The San José Green Alleys Demonstration Project will retrofit up to nine alleys in a disadvantaged community with LID permeable pavement and infiltration facilities to eliminate sediment and ponding in the alleys to improve stormwter quality, and to make the alleys a community ammenity. The project will demonstrate how an LID retrofit project can directly improve water quality and also enhance neighborhood livability.
The San José Green Alleys Demonstration Project will retrofit up to nine alleys in a disadvantaged community with LID permeable pavement and infiltration facilities to eliminate sediment and ponding in the alleys, improve stormwater quality, and make the alleys a community ammenity. The project will to demonstrate how an LID retrofit project can directly improve water quality and also enhance neighborhood livability.
Drinking Water Supply
Water Quality Improvement
Habitat Protection and Restoration
The project improves water quality and reduces flooding by constructing LID- based drainage improvements in alleys that are surfaced with deteriorating pavement, and in places are unpaved and generate substantial dust and sediment. Since each of the alleys lack drainage infrastructure, water floods them and adjacent yards and garages during storms. The project will resurface the alleys with permeable pavement and pavers that will drain to below-grade infiltration galleries. The project benefits a disadvantaged community since it is located within the larger Spartan-Keyes Strong Neighborhood Initiative area (SNI). The San José City Council adopted the Strong Neighborhoods Initiative (SNI) Redevelopment Plan with the purpose of providing for the rehabilitation and redevelopment of blighted areas within the San Jose Redevelopment Project Area. The project site is located in a census tract with a Median Household Income (2009 American Community Survey) of $35,427, which is less than 59% of the State Median Household Income ($60,392). According to the Spartan-Keyes Neighborhood Improvement Plan Amendment (December 2008), the condition of alleyways in the Spartan Keyes SNI Area has been an ongoing concern of residents.
The project is located within the Spartan-Keyes Strong Neighborhood Initiative area. The San José City Council adopted the Strong Neighborhoods Initiative (SNI) Redevelopment Plan with the purpose of rehabilitating and redeveloping blighted areas within the Redevelopment Project Area. The Spartan-Keyes Neighborhood Improvement Plan identifies improving the condition of the alleys with new pavement and proper drainage as a top ten neighborhood improvement and blight reduction objective.
Community educational outreach about the project will promote local stewardship of the watershed. The City will leverage the outreach and education resources of local NGOs such as Acterra and United Neighborhoods of Santa Clara Valley to maximize the educational potential of the project. The project will also yield practical information regarding the cost, design and construction best practices and performance of an LID green infrastructure retrofit of an existing street. The City has developed a water quality monitoring plan specifically for the project that will characterize and measure surface pollutants and runoff volumes both pre- and post project. The monitoring will measure the performance of the project's LID features and contribute to the larger body of BMP effectiveness data, and specifically to the San Francisco Estruary Partnership's Regional Green Infrastructure Capacity Building Project and its LID effectiveness study. The City of San Jose is also part of the Santa Clara Valley Urban Runoff Pollution Prevention Program (SCVURPPP), whose 15 member agencies need to implement LID treatment measures on private and public projects to comply with their stormwater NPDES permit. This project will benefit SCVURPPP agencies by providing information and examples of how to implement LID in an urban retrofit setting. SCVURPPP will provide guidance and technical assistance on LID measure design and help promote the demonstration projects at trainings and workshops.
Yes. Local matching funds may support educational outreach about the project and community watershed stewardship events.
Yes. The project uses a Low Impact Development approach that works with nature to manage rainwater close to where it falls. The LID practices the project will use are percolation through permeable surfaces and infiltration into native soils. By implementing LID principles, water can be managed in a way that reduces the impact of built areas and promotes the natural movement of water within an ecosystem or watershed.
Part 2 - Detail
The San José Green Alley Demonstration Project will create durable, cost-effective Low Impact Development drainage improvements in up to nine alleys in a disadvantaged community to demonstrate how LID strategies work in a retrofit project context. The subject alleys are spread throughout an older neighborhood of San José where adjacent properties that lack BMPs drain to the alleys, and buildings flanking the alleys prevent the use of surface stormwater treatment facilities. Because the alleys lack drainage improvments, ponding during the wet season precludes their use by residents for either transportation or recreation and causes pavement to rapidly deteriorate. Poor surface conditions generate sediment and hinder street sweeping for pollutant control. Because the alleys aren't used by residents, they are frequently used for illegal dumping. During the rainy season, standing water mobilizes pollutants and either flows or is tracked onto adjoining streets where it mixes with less-polluted stormwater. The project will demonstrate how LID methods that maximize storm water infiltration on site can reduce the total runoff and associated pollutants from the alleys and make a useful neighborhood ammenity.
