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HomeMy WebLinkAbout10-04-2016 Item 09 Wastwater Collection System Capacity Constraints Meeting Date: 10/4/2016 FROM: Carrie Mattingly, Utilities Director Prepared By: David Hix, Deputy Director, Wastewater Jennifer Metz, Utilities Project Manager SUBJECT: WASTEWATER COLLECTION SYSTEM CAPACITY CONSTRAINTS RECOMMENDATION Receive a presentation on the impact of inflow and infiltration on the City’s wastewater collection system and current capacity constraints. DISCUSSION Wet weather capacity constraints were identified in the wastewater collection system during the Wastewater Collection System Infrastructure Renewal Strategy presented to City Council on January 19, 2016. Currently development inquiries are taking place in areas that are impacted by these system capacity constraints. Measures which are being required by the City to create wet weather capacity in these problem areas are causing some confusion and concern. Raising general community awareness about these collection system capacity constraints and communicating, at a high level, what is being done to address the problem is the goal of this study session. Background Clean water is critical for sustaining life and the health of any community, yet people often take for granted the flow of used water (wastewater) out of their homes or businesses. Wastewater, once it disappears down sinks, toilets, floor drains or other outlets, flows through a network of underground sewer pipes (known as the wastewater collection system) making its way to water resource recovery facilities where it is cleaned and safely reused and/or released back to the environment. The City of San Luis Obispo’s wastewater collection system includes 137 miles of sewer lines and 2,900 manholes with the majority of the City’s collection system being six-inch clay pipe. Depending on the topography, wastewater flows to the water resource recovery facility either by gravity or with the assistance of lift stations. Like many older cities, portions (about 13%) of the City’s sewer pipe inventory pre-dates World War II. 18 miles of pipeline currently in service was installed prior to 1940. Some pipe installed in 1910 is still in service, well beyond its expected service life. In addition to the main lines, there are 14,000 private sewer laterals (approximately 172 miles in length) that connect individual properties within the City to the wastewater collection system. These private sewer laterals are the property owner’s responsibility and are not maintained or replaced by the City. 9 Packet Pg. 114 Inflow and Infiltration With Council’s and the ratepayers’ support over the past 25 years, progress has been made in reducing sanitary sewer overflows and service interruptions. Between 2007 and 2015 the community has invested over $25 million in replacement and repair projects that benefit the wastewater collection system. Ongoing comprehensive maintenance activities continue to improve the function of the wastewater collection system. Despite these investments, the City’s collection system and the Water Resource Recovery Facility (WRRF) continue to experience problems associated with excessive wet weather inflow and infiltration. Flows into the City’s collection system and, ultimately, to the WRRF increase from an average of 3.5 million gallons to over 25 million gallons a day when it rains. While it may be of little comfort, this problem is not unique to San Luis Obispo as there are many communities in California, and across the country, dealing with similar inflow and infiltration issues. Additionally, the drought may be exacerbating the problem as tree roots searching for a water source can open up ever-larger cracks in pipes. Because of inflow and infiltration’s impact on the community’s ability to safely convey and adequately treat its wastewater, the City’s Water and Wastewater Element of the General Plan has policies and programs to address it. Inflow and infiltration, often referred to as I&I, describes two distinct mechanisms for how stormwater enters the sewer system. Inflow is water that enters the City’s wastewater collection system at points of direct connection and is usually induced by a rain event. Private residences may have roof, yard area, or foundation drains inappropriately and illegally connected to sanitary sewers. Any extra water flowing into wastewater collection systems from above-ground sources, either intentionally or unintentionally, is referred to as inflow. Infiltration is water that flows through the ground that can seep, trickle, or flow into the wastewater collection system through cracks in sewer mains and/or private sewer laterals. These cracks may be caused by age -related pipe deterioration, loose pipe joints, poor design, installation or maintenance errors, damage, or root infiltration. Water can enter these cracks wherever sewer lines lie beneath groundwater tables or the soil above the sewer system becomes saturated. 