As part of our permit to operate our stormwater system, all permit holders are required to develop a stormwater management program that reduces potential pollution through education and outreach, good housekeeping, as well as the use of cutting edge technology and industry-vetted operational practices. The city has established a program that meets and, where feasible, exceeds the requirements of our permit. One example is the voluntary launch of our water quality sampling program in late 2016, which expands upon Miami-Dade County’s existing sampling network.
The Miami Beach water quality sampling program added more than sixty stations to cover areas of Biscayne Bay closer to our shoreline and within our waterways for which data has historically not been collected. The data from this program gives a more robust snapshot of local water quality and allows city staff to make better informed stormwater management decisions.
In 2018, the city completed the first year of data collection and retained an outside water quality expert, Dr. Charles Rowney, to review the data and draw initial conclusions about the health of our waterways. Dr. Rowney presented the results of his analysis, as well as a report with the results, his observations and his recommendations to the SRC and a roundtable of technical stakeholders on September 26, 2018. Based on his analysis of the Miami Beach water quality sampling program and the data collected during the monitoring period, there is no indication of gross or persistent sanitary system contamination into Biscayne Bay from Miami Beach (Attachment A).
The city’s current water quality program design is useful as a screening-level program and according to Dr. Rowney, “could and should be enhanced if uses of data beyond the present screening level are contemplated.” As such, staff is proposing the following six enhancements to the program:
1. Training in-house staff to execute and oversee sample collection.
Dr. Rowney’s report revealed the need for increased oversight during sampling to ensure consistency and protect the integrity of the data. Staff is coordinating with Miami-Dade County to shadow their field crew during the next sampling event and will be pursuing the same industry certifications currently held by their sampling program staff. Trained staff will then be responsible for overseeing all sampling activities and for deploying immediately to collect samples in emergency situations (i.e., illicit discharges). Having trained staff in-house will not only allow the city greater control over our program, but it will also allow staff to respond more quickly and fully to water quality violations, improving enforcement.
2. Removing all "outfall" sampling stations.
When the city initially designed the current water quality sampling program, one of its goals was to identify if a difference exists between outfall and ambient conditions. However, Dr. Rowney’s analysis of the Year 1 data showed that the results from outfall and ambient stations are not statistically different. Therefore, the outfall samples do not reflect true outfall conditions and are solely functioning as duplicates of the ambient samples. Staff is proposing to keep all the ambient sampling stations, remove all the duplicative “outfall” sampling stations, and redirect the program savings toward other types of data collection that will enhance the program beyond the present screening level, in accordance with Dr. Rowney’s recommendations.
3. Adding stations in areas where data is not currently collected.
With some of the savings generated from removing duplicative stations, staff is proposing to add sampling stations at new locations. Specifically, staff is proposing to add ambient stations throughout North Beach that will be sampled on a monthly basis so we have a better understanding of waterway health in the area. Additionally, staff is proposing to collect samples on a quarterly basis from six locations within the stormwater system to better understand the composition of stormwater leaving the city and develop pollutant loading estimates.
It should be noted that water quality monitoring programs do not typically sample within municipal stormwater systems because stormwater is expected to carry pollutants and the primary concern is how those pollutants may affect the receiving waterbody. However, staff is proposing to voluntarily sample inside our system at select locations so we have more detailed information with which to refine our pollution prevention programs. The following six locations were strategically selected to provide a broad picture of in-system conditions from a wide range of upstream land uses:
· Palm Island pump station wet well – single-family residential.
· 10th Street pump station wet well – mixed use entertainment, low intensity multifamily residential, low intensity commercial, and high intensity multifamily residential.
· Sunset Harbour pump station wet well – urban light industrial, medium intensity commercial, and high intensity multifamily.
· Collins Avenue and 41st Street manhole – low and medium intensity residential.
· Bay Drive and Normandy Drive manhole - residential office, low and medium intensity residential, and medium intensity commercial.
4. Sampling for more parameters at existing and new stations.
The current sampling program analyzes for 12 parameters that are physical, chemical and biological indicators of bay health, consistent with the County’s sampling program. Staff is proposing to add parameters to existing and new stations, as applicable. For example, Chlorophyll a is a great indicator of algae growth and can serve as an early warning system that the ecosystem is seeing an increased input of nutrients like Total Nitrogen and Total Phosphorous. Sampling for additional parameters like Chlorophyll a will provide a more holistic picture of bay health.
5. Sampling during rain events.
The new NPDES permit issued in 2018 requires all permit holders to estimate the event mean concentrations (EMC) during rain events. That is, all permit holders must calculate the average loading of nutrients into their stormwater systems during a discharge event such as a rainfall. Staff is proposing to collect samples during a minimum of four rain events per year at major outfalls to account for quarterly variations in rainfall discharges.
6. Installing constant monitoring probes in areas requiring in-depth investigation.
Occasionally, the city will observe illicit discharges and other plumes emanating from an outfall which require further investigation. In these cases, staff conducts in-depth investigations to track the source of and stop the discharge, as well as to enforce upon violators. One facet of these investigations is installing constant monitoring probes that can consistently track physical water quality parameters, such as temperature, dissolved oxygen, turbidity, and conductivity, over time. The use of these sensors, which record data on one-minute intervals, has helped staff determine if the observed discharges are systematic or sporadic by showing the fluctuation of these parameters and also provided insight into the composition of the discharges. As such, staff is proposing to purchase two constant monitoring probes that the city can deploy as needed in areas requiring in-depth investigation.