Item 6 - GSI Plan
PREPARED BY: Matt Morley
Parks and Public Works Director
Reviewed by: Town Manager, Assistant Town Manager and Town Attorney
110 E. Main Street Los Gatos, CA 95030 ● 406-354-6832
www.losgatosca.gov
TOWN OF LOS GATOS
COUNCIL AGENDA REPORT
MEETING DATE: 08/20/2019 ITEM NO: 6
DATE: August 14, 2019
TO: Mayor and Town Council
FROM: Laurel Prevetti, Town Manager
SUBJECT: Adopt a Resolution approving the Town’s Green Stormwater Infrastructure
Plan to Demonstrate a Long-term Commitment to the Implementation of
Green Stormwater Infrastructure Facilities in the Town, as Required by the
Town’s Municipal Regional Stormwater Permit (MRP)
RECOMMENDATION:
Adopt a Resolution approving the Town’s Green Stormwater Infrastructure (GSI) Plan to
demonstrate a long-term commitment to the implementation of Green Stormwater
Infrastructure facilities in the Town, as required by the Town’s Municipal Regional Stormwater
Permit (MRP).
BACKGROUND:
California cities are required to meet the State’s Clean Water Program permit requirements.
Each city in Santa Clara County participates as a permittee member of the Santa Clara Valley
Urban Runoff Pollution Prevention Program (SCVRPPP) and must comply with the requirements
established by the San Francisco Bay Regional Water Quality Control Board (Board). One of
these requirements is Provision C.3.j, which requires the Town to develop and implement a
long-term Green Stormwater Infrastructure (GSI) Plan for the inclusion of “Low Impact
Development” (LID) measures, including site design, pollutant source control, stormwater
treatment, and flow control features into storm drain infrastructure on public and private lands,
including streets, roads, storm drains, parking lots, building roofs, and other elements.
The GSI Plan is the result of a coordination effort led by the West Valley Clean Water Authority
(WVCWA) JPA to assist in the preparation of the Plan for the West Valley communities of Los
Gatos, Campbell, Saratoga, and Monte Sereno. Together, the four municipalities partnered
with EOA, Inc. to prepare their respective plans. EOA is the Town’s stormwater peer review
PAGE 2 OF 3 SUBJECT: Adopt a Resolution approving the Town’s Green Stormwater Infrastructure Plan to Demonstrate a Long-term Commitment to the Implementation of Green Stormwater Infrastructure Facilities in the Town, as Required by the Town’s Municipal Regional Stormwater Permit (MRP) DATE: August 14, 2019
BACKGROUND (continued):
consultant and develops documents, standards, guidelines and handbooks on behalf of all
Santa Clara Valley Urban Runoff Pollution Prevention Program (SCVURPPP) permittees.
The GSI Plan must be completed and submitted to the Board by September 30, 2019 and must
describe the jurisdiction’s goals, targets, and priorities, and identify the resources needed for
implementing GSI into projects over a 20-year time frame (2020 to 2040). The precursor to this
plan was the Green Infrastructure Plan Framework, a workplan that guided the Town in the
development of the Plan that the Town Council authorized the Town Manager to execute on
June 20, 2017.
DISCUSSION:
GSI provides for the filtering and cleaning of stormwater runoff through the construction of
infrastructure, such as biotreatment, rainwater harvesting, and pervious pavement. The GSI
Plan includes a project identification and prioritization mechanism to assist in identifying
projects within which these measures, elements, and features should be included, and which
can then be incorporated into a municipality’s long-term planning and capital improvement
processes. As a result, local jurisdictions will need to include the additional infrastructure in
improvement projects and maintain that infrastructure over time. These improvements will
necessitate increased scope on many capital projects and will likely increase the cost of these
projects. At this point, no additional funding is anticipated for these elements.
It should be noted that many private projects already include these elements through
compliance with section C3 of the Stormwater Permit.
CONCLUSION:
Approval will allow for continued progress in compliance with the Town’s stormwater permit.
COORDINATION:
This report has been coordinated with the West Valley Clean Water Program.
FISCAL IMPACT:
There is no fiscal impact from this action.
PAGE 3 OF 3 SUBJECT: Adopt a Resolution approving the Town’s Green Stormwater Infrastructure Plan to Demonstrate a Long-term Commitment to the Implementation of Green Stormwater Infrastructure Facilities in the Town, as Required by the Town’s Municipal Regional Stormwater Permit (MRP) DATE: August 14, 2019
ENVIRONMENTAL ASSESSMENT:
This is not a project defined under CEQA, and no further action is required.
Attachments:
1. Resolution to approve the Town’s Green Stormwater Infrastructure (GSI) Plan
2. Draft Green Stormwater Infrastructure Plan
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Resolution 2019 - August 20, 2019
ATTACHMENT 1
RESOLUTION 2019-
RESOLUTION OF THE TOWN COUNCIL
OF THE TOWN OF LOS GATOS
TO APPROVE THE TOWN’S
GREEN STORMWATER INFRASTRUCTURE (GSI) PLAN TO DEMONSTRATE A
LONG-TERM COMMITMENT TO THE IMPLEMENTATION OF GREEN STORMWATER
INFRASTRUCTURE FACILITIES IN THE TOWN
WHEREAS, the Town of Los Gatos is a permittee under the San Francisco Bay Regional
Water Quality Control Board’s Municipal Regional Permit (MRP) that regulates stormwater
discharges from municipal storm drain systems throughout Santa Clara Valley; and
WHEREAS, the Town of Los Gatos is a member of the Santa Clara Valley Urban Runoff
Pollution Prevention Program (SCVURPPP), and implements the MRP in collaboration with
other members of SCVURPPP; and
WHEREAS, Provision C.3.j of the MRP requires each permittee to develop and
implement a Green Stormwater Infrastructure Plan that demonstrates how permittees will
utilize “Low Impact Development” (LID) measures for a more sustainable storm drain system
comprised of “green” infrastructure, which captures, stores, and treats stormwater using
natural processes and recreates the predevelopment hydrology and landscape features of a
project site; and
WHEREAS, all permittees under the MRP are required to complete and submit a Green
Stormwater Infrastructure Plan to the Regional Water Quality Control Board by September 30,
2019; and
WHEREAS, the attached Green Stormwater Infrastructure Plan guides the identification,
implementation, tracking, and reporting of green stormwater infrastructure projects within the
Town of Los Gatos over a long-term period of time; and
WHEREAS, the Town of Los Gatos is committed to complying with the requirements of
the MRP as established by the San Francisco Bay Regional Water Quality Control Board, and the
implementation of sustainable approaches and practices within the Town.
NOW, THEREFORE, BE IT RESOLVED that the Town Council of the Town of Los Gatos
does hereby adopt the Town of Los Gatos Green Stormwater Infrastructure Plan to achieve a
more sustainable stormwater management system.
2 of 2
Resolution 2019 - August 20, 2019
ATTACHMENT 1
PASSED AND ADOPTED at a regular meeting of the Town Council of the Town of Los
Gatos, California, held on the 20th day of August 2019 by the following vote:
COUNCIL MEMBERS:
AYES:
NAYS:
ABSENT:
ABSTAIN:
SIGNED:
MAYOR OF THE TOWN OF LOS GATOS
LOS GATOS, CALIFORNIA
DATE: __________________
ATTEST:
TOWN CLERK
LOS GATOS, CALIFORNIA
DATE: __________________
ATTACHMENT 2
Town of Los Gatos
Green Stormwater Infrastructure Plan
DRAFT
Approved on: August 20, 2019
Approved by: The Town Council of the Town of Los Gatos
Prepared by:
Town of Los Gatos
110 East Main Street
Los Gatos, CA 95030
In compliance with Provision C.3.j.i.(2) of Order R2-2015-0049, NPDES Permit No. CAS612008
ATTACHMENT 2
ACKNOWLEDGEMENTS
The Town of Los Gatos gratefully acknowledges the following individuals and organizations that
contributed to this Green Stormwater Infrastructure Plan:
Town of Los Gatos
Parks and Public Works Department
• Jim Harbin
• Mike Weisz, P.E
West Valley Clean Water Authority
• Sheila Tucker
• Julie Schaer
EOA, Inc.
• Jill Bicknell, P.E.
• Vishakha Atre
• Liesbeth Magna
The Town would like to thank and acknowledge the City of Palo Alto, City of San Jose and City of
Campbell for sharing text from their Green Stormwater Infrastructure Plans.
