Los Amigos Park Project Study Report

185 Pages·2014·8.46 MB·English

Los Amigos Park Water Harvest and
Direct Use Project Study Report
FINAL
November 2014
1561 E. Orangethorpe Avenue, Suite 240
Fullerton, California 92831
TEL [phone] | FAX [phone]
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 [phone]

Prepared by:

1561 E. Orangethorpe Avenue, Suite 240
Fullerton, California, 92831

TEL [phone] | FAX [phone] | 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
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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

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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

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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.

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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
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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.

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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.

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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
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