA Region IX Investigation of Backups and Outflows Although CWA requirements are directed at protecting receiving waters, the EPA has expressed concern and initiated an investigation of the City s backups and outflows. This indicates that they believed, at least initially, that the CWA gives them jurisdiction for regulating backups and outflows. EPA inspected the City s wastewater facilities and requested information related to the combined sewer system (CSS). After the inspections EPA requested detailed information and documents related to outflows from the CSS; street flooding; and CSS capacity, maintenance, and capital improvements. EPA issued the Information Request pursuant to section 308(a) of the CWA. The City was requested to submit the information to the Enforcement Officer of Region 9 and to the Regional Water Quality Control Board. The position of the City is that since none of the backups or outflows reached receiving waters, these occurrences are not discharges as defined in the CWA and therefore not under the jurisdiction of EPA or the Regional Board. 4.3 State Water Code: State Sanitary Sewer System Program On May 2, 2006, the State Water Board adopted new general WDRs for sanitary sewer systems and the associated monitoring and reporting program by issuing Order No The new order regulates sanitary sewer overflows (SSOs). The State defines a sanitary sewer overflow as any overflow, spill, release, discharge, or diversion of untreated or partially treated wastewater from a sanitary sewer system. While this definition would appear to include San Francisco s backups and outflows, the Board staff has said that the general WDRs do not apply to combined sewer systems. San Francisco however, must comply with this Order for all of it separate sanitary sewers. 4.4 Property Owners Responsibilities A blockage occurs occurring within the private internal plumbing or in the lateral pipe or side sewer that connects private property to the public sewer, is the responsibility of the property owner or operator of that sewer. For example, a building s drainage system may not be adequate to adequately convey all roof runoff as well as internal sewage during a major downpour. Additionally, the use of backflow prevention devices can help prevent sewer backup events on private property. 2 Posted on the internet at: DRAFT - October 1,

7 5.0 RELATED TECHNICAL ISSUES 5.1 Oil and Grease Blockages Oil and grease are frequently dumped down the drain by residents and businesses, potentially blocking sewer lines and creating backups during major rainstorms. In addition to controlling this dumping via regulations, the City is considering collecting grease directly from restaurants to help prevent sewer blockages and processing it to produce biodiesel for City vehicles. 5.2 Flow Reduction Efforts Changes to the flow regime that reduce peak flows or the duration of flows to the sewers can help prevent backups and outflows. Low impact design (LID) is the designation given to the types of practices intended to reduce storm water runoff. For example, the Shotwell Greenway in the Mission District is a project intended to reduce wet weather flow to overloaded sewers. By replacing hardscape with permeable landscapes, the project reduced storm water runoff to the combined sewer. The project was completed by the San Francisco Department of Public Works in collaboration with the Shotwell Street Neighborhood Association. Current City codes sometimes create barriers to these types of projects. Other cities such as Portland and Seattle have implemented aggressive programs directed at reducing runoff to combined sewer systems. DRAFT - October 1,

8 Technical Memorandum 405 APPENDIX - DEFINITIONS DRAFT - October 1, 2009

9 Technical Memorandum 405 APPENDIX - DEFINITIONS backup - an outflow of combined wastewater from an indoor plumbing fixture (such as floor drain, shower drain, or toilet) caused by blockage or wet weather surcharging in the CSS. outflow - discharge of untreated combined wastewater from sewer manholes, catch basins, sewer vents or any other location other than the permitted CSD outfalls. combined sewer discharges (CSD) The term used in San Francisco planning documents to refer to discharges from the storage/transport facilities to the Bay or Ocean. These discharges have received partial treatment in the storage/transports consisting of screening and settling. combined sewer overflow (CSO) as defined in the Combined Sewer Overflow Control Policy, a discharge of untreated combined wastewater to receiving waters (the Pacific Ocean or San Francisco Bay from any of the CSD outfall structures authorized by NPDES Permits Nos. CA and CA ). sewer cleaning - includes methods such as hydroflushing, root cutting, rodding, bucketing, pigging, or other methods typically used to remove grease, roots, or debris from a sewer pipe. street flooding - inundation of a City street to a depth above the curb with storm runoff or combined wastewater caused by CSS outflows or an inability of the CSS to take in stormwater flowing on the street. wet weather outflows - a CSS outflow caused by surcharging of the CSS during or related to a rain storm. wet weather backups - a backup caused by surcharging of the CSS during or related to a rain storm. DRAFT - October 1, 2009 A-1