Town of Los Gatos
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Table of Contents
EXECUTIVE SUMMARY .................................................................................................................................. v
1. INTRODUCTION ..................................................................................................................................... 1
Purpose and Goals of the GSI Plan ................................................................................................ 1
Town Description .......................................................................................................................... 1
1.2.1 Land Use ................................................................................................................................ 2
1.2.2 Population and Growth Projections ...................................................................................... 2
1.2.3 Transportation and Street Types: ......................................................................................... 3
1.2.4 Water Resources and Water Supply: .................................................................................... 3
1.2.5 Flood Potential ...................................................................................................................... 3
1.2.6 Stormwater Drainage System: .............................................................................................. 4
1.2.7 Open Space, Agriculture and Vacant Land: ........................................................................... 4
Regulatory Context ....................................................................................................................... 4
1.3.1 Federal and State Regulations and Initiatives ....................................................................... 4
1.3.2 Municipal Regional Stormwater Permit ................................................................................ 5
GSI Plan Development Process ..................................................................................................... 6
1.4.1 Regional Collaboration .......................................................................................................... 6
1.4.2 GSI Plan Development and Adoption.................................................................................... 6
1.4.3 Education and Outreach ....................................................................................................... 7
GSI Plan Structure and Required Elements ................................................................................... 8
2. WHAT IS GREEN STORMWATER INFRASTRUCTURE? .......................................................................... 10
Green Stormwater Infrastructure ............................................................................................... 10
Benefits of Green Stormwater Infrastructure ............................................................................. 10
Types of Green Stormwater Infrastructure Facilities.................................................................. 11
2.3.1 Biotreatment/Bioretention ................................................................................................. 11
2.3.2 Stormwater Tree Well Filters and Suspended Pavement Systems ..................................... 11
2.3.3 Pervious Pavement ............................................................................................................. 12
2.3.4 Infiltration Facilities ............................................................................................................ 13
2.3.5 Green Roofs......................................................................................................................... 13
2.3.6 Rainwater Harvesting and Use ............................................................................................ 14
3. INTEGRATION WITH OTHER PLANNING DOCUMENTS ....................................................................... 15
Town Planning Document Review .............................................................................................. 15
3.1.1 General Plan ........................................................................................................................ 15
3.1.2 Sustainability Plan ............................................................................................................... 15
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3.1.3 Bicycle and Pedestrian Master Plan .................................................................................... 16
3.1.4 North Forty Specific Plan ..................................................................................................... 16
3.1.5 Hillside Specific Plan ............................................................................................................ 16
3.1.6 Albright Specific Plan .......................................................................................................... 16
Workplan for Integrating GSI Language into Existing and Future Town Planning Documents .. 16
Regional Plans ............................................................................................................................. 17
3.3.1 Santa Clara Basin Stormwater Resource Plan ..................................................................... 17
3.3.2 Valley Water’s One Water Plan ........................................................................................... 17
3.3.3 Bay Area Integrated Regional Water Management Plan .................................................... 18
4. GSI DESIGN GUIDELINES, DETAILS, AND SPECIFICATIONS .................................................................. 19
Design Guidelines ........................................................................................................................ 19
Details and Specifications ........................................................................................................... 19
Incorporation of SCVURPPP Details and Specifications into Town Standards ............................ 19
5. GSI PROJECT PRIORITIZATION AND IMPERVIOUS TARGETS ............................................................... 21
Project Types ............................................................................................................................... 21
5.1.1 Early Implementation Projects ............................................................................................ 21
5.1.2 Regulated Projects .............................................................................................................. 21
5.1.3 LID Projects ......................................................................................................................... 21
5.1.4 Regional Projects ................................................................................................................. 21
5.1.5 Green Street Projects .......................................................................................................... 22
Identification and Prioritization Process ..................................................................................... 22
5.2.1 Step 1: Stormwater Resource Plan Prioritization ............................................................... 22
5.2.2 Step 2: Town-Specific Prioritization .................................................................................... 26
Specific Plan Areas .............................................................................................................................. 26
Green Stormwater Infrastructure in Industrial Areas ......................................................................... 26
Prioritization Output ................................................................................................................... 26
6. GSI IMPLEMENTATION PLAN .............................................................................................................. 30
Town-wide GSI Strategy .............................................................................................................. 30
Process for Identifying and Evaluating GSI Project Opportunities ............................................. 30
Workplan for Early Implementation Projects ............................................................................. 31
Legal Mechanisms for GSI Implementation ................................................................................ 31
Evaluation of Funding Options .................................................................................................... 32
6.5.1 Current Funding Sources for GSI Program Elements .......................................................... 32
6.5.2 Potential Future Funding Options ....................................................................................... 32
Impervious Area Targets ............................................................................................................. 37
6.6.1 Methodology ....................................................................................................................... 37
6.6.2 Results ................................................................................................................................. 37
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6.6.3 Impervious Surface Retrofit Targets ................................................................................... 38
Project Tracking System .............................................................................................................. 41
6.7.1 SCVURPPP Project Tracking System .................................................................................... 41
6.7.2 Town Project Tracking System (Regulated and GSI) ........................................................... 41
LIST OF TABLES
Table 1-1 Land Uses within the Town of Los Gatos ...................................................................................... 2
Table 1-2 Summary of GSI Plan Elements required by Provision C.3.j.i of the MRP .................................... 8
Table 5-1 Screening factors for parcel-based and right-of-way project opportunities .............................. 23
Table 6-1 Potential GSI Funding Options .................................................................................................... 33
Table 6-2 Projected cumulative land area (acres) anticipated to be addressed via GSI facilities via private
redevelopment in the Town of Los Gatos by 2020, 2030, and 2040 .......................................................... 38
Table 6-3 Actual (2002-2018) and predicted (2019-2040) extent of impervious surface retrofits via GSI
implementation on private and public parcels in the Town of Los Gatos by 2020, 2030, and 2040 ......... 40
LIST OF FIGURES
Figure 2-1 Stormwater curb extension, Hacienda Avenue, Campbell (Source: City of Campbell) ............. 11
Figure 2-2 Stormwater tree well filter conceptual examples: modular suspended pavement system (left),
column suspended pavement system (right). (Courtesy of City of Philadelphia Water Department) ....... 12
Figure 2-3 Permeable Pavers, Mayfield Playing Fields, Palo Alto (Source: City of Palo Alto) ..................... 12
Figure 2-4 Infiltration trench, San Jose (Source: City of San Jose) .............................................................. 13
Figure 2-5 Subsurface infiltration system, (Source: Conteches.com) ......................................................... 13
Figure 2-6 Green Roof at Fourth Street Apartments, San Jose (Source: EOA) ........................................... 13
Figure 2-7 Rainwater Harvesting cistern, Environmental Innovation Center, San Jose (Source: City of San
José) ............................................................................................................................................................ 14
Figure 2-8 Subsurface vault for rainwater harvesting, under construction (Source: Conteches.com) ...... 14
Figure 5-1 Town of Los Gatos Public Parcels and Street Segments with GSI Opportunities (Source: Santa
Clara Basin SWRP) ....................................................................................................................................... 25
Figure 5-2 Town of Los Gatos Specific Plan Areas (Source – Town of Los Gatos General Plan) ................. 27
Figure 5-3 Town of Los Gatos Old Industrial Areas (industrial areas developed prior to 1980) (Source:
SCVURPPP) .................................................................................................................................................. 28
Figure 5-4 Town of Los Gatos GSI Opportunities Overview ........................................................................ 29
Figure 6-1. Existing and projected cumulative land area (acres) anticipated to be addressed via GSI
facilities installed via private redevelopment in the Town of Los Gatos by 2020, 2030, and 2040 ........... 38
LIST OF APPENDICES
Appendix A – GSI Project Prioritization Metrics
Appendix B – Street Segments and Parcels in Los Gatos with Opportunities for GSI
Appendix C – Guidance for Identifying Green Infrastructure Potential in Municipal Capital Improvement
Program Projects
Town of Los Gatos
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LIST OF ACRONYMS
ABAG Association of Bay Area Governments
BASMAA Bay Area Stormwater Management Agencies Association
BPMP Los Gatos Bicycle and Pedestrian Master Plan
Caltrans California Department of Transportation
CASQA California Stormwater Quality Association
CIP Capital Improvement Program
DOF California Department of Finance
EIR Environmental Impact Report
EPA Environmental Protection Agency
FY Fiscal Year
GI Green Infrastructure
GHG Greenhouse Gas
GIS Geographic Information System
GSI Green Stormwater Infrastructure
IRWMP Bay Area Integrated Regional Water Management Plan
LID Low Impact Development
MRP Municipal Regional Stormwater NPDES Permit
MS4 Municipal Separate Storm Sewer System
MTC Metropolitan Transportation Commission
NPDES National Pollutant Discharge Elimination System
O&M Operation and Maintenance
PDA Priority Development Areas
PCBs Polychlorinated Biphenyls
PICP Permeable Interlocking Concrete Pavers
PP Permeable Pavers
Regional Water Board San Francisco Bay Regional Water Quality Control Board
SCVURPPP Santa Clara Valley Urban Runoff Pollution Prevention Program
SJWC San Jose Water Company
State Water Board State Water Resources Control Board
STORMS Strategy to Optimize Resource Management of Stormwater
SWRP Storm Water Resource Plan
SWRCB State Water Resource Control Board
Town Town of Los Gatos
Valley Water Santa Clara Valley Water District
Water Board San Francisco Bay Regional Water Quality Control Board
WVCWA West Valley Clean Water Authority
Town of Los Gatos
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EXECUTIVE SUMMARY
The purpose of the Town of Los Gatos’ (Town) Green Stormwater Infrastructure (GSI) Plan is to describe
how the Town will gradually integrate GSI features into its urban landscape and stormwater conveyance
systems over several decades. GSI uses vegetation, soils, and natural processes to manage stormwater
runoff by utilizing “Low Impact Development” (LID) measures for a more sustainable storm drain system
comprised of “green” infrastructure, allowing runoff to soak into the ground and be filtered by soil via
infiltration. These facilities and features capture, store and treat stormwater using natural processes
and recreates the predevelopment hydrology and landscape features of a particular project site.
The Town, as with other municipalities and agencies in the San Francisco Bay Area, is subject to the
requirements of the Municipal Regional Stormwater National Pollutant Discharge Elimination System
Permit (MRP), which became effective on January 1, 2016. Provision C.3.j of the MRP requires that
Permittees develop and implement a long-term GSI Plan for the inclusion of GSI measures into storm
drain infrastructure on public and (sometimes) private property, including streets, roads, parking lots,
roofs, and other elements. This Plan must also demonstrate the Town’s long-term commitment to GSI
implementation to help reduce loads of pollutants of concern (e.g., mercury and PCBs) discharged to
local waterways (per MRP requirements). The Plan must be completed, approved and submitted to the
San Francisco Bay Regional Water Quality Control Board by September 30, 2019.
This Plan describes the Town’s methodology to identify and prioritize areas for implementing GSI and
estimates targets for the extent of the Town’s area that will be addressed by GSI through the year 2040.
The Plan includes maps of the Town’s potential project opportunities and lays out the Town’s GSI
implementation strategy. Key mechanisms of the strategy include coordination with GSI regulations for
private development projects to identify opportunities in adjacent public rights-of-way; identification of
GSI opportunities in capital improvement projects; and aligning GSI goals and policies with other Town
planning documents to achieve multiple benefits while also providing safer, sustainable, and attractive
public streetscapes. The Plan contains guidance and standards for GSI project design and construction
and describes how the Town will track and map constructed GSI projects while also making the
information available to the public. Lastly, it explains existing legal mechanisms for implementation of
the GSI Plan, and identifies potential sources of funding for the design, construction, and maintenance
of GSI projects.
Town of Los Gatos
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1. INTRODUCTION
Urban development has traditionally involved replacing natural landscapes with solid pavements and
buildings, and using storm drain systems to carry increased amounts of stormwater runoff and
pollutants directly into local streams. Green stormwater infrastructure (GSI), however, uses plants and
soils to mimic natural watershed processes, capture stormwater and create healthier environments. Bay
Area cities and counties are required by State and regional regulatory agencies to move from traditional
(grey) stormwater conveyance systems to GSI systems over time. This GSI Plan serves as an
implementation guide for the Town of Los Gatos (Town) to incorporate GSI into storm drain
infrastructure on public and private lands where feasible over the next several decades.
Purpose and Goals of the GSI Plan
The purpose of the Town’s GSI Plan is to demonstrate the Town’s commitment to gradually transform its
traditional storm drainage infrastructure to green stormwater infrastructure. The GSI Plan will guide the
identification, implementation, tracking, and reporting of green stormwater infrastructure projects
within the Town. The GSI Plan will be coordinated with other Town plans, such as the General Plan, Safe
Routes to School Report and the Bicycle and Pedestrian Master Plan, to achieve multiple potential
benefits to the community, including improved water and air quality, reduced local flooding, increased
water supply, traffic calming, safer pedestrian and bicycle facilities, climate resiliency, improved wildlife
habitat, and a more pleasant urban environment.
Specific goals of the GSI Plan are to:
• Align the Town’s goals, policies and implementation strategies for GSI with the General Plan and
other related planning documents;
• Identify and prioritize GSI opportunities throughout the Town;
• Establish targets for the extent of Town area to be addressed by GSI over certain timeframes;
• Provide a workplan and legal and funding mechanisms to implement prioritized projects; and
• Establish a process for tracking, mapping, and reporting completed projects
Town Description
The Town of Los Gatos occupies approximately 11.5 square miles and is located approximately fifty (50)
miles south of San Francisco in Santa Clara County. Los Gatos is bounded on the north by the City of
Campbell, south by the Santa Cruz Mountains and unincorporated Santa Clara County, east by the City
of San Jose and west by the Cities of Monte Sereno and Saratoga. Los Gatos is characterized by hilly
terrain located on the lower slope of the Santa Cruz Mountains at an elevation of 344 feet.
The Town incorporated in 1887 and has a jurisdictional area of 7,335 acres. In 2010, the Town had a
population of 30,802, with a population density of 2,635 people per square mile and average household
size of 2.35. As of 2019, according to the California Department of Finance (DOF)1, the estimated
population for Los Gatos is 30,988.
1 Source: State of California, Department of Finance, E-1 Population Estimates for Cities, Counties and the State with Annual Percent Change —
January 1, 2018 and 2019. Sacramento, California, May 2018. Online at http://www.dof.ca.gov/Forecasting/Demographics/Estimates/e-1/.
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Los Gatos is home to Netflix, Roku and over 3,700 businesses, which serve residents and draw visitors to
the restaurants, hotels, and shops within a pedestrian-oriented downtown setting. The Town provides
excellent schools, a vibrant Downtown, dynamic neighborhood and diverse shopping experiences and
also features many parks and greenbelt areas. Downtown Los Gatos is listed on the National Register of
Historic Places and is the model of what communities strive to achieve in a downtown. Additional Town
characteristics are provided in the following subsections.
1.2.1 Land Use
Los Gatos is predominantly built-out. Land uses within the Town, as defined in the General Plan, are
provided in Table 1-1. The Town is primary comprised of low-density residential land uses. Los Gatos has
approximately 4,329 acres of woodland/forest communities, including riparian woodlands, oak
woodlands, broadleaved upland forest, and non-native ornamental trees, that support a very green
environment. Other land uses include commercial, office, light industrial, K-12 schools, open space and
urban parks.