The project will first evaluate the feasibility of replacing existing surfaces and constructing underground infiltration features in each of the nine alleys in the Spartan-Keys neighborhood just south of downtown San Jose. Based on 2010 census data, most of Spartan-Keyes is a disadvantaged community. The City will construct at least one demonstration project at the most feasible alley to evaluate an existing conceptual design that installs permeable pavement in low-traffic areas, recycled content, high-albedo green concrete in high traffic areas, and constructs underground infiltration galleries beneath the preamble areas to infiltrate water from the permeable areas. Water quality and quantity monitoring of both pre and post project conditions will quantify pollutant loading and identify the pollutant removal rates and flow reduction benefits of the specific green infrastructure improvements. The design of the first demonstration alley can be modified as necessary for subsequent ally retrofits, to achieve an overall project goal of improving all alleys within the neighborhood where an LID retrofit is feasible.
San Francisco Estuary Project Regional Green Infrastructure Capacity Building Project. The SFEP Green Infrastructure Capacity Building Project. The SFEP Green Infrastructure Capacity Building Project
San Mateo County Green Sustainable Streets and Parking Lots Guidebook: http://www.flowstobay.org/ms_sustainable_streets.php
CEQA Notice Of Exemption: http://www.ceqanet.ca.gov/NOEdescription.asp?DocPK=658848
The EPA's "Protecting Water Quality from Urban Runoff" identifies urban runoff pollutants as sediment, oil, grease from motor vehicles, pesticides and nutrients from lawns, and thermal pollution from dark surfaces. These pollutants can harm fish and wildlife, kill native vegetation, foul drinking water, and make recreational areas unsafe and unpleasant. In their current condition, neighborhood alleys are known sources of sediment and other urban pollutants to the Guadalupe River. Because the alleys lack drainage infrastructure, ponding water has deteriorated the pavement, exposing bare dirt that generates the sediment. The project will provide a durable surface in the alleys to eliminate sediment sources, and will use infiltration to reduce polluted urban runoff and will use permeable pavers to infiltrate stormwater to prevent the transport of urban runoff pollutants. The EPA's "Field Evaluation of Permeable Pavements for Stormwater Management" found that the use of permeable pavement systems dramatically reduced surface runoff volumes by reducing the effective impervious area. Retrofit of the alleys with LID features will reduce runoff volumes and urban runoff pollutants loads, and provide durable light colored surfaces to reduce heat island impacts and encourage beneficial use of the alleys.
The San Jose Green Alley project will reduce the quantity of urban runoff pollutants that enter the Guadalupe River from the local storm drain system by creating permanent permeable surfaces within the alleys that will absorb stormwater runoff. The alley's current lack of drainage infrastructure allows ponding, which concentrates pollutants that are then carried by storm water flows and tracked by vehicles onto adjacent streets. Ponding also creates breeding grounds for mosquitoes and other pests. Sediment control is the primary strategy to address mercury and pesticide toxicity impairments in the Guadalupe River. Through the same mechanism, the project will also curtail local thermal pollution and reduce the amount of oil, gas, diesel, and PAHs that are transported to the Guadalupe River.
i. Water Supply (conservation, recycled water, groundwater recharge, surface storage, etc.)
ii. Water Quality
The project will improve stormwater quality by reducing the overall volume of runoff from the alleys and by preventing the mobilization of urban pollutants through runoff. The project will eliminate sediment sources by replacing deteriorated asphalt in the alleys with a durable surface of high albedo "green concrete" that drains to below-grade infiltration devices. On-site infiltration facilities will be sized to retain and infiltrate 80% of the annual runoff from the alleys drainage area. Successful completion of the project will provide an example of how existing urban streets and alleys can be retrofitted with cost-efficient stormwater management features that provide long-term water quality benefits.
iii. Flood and Stormwater Management
The project will demonstrate how the LID practices of using permeable surfaces and on-site infiltration can be combined to retrofit a typical urban hardscape that lacks stormwater management infrastructure and has no space for above-ground stormwater features. Three functional stormwater management improvements will be provided: elimination of deteriorated sediment-generating asphalt and associated ponding, and conveyance of runoff through a permeable surface to infiltration facilities, and storage and infiltration of the water quality design storm through subsurface infiltration trenches and dry wells. The project will create durable, low-maintenance improvements that provide long-term water quality benefits to alleys in an older neighborhood typical of Bay Area cities.
iv. Resource Stewardship (watershed management, habitat protection and restoration, recreation, open space, etc.)
