The HPWA is monitoring stormwater runoff by taking water samples during rain storms, just before they enter the ponds, and submitting them for analysis of pollutants and sediment. In addition, we are educating the public in ways they can help mitigating this source of pollution.
Around Great Herring Pond (GHP), there are mainly two kinds of runoff locations, man-made ones, with storm drains from roads and streets that have discharge pipes terminating at the lake shore, and natural ones, usually at steep shore configurations, where rainwater accumulates as little or not so little streams and discharges directly into the pond. There are also several locations where drainage canals or pipes from active or inactive cranberry bogs end up in GHP. Finally, there is Carter’s River, the stream connecting Little Herring Pond and GHP. At present, we are sampling stormwater at the first two types of locations (see the map of GHP).
All our stormwater sampling takes place in the middle of a storm, as soon as possible after ½ inch of rain has fallen. This is because the first 1/8 – 1/4 inch of rainfall will be absorbed into the ground, depending on the kind of soil and ground cover. Each sampler is assigned to one location, and is alerted by the sampling supervisor. Details of our stormwater sampling procedure are described in our QAPP. Our first stormwater collection during 2009 was done differently. All locations were visited by the same team.
Some early results: Storms suitable for sampling do not occur frequently. Nevertheless we have already completed three runoff samplings. We usually find e. coli loads very high, compared to regular water sampling. At most locations, phosphorus loads are also very high. As is nitrogen. Acidity is higher than during regular water sampling. Somewhat surprising, conductance is low compared to regular sampling. We are not sure what this indicates. Several locations carry lots of sediment in the samples.