Table 1-1 Land Uses within the Town of Los Gatos
Land Use Category Acres Percent of Town
Acreage
Residential – Single Family 5,911 51.2%
Residential – Multi-Family 407 6.5%
Commercial 164 2.6%
Office Professional 126 2%
Light Industrial 37 0.6%
Public/Quasi-Public 440 4.7%
Public Utilities 39 0.5%
Agricultural 112 1%
Open Space/Recreation 3,841 26.2%
Vacant 399 4.7%
Total 11,476 100%
1.2.2 Population and Growth Projections
The Town of Los Gatos is primarily a built-out community with few opportunities for new large-scale
development to occur. The Town established growth/development forecasts as part of its General Plan
Environmental Impact Report (EIR). The population growth of Los Gatos has remained fairly small and
stable in the last three (3) decades.
Since 2010, the Town has experienced an annual growth rate of 0.5 percent with a total increase of less
than 1,200 persons during that time, which is lower than the County’s rate of 1.2 percent. Similarly,
according to the DOF, the housing stock in Los Gatos has grown by 250 units during this same
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timeframe, an increase of approximately 0.2 percent on an annual basis. This, again, is lower than the
increase in new housing in the County which saw an annual rate of 0.7 percent since 2010.
According to Plan Bay Area 2040, a regional transportation and land use roadmap for future growth
adopted jointly by the Association of Bay Area Governments (ABAG) and the Metropolitan
Transportation Commission (MTC), the Town is projected to increase by around 600 households through
2040.
1.2.3 Transportation and Street Types:
The Town’s inventory of streets is classified based on capacity and intended purpose. Town-owned
streets include arterial streets, collector streets, and local streets. The Town uses a Pavement
Management System to identify and prioritize major preventive and corrective maintenance needs.
Town streets are surveyed and rated on a biennial basis. Maintenance needs are identified by measuring
observed pavement conditions against a Town standard for system-wide average pavement surface
conditions and standards establishing road repair strategies with the condition rating for individual
street segments.
In addition, the Town has private streets that provide direct access to private properties within a
particular subdivision or development. Private streets are maintained and operated by Home Owners
Associations or individual private landowners.
The California Department of Transportation (Caltrans) owns and maintains several freeways serving Los
Gatos. These include California State Route (Highway) 17 (which is the southern extension of Interstate
880), Highway 85 and Highway 9. These highways provide north-south and east-west regional
automobile access.
1.2.4 Water Resources and Water Supply:
Protection of water quality and the provision of adequate water resources is critical for the health and
quality of life of Los Gatos residents and employees. Water quality is a regional issue that is regulated at
the county, State and federal levels. The Town of Los Gatos does not own or operate a water utility. San
Jose Water Company (SJWC) is the local water supplier in Los Gatos. The regional wholesale supplier of
water to the South Bay Area is Valley Water (formerly called the Santa Clara Valley Water District),
which derives water from local, recycled, and imported supplies. Some of Valley Water’s water is
supplied by local rainfall and groundwater. The rainwater is stored in ten local reservoirs and some of it
is transferred to Valley Water’s Groundwater Recharge Facilities. Valley Water owns and operates more
than 30 groundwater recharge facilities. These facilities percolate both local and imported water into
the groundwater aquifer.
One open water body is located within the Town: County owned and maintained Vasona Reservoir.
Creeks in Los Gatos include perennial and ephemeral creek channels with above ground and
underground reaches. Most of these creeks are considered part of the Guadalupe River watershed. Los
Gatos Creek is one of the primary creeks in the area, flowing south to north into and out of the Vasona
Reservoir.
1.2.5 Flood Potential
Some land within the Town of Los Gatos is located in special flood hazard areas. The land adjacent to a
number of creeks, including Ross Creek, Los Gatos Creek, Smith Creek, and San Tomas Aquino Creek,
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may be designated as “Areas of 100-year Flood” by FEMA. In areas with flood potential, the Town
requires that new construction meets State and local standards for construction as mandated by the
Uniform Building Code.
1.2.6 Stormwater Drainage System:
The Town of Los Gatos is served by an extensive man-made storm drainage system including pipe
networks, ditches and culverts. These systems discharge into natural creeks, including Los Gatos Creek,
Ross Creek, San Tomas Aquino Creek, and Smith Creek, which ultimately discharge into San Francisco
Bay. The Town operates and maintains the drainage system and coordinates with surrounding
jurisdictions and Santa Clara County to provide regional storm drainage for the Santa Clara Valley area.
Drainage improvements are planned to enable additional development while preventing flooding.
1.2.7 Open Space, Agriculture and Vacant Land:
The “Open Space/Recreation” land use designation refers to indoor and outdoor recreational facilities,
including public open spaces such as regional parks, community centers, playgrounds and neighborhood
parks, country clubs, and natural open spaces. After “Residential Single-family” land use, Open
Space/Recreation comprises the second highest percentage of total land in Los Gatos. There are
approximately 1,624 acres of open space in the Town. Much of this acreage is contained in four (4) large
facilities: St. Joseph’s Hill, Sierra Azul Open Space, Vasona Lake County Park and La Rinconada Country
Club.
According to the Santa Clara County Assessor’s Office, about 64 acres of land in Los Gatos is currently
devoted to agricultural uses.
Approximately 292 acres within the Town are vacant parcels of varying sizes. Most of the vacant acreage
in Los Gatos is located in the hillside single-family residential area on the eastern side of the Town.
Parcels here are generally larger than they are elsewhere in Los Gatos, and a number of significantly
sized parcels are vacant. Generally, vacancies are more common in residential areas of Los Gatos than in
commercial areas, although a few small, isolated commercial vacancies exist.
Regulatory Context
1.3.1 Federal and State Regulations and Initiatives
The U.S. Environmental Protection Agency (EPA) has authority under the Clean Water Act to promulgate
and enforce stormwater related regulations. For the State of California, EPA has delegated the
regulatory authority to the State Water Resources Control Board (State Water Board), which in turn, has
delegated authority to the San Francisco Bay Regional Water Quality Control Board (Regional Water
Board) to issue National Pollutant Discharge Elimination System (NPDES) permits in the San Francisco
Bay Region. Stormwater NPDES permits allow stormwater discharges from municipal separate storm
sewer systems (MS4s) to local creeks, San Francisco Bay, and other water bodies as long as they do not
adversely affect the beneficial uses of or exceed any applicable water quality standards for those waters.
Since the early 2000’s, the EPA has recognized and promoted the benefits of using GSI in protecting
drinking water supplies and public health, mitigating overflows from combined and separate storm
sewers and reducing stormwater pollution, and it has encouraged the use of GSI by municipal agencies
as a prominent component of their MS4 programs.
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The State and Regional Water Boards have followed suit in recognizing not only the water quality
benefits of GSI but the opportunity to augment local water supplies in response to the impacts of
drought and climate change as well. The 2014 California Water Action Plan called for multiple benefit
stormwater management solutions and more efficient permitting programs. This directive created the
State Water Board’s “Strategy to Optimize Resource Management of Stormwater” (STORMS). STORMS’
stated mission is to “lead the evolution of storm water management in California by advancing the
perspective that storm water is a valuable resource, supporting policies for collaborative watershed-
level storm water management and pollution prevention, removing obstacles to funding, developing
resources, and integrating regulatory and non-regulatory interests.”
These Federal and State initiatives have influenced approaches in Bay Area municipal stormwater NPDES
permits, as described in Section 1.3.2.
1.3.2 Municipal Regional Stormwater Permit
The Town is subject to the requirements of the Municipal Regional Stormwater NPDES Permit (MRP) for
Phase I municipalities and agencies in the San Francisco Bay area (Order R2-2015-0049), which became
effective on January 1, 2016. The MRP applies to 76 municipalities and flood control agencies that
discharge stormwater to San Francisco Bay, collectively referred to as permittees.
Over the last thirteen (13) years, under Provision C.3 of the MRP and previous permits, new
development and redevelopment projects on private and public property that exceed certain size
thresholds (“regulated projects”) have been required to mitigate impacts on water quality by
incorporating “Low Impact Development” (LID) measures, including site design, pollutant source control,
stormwater treatment and flow control measures as appropriate. LID treatment measures, such as
rainwater harvesting and use, infiltration, and biotreatment, have been required on most regulated
projects since December 2011.
Provision C.3.j of the 2016 MRP requires the Town to develop and implement a long-term GSI Plan2 for
the inclusion of LID measures into storm drain infrastructure on public and private lands, including
streets, roads, storm drains, parking lots, building roofs, and other elements. The GSI Plan must be
completed and submitted to the Regional Water Board by September 30, 2019.
While Provision C.3.j of the MRP contains the GSI program planning and analysis requirements, other
provisions (C.11 and C.12) establish a linkage between public and private GSI features and required
reductions of pollutants in stormwater discharges. Permittees in Santa Clara County (County),
collectively, must implement GSI on public and private property to achieve specified pollutant load
reduction goals by the years 2020, 2030, and 2040. These efforts will be integrated and coordinated
countywide for the most effective and resource-efficient program. As an indication as to whether these
load reductions will be met, Permittees must include in their GSI Plans estimated “targets” for the
amounts of impervious surface to be “retrofitted” as part of public and private projects (i.e.,
redeveloped or changed such that runoff from those surfaces will be captured in a stormwater
treatment system or GSI measure) over the same timeframes (2020, 2030, and 2040).
2 Although the MRP uses the term green infrastructure (GI), the agencies within Santa Clara County, including the
Town of Los Gatos, prefer to use the term green stormwater infrastructure (GSI). Therefore, the term GSI is used
in this document.
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A key part of the GSI definition in the MRP is the inclusion of GSI systems at both private and public
property locations. This has been done in order to plan, analyze, implement and credit GSI systems for
pollutant load reductions on a watershed scale, as well as recognize all GSI accomplishments within a
municipality. The focus of the GSI Plan is the integration of GSI systems into public buildings, parks,
parking lots, and rights-of-way (e.g. road or bike path). However, the GSI Plan also establishes
opportunities to include GSI facilities at private properties or in conjunction with private development,
so they can contribute to meeting the target load reductions on a county-wide level as well as
implement GSI on a larger scale.
GSI Plan Development Process
1.4.1 Regional Collaboration
The Town of Los Gatos participates in the West Valley Clean Water Authority (WVCWA), a cooperative
effort of the Cities of Campbell, Monte Sereno, and Saratoga and the Town of Los Gatos
(www.cleancreeks.org). These four municipalities, also referred to as the West Valley Communities,
work together as a group to control discharge of polluted stormwater into local creeks and the San
Francisco Bay. The WVCWA also collaborates with the Santa Clara Valley Urban Runoff Pollution
Prevention Program (SCVURPPP), West Valley Sanitation District, and the Santa Clara County Fire
District.
The West Valley Communities jointly prepared a GSI Plan Framework (Framework), a work plan
describing the goals, approach, tasks, and schedule needed to complete their GSI Plans. Development of
the Framework was a regulatory requirement (Provision C.3.j.i(1) of the MRP) to demonstrate the
Town’s commitment to completing the GSI Plan by September 30, 2019.
The Town of Los Gatos is also a member of the Santa Clara Valley Urban Runoff Pollution Prevention
Program (SCVURPPP), an association of thirteen cities and towns in the Santa Clara Valley, the County of
Santa Clara, and Valley Water that collaborate on stormwater regulatory activities and compliance. This
partnership allows sharing of resources toward permit compliance and collaboration on projects of
mutual benefit. SCVURPPP provided technical guidance, templates, and completion of certain GSI Plan
elements at the countywide level. SCVURPPP guidance and products are discussed in more detail in
relevant sections of the GSI Plan.
The Town, via SCVURPPP, also coordinated with the Bay Area Stormwater Management Agencies
Association (BASMAA) on regional GSI guidance and received feedback through BASMAA from MRP
regulators on GSI expectations and approaches. BASMAA members include other countywide
stormwater programs in Alameda, Contra Costa, and San Mateo Counties, and area-wide programs in
the Vallejo and Fairfield-Suisun portions of Solano County, whose participating municipalities are
permittees under the MRP.
