COMMONWEALTH OF MASSACHUSETTS
EXECUTIVE OFFICE OF ENVIRONMENTAL AFFAIRSBOB DURAND, SECRETARY
MASSACHUSETTS DEPARTMENT OF ENVIRONMENTAL PROTECTION
LAUREN A. LISS, COMMISSIONER
BUREAU OF RESOURCE PROTECTION
CYNTHIA GILES, ASSISTANT COMMISSIONER
DIVISION OF WATERSHED MANAGEMENT
GLENN HAAS, DIRECTOR

This information is available in alternate format by calling our ADA Coordinator at (617) 574-6872.

NOTICE OF AVAILABILITY

Limited copies of this report are available at no cost by written request to:

Massachusetts Department of Environmental Protection

Division of Watershed Management

627 Main Street

Worcester, MA  01608

A complete list of reports published since 1963 is updated annually and printed in July.  This report, titled, ìPublications of the Massachusetts Division of Watershed Management (DWM) ñ Watershed Planning Program, 1963-(current year)î, is also available by writing to the DWM in Worcester.

DISCLAIMER

References to trade names, commercial products, manufacturers, or distributors in this report constituted neither endorsement nor recommendations by the Division of Watershed Management for use.

ACKNOWLEDGMENT

This report was developed by LimnoTech, Inc. through a contract with the Merrimack River Watershed Council and funded by a grant from the National Wildlife Federation.

Draft Total Maximum Daily Loads of Bacteria for Shawsheen River Basin 

DEP, DWM TMDL Draft Report MA83-01-2002-24     February 7, 2002

Figure 1: Location of the Shawsheen Basin in Massachusetts.

Key Feature:Fecal Coliform Bacteria TMDL for the Shawsheen River Watershed.

Location:EPA Region 1.

Land Type: New England Upland

303d Listings:Fecal coliform (MA83-01, MA83-02, MA83-03, MA83-08, MA83-04, MA83-05, MA83-06).

Data Sources:Merrimack River Watershed Council, Massachusetts Department of Environmental Protection, and Land Use information.

Data Mechanism:Massachusetts Surface Water Quality Standards for Fecal Coliform, Ambient Data, and Best Professional Judgment

Monitoring Plan:Merrimack River Watershed Council (MRWC) and  Massachusetts Watershed Initiative Five-Year Cycle 

Control Measures:    Watershed Management, Storm Water Management,

Illicit Discharge Detection and Elimination, Combined and         Sanitary Sewer Overflow Abatement, and Septic System Maintenance.

Shawsheen River Bacteria TMDL Executive Summary

 report represents a TMDL for bacteria in the Shawsheen River, a tributary to the Merrimack River. 

Fecal Coliform Wasteload Allocations (WLAs) and Load Allocations (LAs) for the Shawsheen River and Identified Tributary Streams

Bacteria Source Category

WLA (organisms/100ml)

LA (organisms/100ml)

Point Source

Geomean < 200

10% < 400

Sewer leaks

0

0

Sanitary Sewer Overflow

0

0

Illicit Sewer Connections

0

Failing Septic Systems

0

0

Direct Wildlife

Geomean < 200

10% < 400

Urban Stormwater Runoff

Geomean < 200

10% < 400

Geomean < 200

10% < 400

TABLE OF CONTENTS

 TOC \o "1-3" \h \z  HYPERLINK \l "_Toc520611601" Executive Summary PAGEREF _Toc520611601 \h 1

 HYPERLINK \l "_Toc520611602" 1. Introduction PAGEREF _Toc520611602 \h 2

 HYPERLINK \l "_Toc520611603" 1.1 Background PAGEREF _Toc520611603 \h 2

 HYPERLINK \l "_Toc520611604" 1.2 Shawsheen River Basin PAGEREF _Toc520611604 \h 2

 HYPERLINK \l "_Toc520611605" 2. Problem Assessment PAGEREF _Toc520611605 \h 5

 HYPERLINK \l "_Toc520611606" 3. Water Quality Standards PAGEREF _Toc520611606 \h 7

 HYPERLINK \l "_Toc520611607" 4. Fecal Contamination of the Shawsheen River Basin PAGEREF _Toc520611607 \h 8

 HYPERLINK \l "_Toc520611608" 4.1 Inventory of Fecal Coliform Data PAGEREF _Toc520611608 \h 8

 HYPERLINK \l "_Toc520611609" 4.1.1 Massachusetts Department of Environmental Protection PAGEREF _Toc520611609 \h 8