9 Packet Pg. 115 Sewer Lateral Ownership. High rates of I&I into sewer pipes exceed the capacity of the wastewater collection system which leads to system backups and/or overflows. Overflows occur at manholes and usually flow to nearby storm drains or creeks. Overflows can also occur at private homes or businesses resulting in property damage. Overflows are of considerable concern to the City and our regional regulatory partners. I&I impacts the efficiency of treatment at the City’s WRRF. Peak wet weather flows require treatment processes and equipment to be sized large enough to handle the peak flows. The biological treatment processes become less effective when these large amounts of water come through into the WRRF thereby increasing the chance of NPDES (National Pollutant Discharge Elimination System) permit effluent violations. Past Studies and Programs A study conducted by the City’s wastewater collection system operators in the early 1990s found that private sewer laterals connected to the City’s wastewater collection system contributed to significant I&I problems. The study’s findings indicated that failures were mostly due to poor installation and pipe construction materials including Orangeburg pipe (a coal tar impregnated wood fiber pipe) or joint failure in clay pipe. Due to I&I problems, the City’s lateral construction standard changed during the 1980s to no longer allow the use of Orangeburg pipe for private sewer laterals. In 1996, to help combat I&I problems, Council approved the Voluntary Service Lateral Investigation and Rehabilitation Program. The program provided around 1,000 reimbursements for lateral repair or replacement due to troublesome Orangeburg pipe, structural deficiencies, and root intrusion. The voluntary program provided free construction permits, free technical advice and a rebate of one-half the cost of replacement or repair up to a maximum of $1,000 per property. Funding for this program was discontinued in 2011 to focus resources on conducting a flow study of the collection system, identifying the areas most impacted by I&I, and completing a holistic strategy (including prioritized pipeline replacements) for the management of the City’s wastewater collection system’s infrastructure. Recent Studies The City concluded two years of flow monitoring and data collection with the com pletion of the Sanitary Sewer Flow Monitoring and Inflow/Infiltration Study in March 2012. This study identified base flows, peaking factors, and capacity issues, such as where surcharging (flow in the pipe is more than the pipe can accommodate) is evident and overflows are possible. Incorporating the flow monitoring data from the study and twenty years of maintenance and pipeline condition data collected in its asset management database, the City completed the Wastewater Collection System Infrastructure Renewal Strategy (Renewal Strategy) and hydraulic modeling in January 2016. 9 Packet Pg. 116 The Renewal Strategy presents a fact-based strategy to guide policy, operations, and asset management planning decisions in an efficient and cost effective manner. The Renewal Strategy included the City’s first hydraulic model of the collection system to evaluate growth, based on growth level ‘realistic’ numbers, planned under the 2014 update to the Land Use Element. The hydraulic model is a useful tool to incorporate changes to the infrastructure and test the impacts of actual wastewater generation volumes proposed by new development as opposed to the planning numbers. The Renewal Strategy and the hydraulic model identified that in some areas of the community, I&I is limiting existing capacity in the collection system to safely accommodate additional “normal” wastewater flow that could otherwise be accommodated in the wastewater collection system. The Renewal Strategy estimated the total cost to upsize sewer mains to address peak wet weather capacity deficiencies at $30 million (Attachment A). The total cost to address all wastewater collection system pipeline deficiencies was estimated at over $47 million. So how does something like this I&I problem, that happens only when it rains, impact the ability to accommodate additional “normal” wastewater flows, especially given the reduced “normal” wastewater flows related to water conservation measures? The City’s wastewater system is highly regulated by state and federal agencies. The Ci ty is mandated by the State of California and regulated under a statewide General Waste Discharge Requirement to implement a Sewer System Management Plan that requires the collection system have adequate capacity to convey peak wet weather sewage flows. The City has been making that assurance through an aggressive maintenance, inspection, and capital program that has invested a total of $37.8 million on wastewater collection system and WRRF capital improvements from 2007 to 2015 with another $19.5 million currently underway. These efforts have reduced the number of overflows resulting from stoppages and rainwater I&I in the past 25 years (with 53 stoppages in 1990 and 21 stoppages in 2015). Progress is being made, but evidence of significant I&I continues to be of concern and private sewer