Los Amigos Park Water Harvest and Direct Use Project Study Report FINAL November 2014 1561 E. Orangethorpe Avenue, Suite 240 Fullerton, California 92831 TEL (714) 526-7500 | FAX (714) 526-7004 www.cwecorp.com Los Amigos Park Water Harvest and Direct Use Project Study Report FINAL Prepared for: City of Santa Monica Civil Engineering Division 1437 4th Street, Suite 300 Santa Monica, California 90401 TEL (310) 458-8411 Prepared by: 1561 E. Orangethorpe Avenue, Suite 240 Fullerton, California, 92831 TEL (714) 526-7500 | FAX (714) 526-7004 | www.cwecorp.com November 24, 2014 City of Santa Monica Los Amigos Park Water Harvest and Direct Use Project Study Report Table of Contents TABLE OF CONTENTS ................................................................................................................. iii APPENDICES ............................................................................................................................. iv LIST OF FIGURES ...................................................................................................................... iv LIST OF TABLES ......................................................................................................................... iv ACRONYMS ................................................................................................................................. v 1. PROJECT PURPOSE AND SCOPE ......................................................................................... 6 2. EXISTING CONDITIONS ..................................................................................................... 7 2.1 TOPOGRAPHY ........................................................................................................................... 7 2.2 ON-SITE DRAINAGE ................................................................................................................... 8 2.3 TMDLS AND 303(D) LISTINGS ..................................................................................................... 9 2.4 GEOTECHNICAL FINDINGS .......................................................................................................... 10 2.5 UTILITIES .............................................................................................................................. 10 2.6 HISTORICAL LAND USE ............................................................................................................. 11 3. HYDROLOGY AND HYDRAULICS ....................................................................................... 13 3.1 STUDY AREA .......................................................................................................................... 13 3.1.1 Hydrologic Soil Type ...................................................................................................... 14 3.1.2 Land Use ...................................................................................................................... 15 3.1.3 Watershed Delineation .................................................................................................. 16 3.2 RAINFALL - RUNOFF RELATIONSHIP .............................................................................................. 17 3.3 CATCHMENT RUNOFF FLOW RATE AND VOLUME ............................................................................... 18 3.4 HYDRAULIC ANALYSIS ............................................................................................................... 18 3.4.1 Computer Model ........................................................................................................... 18 3.4.2 Manning's n-values ....................................................................................................... 19 3.4.3 Existing Conditions Model Results .................................................................................. 19 4. PROPOSED CONDITIONS .................................................................................................. 20 4.1 WATER QUALITY IMPROVEMENT ALTERNATIVE #1 ........................................................................... 20 4.1.1 Cost Estimate ............................................................................................................... 21 4.2 WATER QUALITY IMPROVEMENT ALTERNATIVE #2 ........................................................................... 22 4.2.1 Cost Estimate ............................................................................................................... 23 4.3 RISK ASSESSMENT ................................................................................................................... 23 4.4 ALTERNATIVE COMPARISON ....................................................................................................... 24 4.5 PUBLIC EDUCATION AND OUTREACH ............................................................................................. 24 5. APPROVALS AND ANTICIPATED REQUIREMENTS ............................................................ 27 5.1 DIVISION OF STATE ARCHITECTS ................................................................................................. 