First Flush Event Monitoring by the Sanctuary Citizen Watershed Monitoring Network
- Bridget Hoover
Monterey Bay National Marine Sanctuary
- Lisa Emanuelson
Monterey Bay National Marine Sanctuary
- Monterey Bay National Marine Sanctuary
- Monterey Regional Storm Water Management Program
- City of Capitola
- Pillar Point Harbor Department
Pollutants are common in the environment due to our everyday activities, be it driving to work, gardening, walking the dog or making improvements to the exterior of our houses. During dry weather months, pollutants fall and collect on our roadways, sidewalks, in our yards, parks and beaches. Once the winter rains begin to fall these pollutants are swept along with rainwater into nearby creeks, storms drains and eventually into the ocean. The first rain storm picks up about six months worth of pollutants that if measured can give an indication of pollution sources and pollution loads going into the ocean.
Every fall, staff from Monterey Bay National Marine Sanctuary (MBNMS), San Mateo County Resource Conservation District (SMCRCD) and the Coastal Watershed Council (CWC) team up with dedicated volunteers to monitor storm water flowing into the Monterey Bay National Marine Sanctuary from the first major rain storm of the winter season, the First Flush. Prior to the first rains and during daylight hours, volunteers and coordinators gather for training and visit their respective sites to collect water samples of dry weather runoff for comparison to the storm samples. This is called the Dry Run and usually takes place in mid-September each year.
Programs such as the Dry Run and First Flush are important for their monitoring data, but they also educate and inspire the community. First Flush volunteers act as ambassadors in the community by sharing their experience as a First Flush volunteer and the information they learn about the monitoring results and water quality conditions. First Flush results are a cumulative outcome of each person living near the ocean. Our homes, cars, yards, and pets all contribute to the pollutant load flowing into the Monterey Bay National Marine Sanctuary every day, not just when it rains.
Summary to DatePrior to the first major rainstorm, dry weather sampling (Dry Run) is conducted to provide a comparison for wet weather results (First Flush). In 2015 the Dry Run was conducted on Saturday September 12th and September 19th when 7 sites were sampled over all three counties.
The first major rainstorm of the winter season hit the Monterey Peninsula in the early morning hours of November 2, 2015. First Flush volunteers were mobilized at 4 am at the very start of the rain on the Monterey Peninsula. Partner organizations, Coastal Watershed Council (CWC) and the San Mateo County Resource Conservation District (SMCRCD) were both able to mobilize volunteers for First Flush on November 2nd as well: CWC volunteers mobilized at 3 am; SMCRCD volunteers mobilized at 7 am. In total, fifty-nine volunteers monitored 28 sites during the 2015 First Flush event.
All results (field and lab) are compared to receiving water standards set for particular beneficial uses in a stream, lake, or ocean. Metal results are compared to the Central Coast Basin Plan's Water Quality Objectives (WQO) for the protection of marine aquatic life. Nitrate, orthophosphate, and total suspended solids results are compared with the Central Coast Ambient Monitoring Program's (CCAMP) action levels because there are no criteria for these parameters in the Basin Plan. Bacteria (E. coli and enterococcus) are compared to the EPA's ambient water quality criteria (see Table 1).
- Nitrate concentrations were all below the Action Level for the Dry Run and First Flush.
Dry Run results for orthophosphate were all non-detect except for one site in Monterey County. First Flush orthophosphate results from San Mateo showed 89% of sites above the Action Level, Santa Cruz County 86% above and Monterey County 100% of sites were over the Action Level.
- Copper concentrations were below the WQO for the Dry Run. For the First Flush results above the WQO were spread across all three counties with more sites above the WQO in Santa Cruz and Monterey counties. In San Mateo County, 33% of the sites were above the Action Level for copper while 71% of the sites were above in Santa Cruz County and 33% above in Monterey County.
- Zinc concentrations were all below the WQO for the Dry Run, in fact all sites but one in Monterey County had non-detects for Zinc. For the First Flush 22% of sites in San Mateo County exceeded the WQO, 71% exceed the WQO in Santa Cruz County and no site exceeded the WQO in Monterey County.
- Lead concentrations were all below the WQO during the Dry Run at all sites while results from First Flush showed 2 sites with results over the WQO: one in Santa Cruz County and one in Monterey County.
As in previous years, E. coli and enterococcus results during First Flush were all above the WQO except for one site in Santa Cruz County. In 2015, 87% of the sites exceeded the WQO for both E. coli and enterococcus during dry weather and 98% during wet weather.
DiscussionSince 2000, the Dry Run and First Flush have provided Central California coastal area residents and municipalities with valuable information about the quality of water running from the storm drains to the ocean. Results from this and other Dry Run/First Flush events provide resource managers and researchers with pollutant concentrations during two critical times: late season dry weather and the initial flushing events when the most polluted water is expected to flow into the sanctuary.