laterals are known major contributors to the I&I problem. In contrast to City sewer mains, privately owned laterals generally are not maintain ed until they fail. The City’s Municipal Code requires the following maintenance: D. Maintenance of House Sewer Connections. The property owner will be responsible for all construction, maintenance, improvements and repairs of the sewer lateral including all house connections, industrial sewers, private sewage disposal systems and appurtenances thereto, now existing or hereafter constructed. Laterals shall be maintained by the owner of the property in a safe and sanitary condition; and all devices or safeguards which are required for the operation thereof shall be maintained in a good working order. If a property In some areas of the community inflow and infiltration impacts may limit the ability for the wastewater collection system to safely accommodate additional “normal” wastewater flow. -based on 2016 Renewal Strategy data 9 Packet Pg. 117 owner fails to maintain the abovementioned wastewater facilities in a safe and sanitary condition, the director may order and require termination of water service to the parcel and all structures connected to the sewer outlet subject to these conditions. The water service shall not be reinstated until the maintenance or installation of appropriate wastewater disposal facilities has been approved by the director. (Ord. 1598 § 1 (part), 2014) Enforcement of private sewer lateral maintenance is difficult because they met the building code when installed, are primarily “out of sight, out of mind,” and while impacting the City with I/I, may result in no maniantence or service issues to the homeowner. Impacted Areas Although I/I is wide spread throughout the City, Attachment A shows areas most impacted by existing capacity deficiencies in the wastewater collection system during peak wet weather. They include the Laguna Lake area, the areas north and south of Foothill west of Santa Rosa Road, areas north of South Street south of the downtown core, areas south of Pismo Street east of Santa Barbara Road and north of the Union Pacific Railroad tracks. These areas of the collection system experience “surcharging”, a condition where the gravity sewers are overloaded beyond its pipe full flow capacity. (See Attachment B) New development may be proposed in these areas of the City that are currently experiencing surcharging of the collection system due to I&I. In some of these cases, the City would not be able to permit the development unless additional capacity is created in the system . While the collection systems for these areas were designed to accept normal flows, the model shows that peak wet weather flows have the potential to overwhelm the system creating system overflows. When these situations occur, the City will work with developers to identify projects, such as sewer lateral replacements, that mitigate the impact of new wastewater flows. In addition, projects that the City may undertake, such as upsizing sewer mains or other capacity building projects, could accommodate wet weather flows and create additional capacity in these impacted areas. In any case, when new development is proposed, the City will evaluate that development to make sure that a given project’s anticipated “normal” wastewater generation will fit in the pipe during wet weather and not further exacerbate a known surcharge condition. Currently, the City is working on a variety of solutions, and is tracking the capacit y created by new infrastructure projects so that information about capacity in the wastewater collection system can be shared with property owners and developers. If a project cannot reasonably offset its incremental impacts on the wastewater collection system, the City would not be able to issue permits to allow construction of the project as allowing such a connection would be in violation of the City’s State Waste Discharge Requirements. Next Steps There is no quick fix for I&I. This will be a long-term, multi-generational, work effort. The work done to-date provides the foundation for a successful path forward and provides tools that allow for adjusting the plan as more information becomes known. A method to efficiently track metrics that will show to what extent I&I is being impacted by efforts taken must be developed. Staff will be submitting CIP recommendations from the Renewal Strategy and its pipeline repair 9 Packet Pg. 118 prioritization for consideration during the upcoming financial planning process. According to the Environmental Protection Agency, private lateral inspection and repair/replacement programs can be an effective way of addressing I&I. Several programs were reviewed as part of the Renewal Strategy. Through a settlement agreement with a third party, staff will be recommending an ordinance requiring inspections of private laterals which may lead to their repair or replacement. These inspections would be triggered by: 1. The sale or transfer of ownership of a property, 2. If two or more overflows within a year occur at a property, or 3. Where an