Contra Costa Bioretention Performance Monitoring and Modeling

Dubin Environmental performed post-construction hydraulic performance modeling for five bioretention facilities. Initially, Dubin Environmental reviewed the monitoring approach and suggested adding water depth monitoring equipment that would a) help Contra Costa measure storm effects during smaller events that do not generate outflow and b) provide the information needed for model calibration. After the monitoring data became available, Dubin Environmental conducted a QC review of the collected data and used the results to tailor the modeling approach. The performance modeling effort involved calibrating HSPF models to simulate site runoff, percolation through the bioretention soils, infiltration to native soils, and discharge via an underdrain. The facilities were originally sized during Contra Costa’s Hydrograph Modification Plan and this follow-up monitoring and modeling analysis was required by the County’s NPDES permit. The modeling analysis demonstrated that the bioretention facilities are performing in excess of the permit’s requirements. The facilities infiltrate more than 95 percent of annual runoff and no operational problems, such as orifice clogging, have been observed. 

Services: Modeling, LID/GSI