Environmental Task Force SSSMP Summary, September 18, 2011 Scheduled for City Council Approval September 26, 2017

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1 Attachment 1 Environmental Task Force SSSMP Summary, September 18, 2011 Scheduled for City Council Approval September 26, 2017 Sanitary Sewer System Master Plan Summary Points - City s sanitary system has very good system performance Integration of the DCP and other LUCE projections indicates average sewer flows will increase by approximately 10% through build-out Majority of the pipelines meet System Evaluation Criteria Majority of the manholes meet System Evaluation Criteria Collection System has adequate capacity to serve future with certain exceptions Hydraulic Model serves as a valuable tool for future analysis. Additional field data will support validation of CIP projects The sanitary sewer system has minimal potential capacity limitations Integration of SWIP s 1.2 MGD Water Reclamation Plant will provide additional downstream capacity relief City s Net Zero program will benefit overall system capacity however individual new development projects should be included as-is for conservative capacity analysis Current conditions: 1% of existing sewers under capacity Future conditions: 3% of existing sewers under capacity 5 year CIP developed: Description Year 1 Year 2 Year 3 Year 4 Year5 Capacity Improvements $2,000,000 $1,200,000 $1,600,000 $2,000,000 Field Review Services $100,000 $80,000 Pipeline Replacements $900,000 $1,800,000 $1,400,000 $2,920,000 $1,000,000 TOTAL ANNUAL CIP $3,000,000 $3,000,000 $3,000,000 $3,000,000 $3,000,000

2 Background The City of City of Santa Monica (the City) contracted with HDR Engineering, Inc. (HDR) to develop its 2017 Sanitary Sewer System Master Plan (SSSMP). This Master Plan is designed to serve as a roadmap for the City to proactively manage and maintain adequate capacity of the local sanitary sewer system. The primary purpose of this planning document was to evaluate the capacity of the City s existing sanitary sewer system under current conditions, and plan for the capacity required by future conditions associated with a number of new development projects in the City. The City s sewer system consists of a combination of gravity sewers, force mains, monitoring stations and a lift station to help convey sewage to the City of Los Angeles (Los Angeles or LA) Hyperion Wastewater Treatment Plant (HTP). The City s sanitary sewer facilities include approximately 152 miles of pipelines, 2,800 maintenance holes, two permanent flow monitoring and sampling stations and one, 26 million gallons per day (MGD) pumping station, referred to as the Moss Avenue Pump Station (MAPS). The City s system is divided into ten primary service areas or drainage basins, B1 to B10 to collect and convey sewage by gravity towards the ocean for final collection and discharge to Los Angeles for wastewater treatment and disposal. The City s sanitary sewer system is shown on Figure 1. This 2017 SSSMP was prepared to reflect current growth in the City and anticipated future developments, and to provide the City with a tool for planning improvements needed for sanitary sewer collection system infrastructure. These improvements are necessary to accommodate growth within the City and will be implemented within the City s Capital Improvements Program (CIP).

3 Figure 1. City Sanitary Sewer System

4 Current and Projected Sewer Flows To fully understand and plan for the capacity needs of the sanitary sewer system, future flows estimates need to incorporate the changes in sanitary flows from growth, referred to as dry weather sewage flow, and the additional water that enters the sewer system from storm-related events, referred to as wet weather flow. To account for the potential increase and changes in land use and redevelopment density, the City provided a listing of approximately 55 new development opportunities that are filed with the Planning Department. These development projects, including the recently adopted Downtown Community Plan (DCP), and their status in the development process are depicted graphically on Figure 2. The additional sanitary sewer flow associated with these development projects are derived by correlating the applicable sewer discharge factors for the land use types and densities of each development project. Based on these factors, future average dry weather flows are projected to increase by approximately 2.1 million gallons per day (MGD), an increase of approximately 14 percent. Approximately half of this increase is projected to occur in the DCP area. A summary of the average annual existing and future projected flows under dry weather conditions are shown in Table 2.