 HYPERLINK \l "_Toc520611610" 4.1.2 Merrimack River Watershed Council PAGEREF _Toc520611610 \h 8

 HYPERLINK \l "_Toc520611611" 4.2 Analysis of Instream Water Quality Monitoring Data PAGEREF _Toc520611611 \h 8

 HYPERLINK \l "_Toc520611612" 4.2.1 Defining Wet and Dry Weather Samples PAGEREF _Toc520611612 \h 9

 HYPERLINK \l "_Toc520611613" 4.2.2 Data Analysis PAGEREF _Toc520611613 \h 10

 HYPERLINK \l "_Toc520611614" 5. Identification of Fecal Coliform Bacteria Sources PAGEREF _Toc520611614 \h 43

 HYPERLINK \l "_Toc520611615" 5.1 Potential Dry Weather/Continuous Sources PAGEREF _Toc520611615 \h 46

 HYPERLINK \l "_Toc520611616" 5.1.1 Point Sources PAGEREF _Toc520611616 \h 46

 HYPERLINK \l "_Toc520611617" 5.1.2 Sewer Line Breaks/Leaks PAGEREF _Toc520611617 \h 47

 HYPERLINK \l "_Toc520611618" 5.1.3 Illicit Sewer Connections PAGEREF _Toc520611618 \h 48

 HYPERLINK \l "_Toc520611619" 5.1.4 Poorly Performing Septic Systems PAGEREF _Toc520611619 \h 48

 HYPERLINK \l "_Toc520611620" 5.1.5 Direct Wildfowl PAGEREF _Toc520611620 \h 50

 HYPERLINK \l "_Toc520611621" 5.1.6 Livestock PAGEREF _Toc520611621 \h 50

 HYPERLINK \l "_Toc520611622" 5.2 Potential Wet Weather Sources PAGEREF _Toc520611622 \h 50

 HYPERLINK \l "_Toc520611623" 5.2.1 Stormwater Runoff PAGEREF _Toc520611623 \h 50

 HYPERLINK \l "_Toc520611624" 5.2.2 Pump Station Overflows PAGEREF _Toc520611624 \h 52

 HYPERLINK \l "_Toc520611625" 6. Total Maximum Daily Load Development PAGEREF _Toc520611625 \h 52

 HYPERLINK \l "_Toc520611626" 7. Fecal Coliform TMDL PAGEREF _Toc520611626 \h 53

 HYPERLINK \l "_Toc520611627" 7.1 Loading Capacity PAGEREF _Toc520611627 \h 53

 HYPERLINK \l "_Toc520611628" 7.2 Wasteload Allocations and Load Allocations PAGEREF _Toc520611628 \h 53

 HYPERLINK \l "_Toc520611629" 7.2.1 Margin of Safety PAGEREF _Toc520611629 \h 56

 HYPERLINK \l "_Toc520611630" 7.2.2 Seasonal Variability PAGEREF _Toc520611630 \h 56

 HYPERLINK \l "_Toc520611631" 8. Implementation Activities and Future Monitoring PAGEREF _Toc520611631 \h 56

 HYPERLINK \l "_Toc520611632" 8.1 Control of Point Sources PAGEREF _Toc520611632 \h 56

 HYPERLINK \l "_Toc520611633" 8.2 Septic Tank Controls PAGEREF _Toc520611633 \h 57

 HYPERLINK \l "_Toc520611634" 8.3 Urban Runoff PAGEREF _Toc520611634 \h 58

 HYPERLINK \l "_Toc520611635" 8.4 Additional Monitoring PAGEREF _Toc520611635 \h 58

 HYPERLINK \l "_Toc520611636" 8.4.1 Wet Weather Sources PAGEREF _Toc520611636 \h 58

 HYPERLINK \l "_Toc520611637" 8.4.2 Instream Conditions PAGEREF _Toc520611637 \h 59

 HYPERLINK \l "_Toc520611638" 9. References PAGEREF _Toc520611638 \h 59

LIST OF FIGURES

 TOC \h \z \c "Figure"  HYPERLINK \l "_Toc520610949" Figure 1.  Shawsheen River Basin PAGEREF _Toc520610949 \h 4

 HYPERLINK \l "_Toc520610950" Figure 2.  Percent Difference in Dry Weather Geometric Mean Bacteria Concentrations Between 1997 and 1998 PAGEREF _Toc520610950 \h 42

