Background
Dry Weather Urban Runoff (DWUR) is water that is generated by daily activities, such as lawn irrigation, hosing down sidewalks, and car washing. If Best Management Practices are not employed to minimize the amount of runoff generated and to keep areas clean, the DWUR picks up contaminants and other materials based on what the runoff flows over, and the DWUR can make its way to the beach and contribute to beach postings and closures. OC San’s Urban Runoff Program, which began in 1999, is designed to minimize adverse impacts on coastal beaches and public health, while maintaining the high quality of its primary function –collection, treatment and disposal of wastewater.
In 1999, a Huntington Beach closure investigation indicated that the DWUR flowing into the Pacific Ocean may have caused or contributed to shoreline contamination and high bacteria levels. As a result, the Orange County Sanitation District (OC San) began the DWUR Diversion Program.
By accepting DWUR, OC San has helped reduce bacterial exceedances along Orange County’s beaches.
OC San’s Program
As part of a regional best management practice (BMP) to control urban runoff, OC San accepts DWUR from pump stations and channels located in coastal Orange County cities (including of Huntington Beach and Newport Beach) into OC San’s sanitary sewer system for treatment.
The DWUR Program began in December 1999 when OC San’s Board of Directors agreed to temporarily accept DWUR into its sewer system for treatment to assist the region in addressing a fecal contamination issue that impacted Huntington Beach. In April 2000, the board first adopted a resolution for accepting DWUR on a long-term basis during dry weather. Policy modifications have been codified in succeeding resolutions (the most current of which was adopted in 2013). The resolutions clarify OC San's participation to assist regional partners in minimizing adverse impacts on coastal beaches and public health while not jeopardizing OC San's primary function of maintaining high quality collection, treatment, and disposal of wastewater.
In general, OC San accepts DWUR into the sanitary sewers under the following terms:
- The total amount of DWUR flow will not impact OC San nor exceed 10 million gallons per day.
- Dischargers are not required to pay any fees associated with the approved discharge of DWUR into OC San’s sewer system until such time as OC San's Board changes its DWUR fee policy.
- OC San will accept DWUR throughout the year only on days when no measurable rainfall occurs in any portion of OC San's service area (including the period immediately following the cessation of rainfall until such time that OC San’s operations have returned to normal).
Urban Runoff Quality
OC San has tracked and monitored the quality of DWUR discharges into its sewer system since the inception of the DWUR Program. This oversight activity ensures compliance with OC San’s local limits and supports impact assessments of OC San's ability to meet ocean discharge and other regulatory compliance requirements.
Discharge Permits
Dischargers must complete an application and supply required technical information to enter into an Agreement regarding the terms and conditions for discharging DWUR into OC San’s system. Upon entering into such an agreement with OC San, the discharger must then obtain and maintain a valid DWUR diversion permit. The permit issued by OC San establishes terms and conditions necessary for the diversion to comply with OC San’s Wastewater Discharge Regulations.
Diversion Flows
Flows range between 0.2 to 3.0 million gallons per day (mgd).