1.4.2 GSI Plan Development and Adoption
The GSI Plan development process began with the preparation of the GSI Framework. As discussed in
Section 1.5.1, this was a collaborative effort by the WVCWA. The document, titled “Green Infrastructure
Plan Framework, West Valley Communities: Campbell, Los Gatos, Monte Sereno, and Saratoga”, was
reviewed and approved for submittal to the Regional Water Quality Control Board by the Los Gatos
Town Manager on June 16, 2017.
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The Town worked with WVCWA and a consultant team to develop the GSI Plan. The Plan was presented
for approval to the Town Council on August 20, 2019.
1.4.3 Education and Outreach
One of the first and most important steps in the development of the GSI Plan is educating a
municipality’s department staff, managers, and elected officials about the purposes and goals of green
infrastructure, the required elements of the GSI Plan, and steps needed to develop and implement the
GI Plan and get their support and commitment to the Plan and this new approach to urban
infrastructure. Another important first step is local community and stakeholder outreach to gain public
support. The West Valley Communities including Los Gatos began this process in FY 15-16 and FY 16-17
by completing the following tasks:
• Convened interdepartmental meetings with relevant department staff and management to
discuss GSI requirements and assigned tasks.
• Discussed with appropriate department staff the MRP requirements to analyze proposed
capital projects for opportunities to incorporate GSI and completed the first list of planned and
potential GSI projects.
• Provided training to department staff on GSI requirements and strategies using the GSI
workshops and other training tools developed by SCVURPPP.
• Informed elected officials with an informational memo to raise awareness of the goals and
requirements in the MRP and the concepts, intent and multiple benefits of GSI.
• Worked with WVCWA and SCVURPPP to study and possibly develop a GSI resource center
within the West Valley Communities to demonstrate GSI projects specifically for smaller
communities.
• Participated on the stakeholder work group for developing a Storm Water Resource Plan
(SWRP) for the Santa Clara Basin.
• Coordinated with SCVURPPP on a comprehensive outreach and education program. Key
audiences include: the general public (countywide, and in the neighborhood or municipality
where GSI projects are located); the development community (e.g., developers, engineers,
landscape architects, and contractors); and elected officials.
In addition, the Town has coordinated with SCVURPPP on a countywide outreach and education
program about GSI for the general public 3, which includes a GSI website, public presentations, and radio
and online advertising to promote GSI features.
The Town of Los Gatos will continue to conduct internal education and outreach about GSI as the GSI
Plan is implemented and seek community input as specific projects are designed and constructed. In
addition, the West Valley Communities will continue to conduct the following education and outreach
activities as part of the GSI Plan:
• Keep elected officials updated on GSI Plan implementation
• Provide outreach to the general public and development community in coordination with
SCVURPPP
3 http://www.mywatershedwatch.org/residents/green-streets/
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• Conduct internal training, as needed, and send staff to SCVURPPP training sessions
GSI Plan Structure and Required Elements
The remainder of the GSI Plan is structured as follows:
• Chapter 2 provides the definition, purpose, and benefits of GSI, and describes the different
types of GSI facilities.
• Chapter 3 describes the relationship of the GSI Plan to other planning documents and how those
planning documents have been updated or modified, if needed, to support and incorporate GSI
requirements. For documents whose desired updates and modifications have not been
accomplished by the completion of the GSI Plan, a work plan and schedule are laid out to
complete them.
• Chapter 4 outlines the materials being developed by SCVURPPP and the Town to provide
guidelines, typical details, specifications and standards for municipal staff and others in the
design, construction, and operation and maintenance of GSI measures.
• Chapter 5 presents the methodology and results for identifying and prioritizing areas for
potential GSI projects.
• Chapter 6 outlines the Town’s strategy for implementing prioritized potential GSI projects within
the next ten (10) years and through 2040, presents targets for the amounts of impervious
surface to be “retrofitted” with GSI within the Town by 2020, 2030, and 2040, and discusses the
variety of mechanisms to be employed by the Town in order to implement the GSI Plan,
including future planning, tracking, and funding.
The GSI Plan elements required by Provision C.3.j.i.(2) of the MRP and the section of the document in
which each component can be found are summarized in Table 1-2 below.
Table 1-2 Summary of GSI Plan Elements required by Provision C.3.j.i of the MRP
MRP Provision GSI Plan Elements GSI Plan Section
C.3.j.i.(2)(a) Project Identification and Prioritization Mechanism Chapter 5
C.3.j.i.(2)(b) Prioritization Output Section 5.3
C.3.j.i.(2)(c) Impervious Surface Targets Section 6.6
C.3.j.i.(2)(d) Completed Project Tracking System Section 6.7
C.3.j.i.(2)(e,f) Guidelines and Specifications Chapter 4
C.3.j.i.(2)(g) Alternative Sizing Requirements for Green Street Projects Section 4.1
C.3.j.i.(2)(h,i) Integration with Other Municipal Plans Chapter 3
C.3.j.i.(2)(i) Workplan for Integration of GSI Language into Town
Planning Documents Section 3.1.3
C.3.j.i.(2)(j) Workplan for Early Implementation Projects Chapter 6.3
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C.3.j.i.(2)(k) Evaluation of Funding Options Section 6.5
C.3.j.i.(3) Legal and Implementation Mechanisms Section 6.4
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2. WHAT IS GREEN STORMWATER INFRASTRUCTURE?
In natural landscapes, most of the rainwater soaks into the soil or is taken up by plants and
trees. However, in developed areas, building footprints and paved surfaces such as driveways, sidewalks,
and streets prevent rain from soaking into the ground. As rainwater flows over and runs off these
impervious surfaces, this “urban runoff” or “stormwater runoff” can pick up pollutants such as motor oil,
metals, sediment, pesticides, pet waste, and litter. It then carries these pollutants into the Town’s
drainage system, which flows directly to local creeks and San Francisco Bay, without any cleaning or
filtering to remove pollutants. Stormwater runoff is therefore a major contributor to water pollution in
developed areas.
As areas develop, the increase in impervious surface also results in increases in peak flows and volumes
of stormwater runoff from rain events. Traditional “gray” stormwater infrastructure, like portions of the
Town’s drainage system, is designed to convey stormwater flows quickly away from developed areas.
However, the increased peak flows and volumes can cause erosion, flooding, and habitat degradation in
downstream creeks to which stormwater is discharged, damaging habitat, property, and infrastructure.
Green Stormwater Infrastructure
A new approach to managing stormwater is to implement green stormwater infrastructure. GSI uses
vegetation, soils, and other elements and practices to capture, treat, infiltrate and slow urban runoff
and thereby restore some of the natural processes required to manage water and create healthier urban
environments. GSI facilities can also be designed to capture stormwater for uses such as irrigation and
toilet flushing.
GSI integrates building and roadway design, complete streets, drainage infrastructure, urban forestry,
soil conservation and sustainable landscaping practices to achieve multiple benefits. At the city/town or
county scale, GSI is a patchwork of natural areas that provides habitat, flood protection, cleaner air, and
cleaner water. At the neighborhood or site scale, GSI comprises stormwater management systems that
mimic nature and soak up and store water.4
Benefits of Green Stormwater Infrastructure
GSI can provide multiple benefits beyond just managing rainfall and runoff. These benefits include
environmental, economic, and social improvements.
GSI measures can mitigate localized flooding and reduce erosive flows and quantities of pollutants being
discharged to local creeks and the San Francisco Bay. Vegetated GSI systems can beautify public places
and help improve air quality by filtering and removing airborne contaminants from vehicle and industrial
sources. They can also reduce urban heat island effects by providing shade and absorbing heat better
than paved surfaces, and provide habitat for birds, butterflies, bees, and other local species. When GSI
facilities are integrated into traffic calming improvements such as curb extensions and bulb-outs at
intersections, they can help increase pedestrian and bicycle safety and promote active transportation,
which in turn can result in improved human health.
GSI facilities designed with extra storage can capture stormwater for later use as irrigation water or non-
potable uses such as toilet flushing and cooling tower supply, thus conserving potable water supplies.
4 https://www.epa.gov/green-infrastructure/what-green-infrastructure
Green Stormwater Infrastructure Plan
11
Widespread implementation of GSI potentially offers significant economic benefits, such as deferring or
eliminating the need for some gray infrastructure projects. By providing more storage within the
watershed, GSI can help reduce the costs of conveyance and pumping of stormwater. When cost-benefit
analyses are performed, GSI is often the preferred alternative due to the multiple benefits provided by
GSI as compared to conventional infrastructure.
Types of Green Stormwater Infrastructure Facilities
Integrating GSI into public spaces typically involves construction of stormwater capture and treatment
measures in public streets, parks, and parking lots or as part of public buildings. Types of GSI measures
that can be constructed in public spaces include: (1) bioretention; (2) stormwater tree well filters; (3)
pervious pavement, (4) infiltration facilities, (5) green roofs, and 6) rainwater harvesting and use
facilities. A description of these facility types is provided below.
2.3.1 Biotreatment/Bioretention
Bioretention areas are depressed landscaped areas
that consist of a ponding area, mulch layer, plants, and
a special biotreatment soil media composed of sand
and compost, underlain by drain rock and an
underdrain, if required. Bioretention is designed to
retain stormwater runoff, filter stormwater runoff
through biotreatment soil media and plant roots, and
either infiltrate stormwater runoff to underlying soils
as allowed by site conditions, or release treated
stormwater runoff to the storm drain system, or both.
They can be of any shape and are adaptable for use on
a building or parking lot site or in the street right-of-
way.
Bioretention systems in the streetscape have specific
names: stormwater planters, stormwater curb extensions (or bulb-out), and stormwater tree well filters
(described in the next section).
A stormwater curb extension (Figure 2-1) is a bioretention system that extends into the roadway and
involves modification of the curb line and gutter. Stormwater curb extensions may be installed midblock
or at an intersection. Curb bulb- outs and curb extensions installed for pedestrian safety, traffic calming,
and other transportation benefits can also provide opportunities for siting bioretention facilities. Parking
lots can accommodate bioretention areas of any shape in medians, corners, and pockets of space
unavailable for parking.
A stormwater planter is a linear bioretention facility in the public right-of-way along the edge of the
street, often in the planter strip between the street and sidewalk. They are typically designed with
vertical (concrete) sides. However, they can also have sloped sides depending on the amount of space
that is available.
2.3.2 Stormwater Tree Well Filters and Suspended Pavement Systems
A stormwater tree well filter is a type of bioretention system consisting of an excavated pit or vault that
is filled with biotreatment soil media, planted with a tree and other vegetation, and underlain with drain
Figure 2-1 Stormwater curb extension, Hacienda
Avenue, Campbell (Source: City of Campbell)
Green Stormwater Infrastructure Plan
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rock and an underdrain, if needed. Stormwater tree well filters can be constructed in series and linked
via a subsurface trench or underdrain. A stormwater tree well filter can require less dedicated space
than other types of bioretention areas.
Suspended pavement systems (Figure 2-2) may be used to provide increased underground treatment area
and soil volume for tree well filters. These are structural systems designed to provide support for
pavement while preserving large volumes of uncompacted soil for tree roots. Suspended pavement
systems may be any engineered system of structural supports or commercially available proprietary
structural systems.
Stormwater tree well filters and suspended pavements systems are especially useful in settings between
existing sidewalk elements where available space is at a premium. They can also be used in curb
extensions or bulb-outs, medians, or parking lots if surrounding grades allow for drainage to those areas.
The systems can be designed to receive runoff through curb cuts or catch basins or allow runoff to enter
through pervious pavers on top of the structural support.