LIST OF TABLES

 TOC \h \z \c "Table"  HYPERLINK \l "_Toc520610969" Table 1.  Shawsheen River Basin Segments Listed for Pathogens on Massachusettsí 1998 303(d) List PAGEREF _Toc520610969 \h 6

 HYPERLINK \l "_Toc520610970" Table 2.  Shawsheen River Basin Segments Identified as Impaired by Pathogens, Through Analysis of Water Quality Monitoring Data PAGEREF _Toc520610970 \h 6

 HYPERLINK \l "_Toc520610971" Table 3.  Precipitation Analysis PAGEREF _Toc520610971 \h 10

 HYPERLINK \l "_Toc520610972" Table 4.  1989 MDEP Fecal Coliform Data for the Shawsheen River Basin (#/100ml) PAGEREF _Toc520610972 \h 12

 HYPERLINK \l "_Toc520610973" Table 5.  1995-96 MDEP Fecal Coliform Data for the Shawsheen River Basin (#/100ml) PAGEREF _Toc520610973 \h 14

 HYPERLINK \l "_Toc520610974" Table 6.  1996 Merrimack River Watershed Council Fecal Coliform Data for the Shawsheen River Basin (#/100ml) PAGEREF _Toc520610974 \h 18

 HYPERLINK \l "_Toc520610975" Table 7.  1997 Merrimack River Watershed Council Fecal Coliform Data for the Shawsheen River Basin (#/100ml) PAGEREF _Toc520610975 \h 22

 HYPERLINK \l "_Toc520610976" Table 8.  1998 Merrimack River Watershed Council Fecal Coliform Data for the Shawsheen River Basin PAGEREF _Toc520610976 \h 30

 HYPERLINK \l "_Toc520610977" Table 9.  Analysis of All Fecal Coliform Data Collected by MDEP and MRWC (1989-1998)(#/100ml) PAGEREF _Toc520610977 \h 34

 HYPERLINK \l "_Toc520610978" Table 10.  Summary of Fecal Coliform Contamination in the Shawsheen River Watershed within 303(d) Listed Segments and Other Tributaries Identified Through Water Quality Data Analysis as Being Impaired PAGEREF _Toc520610978 \h 44

 HYPERLINK \l "_Toc520610979" Table 11.  Battle Road Wastewater Plant Discharge Limit PAGEREF _Toc520610979 \h 46

 HYPERLINK \l "_Toc520610980" Table 12.  Battle Road Wastewater Plant Discharge Characterization PAGEREF _Toc520610980 \h 47

 HYPERLINK \l "_Toc520610981" Table 13.  Summary of % of Each Town Serviced by Sewer PAGEREF _Toc520610981 \h 49

 HYPERLINK \l "_Toc520610982" Table 14.  Concentrations (Geometric Mean Colonies/100ml) of Fecal Coliforms from Urban Source Areas PAGEREF _Toc520610982 \h 51

 HYPERLINK \l "_Toc520610983" Table 15.  Fecal Coliform Wasteload Allocations (WLAs) and Load Allocations (LAs) for the Shawsheen River and Identified Tributary Streams PAGEREF _Toc520610983 \h 54

 HYPERLINK \l "_Toc520610984" Table 16.  Estimates of Fecal Coliform Loading Reductions to the Shawsheen River and Tributaries PAGEREF _Toc520610984 \h 55

Executive Summary

The Shawsheen River and three tributaries to the Shawsheen River (Rogers Brook, Vine Brook and Elm Brook) were placed on the State of Massachusettsí 303(d) list of water quality impaired water bodies for bacteria.  The applicable State standards specify that the maximum allowable concentration of fecal coliform bacteria shall not exceed a geometric mean of 200 organisms per 100 ml in any representative set of samples, nor shall more than 10% of the samples exceed 400 organisms per 100 ml.  Water quality data collected in the watershed show that bacteria concentrations routinely exceed the State water quality standard.

The Shawsheen River is located in Essex and Middlesex Counties, Massachusetts, with its headwaters beginning approximately 12 miles northwest of Boston, Massachusetts.  The Shawsheen River flows north from its source in Bedford, to Lawrence, where it merges with the Merrimack River.  The Shawsheen watershed is located within the Merrimack hydrologic unit (No. 01070002).  The land area of the Shawsheen River watershed is approximately 78 square miles, with suburban residential as the primary land use.  Also located within the watershed, near the headwaters of the Shawsheen River, is the Hanscom Air Force Base in Bedford.

