An Initiative to Improve Quality and Promote Consistency in Municipal Urban Runoff Program Assessment and Implementation Using Catchment Scale Discharge and Pollutant Loading Information
The Central Coast Regional Water Quality Control Board (RWQCB) has launched an initiative to improve quality and promote consistency in municipal urban runoff program assessment and implementation using catchment scale discharge and pollutant loading information. The initiative addresses both the long term vision of improving urban runoff programs based on assessment information and near term actions municipal stormwater Permittees must take to build the foundation for pursuing that long term vision. Prioritizing by watershed or urban catchment is necessary to focus Effectiveness Assessment (EA) and management activities on hydrologic, land use, and infrastructure conditions that affect stormwater quality. Tools for working at this scale and developed for this initiative can be used to build watershed-based urban runoff management systems that allow Permittees to achieve the long term vision of continuous program improvement. Once urban catchments are selected as the unit of assessment and analysis, Permittees can follow the CASQA EA Outcome Levels to establish a logical and consistent organizational scheme for assessing and relating individual outcomes to program effectiveness.
The sequencing of tool development > tool application > identification of program modifications codified in the 2013 Phase II Municipal Stormwater Permit (2013 General Permit) underscores the importance of using good assessment tools to conduct the iterative process of stormwater management. The time-frame in which Permittees must complete this sequence further points to the urgency in developing those tools. To promote action in the near term, RWQCB staff and a small group of Permittees began working with the Central Coast LID Initiative in fall 2014 to develop urban catchment mapping protocols and to design a method to estimate urban catchment pollutant loads that integrates stormwater BMP assessment and tracking. The Tool for Estimating Load Reduction (TELR) estimates baseline pollutant loads; determines relative spatial risks to receiving water quality; and quantifies the expected load reduction associated with stormwater management actions. Rather than attempting to model multiple pollutant types, TELR uses credible and effective proxies (Total Suspended Solids and Runoff Volume) to create a ranking of urban catchments in terms of relative risk to the receiving water. The result is a powerful prioritization tool as well as an effective communication tool for municipal stormwater program staff and their elected officials (e.g., city councils). The BMP Rapid Assessment Methodology (BMP RAM) is the tool for assessing BMP contribution to load reduction. A final component of the initiative is the RWQCB’s expectations of Permittees during the2013 General Permit term regarding EA. All Traditional Phase II Permittees received correspondence from RWQCB staff clarifying these expectations and requiring Permittees to describe progress in meeting them.
This initiative promises to bring more accurate EA, and greater accountability, understanding, and certainty to Permittees’ overall efforts to improve urban runoff quality. While the 2003 Permit stressed assessment activities that support CASQA EA Outcome Levels 1-3, the 2013 Permit acknowledges the maturity of Permittees’ stormwater programs and explicitly, “requires a quantitative evaluation of Permittees’ MS4 programs.” This imperative of quantitative evaluation will result in significant improvements in EA as Permittees begin longer term assessment of sources and impacts (Outcome Levels 4-6). Furthermore, RWQCB staff believes the tools developed for this initiative will be transformative in helping the Region’s municipalities embrace the contemporary concept of urban stormwater management based on watershed-scale solutions and stormwater as a resource.