Last Updated 07/22/2026
Santa Clara Stormwater Laws & Regulations
The County of Santa Clara has enacted a Stormwater Ordinance in order to establish minimum stormwater management requirements and controls to protect and safeguard the general health, safety, and welfare of the public residing in watersheds within this jurisdiction. The County of Santa Clara is the permitting authority for all land disturbing activities and requires the land owner to maintain all on-site stormwater control facilities and all open space areas (e.g. parks or “green” areas) required by the approved stormwater control plan. The County of Santa Clara will only provide construction permits to projects that establish a plan to manage stormwater runoff occurring during the construction process. The County of Santa Clara, under the NPDES program, also has the authority to inspect properties for noncompliance and can issue a notice of violation (NOV) for any deficiency or infraction onsite. Property owners are responsible for the maintenance of any stormwater facilities or practices located on the property. The County of Santa Clara has the authority to inspect stormwater facilities and practices in order to ascertain that they are properly maintained and functioning.
Excerpt-C.3 Stormwater Handbook
1.1 Purpose of this Handbook
This handbook was written to help developers, builders, and project applicants include appropriate post-construction stormwater controls in their projects, to meet local municipal requirements and requirements of the Bay Area Municipal Regional Stormwater Permit (MRP). Municipalities covered by the MRP must require postconstruction stormwater controls on development projects as part of their obligations under Provision C.3 of the MRP. This permit is a National Pollutant Discharge Elimination System (NPDES) permit issued by the San Francisco Bay Regional Water Quality Control Board (Regional Water Board), allowing municipal stormwater systems to discharge stormwater to local creeks, San Francisco Bay, and other water bodies if municipalities conduct prescribed actions to control pollutants. In case of conflicting information between this handbook and the MRP, the MRP requirements prevail.
The term “post-construction stormwater control” refers to permanent features included in a development project to reduce pollutants in stormwater and/or erosive flows during the life of the project – after construction is completed. The term “post-construction stormwater control” encompasses low-impact development (LID) site design, source control, and treatment measures as well as hydromodification management measures. LID techniques reduce water quality impacts by preserving and recreating natural landscape features, minimizing imperviousness, maximizing opportunities for infiltration and evapotranspiration, and using stormwater as a resource.
Post-construction stormwater controls are required for both private and public projects. Although this handbook is written primarily for sponsors of private development projects, its technical guidance also applies to publicly-sponsored projects. Municipalities may also find the handbook useful for training municipal staff and consulting plan checkers.
It’s important to note that post-construction stormwater design requirements are complex and technical: most projects will require the assistance of a qualified civil engineer, architect, landscape architect, and/or geotechnical engineer.
8.1 Summary of O&M Requirements
Maintenance is essential for assuring that stormwater treatment and hydromodification management (HM) measures continue to function effectively and do not cause flooding, provide habitat for mosquitoes, or otherwise become a nuisance. The maintenance requirements described in this chapter apply to regulated projects with stormwater treatment measures, including areas of pervious pavement, if any, and HM measures included in your project. The operation and maintenance (O&M) process can be organized into five phases, as described below:
- Determining ownership and maintenance responsibility;
- Identifying maintenance requirements when selecting treatment measures;
- Preparing the maintenance plan and other documentation;
- Executing a maintenance agreement or other maintenance assurance; and
- Ongoing inspections and maintenance.
8.1.1. Responsibility for Maintenance
The responsibility for the maintenance of stormwater treatment and structural HM measures belongs to the project applicant and/or property owner unless other specific arrangements have been made. Ownership and maintenance responsibility for stormwater treatment measures and HM measures should be considered at the earliest stages of project planning. The municipal stormwater permit also requires that the project applicant provide a signed statement accepting responsibility for maintenance until this responsibility is legally transferred, as well as ensuring access to municipal, Water Board, and Santa Clara County Vector Control District staff.
Excerpt- Post-Construction Urban Runoff Management
Council Policy
Operation and maintenance
All post-construction treatment measures must be installed as specified on approved construction plans. Treatment measures shall be operated and maintained by qualified personnel consistent with approved development plans and/or supplemental operation and maintenance plans. Property owners must ensure that treatment measures continue to operate effectively for the life of the project. Property owners and/or property managers designated by the owner must keep a maintenance schedule and record of all treatment measures maintenance activities. Copies of maintenance schedules and records will be retained and made available for inspection upon request by the City.
When used, all proprietary treatment measures must be operated and maintained per the manufacturers’ specifications. The City may require additional maintenance beyond the manufacturers’ specifications, if needed.
