Upper/Middle Charles Total Maximum Daily Load (TMDL) Project
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| Stuart Cahill ©Boston Herald |
CRWA is working with the Massachusetts Department of Environmental
Protection (DEP) and U.S. Environmental Protection Agency (EPA) to
develop a nutrient Total Maximum Daily Load (TMDL) for the Upper/Middle
Charles River.
A TMDL is the pollution level that a river can receive and still meet
appropriate water quality or aesthetic standards. TMDLs are created for
all water bodies that fail to meet water quality or aesthetic standards
due to one or more pollutants.
Measured data–both streamflow and water quality data–and water quality
modeling are used to determine the amount of pollutant that the river
can sustain without violating these standards. The percent contribution
from all pollution sources is also established. The Implementation Plan
produced at the end of the TMDL process maps out the regulatory or
voluntary process to reach that level.
The scope of work was recently expanded from just the Upper Charles to
also include the Middle Charles. The Upper/Middle Charles TMDL now
covers 70 miles of the river from the source in Hopkinton to the
Watertown Dam. The period of study is 2002 to 2005 and the project will
be completed in 2008.
Problem
Phosphorus is the primary nutrient of concern in the upper Charles
River. Anthropogenic sources of phosphorus are human waste from
wastewater treatment plant outfalls and septic tanks; improper
use/disposal of pet waste, manure, and fertilizers on pervious areas
like lawns, golf courses, or agricultural areas; and impervious area
sources such as motor vehicle exhaust, fuels, and lubricants, detergents, and car wash products.
“Stormwater in the Charles contributes about two-thirds of the total annual phosphorus pollution load. Runoff from rainfall or snowmelt transports phosphorus-rich dirt, sand, debris, and plant material to the river. Impervious surfaces – such as roads, parking lots, and buildings – especially in commercial, industrial, and high-density residential areas, have the highest contributions of phosphorus, because they are well connected to the river via the stormwater drainage systems. Phosphorus carried by stormwater comes primarily from motor vehicle exhaust, fuels, and lubricants; fertilizers; detergents; car wash products; eroded soils; and pet waste.”
Stormwater in the Charles contributes about two-thirds of the total annual phosphorus pollution load. Runoff from rainfall or snowmelt transports phosphorus-rich dirt, sand, debris, and plant material to the river. Impervious surfaces such as roads, parking lots, and buildings have the highest contributions of phosphorus. Commercial, industrial, and high-density residential areas have the highest phosphorus loads because they have more impervious area and are well connected to the river via the stormwater drainage systems.
Excessive phosphorus enters the upper Charles River disturbing the river's natural nutrient balance and resulting in
excessive algae and aquatic weed growth. In wet weather, stormwater
runoff contributes most of the pollution, while in dry weather or
drought-like conditions, the contaminants originate mostly from
wastewater treatment facilities. There are five active wastewater
treatment plants in the upper watershed–three
on the mainstem in Milford, Medway, and Medfield and two on the Stop
River in Norfolk and Wrentham. In addition, about 40% of the land area
in the upper Charles River watershed is developed thus there are large
source areas of impervious surfaces and lawns from which stormwater
runoff can wash phosphorus into the river.
Objective
CRWA is leading a nutrient TMDL project to quantify
the nutrient loads impacting the upper Charles River. Excessive
nutrients create problems with algae and nuisance aquatic vegetation.
This project seeks to identify, quantify, and reduce phosphorus levels
to acceptable levels for the river and reduce associated algae and
aquatic plant occurrence.
Approach
The TMDL approach uses measured streamflow and water quality concentrations to
establish loads and impacts under certain conditions. Water quality
models are then calibrated to these sampled conditions and used to
determine the long-term contribution of loads. The water quality models
are also used to help evaluate “what if” scenarios and identify the most
appropriate cleanup approach. The TMDL Implementation Plan identifies
primary sources of contamination and most appropriate strategies for
cleanup.
Completed Work
CRWA has completed all the water quality monitoring
and survey requirements for this project and has submitted two data
reports to DEP and a model calibration report. The
TMDL Implementation Plan will be
prepared in the beginning of 2008.
Flow monitoring was expanded from six existing
mainstem sites to include nine additional tributary sites. These
tributaries include Bogastow Brook, Chicken Brook, Fuller Brook, Hopping
Brook, Mill River, Mine Brook, Stop River, Trout Brook, and Waban Brook.
Four rounds of water quality monitoring were
performed in the Upper Charles on all major tributaries and selected
mainstem locations. These water quality monitoring events sampled both
wet- and dry-weather conditions. Impoundments were intensively sampled
because the worst water quality impacts are often manifested in
slow-moving water. Nine impoundments were sampled for dissolved oxygen,
sediment release rates, and extent of aquatic plant coverage.
The Upper/Middle Charles TMDL data were also
supplemented by water quality measurements made by the CRWA IM3, DEP
Water Quality Assessment, MWRA CSO Receiving Water, and EPA Charles
River Core monitoring programs.
CRWA has completed two reports on our TMDL work, which have been submitted to EPA. In May 2004 we released the Phase I Final Report, and in July 2006 we submitted the combined Phase II Final Report and Phase III Data Report. For copies of either of these, please contact Nigel Pickering. Click here for contact information.
Current Work
Calibration of the water quality model is complete
and is currently being used to evaluate different scenarios for
controlling and managing nutrients. In early 2008, using input from
environmental agencies and stakeholders, CRWA will develop the TMDL
Implementation Plan to define concrete regulatory or voluntary
strategies to lower phosphorus levels in the Upper/Middle Charles River,
The end result of the nutrient TMDL in the
Upper/Middle Charles River will be a cleaner, more useable river.
For more information, contact Nigel Pickering.
Click here for contact information.
Updated June 20, 2008 |