The maximum allowable bacteria concentration is defined by the water quality standards for bacteria for Class B waterbodies.  Specifically, the maximum allowable bacteria concentration shall not exceed a geometric mean of 200 colonies per 100 ml in any representative set of samples nor shall more than 10% of the samples exceed 400 organisms per 100 ml. 

Current bacterial source categories addressed in this TMDL include: 1) illicit sewer connections, 2) sewer line leaks, 3) septic systems, and 4) urban stormwater runoff.  Illicit sewer connections, and sewer line breaks were determined to be the source components of greatest significance during dry weather, low flow conditions.  Urban stormwater runoff was determined to be the source component of greatest significance during high flow conditions.

Reductions from sewer breaks and illicit sewer connections will be required in order to achieve compliance with water quality standards during dry weather.  Reductions from urban stormwater runoff and illicit connections to storm sewer lines will be required in order to achieve compliance with water quality standards during wet weather.  Immediate efforts should be devoted to eliminating continuous sources that have the greatest impact during dry weather. Urban stormwater runoff is much more difficult to control, so additional monitoring is recommended to pinpoint urban stormwater runoff sources before implementing controls.  There are a lot of ìgood housekeepingî type practices (e.g., proper pet waste removal, street sweeping, reduction in runoff volumes through diversions of impervious areas to impervious areas, etc.) that should not be delayed until more data are collected.

Introduction

Background

Section 303(d) of the Clean Water Act and EPA's Water Quality Planning and Management Regulations (40 CFR Part 130) require states to develop Total Maximum Daily Loads (TMDLs) for water bodies that are not meeting designated uses under technology-based controls. The TMDL process establishes the maximum allowable loading of pollutants or other quantifiable parameters for a water body based on the relationship between pollutant sources and instream conditions. By following the TMDL process, States can establish water quality-based controls to reduce pollution from both point and nonpoint sources and restore and maintain the quality of their water resources (USEPA, 1999).

High levels of fecal coliform bacteria have been recorded throughout the Shawsheen watershed.  Fecal coliform bacteria are used as indicators for pathogenic microorganisms which can cause gastrointestinal illness through ingestion or by entering through broken skin.  The entire length of the Shawsheen River appears in the "Final Massachusetts Section 303(d) list of waters - 1998" (MDEP, 1999), due to pathogen violations.  In Massachusetts, use of the term "pathogens" on the 303(d) list directly corresponds to fecal coliform (personal communication with Arthur Johnson, 6/24/99).  Additionally, three tributaries to the Shawsheen River, Rogers Brook (from its headwaters to its confluence with the Shawsheen River), Vine Brook (from its headwaters to its confluence with the Shawsheen River), and Elm Brook (from its headwaters to its confluence with the Shawsheen River) are also listed for pathogen violations.

The purpose of this report is to establish a fecal coliform TMDL for segments of the Shawsheen River and tributaries that are currently not meeting Massachusettsí fecal coliform standards and to outline an implementation strategy to abate fecal coliform sources so bacteria standards can ultimately be attained.  This TMDL applies not only to those segments within the Shawsheen River basin that appear on the 1998 303(d) list for pathogen violations, but also to all segments in this basin that are identified as being impaired by pathogens through the evaluation of water quality monitoring data as presented in this report.  The goal of this TMDL is to improve water quality by reducing or eliminating fecal coliform loading from both point and nonpoint sources, such that the beneficial uses of the Shawsheen River and its tributaries are restored.  The implementation strategy is included in Section 9 of this report.

Shawsheen River Basin

The Shawsheen River meanders through relatively flat terrain in the coastal plain region of New England, just north of Metropolitan Boston.  Land use patterns within the watershed have been influenced by its proximity to Boston and by the establishment of the Hanscom Air Force Base in Bedford in 1942 at the headwaters of the Shawsheen.  The watershed is predominantly suburban residential with over 50% of the land area developed (Laffin, et al., 1998).  Impervious surfaces cover a substantial portion of the watershed, especially at the Air Force Base in the headwaters.  Two large wetland areas occur in the middle section of the river, in Tewksbury.  Other smaller wetlands are found throughout the watershed (Mattei et al., 1999).  The Shawsheen River Basin including community boundaries and stream names are illustrated in Figure 1.

Based on rainfall collected in Bedford, the annual average precipitation equals 45.5 inches.  Bedford is located near the headwaters of the Shawsheen River.  November and December are the wettest months on average, with average monthly precipitation totals of 4.5 and 4.2 inches, respectively.  February and August are the driest months on average, with average precipitation totals of 3.4 and 3.43 inches, respectively.  These calculations were based on 37 complete years of precipitation data.  All fecal coliform data analyzed within this report were collected between 1989 and 1998, between the months of June and October.

