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Public Works

STORM WATER PROGRAM

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Low Impact Development (LID)

What is LID?

Low Impact Development (LID) is an innovative approach to managing storm water and urban runoff that mitigates the negative effects of development and urbanization by controlling runoff at the source instead of expensive end-of-line treatment facilities.

LID techniques can be applied to all types and sizes of projects including residential homes, commercial and industrial lots, parking lots, sidewalks, and medians. Design techniques can be used to infiltrate, filter, store, evaporate, and detain runoff reducing storm water runoff from a site which improves water quality and also recharges the groundwater. LID includes a wide variety of techniques which include disconnecting rain gutters, reducing the amount of impervious surface, permeable paving, and infiltration swales.     

Techniques are based on the premise that storm water management should not be seen as storm water disposal. Instead of conveying and managing/treating storm water in large, costly end-of-pipe facilities located at the bottom of drainage areas, LID addresses storm water through small, cost-effective landscape features located at the lot level.

These landscape features, known as Integrated Management Practices (IMPs), are the building blocks of LID. Almost all components of the urban environment have the potential to serve as an IMP. This includes not only open space, but also rooftops, streetscapes, parking lots, sidewalks, and medians. LID is a versatile approach that can be applied equally well to new development, urban retrofits, and redevelopment/revitalization projects.

LID Examples

Small multi-functional detention area at Dove Creek (Atascadero, CA). Source Wallace Group.

Costco Bio-swale (San Luis Obispo). Source Wallace Group.

Porous concrete was used in lieu of traditional asphalt to protect the oak tree adjacent to the parking lot. Source Wallace Group.

A curb cut to allow storm water to run off into a landscaped area to be absorbed.

 

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Links for more information on LID

Central Coast LIDI

www.centralcoastlidi.org
The site is a resource for Central Coast LID practitioners and includes technical, economic, and policy information related to the implementation of LID projects and programs. This site also  includes Central Coast LID Plant Guidance.

LID Informational Brochure
www.coastal.ca.gov/nps/lid-factsheet.pdf

Central Coast Regional Water Quality Control Boards:
Low Impact Development

This link provides more information including why the State Water Resources Control Board requires LID and links to a variety of LID resources.

SLO Green Build
www.slogreenbuild.org

Green building practices include site sustainability, such as:

  • Water conservation/reduction
  • Energy conservation/reduction
  • Materials and resources
  • Indoor environmental quality

EPA Conceptual Guide to Green Streets

A Green Street is a street that uses natural processes to manage storm water runoff at its source.  This guide provides an overview of different strategies that can be used in residential or commercial areas. Download PDF.

Low Impact Development Center

The Low Impact Development Center is a non-profit organization dedicated to the advancement of Low Impact Development technology. Low Impact Development is a new, comprehensive land planning and engineering design approach with a goal of maintaining and enhancing the pre-development hydrologic regime of urban and developing watersheds. Visit: www.lowimpactdevelopment.org 

Low Impact Development Urban Design Tools

This web site provides watershed managers with a new set of tools and techniques that can be used to meet regulatory and receiving water protection program goals for urban retrofits, re-development projects, and new development sites.
Visit: www.lid-stormwater.net.

LID Best Management Practices

The City recommends that the following LID Best Management Practices Manuals be used to determine the best type of LID techniques:

The Low Impact Development Manual for Southern California: Technical Guidance and site Planning Strategies can be downloaded here: California Stormwater Quality Association

The California Storm Water Quality Association’s Storm Water Best Management Practice Handbook for New Development and Redevelopment: Download PDF here.

The Contra Costa Clean Water Program Storm Water C.3. Guidebook: Download PDF here.

The City of Santa Barbara Post-Construction Best Management Practice Manual: Download PDF here.

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LID for Box Stores

This guideline provides large building and high volume retailers with strategies that integrate innovative and highly effective Low Impact Development (LID) Storm water management techniques into their site designs for regulatory compliance and natural resource protection at the local levels. Download LID for Box Stores (pdf).

Attachment 4 Requirements

The City is subject to Attachment 4 of the State General Permit for Small Municipal Separate Storm Sewer Systems (MS4) due to its high growth rate.  All new and redevelopment projects including but not limited to a tentative map, conditional use permit, planned development, or building permit that falls under one or more of the following categories, must include the design standards outlined in Attachment 4.

Please note that the City’s Zoning Code is more strict than Attachment 4 in several categories, therefore, the Zoning code must be followed.  Attachment 4 includes the following types of development:

  1. Single-family Hillside Residences. Hillside means property where the development contemplates grading on any natural slope that is ten percent or greater;
  2. Commercial Developments that create at least 10,000 square feet of impervious surfaces, including parking areas;
  3. Automotive Repair Shops;
  4. Retail Gasoline Outlets;
  5. Restaurants;
  6. Residential developments with 5 or more housing units;
  7. Parking lots 5,000 square feet.

Download the Attachment 4 Requirements.

Low Impact Development Guidelines Handout
The interim Low Impact Development guidelines are a pilot project sponsored by the Municipalities in San Luis Obispo County and the Central Coast Regional Water Quality Control Board. This brochure outlines the transition into the new requirements for hydromodification control criteria, and includes the requirements for Tier 1 and Tier 2 projects.

  • Tier 1 Projects: Projects that create between 2,500 and 5,000 square feet of impervious surface should incorporate LID into site planning and to implement at least one agency approved LID structural practice into the project.
  • Tier 2 Projects: Projects that create over 5,000 square feet of impervious surface should incorporate LID into site planning and to implement at least two agency-approved LID structural practices into the project

LID for Stormwater Control: Interim Design Guidance for New and Redevelopment Projects (Handout)

This handout has step by step instructions for meeting the Interim LID requirements for Projects in Tier 3 or projects with components that meet one or more of the following criteria. The interim guidance must be applied to the entire project, not just that portion that meets the criteria.

  • Commercial developments of over 100,000 square feet of impervious surface.
  • Residential projects with a potential of 10 or more units and over 10,000 square feet of impervious surface.
  • Parking lots with 25 spaces or more than 5,000 square feet of impervious surface.
  • Parking lots with 25 spaces or more than 5,000 square feet of impervious surface.

 LID Parking Lots - Technical Assistance Memo

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Hydromodification

What is Hydromodification?

Hydromodication Illustration - click to enlargeUS EPA (1993) defines hydromodification as the “alteration of the hydrologic characteristics of coastal and non-coastal waters, which in turn could cause degradation of water resources”.

Hydromodification results in the disturbance of the natural plumbing of communities. Examples of hydromodification include indirect, increased runoff from impervious surfaces that increases channel erosion and floodplain dimensions, straightening, stream relocations, construction along streams, narrow bridge spans that pinch or redirects stream flow into stream banks and increases velocities, construction and operation of dams and impoundments, and channelization and maintenance to remove in-stream blockages.

Development, construction, erosion and land use changes that do not attempt to replicate natural functions on-site, will always impact and change the hydrology, shape and function of landforms in and adjacent to stream channels and other water bodies.

Image Caption: Relationship between impervious surface area, surface runoff, infiltration and evapotranspiration (Source: Stream Corridor Restoration: Principles, Processes, and Practices, FISWG 1998)

Links for more information on Hydromodification.

State Water Resources Control Board: Hydromodification, Stream Channel Modification

EPA Hydromodification Website

 

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