Storm Water

Results

Bacterial Densities:  Bacterial densities in stormwater were significantly higher than the recommended state water quality standards of 200 colonies per 100 mL for coliform bacteria in recreational waters and 77 colonies per 100 mL for E. coli in beach waters (Figure 2).  While dilution in the lake would be expected to reduce these densities to acceptable levels, these storm drains clearly were a source of bacterial contamination in the nearshore areas of Burlington Bay.  College Street in particular carried a large bacterial load, but all the drains contribute substantial contamination to the lake.  The source of these bacteria is not known, but could include pet or wildlife waste, leaky sewer lines, and other sources.

Total Phosphorus:  Phosphorus concentrations in most stormwater discharges greatly exceeded those found in Burlington Bay, where concentrations are typically less than 10-15 micrograms/L (Figure 3).  The College Street effluent consistently had phosphorus concentrations above 250 micrograms/L while concentrations at the other drains varied widely among the storms.  Water obtained from Perkins Pier and the Coast Guard boat launch is essentially lake water and, therefore, should have significantly lower phosphorus concentrations than stormwater.

Priority Pollutant Metals:  Samples were analyzed for the presence of priority pollutant metals if they appeared to have high concentrations of particulates or were cloudy.  Metal contamination is generally correlated to increasing particulate content, so effluents with low concentrations of visible particulate material or cloudiness are less likely to have metal concentrations of concern.  Many samples did not appear cloudy and, therefore, were not analyzed for metals.

The College Street drain, the most frequently analyzed site, routinely had concentrations of lead, cadmium, copper and zinc exceeding EPA criteria (Table 1).  The Leddy Beach site may have a metals contamination issue, but further testing is required to confirm this.  The other sites only occasionally exceeded the criteria, and, therefore, are of lesser concern for metals contamination.

Toxicity Testing Utilizing Selenastrum:   In all cases, growth of Selenastrum was enhanced by exposure to stormwater (Figure 4).  No toxic effects, which would have resulted in negative growth rates when compared to the controls, were observed.  The lack of a toxic response is consistent with the results of the tests conducted with Ceriodaphnia in previous years.