Figure  SEQ Figure \* ARABIC 1.  Shawsheen River Basin

Problem Assessment

The Shawsheen River along with three tributaries to the Shawsheen River (Vine Brook, Elm Brook and Rodgers Brook) were listed on the Massachusetts Department of Environmental Protection (MDEP) 1998 303(d) list (MDEP, 1999) as being impaired by pathogens.  The segments listed for pathogens are presented in Table 1.  The Shawsheen River was placed on the Massachusetts 1998 303(d) list due to pathogen violations recorded at MDEP ambient water quality monitoring stations.  According to MDEP (personal communication with Arthur Johnson, 6/24/99) the term pathogens, in this case, directly corresponds to fecal coliform bacteria since that is the parameter represented in the State water quality standard.
   Fecal coliform data collected by the Massachusetts Department of Environmental Protection and the Merrimack River Watershed Council (MRWC) reflect numerous violations of the fecal coliform water quality target.  Data that were analyzed as part of this TMDL include fecal coliform data collected by the Merrimack River Watershed Council in 1996, 1997 and 1998 as well as fecal coliform data collected by MDEP in 1989 and 1995-96.  Beginning in 1997, the Merrimack River Watershed Councilís monitoring activities have been conducted according to an approved Quality Assurance Project Plan (QAPP).  The 1996 MRWC data were not collected according to a QAPP.  
   This TMDL report addresses fecal coliform contamination originating within the Shawsheen River watershed.  It addresses the entire length (25 miles) of the river from the headwaters to the confluence with the Merrimack River as well as all tributaries to the Shawsheen River that were identified as being impaired by pathogens on the 1998 303(d) list or through analysis of water quality monitoring data (Table 2).  It does not address other pollutants identified on the 303(d) list that may be contributing to the non-attainment of water quality standards. 

Table  SEQ Table \* ARABIC 1.  Shawsheen River Basin Segments Listed for Pathogens on Massachusettsí 1998 303(d) List

Segment ID

Waterbody Name and Description

MA83-01

Shawsheen River, Summer Street (historically listed as Maguire Road) to confluence with Spring Brook, Bedford.  Miles 25.0-23.3

MA83-02

Shawsheen River, Confluence with Spring Brook, Bedford to Central Street (historically listed as Horn Bridge), Andover.  Miles 23.3-5.9

MA83-03

Shawsheen River, Central St. (Prior to 1997 cycle listed as Horn Bridge, Miles 5.9-0.0) to confluence with Merrimack River, Lawrence.  Miles 6.2-0.0.

MA83-08

Shawsheen River, Headwater, north of Folly Pond and North Great Road, Lincoln to Summer Street, Bedford.  Miles 27.0, 25.0.

MA83-04

Rodgers Brook, Outlet of first unnamed pond, Andover (Prior to 1997 cycle listed as Headwaters Billerica, Miles 1.1-0.0) to confluence with Shawsheen River, Andover.  Miles 1.3-0.0

MA83-06
Vine Brook, Headwaters (southeast of Granny Hill) near Grant Street, Lexington to confluence with Shawsheen River, Bedford.  Miles 6.8-0.0
MA83-05
Elm Brook, Headwaters, Lincoln to confluence with Shawsheen River, Bedford.  Miles 5.0  0.0

Table  SEQ Table \* ARABIC 2.  Shawsheen River Basin Segments Identified as Impaired by Pathogens, Through Analysis of Water Quality Monitoring Data

Waterbody Name1

Clark Brook

Little Content Brook Tributary (LCB 2.0)

Sandy Brook

Clark Pond

Long Meadow Brook

Spring Brook

Content Brook

Meadow Brook

Strong Water Brook

Elm Brook Tributary

North Lexington Brook

Sutton Brook

Kiln Brook

Pinnacle Brook

Tributary to Content Brook  (COBT 0.0)

Kiln Brook Tributary (KBT 0.2)

Pomp's Pond Outlet

Tributary from Foster's Pond/Foster's Brook  (FPR 2.4)

1MRWC Station ID is in parentheses, when waterbody name is ambiguous

Water Quality Standards

   Fecal coliform bacteria are found in the intestinal tract of warm-blooded animals and their presence in surface waters is an indication of fecal contamination.  The Surface Water Quality Standards for the Commonwealth of Massachusetts are described in 314 CMR 4.00.  For Class B waters such as the Shawsheen River and its tributaries, the water quality standards require that fecal coliform bacteria concentrations shall not exceed a geometric mean of 200 organisms per 100 ml in any representative set of samples, nor shall more than 10 percent of the samples exceed 400 organisms per 100 ml.
   Numeric targets along with the definition of Class B waters, as presented in the Massachusetts State Water Quality Standards, follow below:

