Stormwater Program

Humboldt County Public Works administers a stormwater management program to reduce the discharge of pollutants to the storm sewer systems and associated receiving waters as regulated by the federal Clean Water Act through the National Pollution Discharge Elimination System (NPDES) permit program.

In February 2013, the SWRCB adopted the small Municipal Separate Storm Sewer System (MS4) permit, also known as the Phase II Permit. The MS4 Permit has been amended by the SWRCB several times since its original adoption and is likely to begin the permit revision process soon. The SWRCB’s Municipal Stormwater Program webpage notes the “U.S. EPA defines an MS4 as a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains) owned or operated by a State.” 

The small MS4 Permit applies to stormwater discharges from MS4s, where designation as a “small” MS4 is related to a region’s population. The MS4 Permit provides regulatory consistency across the state to reduce discharge of pollutants to storm sewer systems and the environment. The SWRCB has stipulated the small MS4 Permit applies to McKinleyville, the unincorporated Eureka area, and Shelter Cove (County of Humboldt Phase II MS4 Boundary Maps).  

Stormwater is a valued natural resource, and during many years in Humboldt County it can be an abundant one. During years of drought, as well as years of normal precipitation, insuring this resource is pollution-free has become increasingly important. The United States Environmental Protection Agency (U.S. EPA) and California’s State Water Resources Control Board (SWRCB) have tasked local government agencies, such as Humboldt County’s Department of Public Works, to administer a stormwater management program to reduce discharge of pollutants to storm sewer systems and the associated receiving waters within the County’s MS4 jurisdiction, as regulated by the federal Clean Water Act through the National Pollution Discharge Elimination System permit program. Stormwater management extends beyond managing water quality flowing from our rooftops, driveways, parking lots and streets into storm sewer systems, managing stormwater quality discharging from construction sites and commercial and industrial facilities is required as well. The SWRCB has organized California’s stormwater permitting program to regulate discharges from three potential sources: the Industrial General Permit (IGP), the Construction General Permit (CGP), and the MS4 permit.

Telegraph Creek culvert, Shelter Cove

Telegraph Creek culvert
  1. Industrial Stormwater Permit
  2. Construction Stormwater Permit
  3. Municipal Stormwater Permit

Industrial facilities associated with potentially regulated standard industrial classifications, such as manufacturing a variety of products, livestock feedlots, transportation, and warehousing, which are industries frequently required to obtain Industrial General Permit coverage.

 California Senate Bill 205 “… requires a person applying to a city or county for a new or renewed business license to demonstrate enrollment in a National Pollutant Discharge Elimination System (NPDES) storm water permit, if such a permit is required.” 

Humboldt County’s Department of Public Works recommends reviewing information presented on SWRQB’s Industrial Stormwater Program webpage to learn more about the program and to determine if your business conducts an industrial activity which requires an IGP.

Low Impact Development

The small MS4 Permit mandates Humboldt County to direct certain development projects to comply with post-construction stormwater requirements based on “low impact development” (LID) standards. LID standards are intended to accommodate a site’s pre-development precipitation runoff by incorporating design techniques which capture, treat, and infiltrate stormwater onsite. These standards came into effect July 1, 2015, and the MS4 permit is slated to be updated by the SWRCB in the next few years.

Rain BarrelsThe MS4 Permit specifies two development project size classes for post-construction requirements. Projects creating and/or replacing 2,500 to 5,000 square feet of impervious surface (“small projects”) are required to implement one or more designated site design measures to reduce project site runoff, as described in the LID Stormwater Manual for Humboldt County. An impervious surface is a surface covering or pavement of a developed parcel of land that prevents the land's natural ability to absorb and infiltrate stormwater. Impervious surfaces include, but are not limited to: roof tops, walkways, patios, driveways, parking lots, storage areas, impervious concrete and asphalt, and any other continuous watertight pavement or covering. Examples of site design measures include disconnection of rooftop drainage from impervious areas, tree planting and preservation, rain barrels, vegetated swales, and porous pavement. Projects creating and/or replacing 5,000 square feet or more of impervious surface (“regulated projects”) are required to implement site design measures based on more detailed procedures and are required to demonstrate compliance with runoff reduction thresholds. Some projects may be required to construct bioretention facilities to promote infiltration of stormwater, while other projects in the larger size category will need to employ source control measures to minimize the contact between pollutants and stormwater runoff. 

Procedures, standards, and specifications for implementing the post-construction requirements of the MS4 Permit are contained in the Humboldt Low Impact Development Stormwater Manual V3.0. This manual is also used by the Cities of Eureka, Arcata, Fortuna, and Trinidad for compliance with the MS4 Permit. Humboldt LID Stormwater Manual V3.0 and associated documents are available on the North Coast Stormwater Coalition w

Low Impact Development for Existing Sites

LID measures need not to be solely for new development projects, LID measures can, and are encouraged to be, incorporated into existing sites to enhance stormwater retention and infiltration onsite, with LID measures often being considered not only beneficial to water quality, but also attractive assets to a site. Site design measures include tree planting and preservation, rain capture and storage for later use, directing rooftop drainage systems to discharge to vegetated areas, and incorporation of permeable driving surfaces, such as driveways constructed using pavers which allow for infiltration of stormwater.

Working Together on the Humboldt Bay

The County of Humboldt, the City of Eureka, and the Humboldt Community Services District collaborated to develop the Eureka Area Watershed Storm Water Resource Plan (EAWSWRP), which was made public in August 2018. The EAWSWRP is a regional stormwater planning document that facilitates a watershed-based analysis and planning effort within watersheds that drain to Humboldt Bay. The EAWSWRP is intended to maximize cooperation and collaboration among state, regional, and local agencies, and other stakeholders during the identification, development, and implementation of stormwater projects. 

North Coast Stormwater Coalition

Humboldt County participates in the North Coast Stormwater Coalition (NCSC), which coordinates regional stormwater management efforts. The NCSC is an alliance of regional county and city governments collaborating to reduce stormwater pollution and protect local watersheds. Coalition members include stormwater management staff from the participating Cities of Arcata, Eureka, Fortuna, Ft. Bragg, Trinidad and Yreka, the Counties of Humboldt and Mendocino, and Humboldt State University, as well as representatives of other local, state, and federal agencies, non-profit organizations, tribes, the State and Regional Water Boards, consultants, engineers, and interested community members. We are a robust group that meets monthly, with public education and outreach events and workshops occurring throughout the year. More information is provided on the North Coast Stormwater Coalition website.

Community Efforts

There are many Humboldt County groups and residents whose efforts to keep Humboldt free of litter and other pollution deserve a note of gratitude; their volunteer efforts promote a healthy environment for County residents and visitors to enjoy and experience. An incomplete listing of groups who step up for our community include:

 There are also numerous Humboldt County residents who show initiative and dedication to the community by cleaning up litter encountered during their daily activities, and Public Works wants these folks to know their efforts are appreciated. Thank you to those whose commitment extends to the community at large.

Documents for Viewing and Download

The following State, Federal and Association websites contain technical and regulatory information regarding Municipal, Construction, and Industrial stormwater programs and stormwater pollution prevention resources.

Humboldt Waterways Poster