applicant for a planning or building project indicates the addition of sewer flow such as a bedroom or bathroom addition. Staff will also be requesting a voluntary lateral replacement rebate program to assist homeowners with needed or required repairs or replacements for the 2017-19 Financial Plan. Once multiple options to reduce I&I from private laterals have been identified and developed to a point allowing for meaningful discussion, community stakeholder engagement will occur prior to bringing recommendations to Council. In the meantime, the Utilities Department will work with applicants proposing development in impacted areas to identify ways to create additional peak wet weather capacity in the collection system so projects can move forward. The following table provides the range of potential options that Staff will be evaluating to comprehensively address the I&I issue. Table 1: Inflow and Infiltration Reduction Measures Short-term Measures:  Work with developers to create peak wet weather capacity to accommodate new development in capacity constrained areas  Continue to require inspection of private sewer laterals as condition of approval on discretionary projects that generate wastewater Moderate-term Measures:  Develop private sewer lateral rehabilitation program for Council consideration.  Develop ordinance identifying additional triggering events for private sewer lateral inspections for Council consideration.  Develop options or requirements for new development to mitigate new wastewater flows. Long-term Measures:  Sewer main replacement to address capacity constraints as part of Sewer Fund capital improvement program  Continued monitoring of wastewater flows 9 Packet Pg. 119 FISCAL IMPACT This is a study session and there is no fiscal impact associated with it. Fiscal impacts will be developed in conjunction with any I&I program developed for Council consideration. Attachments: a - Pipes Over Capacity b - Capacity Constrained Areas 9 Packet Pg. 120 City of San Luis Obispo                                                                Capacity Evaluation Wastewater Collection System Infrastructure Renewal Strategy                  December 2015        40  Figure 6‐1.   Pipes Over Capacity – Existing PWWF9.a Packet Pg. 121 Attachment: a - Pipes Over Capacity (1458 : Wastewater Collection System Capacity Constraints) EVANSPOLY CANYONLIM A M IO S S ISI E R R A ELM HANSEN OJAI DALY ETO T O N I NI DEER CLARIO N ZACA G U L F H U A S N A DLABIRAGITIBURO NLOOMISROYALBOYSEN KINGOAK EPSEARAZNNOSREPSEJVENTURE ALDE R RAMONA DEL SUR NALLIMcMFEL-MAR ALBERT PINE REDWOOD MAPLE WOODSIDEVI C E N T E IROHZONHAZELGOLDENRODMUGUB A L B O A S E Q U O I A FEE D MI L L HARMON YVERDEDEL NORTE BRANCH A V AL O N SPIT F IR E MARLEN E RACHELDEL MAR HERM O SA PORTOLACUYAMA V E G A TRUCKEE MIS SIONRAFAEL WI LD IN GTULIPPIN E C O V E ADANAC ALPASEO BELLAMONTANANOITISOPXELLEMOBEDFORDJANETHELM AHAYS GAILCRELDNAHERHTDAALTAACNUDNCACHUMA EMPLEOYAWHTAHPNEVADROEERC TKS E AW A R D HOPE LOOMIS TAFT S U N S E T CAUDILL PACIFICALRITA R ANCHOEGNARONELLEE L C A P IT A NEVORGNOTNEBQUAILE L TIG R E MARIPOS A PER K IN S C O R A L YAJCEEL OBELI ASANTA LUCIACAVALIERP AC HE CO WAY PH ILLIPSMIRA SO L CHUP ARROSA CONEJOARALIA LOS PALOSRO SESMITH VENABL E G R E T A WARREN RICARDOVIA ESTEBA NWARDYLIMELAWRENCE MAGNOLIA IRON BARK G EORG ESTENNERCENTER P A R K MASON RUBI OTWALNOGARCI A REBAYSEROMACS WEE N E YNAMNEPS W EE TB A YLEXINGTONBONDPMOLCOFONTANA VILLAGE VILLAGE GARNETTEENILYKSW EST NEW PORTSWYEZACL E A RV I E W PIN N A C L E S C O RD O VA TSACIACFERNAN D EZ A U TO PA R KN ARAJASSATCREEKSIDE SNAPDR AGON HILLC RESTBROOKRAILROADAPRAMOLTISORASUELDOP A R K L A N D PO PPYMcC OLLUM L EM O N IRRAHSAL MONDFR ANC ISFRAM BUESAWILSON LOS VERDESD E V A U L R A N C H WESTMONT SKYLARKBRESSI ABBO TT BIRCH CORRALITOSRICHARDCOLLEGEN E WP O R T MACIRBAC A R LA P E P 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R IA L F IE R O AIRP ORTREKRAPHIND R OC K V IE WSACR A M EN TO A ER O VI STAELLA MURR AYMURRAY TROHSO C E A N A IR E GR ANADABEEBEE BUCH O N C A P IT O LI O MEINECKE W A LNU TSTAFFORD SERPMEAMITCHELLDESCANSOMOR R OMO R R OOS O S SAN LUISC A R ME L STONERIDGE A R C H E R G A R D E N SANDERCOCK MARGARI TA ROUNDHOUSEFOOTHILL DAEMOWT O R O SL ACK HIGH G ALL EO N CUESTAINIRREFS ATSSAJARAN IP OMO PA LM BRIDGE BISHOPBUCKLE Y HATHWAYFREDERICKS M ONTE REYDAORBM A DO N N A PA CI FICOCEANAIRESOUTHW OOD B R O A D NLOCNILM ILLPALMPEACH LEFFO LIV EAICIRTAPPATRIC I ASYD N EYDIABLOHIGHLAND OCEANAIRECALLE JOAQUINRAMONA SUBURBANYERFFEJCERRO ROMAULDO K E N TUCKYSPANISH O A KSBAHIASAN MIGUELBUENA VISTABRITTANYLA LOM A MONTAL B A N SP OR TS C O M P LEX ACCE S S CERRO VIS T A BUENA VISTAPASO ROBLES SANTA MARIA BI N NS LA CITA ENC INO SAN C A R L O SSAN M A T E O PAULI N E EL CERRITOK N OLLTWIN RIDG E M O NT R OSE SAN J O SEPRI NC E T ONP O LY VUE S OUT H P E R IM ETERS A N T A Y NEZ L O O M I SST A NF OR DC 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ADON NAM ADONN A HIGUERALAURELC A LIF O R N I ASAN TA ROSAPISM O F O OTHIL L M A RSH C H OR R O S AN T A RO S A C H O R R OO R C