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 analyzes 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.  TMDLs are also used to establish pollutant limits on certain permits, such as those governing wastewater treatment plants, new developments, and regulated industries.

Measured data–both streamflow and water quality data–and computer simulated modeling are used to determine the amount of pollution 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 for this project 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 June 2009.

Problem

Phosphorus is the primary nutrient of concern in the upper Charles River.  Natural sources of phosphorus include soil and plant materials (like leaf litter) and small amounts of atmospheric deposition.  Anthropogenic (human caused) sources of phosphorus include human waste from wastewater treatment plants and septic tanks; pet waste, manure, and fertilizers on pervious areas like lawns, golf courses, or agricultural areas; and sources such as motor vehicle exhaust, fuels, and lubricants, detergents, and car wash products.

Stormwater runoff in the Charles contributes about two-thirds of the total annual phosphorus pollution load.  This phosphorus may be natural, or caused by human activities, but much of it comes from impervious surfaces such as roads, parking lots, and buildings, especially in commercial, industrial, and high-density residential areas.  These areas have the highest contributions of phosphorus because they are well connected to the river via the stormwater drainage systems.  Natural areas such as forests and wetlands contribute relatively small amounts compared to developed areas.

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 plant outfalls.  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.  About 40% of the land area in the Upper/Middle Charles River watershed is developed thus there are large areas of impervious surfaces and lawns that act as a phosphorus source for stormwater transport to the river.

Objective

CRWA is leading a nutrient TMDL project to quantify the nutrient loads impacting the Upper/Middle 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 measured streamflow and water quality concentrations to establish loads and impacts under existing conditions.  Water quality models are then calibrated to these sampled conditions and used to determine the existing contribution to annual and seasonal 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 field work required for this project and submitted two data reports to DEP.  An HSPF water quality model was implemented and calibrated to existing data and a draft model calibration report was submitted to DEP.  A preliminary TMDL Implementation Plan is being been prepared.

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 surveyed because the worst water quality impacts are often manifested in slow-moving water.  Nine impoundments were surveyed for bathymetry, sediment thickness, 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 data reports for the TMDL work and submitted them to DEP.  In May 2004, CRWA 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 reports, 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.  A draft TMDL Implementation Plan will be prepared for the beginning of 2009.

In early 2009, using input from environmental agencies and stakeholders, CRWA will develop the final 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 November 3, 2008