Figure 2-2 Stormwater tree well filter conceptual examples: modular suspended pavement system (left), column
suspended pavement system (right). (Courtesy of City of Philadelphia Water Department)
2.3.3 Pervious Pavement
Pervious pavement is hardscape that allows water to pass through its surface into a storage area filled
with gravel prior to infiltrating into underlying soils. Types of pervious pavement include permeable
interlocking concrete pavers, pervious concrete, porous asphalt, and grid pavement. Pervious pavement
is often used in parking areas or on streets where bioretention is not feasible due to space constraints or
if there is a need to maintain parking. Pervious pavement
does not require a dedicated surface area for treatment and
allows a site to maintain its existing hardscape.
There are two (2) types of pervious pavers: Permeable
Interlocking Concrete Pavers (PICP) and Permeable Pavers
(PP). PICP (Figure 2-3) allows water to pass through the joint
spacing between solid pavers, and PP allows water to pass
through the paver itself and therefore can have tighter
joints. Porous asphalt and pervious concrete are similar to
traditional asphalt and concrete, but do not include fine
Figure 2-3 Permeable Pavers, Mayfield Playing
Fields, Palo Alto (Source: City of Palo Alto)
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aggregates in the mixture, allowing water to pass through the surface. All types are supported by several
layers of different sizes of gravel to provide structural support and water storage.
2.3.4 Infiltration Facilities
Where soil conditions permit, infiltration facilities can be
used to capture stormwater and infiltrate it into native soils.
The two primary types are infiltration trenches and
subsurface infiltration systems.
An infiltration trench is an excavated trench backfilled with
a stone aggregate and lined with a filter fabric. Infiltration
trenches collect and detain runoff, store it in the void spaces
of the aggregate, and allow it to infiltrate into the underlying
soil. Infiltration trenches can be used along roadways,
alleyways, and the edges or medians of parking lots. An
example of an infiltration trench is shown in Figure 2-4.
Subsurface infiltration systems are another type of GSI
measure that may be used beneath parking lots or parks to
infiltrate larger quantities of runoff. These systems, also
known as infiltration galleries, are underground vaults or
pipes that store and infiltrate stormwater while preserving
the uses of the land surface above parking lots, parks and
playing fields. An example is shown in Figure 2-5. Storage can
take the form of large-diameter perforated metal or plastic
pipe, or concrete arches, concrete vaults, plastic chambers
or crates with open bottoms. Prefabricated, modular
infiltration galleries are available in a variety of shapes, sizes,
and material types that are strong enough for heavy vehicle loads.
2.3.5 Green Roofs
Green roofs are vegetated roof systems that filter, absorb,
and retain or detain the rain that falls upon them. Green
roof systems are comprised of a layer of planting media
planted with vegetation, underlain by other structural
components including waterproof mem branes, synthetic
insulation, geofabrics, and underdrains. A green roof can be
either “extensive”, with 3 to 7 inches of lightweight planting
media and low-profile, low-maintenance plants, or
“intensive”, with a thicker (8 to 48 inches) of media, more
varied plantings, and a more garden-like appearance. Green
roofs can provide high rates of rainfall retention via plant
uptake and evapotranspiration and can decrease peak flow
rates in storm drain systems because of the storage that occurs
in the planting media during rain events. An example is shown
in Figure 2-6.
Figure 2-4 Infiltration trench, San Jose
(Source: City of San Jose)
Figure 2-5 Subsurface infiltration system,
(Source: Conteches.com)
Figure 2-6 Green Roof at Fourth
Street Apartments, San Jose (Source:
EOA)
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2.3.6 Rainwater Harvesting and Use
Rainwater harvesting is the process of collecting rainwater from
impervious surfaces and storing it for later use. Storage facilities that
can be used to capture stormwater include rain barrels, above-ground
or below-ground cisterns, open storage reservoirs (e.g., ponds), and
various underground storage devices (tanks, vaults, pipes, and
proprietary storage systems). The captured water is then fed into
irrigation systems or non-potable water plumbing systems, either by
pumping or by gravity flow. Uses of captured water may include
irrigation, vehicle washing, and indoor non-potable use such as toilet
flushing, heating and cooling, or industrial processing.
The two most common applications of rainwater harvesting are 1)
collection of roof runoff from buildings; and 2) collection of runoff from
at-grade surfaces or diversion of water from storm drains into large
underground storage facilities below parking lots or parks. Rooftop
runoff usually contains lower quantities of pollutants than at-grade
surface runoff and can be collected via gravity flow. Underground
storage systems typically include pre-treatment facilities to remove
pollutants from stormwater prior to storage and use.
Figure 2-7 Rainwater Harvesting
cistern, Environmental Innovation
Center, San Jose (Source: City of San
José)
Figure 2-8 Subsurface vault for rainwater
harvesting, under construction (Source:
Conteches.com)
Town of Los Gatos
15
3. INTEGRATION WITH OTHER PLANNING DOCUMENTS
To ensure the success of the GSI Plan and its implementation, its goals, policies and implementation
strategies should align with the Town’s General Plan and other related planning documents. The MRP
requires that municipal agencies review such documents and include in their GSI Plans a summary of any
planning documents aligned with the GSI Plan or updated or modified to appropriately incorporate GSI
requirements. The GSI Plan must also include a workplan identifying how GSI measures will be included
in future plans.
Town Planning Document Review
The Town completed a review of its existing planning documents to determine the extent to which GSI-
related language, concepts and policies have been incorporated. The plans that were reviewed are listed
below:
• General Plan (Overall)
• Sustainability Plan
• Bicycle and Pedestrian Plan
• North Forty Specific Plan
• Hillside Specific Plan
• Albright Specific Plan
The following sections provide a brief discussion for each plan and identify whether GSI-related
language is included in the plans. A prioritized workplan for the integration of GSI language into existing
and future Town planning documents is provided in Section 3.2.
3.1.1 General Plan
The Town of Los Gatos General Plan is a policy document to assist and guide local decision makers. The
General Plan explains how the Town’s natural resources and physical features are to be maintained and
enhanced and directs how the Town incorporates them into infill projects, new projects, and community
investments. The 2020 General Plan was adopted in January 2011. The 2020 General Plan includes broad
language requiring compliance with requirements in the stormwater permit and stormwater best
management practices. However, it does not include GSI-related language. A General Plan update is
currently in progress.
3.1.2 Sustainability Plan
This Sustainability Plan, developed in 2012, is a key tool in implementing the 2020 General Plan. It is a
detailed, long-range strategy to achieve sustainability in transportation and land use, energy, water,
solid waste, and open space. The Sustainability Plan addresses the major sources of greenhouse gas
(GHG) emissions in Los Gatos and sets forth a detailed and long-term strategy that the Town and
community can implement to achieve the GHG emissions reduction target. It does not include specific
GSI-related language.
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3.1.3 Bicycle and Pedestrian Master Plan
The Los Gatos Bicycle and Pedestrian Master Plan (BPMP), developed in 2017, proposes an enhanced
bicycle and pedestrian network that expands safe access to key community destination points. It does
not include GSI-related language.
3.1.4 North Forty Specific Plan
The North Forty Specific Plan, developed in 2015, establishes appropriate land uses, development
standards, urban design concepts, and architectural design guidelines for the specific plan area. The
development projects and new streets in the North Forty Specific Plan area will be regulated under
Provision C.3 of the MRP and will be required to implement Low Impact Development source control,
site design and stormwater treatment. Therefore, additional language supporting GSI implementation is
not required.
3.1.5 Hillside Specific Plan
The purpose of the Hillside Plan (1978) is to make recommendations for future development in the
Hillside planning area. The current Hillside Specific Plan does not include language supporting GSI.
However, a substantial portion of the Hillside Specific Plan area is steeper than a 50% slope, and either
inaccessible or virtually undevelopable. Therefore, the Town does not plan to implement GSI in the
Hillside Specific Plan area.
3.1.6 Albright Specific Plan
The Albright Specific Plan, developed in 2013, establishes the policies and development standards for
the development of the 21.6-acre project site located at 90-160 Albright Way and 14600 Winchester
Boulevard. Specified within the plan are items such as design guidelines pertaining to the site design,
sustainability and streetscape landscaping. The plan also required that stormwater runoff from the
project’s new impervious surfaces be conveyed towards and filtered through a collection of bioretention
areas and self-retaining treatment basins, and that future development within the Specific Plan
implement additional bioretention areas as needed.
Workplan for Integrating GSI Language into Existing and Future Town Planning
Documents
Some Town plans could benefit from the inclusion of additional GSI-related language. The following
plans will be updated in accordance with each document’s scheduled update in the table below:
Table 3.1. Workplan for Integration of GSI Language into Existing Town Planning Documents
Name of Plan To Be Updated
Anticipated Date of
Completion/Update
General Plan 2020
Sustainability Plan TBD
Bicycle and Pedestrian Master Plan TBD
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When preparing new planning documents, the Town will review GSI Plan requirements during the
planning process to ensure that GSI requirements and policies are incorporated. Examples of GSI related
language can be found in SCVURPPP’s Model Green Infrastructure Language for Incorporation into
Municipal Plans (2016).
Regional Plans
The Town is collaborating with SCVURPPP, Valley Water, and other agencies on several large-scale
planning efforts including those described below.
3.3.1 Santa Clara Basin Stormwater Resource Plan
A collaboration between SCVURPPP and Valley Water during 2017 and 2018, the Santa Clara Basin
Storm Water Resources Plan (SWRP) supports municipal GSI Plans by identifying and prioritizing
potential multi-benefit GSI opportunities on public parcels and street rights-of-way throughout the Basin
(i.e., Santa Clara Valley) and allows them to be eligible for State bond-funded implementation grants.
The SWRP includes a list of prioritized GSI opportunity locations for each SCVURPPP agency, including
Los Altos. As described in section 5.2, the Town’s GSI Plan builds on the SWRP output to further identify,
evaluate, and prioritize potential projects.
3.3.2 Valley Water’s One Water Plan
The Watershed Division of Valley Water is leading an effort to develop an Integrated Water Resources
Master Plan to identify, prioritize, and implement activities at a watershed scale to maximize established
water supply, flood protection, and environmental stewardship goals and objectives. The “One Water
Plan” establishes a framework for long-term management of Santa Clara County water resources, which
eventually will be used to plan and prioritize projects that maximize multiple benefits. The One Water
Plan incorporates knowledge from past planning efforts, builds on existing and current related planning
efforts; and coordinates with relevant internal and external programs. The One Water Plan has five (5)
goals:
1. Valued and Respected Rain – Manage rainwater to improve flood protection, water supply, and
ecosystem health.
2. Healthful and Reliable Water – Enhance the quantity and quality of water to support beneficial
uses.
3. Ecologically Sustainable Streams and Watersheds – Protect, enhance and sustain healthy and
resilient stream ecosystems.
4. Resilient Baylands – Protect, enhance and sustain healthy and resilient baylands ecosystems
and infrastructure.
5. Community Collaboration – Work in partnership with an engaged community to champion wise
decisions on water resources.
Tier 1 of the effort, for which a draft plan was completed in 2016 5, is a countywide overview of major
resources and key issues along with identified goals and objectives. Tier 2 (2016 to 2020) will include
greater detail on each of the County’s five major watersheds, including the West Valley Watersheds in
which the Town of Los Gatos is located. The Town’s GSI Plan aligns with the goals of the One Water Plan
5 Santa Clara Valley Water District. 2016. One Water Plan for Santa Clara County. An Integrated Approach to Water
Resources Management. Preliminary Draft Report 2016.
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and may be able to coordinate with specific projects yet to be identified in the West Valley Watershed
area.
3.3.3 Bay Area Integrated Regional Water Management Plan
The Bay Area Integrated Regional Water Management Plan (IRWMP) is a comprehensive water
resources plan for the Bay region that addresses four functional areas: 1) water supply and water
quality; 2) wastewater and recycled water; 3) flood protection and stormwater management; and 4)
watershed management and habitat protection and restoration. It provides a venue for regional
collaboration and serves as a platform to secure state and federal funding. The IRWMP includes a list of
over three hundred (300) project proposals, and a methodology for ranking those projects for the
purpose of submitting a compilation of high priority projects for grant funding. The Santa Clara Basin
SWRP was submitted to the Bay Area IRWMP Coordinating Committee and incorporated into the
IRWMP as an addendum. As SWRP projects are proposed for grant funding, they will be added to the
IRWMP list using established procedures.