5 Figure 2. City New Development Project Status

6 Table 2. Sanitary Sewer Flow Projections Existing Flows Conditions Future Conditions Average Flows (MGD) Note: Average annual flows shown herein exclude areas of the City that do not discharge sewage to City facilities, and the impact of other future flow reducing programs described herein. It is important to note that the City has adopted a number of activities to continue to support its sustainability goals and minimize its local footprint. Foremost among these programs is the recently adopted Water Neutrality Program and the programmatic efforts of a Sustainable Water Infrastructure Project (SWIP). Each of these programs will affect the projected overall increase in sewer flows shown in Table ES-2, and are summarized below. Water Neutrality Program In May 2017, the Santa Monica City Council adopted a Water Neutrality Ordinance to require that new development offset water use on site or off site, or alternately, pay the City an in-lieu fee to fund retrofitting of plumbing fixtures offsite. The ordinance would not allow a new development to exceed the water use of the existing development on that property. If that requirement could not be met onsite, the excess water demand would have to be offset by reducing the water demand (through fixture replacement) at other sites within the City. Given this water neutrality requirement, much if not all of the projected overall increase in future sewage flow should be offset through this growth funded plumbing fixture retrofit program. It should be noted that while this water neutrality program may offset an increase in overall sewage flows, the program does allow for an increase in flows at any specific site. With this program provision, some of the large future developments could still have a substantial point load increase in sewage discharges. To plan for this potential increase associated with these developments and to assure adequate capacity in the sanitary sewer system collection system network, the impact of site specific increases have been incorporated in the hydraulic model. Proceeding in this manner, the impact of new development is conservatively included in the system capacity assessment to reduce the risk of sanitary sewer overflows throughout the City and in the Downtown Community Plan area. SWIP Water Reclamation Facility (WRF) The City of Santa Monica Sustainable Water Infrastructure Project (SWIP) is comprised of three elements which are integrated to provide for treatment and conjunctive reuse of brackish/saline impaired groundwater, recycled municipal wastewater, and stormwater

7 runoff. In addition, the SWIP will help improve the water quality in the Santa Monica Bay by increasing non-point source control. The three elements of the City s SWIP program are: SWIP Element 1: Brackish/Saline Impaired Groundwater Reuse, SWIP Element 2: Recycled Water Production and Conjunctive Reuse, and SWIP Element 3: EWMP Stormwater Harvesting and Reuse. It is SWIP Element 2 that has the greatest benefit to the City s sanitary sewer system as it will be designed to recycle approximately 1 MGD of its municipal wastewater for local reuse. The planning and long-term funding of this new underground water reclamation facility (WRF) is well underway, with the final plant being sited near the Civic Auditorium. When completed, this WRF will benefit the City s sanitary sewer system by removing approximately 1.2 MGD of sewage from the 39-inch/54-inch sewer pipelines near Ocean Avenue, and return only 0.2 MGD of sludge and brine from the WRF to an 18-inch line near Pico Blvd. and 3 rd Street. The removal of the 1 MGD of flow will provide additional pipeline capacity from the WRF to the City s outfall, and reduce the cost of wastewater treatment and disposal currently charged by the City of Los Angeles. The projected configuration of the new SWIP WRF is shown in Figure 3. Figure 3 - SWIP Projected Flow Diversion and Disposal Plan

