What will be asked of developments that employ LID for large scale projects (4 units or more)?
LID project applicants for all developments and redevelopments will be required to incorporate stormwater mitigation measures into their design plans and submit the plans to the City for review and approval.
Projects that are part of a larger common plan of development involving five units or more will be subject to the requirements for “All Other Development”. This includes projects that are subject to one common grading permit and projects that have phased schedules or are intended to be sectioned off for sale to individual homeowners.
Project applicants for all developments and redevelopments will also be required to incorporate the following performance measures and practices into their design plans.
Conserve Natural Areas
Each project site possesses unique topographic, hydrologic and vegetative features, some of which are more suitable for development than others. Locating development on the least sensitive portion of a site and conserving naturally vegetated areas can minimize environmental impacts in general and stormwater runoff impacts in particular.
If applicable and feasible for the given site conditions, the following measures are required and should be included in the project site layout:
- Concentrate or cluster improvements on the least sensitive portions of the site, while leaving the remaining land in a natural undisturbed state;
- Limit clearing and grading of native vegetation at the site to the minimum area needed to build the home, allow access, and provide fire protection;
- Maximize trees and other vegetation at the site by planting additional vegetation, clustering tree areas, and promoting the use of native and/or drought tolerant plants; and
- Preserve riparian areas and wetlands.
Protect Slopes and Channels
Erosion of slopes and channels can be a major source of sediment and associated pollutants, such as nutrients, if not properly protected and stabilized.
Slope protection practices must conform to design requirements or standards set forth by local permitting agency erosion and sediment control standards and design standards. The post construction design criteria described below are intended to enhance and be consistent with these local standards.
- Slopes must be protected from erosion by safely conveying runoff from the tops of slopes.
- Slopes must be vegetated with first consideration given to native or drought tolerant species.
The following measures should be implemented to provide erosion protection to unlined receiving streams on the project site. Activities and structures must conform to applicable permitting requirements, standards and specifications of agencies with jurisdiction (e.g., U.S. Army Corps of Engineers, California Department of Fish and Game, or Regional Water Quality Control Board).
- Utilize natural drainage systems to the maximum extent practicable, but minimize runoff discharge to the maximum extent practicable.
- Stabilize permanent channel crossings.
- Install energy dissipaters, such as rock riprap, at the outlets of storm drains, culverts, conduits or channels that discharge into unlined channels.
Provide Storm Drain System Stenciling and Signage
Storm drain message markers or placards are required at all storm drain inlets within the boundary of the project. The marker should be placed in clear sight facing toward anyone approaching the inlet from either side. All storm drain inlet locations must be identified on the development site map.
Some local agencies within the City have approved storm drain message placards for use. Consult local permitting agency stormwater staff to determine specific requirements for placard types and methods of application.