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Summary of Health Hazards in Cambridge and Belmont
Winter 2003, Little River - Alewife Brook subwatershed
Mark Kirk of FAR with information from the water quality testing team of the Mystic River Watershed Association.
Mystic River Monitoring Network - Libby Larson: Coordinator
For baseline monitoring, samples are collected the second Wednesday of each month from the Somerville side of the Brook, just downstream of the Broadway Bridge. This site is referred to as ALB006.
For the samples collected from pipes, the following abbreviations were used:
For centerline sampling, the last 3 digits of the site ID indicate the location of the site in river miles from the mouth, e.g. ALB006 is 0.6 miles from the mouth at the Mystic River.
All of the waters tested have been classified as Class B waters, meaning that the water should meet fishable and swimmable standards. The Massachusetts Surface Water Quality Standards (MASWQS, 314 CMR 4.00) for primary and secondary contact are 200 cfu/100ml and 1,000 cfu/100ml, respectively, of fecal coliform from a single sample.
For the June 2002 sampling event, again four out of twenty-seven samples met the MASWQS for swimming, with the same three Little River samples coming up "clean." None of the samples violated the criteria for boating. The geometric mean for this event was 296 cfu/100 ml. Rainfall prior to the event was 0 inches, except 0.07 inches was recorded two days before the event.
Pipes monitoring – Most of the pipes sampled in April 2002 were clean, however there are several exceptions to note: MBTA48, HWY001, WEB013, MDCX01, SOMD07, ARL014, ARL013, MARSH1, BEL013, BEL011 (with exceptionally high results above 100,000 cfu/100 ml), and WIB001. There was only trace rainfall in the three days prior to this event. Repeated sampling of select pipes in June 2002 showed reduced levels at both ARL014 and ARL013, and increased levels at BEL013, BEL011, and WIB001. BEL011 had results greater than 200,000 cfu/100 ml.
It is quite striking that during dry weather, the centerline results for Alewife Brook have consistently across time and space come up relatively "clean," despite some very large inputs from area pipes. The high inputs into Little Pond clearly settle out so that the Little River water is very clean. Following the Brook downstream, however, inputs from Wellington Brook again raise the bacteria levels, which then generally decline as the Brook flows to the Mystic, although there is some elevation in the ALB009 - ALB015 range.
The variation seen in the "Alewife Brook Centerline Fecal Coliform Results" could be due to the poor precision of bacteria analysis methods alone (i.e. culturing bacteria from the same sample bottle often yields results that differ widely but are the same order of magnitude). The results are all in the same order of magnitude and the graph could be considered essentially flat line. Eliminating these large point sources and improving the flow conditions of the Alewife could potentially lead to the development of a dry-weather TMDL for Alewife well within the limits of the MASWQS for Class B waters.
Baseline monitoring at ALB006 revealed that the Brook violates both the primary and secondary standards for Class B waters, especially during rain events. In October 2002 we completed some wet-weather sampling of select pipes along the Brook, although we have not yet received the results from the Lab. We hope to do more in the future as weather and resources permit, in order to evaluate the impact of wet weather pipes and non-point sources on the system.
All of the waters tested have been classified as Class B waters, meaning that the water should meet fishable and swimmable standards. For fecal coliform, all but two of the results violated the Massachusetts Surface Water Quality Standards (314 CMR 4.00) for primary and secondary contact. The two sites which met primary contact standards were Belmont in the NE corner of Claypit Pond (WEB005), and Junction Brook at Pleasant Street (WEB020). The highest result for fecal coliform (65,000 cfu/100 mL) was at WEB013, Wellington Brook behind the library.
Two sampling locations had dissolved oxygen (DO) results below one of the criteria established by the state. Wellington Brook in Cambridge before Perch Pond (WEB001), and Wellington Brook in Cambridge at Blair Pond (WEB002) both had percent saturation readings below the MASQWS standard of 60%.
The high levels of fecal coliform and E. coli bacteria are of concern for public health, especially because many of the sampling locations have easy public access. The two locations nearest the Library have the easiest and most frequent public use. However, during these winter months the potential for public contact is reduced. Due to the very high results at several locations (particularly the location behind the Library), we hypothesize that sewage is contaminating the Brook at points currently culverted. Additional bracket sampling would be required via manholes to determine precise locations. The Mystic River Watershed Association would be happy to assist the town of Belmont in any further sampling and investigation.
For the baseline monitoring, the geometric mean for WIB001 is 844 cfu/100 ml for the period 7/2000 – 5/2002. For these samples, 75% violated the standard for primary contact, and 46% violated the standard for secondary contact.
For the March 26th monitoring, 4 samples violated the primary contact standard, and only 2 violated the secondary contact standard. The two violations occurred at WIB001 and WIB005 (Grate over Brook North side of Sherman Street).
One sampling location had dissolved oxygen (DO) results below one of the criteria established by the state. Atkin's Brook had a percent saturation of 58.3%, just below the state standard of 60%. This is probably due to the effect of the nearby wetland on the Brook.
While there are no state standards for salinity, salinity can be an indicator of probable contamination. For the March 26th sampling, salinity ranged from 0.2 ppt at Tributary A (WIBUTA) to 0.6 ppt at Tributary B (WIBUTB) and WIB003.
The high levels of fecal coliform and E. coli bacteria are of concern for public health, especially because Winn's Brook discharges into Little Pond, which is used recreationally. Atkins Brook and upstream sections of Winn's Brook are very clean. Due to the higher concentrations of fecal coliform downstream at WIB001 and WIB005, we hypothesize that sewage is contaminating the Brook at points currently culverted. Additional bracket sampling would be required via manholes to determine precise locations. The Mystic River Watershed Association would be happy to assist the town of Belmont in any further sampling and investigation.