The Ultimate Bean Counter: A Tool for Tracking, Reporting, and Planning of Watershed Programs for BMP-Based Permit Compliance
Municipal stormwater permits in California are increasingly incorporating BMP-based compliance provisions to address TMDLs and receiving water limitations. The BMP-based provisions allow municipalities to remain compliant as long as the watershed program (e.g., Enhanced Watershed Management Programs [EWMPs] in Los Angeles County and Water Quality Improvement Plans [WQIPs] in the San Diego region) is approved by the Regional Board and implemented as specified. Over time, the progress toward implementation milestones are tracked and reported to the Regional Board, along with updates being made to the program for adaptive management. This approach to permitting offers municipalities increased certainty of compliance and improved understanding of the extent of BMPs needed to comply and their costs. At the same time, these programs require a new type of tracking and reporting of BMPs that have been implemented and estimates of their corresponding reductions in stormwater volumes and pollutants.
The City of Los Angeles led development of four EWMPs in coordination with 25 copermittees – Upper Los Angeles River, Ballona Creek, Santa Monica Bay and Dominguez Channel. These EWMPs describe large-scale implementation programs for LID, green streets and regional BMPs – with the networks of BMPs equaling the capacity of over 25 Rose Bowl stadiums and having capital costs estimated at over $10 billion. As a component of EWMP implementation, the Regional Board is requiring annual tracking and reporting of BMP implementation as it relates to the milestones in the EWMPs / TMDLs. As such, the City of LA is spearheading development of an EWMP Reporting Tool (ERT) that allows participating jurisdictions to track BMP implementation and quantify the effectiveness of the BMPs for stormwater volume and pollutant reduction. The ERT facilitates consistent reporting for each EWMP group and streamlines end-of-year data gathering. The EWMPs were developed using a set of assumptions regarding anticipated BMP designs including storm sizing (critical conditions), dimensions, footprints and drainage areas. As projects are implemented, the as-built designs will vary and the ERT estimates the effectiveness of the actual design in terms of stormwater volume and pollutant reduction. Also the ERT provides an “equivalency” calculation that allows jurisdictions to substitute BMPs among the different categories, for example, implementing regional projects in place the green streets specified in the EWMP. A map-based interface allows the user to easily specify project locations, while (in the background) the ERT relates the project location to nearby rainfall gages, required pollutant reductions for the nearby receiving water, and the corresponding BMP capacities that were specified in the EWMP. After implemented projects are entered into the ERT, a dashboard is displayed that reports the jurisdiction’s progress towards its overall EWMP / TMDL implementation goals. Finally, the ERT includes a project planning module where jurisdictions can enter the location and drainage area of potential projects and the ERT provides “performance curves” that support project sizing decisions (e.g., footprint size, depth, etc.) in terms of the storm size and pollutant reductions that are being targeted by the EWMP.
This presentation will describe the details of the ERT prototype along with overall context of the importance of these tracking tools as BMP-based permit provisions become more commonplace. These types of quantification tools are fundamental to estimating the effectiveness of structural BMPs that are implemented by municipal programs and evaluating the progress being made toward water quality improvement.