27 5.2 CALIFORNIA COASTAL COMMISSION ............................................................................................. 27 5.3 LOS ANGELES COUNTY HEALTH DEPARTMENT ................................................................................. 28 5.3.1 Irrigation Reuse ............................................................................................................ 28 5.3.2 Toilet Flushing Reuse .................................................................................................... 28 5.4 LOS ANGELES COUNTY FLOOD CONTROL DISTRICT .......................................................................... 28 5.5 SANTA MONICA-MALIBU UNIFIED SCHOOL DISTRICT ........................................................................ 29 5.6 ADDITIONAL REQUIREMENTS ...................................................................................................... 29 6. REFERENCES ..................................................................................................................... 30 - iii - City of Santa Monica Los Amigos Park Water Harvest and Direct Use Project Study Report Appendices Appendix A Hydrologic Calculations using the Time of Concentration Calculator Appendix B Existing LACDPW Hydrology/Hydraulic Calculations and WSPG Hydraulic Model Results Appendix C WSPG Hydraulic Model Output Appendix D Water Quality Results from the Diversion Manhole Appendix E Contact List Appendix F DSA References Appendix G October 13, 2014 Meeting Summary Appendix H California Coastal Commission References Appendix I LACDPH Permit References Appendix J LACFCD Connection Permit References Appendix K City of Santa Monica Permit References List of Figures Figure 2-1 Location Map ..................................................................................................................... 7 Figure 2-2 Topographic Map ............................................................................................................... 8 Figure 2-3 On-Site Drainage ............................................................................................................... 9 Figure 2-4 Sewer, Water, and Storm Drain Utilities............................................................................. 11 Figure 3-1 Los Amigos Park Study Area ............................................................................................. 14 Figure 3-2 Hydrologic Soil Type ........................................................................................................ 15 Figure 3-3 Land Use ......................................................................................................................... 16 Figure 3-4 Longest Flow Path ........................................................................................................... 17 Figure 4-1 Schematic Layout of Project Alternative #1 ....................................................................... 20 Figure 4-2 Schematic Layout of Project Alternative #2 ....................................................................... 22 List of Tables Table 3-1 Land Use Summary ........................................................................................................... 15 Table 3-2 Summary of Rainfall-Runoff Relationships ........................................................................... 17 Table 3-3 Summary of Hydrologic Calculations for the 85th Percentil Rain Event ................................... 18 Table 3-4 Summary of Hydrologic Calculations for the 10-year Rain Event ........................................... 18 Table 3-5 Existing Conditions Summary of Hydraulic Calculations ........................................................ 19 Table 4-1 Preliminary Class D Cost Estimate for Alternative #1 ........................................................... 21 Table 4-2 Preliminary Class D Cost Estimate for Alternative #2 ........................................................... 23 Table 4-3 Project Risk Assessment Summary ..................................................................................... 23 Table 4-4 Pros and Cons for Project Alternatives ................................................................................ 24 - iv - City of Santa Monica Los Amigos Park Water Harvest and Direct Use Project Study Report Acronyms CDS Continuous Deflection Separation CWA Clean Water Act DSA Division of State Architects EGL Energy Grade Line GIS Geographical Information System LACDPH Los Angeles County Department of Public Health LACDPW Los Angeles County Department of Public Works LACFCD Los Angeles County Flood Control District LCP Local Coastal Program LUP Land Use Plan MODRAT Modified Rational Method MSL Mean Sea Level PTSA Parent Teacher Student Association RCP Reinforced Concrete Pipe SMASH Santa Monica Alternative School House SMMUSD Santa Monica-Malibu Unified School District TMDL Total Maximum Daily Load USEPA United States Environmental Protection Agency USGS United States Geological Survey WSE Water Surface Elevation WSPG Water Surface Pressure Gradient - v - City of Santa Monica Los Amigos Park Water Harvest and Direct Use Project Study Report 1. Project Purpose and