First Flush data helps us to better understand what our pollutants of concern are and help to identify where concentrations are highest. Our hope is that this informs storm water managers and assists them in prioritizing Best Management Practices (BMPs) to address and minimize specific contaminants. After 16 years of monitoring, collected data has been able to inform us as to whether water quality conditions are improving. A recent analysis of 14 years of monitoring data from the years prior to the Monterey Regional Stormwater Management Program (MRSWMP) and data from years during the MRSWMP program have allowed insight into conditions that show an improvement of water quality. Local cities have used First Flush information and addressed pollutant concentrations by cleaning out storm drains prior to the rains, installing dry weather diversions and litter/debris removal systems (CDS units) as well as identifying opportunities to slow down runoff through vegetation and permeable surfaces. By addressing these issues on a watershed level more improvements in water quality may be achieved.
First Flush reports are available through the Monterey Bay National Marine Sanctuary Water Quality Protection Program:
- Total suspended solids (TSS)
- Total metals - copper, lead and zinc
- Nitrate N
- Orthophosphate P
- E. coli and enterococcus
- water temperature
Study MethodsIn early September volunteers were trained to follow standardized procedures for field measurements and to collect water samples for laboratory analysis. Following the classroom training, field training was conducted at a local outfall focusing on a demonstration of field measurements and sample collection. This day is known as the Dry Run and is conducted on a weekend day after the classroom training. In 2015 First Flush training was on September 10th and the Dry Run was conducted on September 12th or 19th depending upon the region. After sample collections and field measurement demonstrations, volunteer teams went to their respective sites for area familiarization, took field measurements, and collected water samples following the established protocols. The Dry Run was conducted well ahead of any predicted rain and provided the volunteers with a chance to test equipment at their specific sites and collect water quality information for any dry weather runoff.
For both the Dry Run and the First Flush, a detailed field instruction sheet was given to each team along with site directions and data sheets. Field instruction sheets provide a step-by-step description beginning with arriving at the site, determining if samples can be collected based upon flow and conductivity criteria and instructions to collect lab samples and field measurements.
Leading up to the First Flush event, the coordinators from the SMRCD, CWC and MBNMS closely monitored the weather, and notified volunteers of approaching storms. When a storm had the potential to generate enough rainfall for First Flush mobilization, the coordinators placed the volunteers on standby until mobilization criteria were met. Mobilization criteria for First Flush volunteers included rain of at least 0.1”, sheeting water on roadways, heavy flow through the storm drain system and conductivity levels less than 1000 micro Siemens (μS) and declining. For the San Mateo County sites one sample and one set of field measurements were taken at each outfall for First Flush. In Santa Cruz County, samples were collected twice at each outfall, at the beginning of sampling and after 60 minutes, while field measurements were collected at 0, 30 and 60 minutes. In Monterey County, samples and field measurements were collected twice per outfall at 0 and 30 minutes.
Figures and Images
First Flush sampling at Bay Street in Sand City.
Figure 2. Results for nitrate as N for San Mateo and Santa Cruz Counties. Each site has dry weather and wet weather results separated in order to understand the concentration of analytes during different weather conditions. Sites are grouped by city from north to south: Montara, Santa Cruz, Capitola.
Figure 3. Results for nitrate as N for Monterey County. Each site has dry weather and wet weather results separated in order to understand the concentration of analytes during different weather conditions. Sites are grouped by city from north to south- Pajaro, Seaside, Monterey, Pacific Grove, Carmel.
Figure 4. Results for total copper for San Mateo and Santa Cruz Counties. Each site has dry weather and wet weather results separated in order to understand the concentration of analytes during different weather conditions. Sites are grouped by city from north to south- Montara, Santa Cruz, Capitola.
Figure 5. Results for total copper for Monterey County. Each site has dry weather and wet weather results separated in order to understand the concentration of analytes during different weather conditions. Sites are grouped by city from north to south: Pajaro, Seaside, Monterey, Pacific Grove, Carmel.
Figure 6. Results for total zinc for San Mateo and Santa Cruz Counties. Each site has dry weather and wet weather results separated in order to understand the concentration of analytes during different weather conditions. Sites are grouped by city from north to south: Montara, Santa Cruz, Capitola.
Figure 7. Results for total zinc for Monterey County. Each site has dry weather and wet weather results separated in order to understand the concentration of analytes during different weather conditions. Sites are grouped by city from north to south: Pajaro, Seaside, Monterey, Pacific Grove, Carmel.
Volunteers collect First Flush samples at designated sites.