Upper/Middle Charles Total Maximum Daily Load (TMDL) Project

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.

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