Scope The Los Amigos Park Water Harvesting and Direct Use Demonstration Project (Project) is undertaken by the City of Santa Monica (City) to demonstrate the effectiveness of harvesting urban runoff for beneficial uses. The harvested urban runoff will replace indoor flushing and a portion of the irrigation demands, which were previously satisfied by potable water supplies. The direct harvest of wet- and dry-weather urban runoff will also aide in the restoration and protection of Santa Monica Bay through the removal of potential pollutants that may be present in runoff. The Project is expected to treat up to 100,000 gallons of stormwater and dry-weather runoff annually. The demonstration project will provide insight into the feasibility of using runoff for non-potable purposes and will provide results on design, installation, water quality improvements, and operation which will be relevant and transferable to other Southern California projects. Benefit-cost analysis and technical knowledge will be obtained to help decision-makers in future water harvesting and water quality projects. Data on water quality will be generated through monitoring of the influent and effluent, which can be used to help water management professionals meet the water quality requirements and TMDLs of downstream water bodies. Results can also be used by public health, building, and safety officials to help implement standards and codes that enhance the implementation of future projects. Upon completion, the Project will provide an innovative water resource which will break down barriers to local water resource development. Los Amigos Park, a combined use public community park and athletic field for the Santa Monica-Malibu Unified School District (SMMUSD), is located in the south-western quadrant of the City. The northwest portion of the park, adjacent to Hollister Avenue, is planned to house the majority of the Project. A Los Angeles County Flood Control District (LACFCD) storm drain runs west, adjacent to the park under 5th Street. The storm drain receives runoff from a 50-acre densely urbanized watershed. Stormwater and dry-weather discharges will be diverted from the storm drain into a pre-treatment system before entering an underground cistern for storage. After passing through a multi-stage treatment, water will be delivered into the adjacent park restrooms for indoor flushing, as well as the park irrigation system. - 6 - City of Santa Monica Los Amigos Park Water Harvest and Direct Use Project Study Report 2. Existing Conditions Los Amigos Park is surrounded by urban development including high- and medium-density housing, educational facilities, and park open spaces. Located in the City of Santa Monica, the park is in close proximity to the City of Los Angeles’ neighborhood of Venice, as well as the Pacific Ocean. Los Amigos Park is adjacent to John Muir Elementary and Santa Monica Alternative School House (SMASH), and is associated with the address 500 Hollister Avenue, Santa Monica, California. The County Assessor’s Parcel Number for the property is 4287-006-900, of which the park occupies the northwest portion, with John Muir Elementary and SMASH occupying the rest of the parcel. The parcel is bound by Hollister Avenue to the north, 6th Street to the east, Ocean Park Boulevard to the south, and 5th Street to the west. Figure 2-1 shows the location of the project site. Figure 2-1 Location Map 2.1 Topography Los Amigos Park is approximately 4 acres, not including John Muir Elementary School, and is fully developed as a recreational field and athletic facility. The park contains a multi-use athletic field, baseball field, tennis courts, basketball court, and handball court. As such, the topography of the Project site is nearly flat, with a very mild slope in the southwest direction. The slope of the site is not continuous with the surrounding area; the northeast edge of the park is below street level, while the southwest edge is offset approximately 2 feet above curb level. The elevation within the park is approximately 70 feet - 7 - City of Santa Monica Los Amigos Park Water Harvest and Direct Use Project Study Report above mean sea level (MSL). Figure 2-2 illustrates 20-foot contours as identified by the United States Geological Survey (USGS) topographic maps (USGS, 2014). Figure 2-2 Topographic Map 2.2 On-Site Drainage Stormwater runoff from Los Amigos Park sheet flows into the unpaved athletic field. The athletic field has several french drains which convey runoff onto 5th Street on the southwest edge of the park. A curb inlet on the corner of 5th Street and Hollister Avenue collects runoff from the park and conveys it to Project No. 578. Project No. 578 is a 45-inch Reinforced Concrete Pipe (RCP) adjacent to the park and a 48-inch RCP downstream of the manhole on 5th Street and Hollister Avenue. Figure 2-3 illustrates the Project's on-site drainage patterns. - 8 - City of Santa Monica Los Amigos Park Water Harvest and Direct Use Project Study Report Figure 2-3 On-Site Drainage 2.3 TMDLs and 303(d) Listings Section 303(d) of the Clean Water Act (CWA) requires the establishment of a list of impaired and threatened waters