U T T SOUTH G R A N D T A N K F A R M J O H N S O N C A L IF O R N I A BROADSOUTH HIGUERAO S O S ORCUTT HIGUE RA PISM O M ARSH M ONT EREY L O S O SO S V A L L E Y B R O A D SOUTH HIGUERAORROHCJ O HN S O N HIGUERAB R OADFOOTHILL JOHN S ONNOR T H C HOR R OTAN K FARM S AN LUISSANTA BARBARAORCUTT E F G H I J K L M N O P E F G H I J K L M N O P 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20© Copyright 2009 City of San Luis Obispo. All rights reserved. Basemap produced by the GIS Division, City of San Luis Obispo Public Works Department. N S W E MILES ½¾¼1 KILOMETERS ½1 CITY LIMITS Source: City of San Luis Obispo Utilities Department., Wastewater Collections, 2016. Wastewater Collection System Peak Wet Weather Capacity Constrained Areas Due to Inflow and Infiltration 9.b Packet Pg. 122 Attachment: b - Capacity Constrained Areas (1458 : Wastewater Collection System Capacity Constraints) Page intentionally left blank. Wastewater Collection System Capacity Constraints Study Session October 4, 2016 We can’t fit any more Katie! Like the Mississippi River… Wastewater Collection System Capacity Constraints Study Session October 4, 2016 Like the Mississippi River… Wastewater Collection System Capacity Constraints Study Session October 4, 2016 Water Resource Recovery Facility Wastewater Collection 101: City Collection System 137 miles Well-documented condition Regularly maintained and repaired Under streets Private Sewer Laterals 172 miles / ~14,000 connections Condition largely unknown Repaired and replaced at complete failure Under yards Wastewater Collection System Capacity Constraints Study Session October 4, 2016     Wastewater Collection 101: City Collection System 137 miles Well-documented condition Regularly maintained and repaired Under streets Private Sewer Laterals 172 miles / ~14,000 connections Condition largely unknown Repaired and replaced at complete failure Under yards Wastewater Collection System Capacity Constraints Study Session October 4, 2016     City Collection System Since 2007,the City has invested $25 million in upgrades to the collection system Wastewater Collection System Capacity Constraints Study Session October 4, 2016 City Collection System $1.2 million invested annually on collection system maintenance Wastewater Collection System Capacity Constraints Study Session October 4, 2016 Private Sewer Laterals Private system is larger than the City’s system Constructed of inferior materials located under porous surfaces Out of sight out of mind, not inspected or maintained routinely Property owners unaware that they own the lateral until there is a problem Orangeburg Pipe Cracked Clay Lateral with Roots Inflow and Infiltration 101: Wastewater Collection System Capacity Constraints Study Session October 4, 2016 Inflow and Infiltration 101: Inflow is water that enters the City’s wastewater collection system at points of direct connection Infiltration is water that flows through the ground that can seep, trickle, or flow into the wastewater collection system through cracks in sewer mains and/or private sewer laterals Past Studies and Programs Studies in the 1990’s Laterals identified as a major contributor of I&I Voluntary program contributed funding toward replacement of about 1,000 bad residential laterals Significantly reduced overflows and stoppages Wastewater Collection System Capacity Constraints Study Session October 4, 2016 Recent Studies Flow Study completed in 2012 Infrastructure Renewal Strategy completed in 2016 Hydraulic model incorporates land use assumptions from the 2014 LUCE Update for future development Identifies capacity constrained areas Recommends capital improvement projects Includes reduction strategies for inflow and infiltration So why are we talking about this? Inflow and infiltration is wide spread, but certain areas have capacity constraints Wastewater Collection System Capacity Constraints Study Session October 4, 2016Flow Basins Development areas with capacity constraints will require mitigation So why are we talking about this? What can be done? Wastewater Collection System Capacity Constraints Study Session October 4, 2016 Engage stakeholders about the issues and potential solutions/programs to mitigate capacity constraints in identified areas Solutions may be: a flow offset program, contributions toward lateral replacements, or other improvements in the collection system What can be done? Wastewater Collection System Capacity Constraints Study Session October 4, 2016 Sale or transfer of ownership of a property If two or more overflows occur at a property Where an applicant for a planning or building project indicates the addition a bedroom or bathroom that may contribute sewer flow A new ordinance requiring private lateral inspection, repair, or replacement triggered by: What can be done? Wastewater Collection System Capacity Constraints Study Session October 4, 2016 Voluntary Sewer Lateral Rebate Program for homeowners Inflow and Infiltration Wastewater Collection System Capacity Constraints Study Session October 4, 2016 No quick fix Long-term, multi- generational effort