This Caltrans-funded regional stormwater quality project included diversions from the San Gabriel River Watershed into a 19.5ac-ft underground stormwater capture facility. Untreated discharges are sent to the adjacent sanitary sewer and overflows were treated on site and then released into Sorensen Drain. Flows into the sanitary sewer are treated at the Los Coyotes Reclamation Plant and reused as non-potable irrigation water. Watearth managed the project and performed civil design, permitting, Phase I and Phase II Environmental Site Assessments, groundwater monitoring, sampling of the receiving/contributing stream (Sorenson Drain), development of surface water and groundwater sampling plans, development of a plan for pumping tests, oversight of 50-foot depth monitoring well and extraction well installations, oversight of geotechnical studies, performing groundwater sampling and monitoring activities, and preparation of technical memorandums documenting the results of the surface water and groundwater sampling activities.
Also provided geotechnical studies (field testing of soils using the double ring infiltrometer method), field identification of plants and trees, development of a Water Quality Management Plan (WQMP), erosion and sediment controls, Operations & Maintenance (O&M) Plan for the Low Impact Development (LID), bioretention LID design (featuring native and low water use plants), development of interpretive signs, and stakeholder outreach. Watearth performed hydrologic, hydraulic, and water quality modeling and final design for civil and landscape design. We performed CAD operations. Permits included LA County Sanitation District Buildover Agreement, CA Dept of Fish and Wildlife Notification of Streambed Alteration, LA Regional Water Quality Control Board, Section 401 Water Quality Application and Certification, Electrical Permit with Southern California Edison, EPIC-LA Application for the LACFCD Diversion Permit, EPIC-LA Los Angeles County Regional Planning Division Site Plan Review, Sanitation Districts of LA County Industrial Permit, and USACE Section 404 Minor Discharge Application.
By applying our robust project management processes, we kept this project on-track to meet tight deadlines with regards to project spend required to ensure Los Angeles County received the full $15M Caltrans grant as well as additional grant monies from the Safe Clean Water program. Team coordination and collaboration and regular contact with multiple departments and stakeholders within and outside of Los Angeles County Department of Public Works is emphasized to identify and address project challenges immediately instead of waiting for the next review cycle. Watearth also worked collaboratively with Los Angeles County Sanitation Department to get real-time review and ensure the lengthy approval process for discharge to the sanitary sewer and recycling plant did not delay project approvals or construction start date. Because the project EIR was still in process at 90% design, we used a rolling approach to incorporate CEQA mitigation measures, ensuring there were no surprises at the 100% design. Implementation of several mitigation measures, such as avoiding any impacts to existing trees, significantly affected the above ground layout of the site. Watearth worked with Los Angeles County, Department of Parks and Recreation, and the project team to adjust our modeling methodology to ensure the intent of the Safe Clean Water grant was met along with expectations from Parks and Recreation and the required CEQA mitigation measures. Included structural plan checks of underground infrastructure and controls building.
Worked collaboratively with the County to develop a project management approach to achieve required grant spending even with delays in County reviews due to COVID.