also known as the 303(d) List. The 303(d) List identifies water bodies where required pollution controls are not sufficient to attain or maintain applicable water quality standards and establishes priorities for development of Total Maximum Daily Loads (TMDLs) based on the severity of the pollution and the sensitivity of the beneficial uses (USEPA, 2012). A TMDL is the maximum amount of specific pollutant that a water body can receive from all sources in addition to a margin of safety while still meeting water quality standards. The Project involves the diversion and use of urban runoff (wet- and dry-weather) that would normally discharge into the Santa Monica Bay, therefore the 303(d) listed water bodies of Santa Monica Beach and Santa Monica Bay are applicable to this project. The Basin Plan for the Coastal Watershed of Los Angeles and Ventura (Basin Plan) defines the water bodies in the Los Angeles and Ventura region and designates beneficial uses for each of the water bodies which impact the development of TMDLs (LARWQCB, 1994). Santa Monica Bay and Beach are designated Recreation 1 (REC-1) and Recreation 2 (REC-2) beneficial uses, meaning that recreational activities occur with and without contact with the water. Additionally, navigation (NAV), commercial and sport fishing (COMM), marine habitat (MAR), wildlife habitat (WILD), migration of aquatic organisms (MIGR), spawning, reproduction, and/or early development (SPWN), and shellfish harvesting (SHELL) beneficial uses are also identified in the Basin Plan. - 9 - City of Santa Monica Los Amigos Park Water Harvest and Direct Use Project Study Report The following impairments, through TMDLs and 303(d) Listings have been identified for the Santa Monica Beaches and/or Bay: TMDLs • Santa Monica Bay Beaches Bacteria TMDL • Santa Monica Bay Nearshore and Offshore Debris TMDL • Santa Monica Bay TMDL for DDTs and PCBs 303(d) Listings • Santa Monica Bay Nearshore and Offshore Fish Consumption Advisory • Santa Monica Bay Nearshore and Offshore Sediment Toxicity The Santa Monica Bay Beaches Bacteria TMDL became effective July 15, 2003 and was reconsidered and modified. The modifications became effective on July 2, 2014. This TMDL protects the beaches from high indicator bacterial counts during both dry- and wet-weather. The Santa Monica Bay Nearshore and Offshore Debris TMDL became effective March 20, 2012 and requires zero trash discharge by May 2020. The Santa Monica Bay TMDL for DDTs and PCBs was established in 2012 by the USEPA and is associated with fish consumption advisories, setting compliance limits for fish tissue. 2.4 Geotechnical Findings The J. Byer Group, Inc. performed geotechnical engineering exploration for Los Amigos Park on June 25 and 27, 2002. The resulting report, Geotechnical Engineering Exploration, Santa Monica Parks Building Replacement Project – Phase I, exhibits geotechnical considerations relevant to the Project. Seven hand auger borings were performed to a maximum depth of 10 feet, with samples obtained throughout the borings. Five borings were performed near the northeast edge of the park, where the restroom, concession stand, and baseball field are located, and the other two borings were performed near the southwest corner of the park. Groundwater was not encountered during any of the seven borings. Earth materials discovered in the borings consisted mainly of fill and disturbed alluvium, consisting of silty sand and light gray to brown sand of high moisture content and medium density. Natural alluvium was found underlying the park, with layers of sand, clayey sand, sandy clay, and clay. The clays encountered were found to be gray to dark gray, moist to very moist, and firm to stiff. Geotechnologies Inc. performed a geotechnical investigation along Ocean Park Boulevard, that included Los Amigos Park, in September 2009 and June 2010, for which the findings were summarized in a geotechnical report (2010). The investigation included two borings within the southern area of the park which encountered fill deposits underlain by alluvium and shallow marine sediments. Groundwater was not encountered during the exploration within the park, but the investigation included a review of the applicable Seismic Hazard Evaluation Report, Plate 1.2, Historically Highest Groundwater Contours which indicated the highest groundwater levels along Ocean Park Boulevard being forty feet below grade. Percolation tests were performed during the geotechnical investigation and found a percolation rate of ½ inch per hour in the underlying native soils Additional soil borings will be required prior to the final design of the Project. The boring(s) must be performed to a depth greater than the proposed system invert, which is dependent on the chosen alternative discussed in Section 4. 2.5 Utilities A review of the utilities in and around Los Amigos Park shows minimal intrusion within the park. The City maintains nine street light fixtures within the park, with connections maintained along 6th Street near Hollister Avenue and a pad mounted cabinet and pull box nearby. Irrigation piping, sourced from water - 10 -
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