BACKGROUND
The Federal Clean Water Act requires the City of San José to operate under a Municipal Stormwater NPDES Permit for the discharge of stormwater via the City’s stormwater collection system. On October 14, 2009, the Regional Water Control Board adopted the Municipal Regional Stormwater NPDES Permit (Permit Number CAS612008) for the San Francisco Bay Region. In an effort to standardize stormwater management requirements throughout the nine county region, this permit replaces the formerly separate countywide municipal stormwater permits with a regional permit for 76 Bay Area municipalities, including the City of San José.
The Municipal Regional Permit mandates the City of San José to use its planning and development review authority to require that stormwater management measures such as Site Design, Pollutant Source Control and Treatment measures are included in new and redevelopment projects to minimize and properly treat stormwater runoff. The MRP requires use of Low Impact Development (LID) techniques including infiltration, harvest and reuse, evapotranspiration, or biotreatment to manage stormwater. The objective of LID is to maintain predevelopment rates of infiltration, evaporation, and runoff from the property being developed. Treating stormwater as a resource, rather than a waste product is a central tenet of the MRP’s LID requirements.
City Council Policy 8-14: Post-Construction Hydromodification Management (last revised February 23, 2010), is a related companion policy that addresses the management of stormwater runoff to minimize erosion and sedimentation in local rivers and creeks.
View State Page
Resources
County of Santa Clara Stormwater Management Page
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California Stormwater Website
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Stormwater Multiple Application and Report Tracking System (SMARTS) Login
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Santa Clara C.3 Stormwater Handbook Guidance for Implementing Stormwater Requirements for New Development and Redevelopment Projects
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Frequently Asked Questions
What is the C.3 Stormwater Handbook, and why does it matter for my Santa Clara County project?
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It’s the guidance document municipalities in the county use to help developers and project applicants meet post-construction stormwater control requirements under Provision C.3 of the Bay Area Municipal Regional Stormwater Permit. That permit is what allows local stormwater systems to discharge into creeks and San Francisco Bay in the first place, so C.3 compliance isn’t optional for qualifying development.
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What counts as a post-construction stormwater control under the MRP?
More than just a detention pond. The term covers low-impact development site design, source control measures, treatment measures, and hydromodification management measures, all working together to reduce pollutants and control erosive flows for the life of the project after construction ends.
Do I need an engineer to design my stormwater controls in Santa Clara County?
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Likely yes. The C.3 Handbook is explicit that post-construction design requirements are complex and technical, and most projects will need a qualified civil engineer, architect, landscape architect, or geotechnical engineer involved, not just a general contractor working from a template.
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What are the five phases of stormwater operation and maintenance under Santa Clara County's C.3 requirements?
Determining who owns and maintains the system, identifying maintenance needs when selecting which treatment measures to use, preparing the maintenance plan and supporting documentation, executing a maintenance agreement or similar assurance, and then ongoing inspection and maintenance once the project is complete.
Who is responsible for maintaining stormwater treatment measures on my property in Santa Clara County?
The project applicant or property owner, unless a different arrangement has been specifically made. The regional permit also requires the applicant to sign a statement accepting that responsibility until it’s legally transferred, and to guarantee access for municipal staff, Water Board staff, and the Santa Clara County Vector Control District.
Why does the Vector Control District need access to my stormwater system?
Because treatment and hydromodification measures that aren’t maintained properly can end up holding standing water and providing mosquito habitat. That’s one of the specific failure modes the C.3 Handbook calls out as a reason maintenance matters beyond simple water quality.
Does the City of San José have its own separate stormwater maintenance rules on top of the county's?
Yes. San José operates under the same regional MRP but enforces its own Council Policy on post-construction runoff management. That policy requires treatment measures to be maintained by qualified personnel consistent with approved plans, and requires property owners or their designated managers to keep maintenance schedules and records available for city inspection on request. Proprietary treatment systems also have to be maintained per manufacturer specifications, and the city can require more maintenance than the manufacturer calls for if it decides that’s necessary.
Does the City of San José have its own separate stormwater maintenance rules on top of the county's?
AQUALIS helps Santa Clara County property owners and developers prepare the maintenance plans and agreements the C.3 Handbook requires, maintain treatment and hydromodification measures to the standard qualified personnel are expected to meet, and keep the inspection records municipalities like San José require on request.
The information on this page is provided for general informational purposes only and is not legal advice. Regulations change frequently — AQUALIS makes no warranty as to the accuracy or completeness of this content, and any reliance on it is at your own risk. Consult a qualified professional or your local regulatory authority to confirm requirements applicable to your specific property.