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4. GSI DESIGN GUIDELINES, DETAILS, AND SPECIFICATIONS
The MRP requires that the GSI Plan include general design and construction guidelines, standard
specifications and details (or references to those documents) for incorporating GSI components into
projects within the Town. These guidelines and specifications should address the different street and
project types within the Town, as defined by its land use and transportation characteristics, and allow
projects to provide a range of functions and benefits, such as stormwater management, bicycle and
pedestrian mobility and safety, public green space, and urban forestry.
The Town, along with other SCVURPPP agencies, helped fund and provided input to the development of
countywide guidelines by SCVURPPP to address the MRP requirements and guide the implementation of
GSI Plans. The resulting SCVURPPP GSI Handbook (Handbook) is a comprehensive guide to planning and
implementation of GSI projects in public streetscapes, parking lots and parks. The Handbook consists of
two parts, the contents of which are described in the following sections. The Town intends to use this
Handbook as a reference when creating Town -specific guidelines and specifications to meet the needs
of the various departments.
Design Guidelines
Part 1 of the Handbook provides guidance on selection, integration, prioritization, sizing, construction,
and maintenance of GSI facilities. It includes sections describing the various types of GSI, their benefits,
and design considerations; how to incorporate GSI with other uses of the public right-of-way, such as
bicycle and pedestrian infrastructure and parking; and guidelines on utility coordination and landscape
design for GSI. In addition, the Handbook also provides guidance on post-construction maintenance
practices and design of GSI to facilitate maintenance.
Part 1 also contains a section on proper sizing of GSI measures. Where possible, GSI measures should be
designed to meet the same sizing requirements as Regulated Projects, which are specified in MRP
Provision C.3.d. In general, the treatment measure design standard is capture and treatment of 80% of
the annual runoff (i.e., capture and treatment of the small, frequent storm events). However, if a GSI
measure cannot be designed to meet this design standard due to constraints in the public right-of-way
or other factors, the Town may still wish to construct the measure to provide some runoff reduction and
water quality benefit and achieve other benefits. For these situations, the Handbook describes regional
guidance on alternative design approaches developed by the Bay Area Stormwater Management
Agencies Association (BASMAA) for use by MRP permittees.
Details and Specifications
Part 2 of the Handbook contains typical details and specifications that have been compiled from various
sources within California and the U.S. and modified for use in Santa Clara County. The Handbook
includes details for pervious pavement, stormwater planters, stormwater curb extensions, bioretention
in parking lots, infiltration measures, and stormwater tree wells, as well as associated components such
as edge controls, inlets, outlets, and underdrains. It also provides typical design details for GSI facilities
in the public right-of-way that address utility protection measures and consideration of other
infrastructure in that space.
Incorporation of SCVURPPP Details and Specifications into Town Standards
The Town will refer to the GSI Handbook for typical details as needed, as well as the SCVURPPP GSI
Guidelines and Specifications for design of GSI projects. Over time, the Town may choose to customize
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some commonly used details and incorporate these into Town Engineering Design Standards and
Standard Plans.
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5. GSI PROJECT PRIORITIZATION AND IMPERVIOUS TARGETS
To meet the requirements of the MRP, the Town’s GSI Plan must contain a project identification and
prioritization mechanism. The mechanism must include the criteria for prioritization and outputs that
can be incorporated into the Town’s long-term planning and capital improvement processes.
This chapter describes different GSI project categories considered within the Town, followed by a
description of the process employed by the Town to identify public lands that offer opportunities to
implement GSI and prioritize those opportunities, and the results of the process.
Project Types
GSI project types that have been or may be implemented in the Town fall into the following categories:
Early Implementation Projects, C3 Regulated Projects, Green Streets, LID Retrofits, and Regional
Projects. All categories, except C3 Regulated projects, are considered GSI capital projects, and are
primarily public projects under control of the Town. Green Streets, LID Retrofits, and Regional Projects
are the focus of the prioritization process described in Section 5.2, but all five GSI project types are
considered as part of the Town wide GSI strategy presented in Chapter 6. Several factors, such as change
in scope of work, funding, site conditions, etc. determine the ability of the Town to implement GSI
capital projects.
5.1.1 Early Implementation Projects
Early Implementation Projects are GSI projects that have already been implemented by the Town or are
planned for implementation in during the permit term (i.e., before December 2020), or have been
identified as the Town as having potential for GSI.
5.1.2 Regulated Projects
C3 Regulated Projects are those implemented as part of new and redevelopment within the Town, both
private and public, that must meet the post-construction stormwater treatment requirements per
Provision C.3 of the MRP. Regulated projects include private development or redevelopment projects,
such as multi-family residential buildings, commercial office buildings, or shopping plazas, as well as
public projects, such as libraries, police stations, and parking lots, exceeding the impervious surface
thresholds.
5.1.3 LID Projects
LID projects mitigate stormwater impacts by reducing runoff through capture and/or infiltration and
treating stormwater on-site before it enters the storm drain system. LID projects may include
bioretention facilities, infiltration trenches, detention and retention areas in landscaping, pervious
pavement, green roofs, and systems for stormwater capture and use. For the purposes of the GSI Plan,
LID projects are GSI facilities that treat runoff generated from a publicly-owned parcel on that parcel.
5.1.4 Regional Projects
Regional projects capture and treat stormwater runoff from on-site and off-site sources, including
surface runoff and diversions from storm drains. Benefits of regional stormwater capture projects can
include flood risk reduction, stormwater treatment and use, and groundwater recharge. These projects
may take a variety of forms such as detention and retention basins and subsurface vaults and infiltration
galleries. The site characteristics will determine what types of regional projects are feasible, e.g.,
whether a project is on-line or off-line from the storm drain network, whether it is desirable to change
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the functionality of the site, whether the project is above ground or underground, and the size of the
project.
5.1.5 Green Street Projects
Green street projects are GSI opportunities in the public right-of-way that capture runoff from the street
and adjacent areas that drain to the street. The technologies used for green streets are similar to those
used in LID projects but are limited to designs that can be used in the right-of-way. Green street projects
may include bioretention (e.g., stormwater planters, stormwater curb extensions or stormwater tree
filters), pervious pavement, and/or infiltration trenches. Green street GSI features can be incorporated
into other improvements in the right-of-way, including complete streets designs and improvements for
pedestrian and cyclist safety.
Identification and Prioritization Process
The Town of Los Gatos GSI opportunity identification and prioritization process involved two steps. The
first step was the screening and prioritization methodology used in the Santa Clara Basin SWRP (see
Section 3.2.1) to identify and prioritize GSI opportunities on public parcels and street segments within
the region. The second step in the process involved overlaying Town-specific priorities and planning
areas onto the regional prioritization results to align the results of the SWRP prioritization process with
the Town’s priorities. These steps are described in detail below.
5.2.1 Step 1: Stormwater Resource Plan Prioritization
Building on existing documents that describe the characteristics and water quality and quantity issues
within the Santa Clara Basin (i.e., the portion of Santa Clara County that drains to San Francisco Bay), the
SWRP identified and prioritized multi-benefit GSI opportunities throughout the Basin, using a metrics-
based approach for quantifying project benefits such as volume of stormwater infiltrated and/or
treated, and quantity of pollutants removed. The metrics-based analysis was conducted using
hydrologic/ hydraulic and water quality models coupled with Geographic Information System (GIS)
resources and other tools. The products of these analyses were a map of opportunity areas for GSI
projects throughout the watershed, an initial prioritized list of potential project opportunities, and
strategies for implementation of these and future projects.
The process began by identifying and screening public parcels and public rights-of-way that can support
GSI. Project opportunities were split into the three categories described above – LID, regional, and green
streets projects -- because of fundamental differences in GSI measures used, project scale, and
measures of treatment efficiency. Screening factors are presented in Table 5-1.
After the identification of feasible GSI opportunity locations, screened streets and parcels were
prioritized to aid in the selection of project opportunities that would be the most effective and provide
the greatest number of benefits. In addition to physical characteristics, several special considerations
were included in the prioritization methodology to consider coordination with currently planned
projects provided by agencies, as well as consideration of additional benefits that projects could
provide. A discussion of the screening and prioritization process for each project category is presented
in the subsequent sections.
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Table 5-1 Screening factors for parcel-based and right-of-way project opportunities
Screening
Factor Characteristic Criteria Reason
Parcel-based
Public Parcels
Ownership
County, City, Town,
Valley Water, State,
Open Space Agencies
Identify all public parcels for regional
stormwater capture projects or onsite
LID retrofits Land Use Park, School, Other
(e.g., Golf Course)
Suitability
Parcel Size
≥ 0.25 acres Opportunity for regional stormwater
capture project
< 0.25 acres Opportunity for on-site LID project
Site Slope < 10 % Steeper grades present additional
design challenges
Right-of-Way
Selection Ownership Public Potential projects are focused on
public right-of-way opportunities
Suitability
Surface Paved Only roads with paved surfaces are
considered suitable. Dirt roads were
not considered.
Slope < 5%
Steep grades present additional design
challenges; reduced capture
opportunity due to increased runoff
velocity
Speed ≤ 45mph Excludes higher speed roads such as
major arterials and highways
LID and Regional Stormwater Capture Project Opportunities
The screening criteria for LID and regional projects were ownership (focusing only on public parcels),
land use, and site slope. As shown in Table 5.1, parcel size was used to determine whether a location
could support a regional or LID project.
Parcels that met the screening criteria were prioritized based on physical characteristics such as soil
group, slope, and percent impervious area, proximity to storm drains, proximity to flood-prone creeks
and areas, proximity to potential pollutant sources, whether they were in a priority development area,
whether they were within a defined proximity to a planned project, and whether the project was
expected to have other benefits such as augmenting water supply, providing water quality source
control, re-establishing natural hydrology, creating or enhancing habitat, and enhancing the community.
Prioritization metrics for LID project scoring and regional project scoring are shown in separate tables in
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Appendix A. The result of the parcel prioritization was a list and map (Figure 5-1) of potential project
locations based on the above criteria. This list was reviewed and updated by the Town as part of Step 2
Town-Specific Prioritization (Section 5.2.2).
Green Street Project Opportunities
The screening criteria for green streets projects in the public right-of-way were ownership, surface
material, slope, and speed limit (Table 5-1). The screened public right-of-way street segments were then
prioritized based on physical characteristics, proximity to storm drains, proximity to flood-prone creeks
and areas, proximity to potential pollutant sources, whether they were in a priority development area,
whether they were in proximity to a planned project, and whether the project was expected to have
other benefits (similar to LID and regional projects). Prioritization metrics for green streets projects are
shown in Appendix A.
The initial prioritization process resulted in a large number of potential green streets project
opportunities within the Santa Clara Basin. In order to identify the optimal locations for green street
projects, the street segments in each municipality’s jurisdiction with scores in the top 10 percent of
ranked green street opportunities were identified and mapped. The public parcels and top 10 percent
street segments in, and owned by, the Town with potential for GSI are shown in Figure 5-1. Although
school properties are owned by the school districts and not the Town, these areas are also shown on the
map as there may be future opportunities to coordinate on GSI projects. The projects from the SWRP on
property owned by the Town or public school districts as shown on Figure 5-1 were carried over into
Step 2 Town-Specific Prioritization (Section 5.2.2).
This subset of projects from the SWRP was carried over into Step 2 Town-Specific Prioritization (Section
5.2.2).
