When to Say When - Adaptive Management of Permit-Driven Monitoring
The Municipal Regional Permit and the Central Valley Permit.
The Contra Costa Clean Water Program (CCCWP) is one of four Countywide stormwater programs in the Bay Area that are required to monitor pollutants of concern (POCs), including mercury, methylmercury, and polychlorinated biphenyls (PCBs) in urban creeks that discharge to the San Francisco Bay Estuary. The National Pollutant Discharge Elimination System (NPDES) permit provisions that drive tributary loads monitoring come from Total Maximum Daily Loads (TMDLs) for POCs that require massive (e.g., fifty to ninety percent) POC load reductions from stormwater within the next two decades.
The goals of POC loads monitoring in Bay Area tributaries, as framed in NPDES permits, are:
• Identifying which Bay tributaries (including stormwater conveyances) contribute most to Bay impairment from pollutants of concern;
• Quantifying annual loads or concentrations of pollutants of concern from tributaries to the Bay;
• Quantifying the decadal-scale loading or concentration trends of pollutants of concern from small tributaries to the Bay; and
• Quantifying the projected impacts of management actions (including control measures) on tributaries and identifying where these management actions should be implemented to have the greatest beneficial impact.
The CCCWP is unique among Bay Area Phase I stormwater programs in that it is governed by two different NPDES Permits for Municipal Stormwater Discharges. The Municipal Regional Stormwater NPDES Permit (MRP), issued by the San Francisco Bay Regional Water Quality Control Board, requires POC loads monitoring from Bay Area Phase I NPDES permittees. The East Contra Costa County Municipal NPDES Permit (East County Permit) requires POC loads monitoring from eastern Contra Costa County permittees within the Central Valley Regional Water Quality Control Board’s jurisdiction. Both of these permits are implemented through a coordinated countywide program.
Monitoring in the Marsh Creek watershed addressed interests articulated in both the MRP and the East County Permit – does the Mount Diablo Mercury Mine impact mercury and methylmercury loads discharged from Marsh Creek to the San Francisco Bay Delta / Estuary? Monitoring in the North Richmond Pump Station watershed addressed POC concerns unique to the MRP – what is the baseline load of mercury and PCBs in urban stormwater discharged from a 900 acre, old industrial watershed?
C. Summary of Lessons Learned
Lessons learned to be presented in the talk, include:
• Monitoring POCs at the base of watershed is not the most cost effective way to show progress towards TMDL goals – given the inherent variability of tributary monitoring data, it would take decades to show measureable progress.
• The most cost-effective way to show measureable progress is to move the point of monitoring closer to known or suspected sources of POCs.
• Establishing numeric requirements for number of storms to sample annually in NPDES permits will bias monitoring data towards smaller, more high frequency storms.
• In the unique setting of the Marsh Creek Watershed, the bias towards smaller storms risks missing important information about upper watershed flow, which is at most risk from legacy mine site discharges
• Making adaptive management decisions within the constraints of NPDES permit compliance is challenging, but the extra effort adds value.