Summary
Beaver Brook winds from Hardy Pond through Lexington and Waltham to
meet up with the Charles River near the Newton Street Bridge in
Waltham. The Brook is culverted between Route 20 and its discharge
point. CRWA conducted water quality monitoring on Beaver Brook on three
occasions: 1) December 21, 2006 – a dry weather monitoring event, 2)
January 12, 2007 – a dry weather monitoring event, 3) November 6, 2007 –
a wet weather monitoring event.
Samples were collected at eighteen sites along
Beaver Brook. Click here for a site map.
Samples were analyzed for several pollutants of most concern in the
watershed: E. coli bacteria, total suspended solids (TSS), and
total phosphorus. CRWA also measured several in situ parameters
including pH, dissolved oxygen, specific conductivity and water
temperature.
E. coli levels at fifteen sites exceeded the
Massachusetts Surface Water Quality Standard for swimming, 126cfu/100mL,
during at least one of the sampling events. Fourteen sites also
exceeded State Boating Standards, 630cfu/100mL, during at least one
sampling event. Certain sites, such as BEA_OUT1, BEA6, BEA8, BEA_OUT7,
BEA9, BEA10 and BEA11 exhibited high bacterial counts during both dry
and wet weather. BEA6 stands out particularly as E. coli levels
there exceeded 10,000 cfu/100mL during both wet and dry weather. Such
high E. coli levels observed during dry weather are usually
indicative of illicit connections to the stormwater drainage system, causing
raw, untreated sewage to flow directly into Beaver Brook and eventually
the Charles River. CRWA observed further evidence that illicit
connections are likely flowing into Beaver Brook during our November 6,
2007 wet weather sampling event when soap suds were observed flowing out
of the outfall pipe at Site BEA_OUT1 and a sewage smell was present at
Site BEA_OUT4.
The City of Waltham
has begun efforts to identify and remove such connections. However,
identifying and removing all illicit connections will take the
continued effort of the City of Waltham and the support of its
residents. Pet and wildlife waste may also be increasing bacteria
levels in the brook.
Also of water quality
concern were the high total phosphorus concentrations observed during
all three monitoring events. During dry weather, Sites BEA_OUT1, BEA2,
BEA5, BEA6, BEA8, BEA_OUT6, BEA10 and BEA11 all exceeded 0.0238 mg/L, US
EPA’s recommended total phosphorus criteria in Level III, Ecoregion
XIV. During wet weather, all sites sampled well exceeded the EPA’s
recommended total phosphorus criteria. Total phosphorus concentrations
ranged from 0.09 mg/L at Site BEA_OUT6 to 0.24 mg/L at Site BEA_OUT3,
which exceeded the recommended criteria by an entire order of
magnitude. Excessive nutrients are a significant problem throughout the
Charles River, which requires the development and implementation of
nutrient TMDLs. Runoff from large impervious surfaces is particularly problematic for urban and suburban waterways like Beaver Brook. Fertilizers from lawns,
playing fields and golf courses, as well as pet and wildlife waste,
organic matter from lawn clippings and leaf litter, detergents and
automobile emissions, are some of the likely sources of nutrients to
this brook.
Elevated concentrations of TSS were observed during
our wet weather monitoring event on November 6, 2007. Three sites
exceeded CRWA’s action limit for TSS, 30 mg/L, which is based upon EPA
recommended water quality criteria. Significant bank erosion has been
observed near Site BEA6, and very severe erosion was observed
surrounding an outfall pipe on the south side of the stream bank near
Site BEA9. High concentrations of TSS can also result from large areas
of impervious surfaces, poorly managed constructions sites, road
sanding, and stream banks with inadequate vegetation.
In addition to the degraded instream water quality,
large amounts of trash were observed both along the banks and in the
brook during all three monitoring events. See
sampling map,
sampling site descriptions,
Beaver Brook photos, and
water quality monitoring
results for further information about Beaver Brook. |
WATERSHED INFO