Increases Water Supply Reliability
Advances/ Expands Conjunctive Management of Multiple Water Supply Sources
Increases Water Use and/or Reuse Efficiency
Provides Additional Water Supply
Promotes Water Quality Protection
Reduces Water Demand
Advances/Expands Water Recycling
Promotes Urban Runoff Reuse
Addresses Sea Level Rise
Addresses other Anticipated Climate Change Impact (e.g. through water management system modifications)
Improves Flood Control (e.g. through wetlands restoration, management, protection)
Storm Sewer Operating funds, Storm Sewer Capital funds
None. Public rights of way.
Less than $200 per alley annually
Storm Sewer Operating funds
Use and Reuse Water More Efficiently
Climate Change Response Actions (Adaptation to Climate Change, Reduction of Greenhouse Gas Emissions, Reduce Energy Consumption)
Expand Environmental Stewardship
Practice Integrated Flood Management
Protect Surface and Groundwater Quality
Improve Tribal Water and Natural Resources
Ensure Equitable Distribution of Benefits
Reduce Reliance on the Bay-Delta
Reduce Water Demand
Improved Operational Efficiency and Transfers
Increase Water Supply
Improve Water Quality
Improve Flood Management
Practice Resources Stewardship
Other Strategies (Please Describe)
Groundwater Management Plan
Urban Water Management Plan
Water Meter Requirements
Groundwater Monitoring Requirements
AB 1420 Compliance
Water supply reliability, water conservation and water use efficiency
Stormwater capture, storage, clean-up, treatment, and management
Removal of invasive non-native species, the creation and enhancement of wetlands, and the acquisition, protection, and restoration of open space and watershed lands
Non-point source pollution reduction, management and monitoring
Groundwater recharge and management projects
Contaminant and salt removal through reclamation, desalting, and other treatment technologies and conveyance of reclaimed water for distribution to users
Water banking, exchange, reclamation and improvement of water quality
Planning and implementation of multipurpose flood management programs
Watershed protection and management
Drinking water treatment and distribution
Ecosystem and fisheries restoration and protection
Reduced Reliance on the Bay-Delta
Projects that directly address a critical water quality or supply issue in a DAC
Urban water suppliers implementing certain BMPs as on page 17 of Guidelines
Be designed to manage stormwater runoff to reduce flood damage (PRC §5096.827)
Be consistent with the applicable Regional Water Quality Control Plans (Basin Plans) (PRC §5096.827)
Not be a part of the State Plan of Flood Control (SPFC) (PRC §5096.827)
With regard to the project's water quality benefits, the EPA's "Protecting Water Quality from Urban Runoff" identifies urban runoff pollutants as sediment, oil, grease from motor vehicles, pesticides and nutrients from lawns, viruses and bacteria from pet waste, and thermal pollution from dark surfaces. These pollutants can harm fish and wildlife, kill native vegetation, foul drinking water, and make recreational areas unsafe and unpleasant. In their current condition, the deteriorated alleys that will be improved by the project are known to contribute sediment and other urban pollutants to the Guadalupe River. Because the alleys lack drainage infrastructure, ponding water has deteriorated the pavement, exposing bare dirt that generates the sediment. Potholes and stretches of bare soil have been filled by residents with additional dirt, gravel, wood chips and carpet scraps that break down and are washed to the storm drain system, and ultimately the Guadalupe River. The project will provide a durable surface in the alleys to eliminate sediment sources and will use infiltration to reduce polluted urban runoff and will use permeable pavers to infiltrate stormwater to prevent the transport of urban runoff pollutants. The EPA's "Field Evaluation of Permeable Pavements for Stormwater Management" found that the use of permeable pavement systems dramatically reduced surface runoff volumes by reducing the effective impervious area. The project's reduction of runoff volumes will result in reductions of urban runoff pollutants, and preserve the capacity of the storm sewer collection system to handle storm events that are expected to become more intense as a result of climate change.