Q3 team members provided planning, design, permitting, and construction support for modification to the Marshburn Basin Dam (Dam #1012.011).  The dam and basin are a State jurisdictional facility.  The existing facility was enlarged to address issues with the outlet works, and to provide additional storage for a natural treatment system within the basin.  The basin has been identified as a site included in the Irvine Ranch Water District’s (IRWD) natural treatment system.  Extended detention times and designed water quality wetlands were proposed to treat dry weather low flows and first flush storm flows for the surrounding watershed within the existing basin.

Team members provided engineering services to develop improvement plans to lower the basin to obtain the additional storage volume requirements, improve the intake tower and outlet works, and prepared detailed hydrology and hydraulic analysis to document the operation of the basin under the proposed conditions.  The team processed the proposed modifications with DSOD for a dam alteration permit, and the County of Orange for an encroachment permit.