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Figure 5-1 Town of Los Gatos Public Parcels and Street Segments with GSI Opportunities (Source: Santa Clara
Basin SWRP)
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5.2.2 Step 2: Town-Specific Prioritization
The results of the SWRP project identification and prioritization process for the Town of Los Gatos were
mapped in GIS, and then additional priorities for the Town were overlaid on that map, as described
below.
Specific Plan Areas
The Town’s General Plan identifies two Specific Plan areas: North Forty Specific Plan and Hillside Specific
Plan. The Specific Plans establish appropriate land uses, development standards, urban design concepts,
and architectural design guidelines for the areas. The two Specific Plan areas are shown in Figure 5-2.
The development projects and new streets in the North Forty Specific Plan area will be regulated under
Provision C.3 of the MRP and will be required to implement Low Impact Development source control,
site design and stormwater treatment. Additional GSI implementation within this area is not required;
however, there may be some opportunities on adjacent existing streets to incorporate GSI.
A substantial portion of the Hillside Specific Plan area is steeper than a 50% slope, and either
inaccessible or virtually undevelopable. Therefore, the Town does not plan to implement GSI in or near
the Hillside Specific Plan area.
The Albright Specific Plan, established after the last General Plan update, requires that future
development within the Specific Plan implement additional bioretention areas.s Opportunities for GSI
implementation in the public right-of-way will be evaluated as applications are received.
Green Stormwater Infrastructure in Industrial Areas
Stormwater runoff from industrial areas can contain pollutants such as metals, chemicals, trash, oil and
grease. GSI installations in public streets near industrial areas may help remove these pollutants from
stormwater runoff. Old industrial areas (i.e., industrial areas developed before 1980) located in the
Town of Los Gatos are shown in Figure 5-3. As these industrial areas are redeveloped, the Town will
explore installing GSI features in the public right-of-way.
Prioritization Output
A compilation of the factors involved in prioritizing the Town’s opportunities for GSI projects is shown in
Figure 5-4. The parcel-based and green street project opportunities as identified by the SWRP
prioritization are overlaid here along with the Town’s North Forty Specific Plan area, Hillside Specific
Plan Area, and the Industrial Areas.
An implementation plan is described in Section 6 to guide the identification, development, design, and
construction of GSI projects.
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Figure 5-2 Town of Los Gatos Specific Plan Areas (Source – Town of Los Gatos General Plan)
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Figure 5-3 Town of Los Gatos Old Industrial Areas (industrial areas developed prior to 1980) (Source: SCVURPPP)
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Figure 5-4 Town of Los Gatos GSI Opportunities Overview
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6. GSI IMPLEMENTATION PLAN
This chapter provides an overall strategy and steps for implementing GSI within the Town of Los Gatos
over the long term. The implementation plan has the following components: (1) the Town-wide GSI
strategy; (2) a workplan to identify and complete Early Implementation projects (3) a workplan for
identifying additional, future GSI opportunities (4) the legal and funding mechanisms that enable
implementation, (5) estimated targets for the amounts of impervious surface to be “retrofitted” (i.e.,
redeveloped with GSI facilities to treat runoff from impervious surfaces), and (6) the technical tools that
ensure the tracking of implemented projects.
Town-wide GSI Strategy
As Los Gatos considers the future needs of the Town and the community it serves, achieving
environmental sustainability is an important goal. GSI is a concept and tool that Los Gatos will use to
make the built environment more environmentally sustainable. The implementation of GSI jurisdiction-
wide will occur over several decades and into the next century, therefore long-range planning is
essential in determining the prioritization and strategy for the most cost-effective use of limited public
funds.
The Town’s GSI implementation strategy consists of the following:
• GSI in Planning Documents – As described in Section 3, the Town will include GSI goals and
policies in their General Plan and other planning documents. The Town may also potentially
create a policy for parks and public works projects to consider GSI with all public projects.
• Evaluation of CIP projects for opportunities – The Town will continue to review its CIP list
annually for opportunities to incorporate GSI into CIP projects and evaluate the feasibility of
such projects. The Town has established a process for CIP review to avoid missing GSI
opportunities (see Section 6.2).
• Evaluation of Opportunities Identified in the Stormwater Resource Plan – The public
parcels and street segments identified in the SWRP (See Section 5.1 of this report) are
opportunity areas for GSI projects. The Town will use the SWRP list to help identify potential
project locations for GSI implementation.
• Coordination with Private Development – The Town will explore working with private
property developers to install green infrastructure facilities in public rights-of-way near the
properties they are developing, such as along street frontages.
• Evaluation of non-CIP project opportunities - As awareness of GSI increases, municipal staff
or local community members may also identify and recommend GSI project opportunities.
These projects will be considered using the methodology described in Section 6.3.
• Regulated projects – The Town will continue to implement requirements for regulated
projects under Provision C.3 and track completed projects as described in Section 6.7.
Process for Identifying and Evaluating GSI Project Opportunities
As stated in Section 6.1, the Town will use various mechanisms to identify GSI opportunities in capital
projects.
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The Town will use the guidance developed by BASMAA 6 (Attachment C) to evaluate capital projects to
determine the potential for the inclusion of GSI measures at the project planning level. The evaluation
may include site reconnaissance, drainage area delineation, cost analysis, etc. If not already in the CIP
list, projects identified through this process will be included in the CIP list when it is updated. Projects
with a GSI component may be included in the CIP as funded or unfunded projects. An unfunded project’s
inclusion in the CIP demonstrates that it is a Town priority pending adequate funding.
The Town will map all potential GSI project opportunities to determine their proximity to green street or
parcel-based project opportunities identified in the SWRP (Section 5.2.1). Potential GSI projects that are
adjacent to the SWRP opportunity areas may be eligible for state bond funding.
Projects with opportunities for GSI measures may be submitted to the SWRP during the SWRP update
process if they are not already included in the SWRP. This will allow those projects to be eligible for
future state bond funding. The SWRP will likely be updated in the 2022-2023 timeframe. At this time,
SCVURPPP will reach out to all member agencies to provide their project lists for prioritization and
inclusion in the updated SWRP.
Workplan for Early Implementation Projects
As discussed in Section 5.2.2 of this GSI Plan, Provision C.3.j. of the MRP requires that the Town identify,
prepare, and maintain a list of GSI projects that are planned for implementation during the permit term,
and infrastructure projects that have potential for GSI measures. The list is reviewed and submitted with
each Annual Report to the Regional Water Board. The Town has not identified any Early
Implementation Projects to date.
The Town will continue to review its CIP list annually, using the SWRP prioritization, as well as the
guidance developed by BASMAA for identifying opportunities to incorporate GSI into CIP projects.
Legal Mechanisms for GSI Implementation
Provision C.3.j.i.(3) of the MRP requires permittees to “Adopt policies, ordinances, and/or other
appropriate legal mechanisms to ensure implementation of the Green Infrastructure Plan in accordance
with the requirements of this provision.”
As described in Section 1.3.2, the Town of Los Gatos and other municipalities subject to Provision C.3 of
the MRP must require post-construction stormwater control measures on regulated development
projects. Post-construction stormwater controls reduce pollutants from flowing to streams, creeks, and
the Bay and help address local flooding by reducing peak flows. Section 22.30.035. - New
development/redevelopment of the Town’s Municipal Code provides legal authority for the Town to
require regulated private development projects to comply with MRP requirements.
GSI projects are typically not regulated projects (although they must conform to the sizing and design
requirements contained in Provision C.3, except under certain circumstances) and they are primarily
public projects under control of the Town. As part of the GSI Plan process, the Town reviewed its existing
policies, ordinances, and other legal mechanisms related to the implementation of stormwater NPDES
6 BASMAA Development Committee (2016) Guidance for Identifying Green Infrastructure Potential in Municipal
Capital Improvement Program Projects. May.
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permit requirements and found that it has sufficient legal authority to implement the GSI Plan. Adoption
of the GSI Plan by the Town Council will further strenghten the authority.
Evaluation of Funding Options
The GSI Plan prioritizes specific projects for near-term integration into CIPs and long-term integration into
Town planning efforts. Implementation of these projects is contingent upon the Town identifying funding
sources for GSI planning, design, construction, and maintenance.
The total cost of GSI includes costs for planning, capital (design, engineering, construction) and ongoing
expenditures, including operations and maintenance (O&M), utility relocation, and feature replacement.
It is likely that no single source of revenue will be adequate to fund implementation of GSI, and a
portfolio of funding sources will be needed. There are a variety of approaches available to help fund up-
front and long-term investments. This section discusses the Town’s current stormwater management
funding sources and then describes additional funding strategies available to implement GSI that are
being considered by the Town for future funding.
6.5.1 Current Funding Sources for GSI Program Elements
The Town of Los Gatos currently uses a combination of federal and state grants and local revenues to
fund construction of projects in its capital improvement program (CIP) and other projects.
6.5.2 Potential Future Funding Options
As required by the MRP, the Town analyzed possible funding options to raise additional revenue for
design, construction, and long-term operation and maintenance (O&M) of GSI projects. The Town used
the guidance on stormwater funding options developed by SCVURPPP (2018) as a reference for
conducting its analysis. Table 6-1 summarizes the funding options that will be considered by the Town
as the Plan is implemented. For each type of funding mechanism, the table provides a brief overview
and specifics related to GSI, pros and cons, and applicability to funding planning, capital, and/or long-
term O&M costs.
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Table 6-1 Potential GSI Funding Options
Section/Overview GSI Specifics Pros Cons Type of Funding
Parcel Taxes: revenue
stream through taxing
property or other
system.
Can be used to set up,
fund and maintain a
stormwater program
and MRP compliance.
• Well understood tax
• Stable revenue stream
over many years
• Legally reliable
• Can also be done by
mail.
• High political threshold
• Vulnerable to competition with other
measures on the ballot.
• Considerable effort and resources
required with uncertain odds of
success.
• Planning
• Capital
• O&M
Property-related Fees:
fees on real property.
• Fee on property
contributing
stormwater
runoff to MS4.
• Can be used to
set up, fund and
maintain a
stormwater
program and MRP
compliance.
• Most-commonly used
mechanism for funding
stormwater programs.
• Easier to pass with 50%
threshold and mailing
process.
• Property-based fees must use a
standardized methodology for
calculating the fee.
• Considerable effort and resources
required with uncertain odds of
success.
• Approval process is more time
consuming and expensive for staff.
• Schools may have large fees and public
schools may be exempt from fees
depending on the agency’s specific
ordinance.
• Planning
• Capital
• O&M
Development Impact
Fees: paid by an
applicant seeking
approval of a
development project.
Could potentially be
used to fund retrofits
of adjacent public
right-of-way areas
with GSI as part of
development or
redevelopment
projects.
Cost for retrofitting streets
can be leveraged through
development activities.
If a fee is found to not relate to the impact
created by the development project, or to
exceed the reasonable cost of providing
the public service, then the fee may be
declared a “special tax” subject to approval
by a two-thirds majority of voters.
• Planning
• Capital
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Section/Overview GSI Specifics Pros Cons Type of Funding
Grants: one time funds
that require an
application from a
funding agency.
Could be used to plan,
design and/or build
GSI.
Can fund programs or
systems that would
otherwise take up significant
general fund revenues.
• Usually a one-time source of funding
only.
• May need to create new programs and
systems for each grant.
• Usually have strings attached for
matching funds and other
requirements.
• Little control over timing of
applications and payment can lead to
difficulties in coordination with other
programs and grants.
• Can be very competitive and resource
intensive to apply.
• No guarantee of success.
• Post-project O&M costs must be
borne by the agency.
• Planning
• Capital
Benefit Assessment and
Community Facility
Districts
Typically used to build
and/or maintain
facilities such as GSI
improvements and/or
services.
Can be used to fund
maintenance and
operations.
Requires property owners and/or
businesses to agree that the need is
present and that they should be (at least
partially) responsible for funding it.
• Capital
• O&M
Business Improvement
Districts
Businesses and
property owners tax
themselves and
manage the funds to
build or maintain GSI
assets.
Can provide sense of
ownership and pride in the
neighborhood when results
are visible.
