Data to Doorsteps: A Rapid Feedback Loop of Low-Flow Data to Inform Outreach Results in Successful Dry Weather Flow Reductions
The San Diego Regional MS4 Permit requires responsible agencies to eliminate non-storm water (dry weather) flow within their respective MS4 systems. The County of San Diego has developed an effective program of highly accurate low-flow data collection coupled with priority outfall surveys to target dry weather flow sources such as over-irrigation or car washing. These two programs work together simultaneously in a near real-time feedback loop, where the monitoring data is used to guide survey scheduling; outreach flyers or door hangars are left at locations where discharge is observed; monitoring data is reviewed to see if noticeable reductions have occurred; and follow-up visits are made as needed. Data is downloaded and processed on a biweekly basis, which provides rapid guidance and feedback for the residential survey program. Wide spread observations efforts are made at the beginning of each month, with follow up visits during the subsequent weeks.
Low flow data is collected using custom built v-notch weirs. In some cases where County Flood Control expressed concerns about weir installation, we’ve developed breakaway weir that will fall away during high flows, allowing discharge to freely flow during the high flow period. The weir can be quickly restored to a functional state once the high flow event is over. This program has grown over the past four dry weather seasons (May – September) from 13 monitored locations to currently 51 locations, including 30 major outfalls and special study sites to evaluate varying inputs to the primary outfall monitoring locations. The program incorporates telemetered data loggers and in-house Python coding to provide efficient, rapid turnaround of flow data sets biweekly.
The County’s priority outfall survey program has also grown over the past four dry weather seasons from 2 rounds of observations at 15 priority outfall drainage areas to the current program that includes 4 rounds of observations at 15 priority outfall drainage areas and two special study locations during each month of the dry weather period (May through September). Observation periods occur night and day, based on patterns demonstrated in the flow data and other targeted areas of know pollutant generating activities (PGAs). The County has developed a variety of outreach materials (including flyers and door hangers) encouraging residents to reduce PGAs and tips on eliminating dry weather flows to the MS4. Outreach materials are left at locations where PGAs have been observed, and follow-up surveys are performed at the same location one to two weeks later to determine if the PGA has ended.
The County’s effective implementation of these two programs has provided real, measurable reductions in dry weather flows and achieve compliance with interim reduction goals stated in the WQIPs.
This presentation summarizes a proven approach of using highly accurate low-flow data collection with informed surveys to identify PGAs and provide outreach to reduce or eliminate dry weather discharge. The audience will participate through a Q&A session following the presentation.
This presentation addresses the conference theme by demonstrating the connection between data collection and outreach to reduce PGAs, including over irrigation, also resulting in water conservation. It also addresses the CASQA Vision by highlighting an efficient and effective means of management by providing informed surveys based on site data resulting in an organized use of resources.
This presentation is intended to be third in a three-part series linked to two other presentations:
1) What’s in my MS4 Discharge, Wisniewska, Joanna
2) Isotope Isolation, Messina, Alex