The Environmental Engineering unit of OC Watersheds works to solve multifaceted issues with a mixture of technical expertise and policy integration. This unit is responsible for exploring and managing innovative approaches to address complex water resource management issues within Orange County’s three Watershed Management Areas (WMA). By incorporating science, policy, and public opinion, the Project Management Group works with local stakeholders to develop integrated watershed management plans and projects that address flood management, water use efficiency, water supply and reliability, recycled water, habitat preservation and conservation, and water quality protection and improvement.
Additionally this unit provides technical engineering services in support of OC Watershed water quality objectives. Expertise and assistance are primarily in the planning, design, implementation, and performance evaluation of structural best management practices (BMPs) for both dry weather urban and storm runoff. Such facilities include: dry weather runoff mechanical treatment facilities at either streamside or ocean side locations; mechanical facilities which divert dry weather runoff from major flood control channels to sanitary sewers; and public domain BMPs such as water quality basins, constructed wetlands, and passive sand filters. Staff provides technical and contract oversight for consultant design of both public domain and proprietary BMPs, oversight during construction, and conducts or assists in performance evaluations of treatment efficiency prior to facility acceptance by the County.
Once facilities are constructed, staff coordinates with Operations & Maintenance on facility operation, performance monitoring, refinement, local agency coordination, and resource agency permit compliance. In addition to facilities specifically constructed by OC Watersheds, staff also provides management services for stream bank restoration and Clean Beach Initiative projects on behalf of other County agencies, and offer design guidance on runoff BMPs proposed by private entities, local agencies, and as mitigation features of County flood and road-related projects. Watershed issues including coastal erosion, dredging and sediment flow through coastal watersheds are facilitated using a regional approach to protecting, enhancing and restoring County beaches and watersheds. Engineers participate in cooperative projects co-designed with engineers from other state, federal and local agencies
Water Quality Projects
Urban Runoff Diversion Facilities
NPDES Permittees countywide are employing urban runoff diversion to sanitary system collection/treatment facilities as an effective measure to minimize water quality impacts of urban runoff to Orange County swimming beaches.
The County constructed and operates diversion facilities at Huntington Beach pump station, Talbert Channel, Greenville Banning Channel, and the Lower Santa Ana River. The Huntington Beach, Talbert, and Greenville Banning diversions are operational throughout the year, while the Santa Ana River diversion is seasonally operated (June – October). Dry weather urban runoff is diverted to the sanitary sewer collection system for conveyance to the Orange County Sanitation District (OCSD) Reclamation Plant in Fountain Valley for treatment and offshore ocean outfall discharge. Semiannual monitoring for pesticides and heavy metals ensures that diverted runoff does not disrupt the biological treatment process or materially affect OCSD’s own outfall discharge permit. From 2005 to 2012 the facilities have diverted between 147-327 million gallons of dry weather runoff per year over the last several years.
| || |
|Santa Ana River Diversion ||Talbert Channel Diversion |
|Greenville Banning Channel Diversion |
Urban Runoff Treatment Facilities
OC Watersheds constructed and presently supervises operation of two urban runoff treatment facilities in South Orange County for the purposes of water quality protection. Both County facilities employ sand filtration and ultraviolet (UV) light disinfection processes to remove bacteria, suspended solids, and other particulate pollutants from dry weather runoff prior to its discharge to receiving waters.
Aliso Creek (J01P28) Urban Runoff Treatment Facility
This County facility is co-located with an energy dissipation basin adjacent to Aliso Creek in the city of Aliso Viejo. To improve operation system performance efficiency, trash is screened in the basin prior to pumping influent into the treatment system. The treatment facility is designed to filter and disinfect a maximum of 100,000 gallons per day of dry-weather urban runoff from the Town Center area of Aliso Viejo. . The objective of the treatment facility is to decrease bacteria loading and other pollutants in Aliso Creek and subsequently reduce beach postings or closures at Aliso Beach. Facility operations initiated in July 2003. Following extensive reconditioning during 2007-09, the facility restarted in June 2010 and has provided very effective and reliable treatment performance, with average flows of 43,000 gallons per day and 96% bacteria removal efficiency. Reduced bacterial loadings in treated urban runoff to Aliso Creek contribute to downstream water quality improvements and enhanced water contact beneficial use at Aliso Beach.
Poche Clean Beach Project
This urban runoff treatment facility is located at Poche Beach on the city boundary of San Clemente and Dana Point. The facility treats urban runoff from Prima Deshecha Channel prior to its discharge to the surf zone at Poche Beach. The County beach is chronically posted for exceeding AB 411 bacteria standards. Facility operation is intended to reduce bacteria levels in the surfzone and minimize the incidence of water quality advisory postings at the beach. Urban runoff flows from the channel is diverted into the treatment facility by an inflatable diversion gate within the channel. The Poche Clean Beach Project can treats flows up to 1 million gallons per day (MGD) using filter panel screening, sand media filtration, and UV light disinfection.
The Poche Clean Beach Project was completed in 2009, passed water quality performance trials in May 2010, and formally initiated operation in July 2010. Over the first two years of operation, the facility treated average flows of 0.58 – 0.75 MGD, and now produces average bacteria removal efficiencies of 98 – 99%. Despite facility performance, additional issues have prevented a corresponding improvement in surfzone water quality. Initial permit conditions required that the facility discharge treated outflow to a location that was found to be ineffective in delivering the water quality benefit to the surfzone. The County is presently seeking resource agency approval for permanent relocation of treated outflow to a more effective discharge site. In addition, it is increasingly apparent that poor surfzone quality may also be attributable to inordinately large numbers of shorebirds congregating at the intertidal area of the beach. The County and City of San Clemente are further investigating the contribution of shorebirds to beach bacteria levels in order to develop appropriate pollution prevention strategies. Poche Clean Beach Project facility development costs were approximately $3 million, with funding support from the State Clean Beaches Initiative, the City of San Clemente, the County, and the Miocean public interest group. The South Coast Water District presently operates the facility on the County’s behalf, where operations costs are funded by the County and the City of San Clemente.