Can burden businesses, property owners
and others to the extent that they are
unwilling to approve other funding
measures.
• Planning
• Capital
• O&M
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Section/Overview GSI Specifics Pros Cons Type of Funding
Integration with
Transportation Projects:
transportation funding is
leveraged to cost-
effectively include
stormwater quality
elements.
Installation and
maintenance of GSI
facilities as part of
integrated roadway
programs.
• Roadway projects have
more funding than
stormwater programs
and are generally more
popular with the public.
• Complete and green
streets may be more
popular with the public
than traditional car-
focused streets.
• Green streets may be
less expensive than
traditional streets based
on a life cycle cost
analysis.
• Roadways have been designed in
certain ways with expectations of
costs and purposes for decades.
• Many roadways are in poor condition
and there is not enough funding to fix
them all.
• GSI is perceived as an “added” cost
which, could reduce the number of
roadways that can be maintained.
• Transportation funding is often
restricted to certain roadway
construction elements.
• Planning
• Capital
Alternative Compliance:
Allows developers the
flexibility to build, or
fund through payment of
an in-lieu fee, off-site
stormwater treatment
systems for regulated
projects or set up credit
trading programs.
Leveraging
development activities
to build and maintain
GSI systems. In lieu
fees can be used by
developers who would
rather make a lump
sum payment and
quickly complete their
compliance
requirements. Credit
trading programs can
incentivize non-
regulated properties
to retrofit impervious
surfaces.
• Gives flexibility to site
GI systems in locations
that optimize pollutant
loading reduction and
other benefits to the
community.
• Allows for off-site
stormwater treatment
when stormwater
management
requirements can’t be
met within a regulated
project site.
• An in-lieu fee and/or
credit trading system
can be used to achieve
additional retrofits and
installation of GSI.
• Can be difficult to come up with viable
alternative locations for GSI
installations.
• Can be difficult to quantify how much
a developer should pay upfront for
long-term maintenance costs that the
municipality will bear.
• May require agencies to modify the
stormwater sections of their municipal
codes to allow for the creation and/or
use of the desired options/programs.
• Planning
• Capital
• O&M
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Section/Overview GSI Specifics Pros Cons Type of Funding
Existing Permittee
Resources: Utilize
general funds for GSI.
Could be used to plan,
design, build and/or
maintain GSI.
Voter approval or new
revenue sources not
required.
• GSI must compete with many other
municipal priorities and essential
services.
• Normally not a viable option for
substantial GI implementation.
• Planning
• Capital
• O&M
Volunteer Programs:
provide community-
based volunteer labor for
specific tasks.
Use volunteer
programs to help build
or maintain GSI
facilities.
• A low-cost source of
labor.
• Educational program for
community.
• Can build support for a
stormwater fee or other
funding source.
• Can be time intensive for staff to set
up and administer.
• May not be dependable in the long
run
• May result in loss of municipal control
depending on program specifics.
• Planning
• Capital
• O&M
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Impervious Area Targets
As mentioned in Section 1.3.2, the focus of the GSI Plan is the integration of GSI systems into public
rights-of-way. However, the MRP (Provisions C.11 and C.12) establishes a linkage between public and
private GSI features and required reductions of pollutants in stormwater discharges. To help estimate
the pollutant load reductions that can achieved by GSI during the 2020, 2030, and 2040 timeframes, the
MRP requires that Permittees include in their GSI Plans estimated targets for the amounts of impervious
surface to be “retrofitted” (i.e. redeveloped with GSI facilities to treat runoff from impervious surfaces)
as part of public and private projects during the same timeframes.
The Town worked with SCVURPPP staff to develop a methodology to predict the extent and location of
privately- and publicly-owned land areas that will be redeveloped in their jurisdictions and whose
stormwater runoff will be addressed via GSI facilities, and to derive impervious surface targets for GSI
retrofits associated with these redevelopment projects. The methodology and results are described in
Sections 6.6.1 and 6.6.2 below.
6.6.1 Methodology
The first step in the process used historic development trends to estimate the acres of redevelopment
that will occur in the Town by 2020, 2030, and 2040 from redevelopment of privately- and publicly-
owned parcels that that would trigger C.3 requirements under the current MRP (i.e. C.3 regulated
projects). Stormwater runoff associated with these parcels will be addressed via GSI facilities, as
required by the permit.
The second step was to estimate the acres of impervious surface associated with future redevelopment
of these private and public parcels. To do this, it was necessary to predict the likely locations and types
of land areas that are anticipated to be addressed by GSI in the future. Growth patterns and time
horizons for development, along with algorithms to identify which parcels were likely to redevelop,
resulted in preliminary estimates of the land area that is predicted to be addressed by GSI facilities in
the Town of Los Gatos by 2020, 2030, and 2040. Using the current land uses of the predicted locations
of GSI implementation and associated impervious surface coefficients for each land use type, estimates
of the amount of impervious surface that would be retrofitted with GSI on privately-owned parcels were
developed.
The methodology focused on parcel-based redevelopment as the location and timing of projects in the
public right-of-way is uncertain and the contribution to overall impervious surface treated by GSI
expected to be minor relative to the acreage treated by C.3 projects.
6.6.2 Results
Using the methodology described above, a predicted redevelopment rate of 4.4 acres per year was
calculated for the Town of Los Gatos. “Best” estimates of the magnitude of land areas that is predicted
to be addressed by future GSI facilities by the 2020, 2030, and 2040 milestones were calculated using
this rate. “High” (i.e., 50% > “best”) and “Low” (i.e., 50% < “best”) estimates of future GSI
implementation were also calculated to provide a range of potential redevelopment levels and account
for uncertainty in the “Best” estimate. Figure 6-1 and Table 6-2 present the outputs of the analysis and
represent the total acreage known to be addressed by GSI in Los Gatos through 2018, and the best
Green Stormwater Infrastructure Plan
38
estimate of the cumulative land area that will be addressed in 2020 (90 acres), 2030 (134 acres), and
2040 (178 acres) by GSI on private and public parcels in the Town of Los Gatos.
1High estimate – 150% of Best Estimate; 2Best estimate – rate of redevelopment based on 6-year average (2007-2012); and 3Low estimate –
projected from 50% of “Best Estimate”
Figure 6-1. Existing and projected cumulative land area (acres) anticipated to be addressed via GSI facilities
installed via private redevelopment in the Town of Los Gatos by 2020, 2030, and 2040
Table 6-2 Projected cumulative land area (acres) anticipated to be addressed via GSI facilities via private
redevelopment in the Town of Los Gatos by 2020, 2030, and 2040
Year Low1 Best2 High3
Existing GSI 4 - 81 -
2020 85 90 94
2030 107 134 160
2040 129 178 226
1Low estimate – projected from 50% of “Best Estimate”; 2Best estimate – rate of redevelopment based on 6-year average (2007-2012); and 3High
estimate – projected from 150% of “Best Estimate”; 4Total area addressed by parcel-based redevelopment projects with GSI completed as of
2018 (excludes non-jurisdictional and green street and regional projects).
6.6.3 Impervious Surface Retrofit Targets
Provision C.3.j.i.2.(c) of the MRP requires the Town to develop (and include in its GSI Plan) targets for
the amount of impervious surface from public and private projects to be retrofitted by 2020, 2030 and
2040. Using the projected redevelopment rate for the Town (Section 6.6.2), current land uses of the
predicted locations of GSI implementation selected using a redevelopment model, and associated
0
50
100
150
200
250
Area (acres) Addressed by GSIProjectedReported
Green Stormwater Infrastructure Plan
39
impervious surface coefficients for each land use type, estimates of the amount of impervious surface
that would be retrofitted with GSI on privately and publicly-owned parcels were developed.
Table 6-3 lists the impervious surface percentage for each land use class, based on impervious surface
coefficients typically utilized, and the estimated impervious surfaces that are predicted to be retrofitted
by 2020, 2030, and 2040 in the Town via GSI implementation on private and public parcels: 68 acres by
2020, 74 acres by 2030 and 110 acres by 2040. Note that these predictions do not include impervious
surface that may be addressed by projects in the public right-of-way, and that these predictions have a
high level of uncertainty because future redevelopment rates may increase or decrease relative to the
historic development trends that the rate for Los Gatos was based on. Therefore, actual impervious
surface addressed by GSI by the various milestones may increase or decrease relative to what is
presented in Table 6-3.
Green Stormwater Infrastructure Plan
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Table 6-3 Actual (2002-2018) and predicted (2019-2040) extent of impervious surface retrofits via GSI implementation on private and public parcels in the
Town of Los Gatos by 2020, 2030, and 2040
Previous Land Use % of Area
Impervious a
Retrofits via GSI Implementation
2002-18 2019-20 2021-30 2031-40 Total (2002-40)
Total
Area
(acres)
Impervious
Area
(acres)
Total
Area
(acres)
Impervious
Area
(acres)
Total
Area
(acres)
Impervious
Area
(acres)
Total
Area
(acres)
Impervious
Area (acres)
Total
Area
(acres)
Impervious Area
(acres)
Commercial 83% 33 28 5 4 2 1 30 25 71 59
Industrial 91% 15 13 - - 3 3 2 1 19 18
K-12 Private Schools 67% - - 8 5 - - 2 1 10 6
Residential - High Density 82% 10 8 - - - - 2 1 12 10
Residential - Low Density 47% 11 5 - - 2 1 <1 <1 14 6
Residential - Rural 10% 4 <1 - - 3 <1 1 <1 7 1
Retail 96% 4 4 - - - - 7 6 11 10
Open Space 1% 3 <1 - - 33 <1 - - 36 0.4
Totals 81 59 13 9 43 6 43 36
180 110
Cumulative d 81 59 93 68 136 74 180 110
a Source: Existing Land Use in 2005: Data for Bay Area Counties, Association of Bay Area Governments (ABAG), January 2006
b Development totals from 2002-2018 may include new development of open space and vacant properties.
c The total area for 2019-2020 is based on facilities that are currently under construction or planned to occur prior to 2020 and not the Phase I redevelopment rate and may therefore deviate from the
“Best” acres presented for 2020 in Table 1.
d Totals in this table differ slightly from predictions presented in Table 6-2 due to the inclusion of entire parcels in this table, as opposed to more generic “land areas” projections presented in Table 6-2.
.
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Project Tracking System
A required component of the GSI Plan is to develop a process for tracking and mapping completed
public and private GSI projects and making the information available to the public. The Town will
continue to implement existing internal tracking procedures for processing public and private projects
with GSI, meeting MRP reporting requirements, and managing inspections of stormwater treatment
facilities. In addition, the Town will provide data to SCVURPPP for countywide tracking of completed
public and private GSI projects.
6.7.1 SCVURPPP Project Tracking System
SCVURPPP has developed a centralized, web-based data management system, with a connection to GIS
platforms, for tracking and mapping all GSI projects in the Santa Clara Valley. This product is called the
SCVURPPP Green Stormwater Infrastructure (GSI) Database The GSI Database provides a centralized,
accessible platform for municipal staff to efficiently and securely collect, upload, and store GSI project
data, and enhances SCVURPPP’s ability to efficiently and accurately calculate and report water quality
benefits associated with GSI projects. It also allows portions of the GSI project information to be made
publicly available.
6.7.2 Town Project Tracking System (Regulated and GSI)
The Town is following the process described below to collect and track project information:
• Information on regulated projects is collected using the SCVURPPP C.3 Data Form. A table on the
project plan sheets is used to collect data on site design or treatment measures installed for
each drainage management area.
• Collected information is entered into a spreadsheet. This spreadsheet is updated as the project
moves through the Town’s approval process. After the project is constructed, the spreadsheet is
used to manage treatment measure inspections and enforcement actions.
• The same spreadsheet will be used to collect and track information on non-regulated GSI
projects.
Town staff will collect and manage information on GSI projects locally using the data management
systems described above, and upload it annually to the SCVURPPP GSI Database for tracking and
mapping.