8 System Analysis, Findings and Recommendations An integral element of the Master Plan was the development and deployment of a temporary flow monitoring program at strategic locations throughout the City. In addition to the City s permanent flow meter data, 12 temporary flow meters were installed. This temporary flow monitoring program was conducted in April 2016, measuring 5-minute intervals throughout the dry weather flow monitoring period at the 12 locations. Flow meter data collected by the 12 temporary meters were also used along with permanent flow meter data to develop diurnal patterns, unit generation rates, and calibration data points for the hydraulic model. Field survey services were also performed to collect elevation information that was required to develop the City s updated hydraulic model. As part of the Master Plan, approximately 200 locations were field surveyed for the collection of elevation data for the City s maintenance holes and pipe inverts. This information, combined with field survey data obtained in the 2011 study, was used to improve the accuracy of the sewer system hydraulic model. To support the evaluation of the City s sanitary sewer system for both existing and build-out conditions, a hydraulic model was developed. The hydraulic model development activities included a comprehensive review of the GIS/SCADA/Billing data, sewer flow analysis and allocation, elevation extraction for the model facilities based on survey data, diurnal pattern assignments, analysis of dry and wet weather peaking factors and model calibration based on flow monitoring data. The calibrated sanitary sewer system hydraulic model was used to perform a comprehensive capacity analysis of the sewer system under current and build-out conditions. These modeling simulations determined the adequacy of the system capacity under dry weather and wet weather conditions, and subsequently identified potential improvements. Capital improvement projects were identified to support the City in its planning and budgeting processes. In summary, the analysis found the City s sanitary sewer system performs exceedingly well and there are very limited areas where the hydraulic capacity of the existing sewer system may fall short of the applicable evaluation criteria for both depth of flow in the pipeline or level of flow surcharging in a sewer maintenance hole. Under existing conditions, approximately 1% of the system may experience a capacity shortfall. In utilizing the model to simulate future build out conditions, the City s sewer system continues to perform well. In fact, under future conditions, only 3% of the modeled pipelines exceeded the evaluation depth of flow criteria. During the development of the City s sanitary sewer system Capital Improvement Program (CIP), the recommended improvement projects were classified into the following categories, Table 3: Priority 1: Priority 2A: Facilities with model predicted capacity limitations under existing conditions scenario. Potential Capacity-Related Improvements are provided in Figure 4 Field verification candidates requiring additional facility information. Priority 2B: Field verification candidates requiring additional flow information. Priority 3: Facilities with model predicted capacity limitation under future conditions scenario

9 Priority 4: Facilities identified by the City as replacement candidates and warrant additional attention or replacement under the City s programmatic facility condition assessment and replacement program. Figure 4. Summary of Potential Capacity-Related Improvements Table 3 Potential Capacity-Related Improvement Projects CIP Priority Total Pipe Length (feet) CIP Year 1 (Existing Conditions Capacity Projects) 2A (Field Facility Information Verification 5,800 Year 1 3,000 Year 1, 2 2B (Flow Verification) 4,650 Year 3, 4 3 (Future Capacity Projects) 5,750 Year 5

10 The recommended capacity improvement-related projects include required capacity expansions of the existing system to convey future/ultimate flows under design flow conditions. The resulting capacity improvement projects are prioritized by considering the following factors: Model-predicted overflows Model-predicted surcharging Reported recurring overflows In addition to the capacity-related facility improvement recommendations, the City maintains an ongoing asset management program to facilitate the programmatic assessment of facility condition and replacement. Through this program, the City has identified a number of pipeline segments that warrant additional attention or are in need of replacement. The location of these pipelines are shown on Figure 5. Figure 5. Summary of Condition-Related Improvements The condition related improvements shown represent approximately 52,000 ft., with a cost to replace of approximately $18.3 million. As an element of the City s Pipeline (Main) Replacement Program, these City-identified pipelines are flagged with a higher risk of failure, and should receive priority funding under the sewer main replacement program activity. Discussions with City staff suggest these improvements could be phased in over the next 12 years. It is recommended that as part of the City s CIP, candidate projects be selected from this list based on other water main replacements/street paving projects to help the City align their replacement program with other Departments.

11 Table 4 summarizes the recommended costs for the annual CIP recommendations over the next 5 years to meet the needs in the improvement categories. Of note, the 5-year CIP shown herein is designed to combine the various improvements under the currently budget $3 Million per year Main Replacement Program. With no additional funding required, this improvement program could be seamlessly integrated in the City s available CIP resources. Table 4. 4-Year CIP Summary Description Year 1 Year 2 Year 3 Year 4 Year5 Capacity Improvements $2,000,000 $1,200,000 $1,600,000 $2,000,000 Field Review Services $100,000 $80,000 Pipeline Replacements $900,000 $1,800,000 $1,400,000 $2,920,000 $1,000,000 TOTAL ANNUAL CIP $3,000,000 $3,000,000 $3,000,000 $3,000,000 $3,000,000