While sewer pollution problems in the Neponset Watershed have been largely eliminated, a few problem areas remain where streams exhibit high bacteria levels that seem to indicate the presence of sewage pollution. These problem areas include Pine Tree Brook and Unquity Brook in Milton, Mother Brook in Dedham and Boston, the Lower Neponset in Hyde Park, Mattapan and Dorchester, along with Hawes Brook, Meadow Brook and Purgatory Brook all in Norwood.

All of these areas are characterized by older sewer and drain systems which can malfunction in various ways (e.g., leaking, overflowing or cross connections) that result in sewage entering the storm drain systems.

Storm drain systems are designed to collect rainwater from streets and neighborhoods and convey it to the nearest brook. When sewage finds its way into the storm drain, it too gets conveyed straight to the brook, creating an unhealthy condition for people and animals that live or play near the brook, and negatively impacting the overall environmental health of the stream.

The challenge with these relatively small sewer discharges is in finding them. For several years now, Bill Guenther, NepRWA’s Environmental Scientist, has been using a variety of “conventional” bacterial source tracking techniques to try to find these polluted storm drains so that the responsible municipality can make repairs. Bill has used simple visual (and olfactory) inspections at the end of each pipe, as well as collected grab samples for E. coli bacteria, detergents and ammonia, all of which are common components of sewage.

Bill has made substantial progress using these techniques, locating numerous polluted drains which now have been, or are in the process of being, cleaned up.

Despite these efforts, there are several areas where conventional techniques have not been able to locate the source of the problem (or at least not all of the sources). NepRWA has suspected that the problem has been various kinds of intermittent discharges, which are hard to find unless you happen to be standing at the end of the pipe at just the right moment.

This prompted Bill to pursue a different kind of storm drain outfall survey, one using optical brightener testing. Optical brighteners are chemicals that are present in most laundry detergents and a number of other products. As such, they also are present in sewage.

Testing for optical brighteners is simple and inexpensive. Place a special type of cotton pad in the area to be tested, and leave it there for three to ten days. If water polluted with optical brighteners comes in contact with the pad even for a few minutes over that ten day period, some of the optical brighteners will adhere to the pad. When you bring the pad back to the office and dry it out, the optical brighteners will visibly fluoresce when placed under ultraviolet (UV) light.

With funding generously provided by the Mass Environmental Trust and the George H. and Jane A. Mifflin Memorial Fund, Bill launched a pilot study of optical brighteners in storm drains along Pine Tree Brook and Unquity Brook in Milton and Mother Brook in Dedham and Boston.

Simple as the process is, it resembles the proverbial search for a needle in the haystack. Over the course of a year, Bill waded these streams to repeatedly visit 88 storm drain outfalls and collect 349 optical brightener samples. Out of all those samples he had only 20 positive tests for brighteners, that pointed to just three storm drains and one seemingly privately owned pipe, as probable sources of pollution.

The survey found two drains that appear to be contaminated along Pine Tree Brook in Milton, one near where Central Avenue crosses the brook and the other near the brook’s crossing with School Street. Bill also discovered an additional drain between Thacher Street and Brook Road in Milton where it appears a sewer may have backed up into a storm drain during the heavy spring rains earlier this year. An additional problem pipe that seems to be seeping sewage into Mother Brook was found where Washington Street crosses Mother Brook on the Boston/Dedham line. Although this drain outfall appears to be located in Dedham, drain maps show that it is collecting runoff mostly from areas in the City of Boston. Lastly, a small, seemingly privately owned pipe along Milton’s Unquity Brook between Roe Street and Reservation Road also was found to be contaminated with optical brighteners.

Over the next few months we will work with the Milton Department of Public Works and the Boston Water and Sewer Commission to conduct further investigations of the suspected pollution sources and implement repairs as needed.

In the end, optical brighteners have proved an effective addition to NepRWA’s pollution detection toolbox—one we will undoubtedly use again and one that also may be a good choice for municipalities seeking to comply with new DEP and EPA requirements.

Read the final report.

We especially would like to thank the Mass Environmental Trust for providing major support for this project, and the motorists who purchase the special license plates that provide funding for the Trust. Fifty-percent of the cost of purchasing brook trout, whale tail, Blackstone mill and land and water plates at the Department of Motor Vehicles goes directly back to the Mass Environmental Trust to support grants for a wide variety of environmental initiatives. During 2009, the Mass Environmental Trust provided more than $500,000 in grants to support 30 projects.

Over the years, the Trust has provided support not only for NepRWA’s Optical Brightener project, but for numerous other projects. We urge all motorists to show your support for a healthy environment by purchasing one of the Trust’s license plates. Click on one of the license plates below for more information.