Class B  "These waters are designated as a habitat for fish, other aquatic life, and wildlife, and for primary and secondary contact recreation.  Where designated they shall be suitable as a source of public water supply with appropriate treatment.  They shall be suitable for irrigation and other agricultural uses and for compatible industrial cooling and process uses.  These waters shall have consistently good aesthetic value."

Fecal Coliform Bacteria  "Shall not exceed a geometric mean of 200 organisms per 100 ml in any representative set of samples nor shall more than 10% of the samples exceed 400 organisms per 100 ml.  This criterion may be applied on a seasonal basis at the discretion of the Division."

Fecal Contamination of the Shawsheen River Basin

   This section provides an inventory and analysis of available observed instream fecal coliform monitoring data in the Shawsheen River watershed.  This section includes the following:

Inventory of fecal coliform data

Analysis of instream water quality monitoring data

Inventory of Fecal Coliform Data

   This section provides an overview of fecal coliform data available for this report.  The Shawsheen River and its tributaries have been monitored for fecal coliform since 1989.  The database used for this TMDL contains over 1,200 fecal coliform samples collected by both the Massachusetts Department of Environmental Protection (1989, 1995-1996) and the Merrimack River Watershed Council (1996, 1997, 1998).  All fecal coliform data were collected between the months of June and October.  Fecal coliform data obtained from the following sources are discussed further below:

Massachusetts Department of Environmental Protection

Merrimack River Watershed Council

Massachusetts Department of Environmental Protection

   The Massachusetts Department of Environmental Protection (MDEP) conducted two monitoring programs for fecal coliform on the Shawsheen River and its tributaries.  Ten stations were sampled in the 1989 study, while samples were collected at 27 stations during the 1995-96 study.  Of the stations in the MDEP surveys, a total of 8 and 16 were located on the Shawsheen River during the 1989 and 1995-96 surveys, respectively.  All data were collected between June and October. 

Merrimack River Watershed Council

   The Merrimack River Watershed Council (MRWC) conducted three monitoring programs for fecal coliform on the Shawsheen River and its tributaries.  Thirty-six stations were sampled in 1996, seventy-seven were sampled in 1997 and sixty-nine stations were sampled in 1998.  Of these stations, a total of 3, 35 and 24 were located on the mainstem of the Shawsheen River in 1996, 1997 and 1998, respectively.  All data were collected between June and October.  The 1997 and 1998 MRWC data were collected using a QAPP; however, the 1996 data were not.  All data are included in the analyses that follow.

Analysis of Instream Water Quality Monitoring Data

   This section presents an analysis of fecal coliform data collected within the Shawsheen River Basin between 1989 and 1998.  Although only the MDEP data were considered in the decision to list the Shawsheen River on the 303(d) list (personal communication, Arthur Johnson, 6/99), data collected by both the MDEP and MRWC are compared to the State Water Quality Standards in this assessment, to determine exceedances within the watershed.  Over 1,200 samples were collected within the Shawsheen River basin between 1989 and 1998.  450 of these samples were collected from the mainstem of the Shawsheen River between 1989 and 1998 at a total of 45 different locations along the length of the river. 

Individual data may be obtained from the Merrimack River Watershed Council or the Massachusetts Department of Environmental Protection.  Additional discussion of the data and figures showing monitoring locations may be found in the following reports:

Department of Environmental Protection, Massachusetts Division of Water Pollution Control.  1990.  Shawsheen River 1989 Water Quality Survey Data and Water Quality Analysis.  Publication No. 16, 483-25-25-10-90-CR.

Merrimack River Watershed Council.  1999.  Shawsheen River Watershed 1996-1998 Volunteer Monitoring Report.

Massachusetts Department of Environmental Protection.  1995.  1996 Shawsheen Assessment Summary Report.

Defining Wet and Dry Weather Samples
   A rain gage located in Bedford, Massachusetts was used for the wet and dry weather data analyses.  Over the 1989-1998 period, 45% of the samples were dry weather samples, while 19% were wet weather samples.  Wet weather samples were only available for 1996 and 1997.  36% of the samples fell into neither the wet nor the dry weather category.  In order to make best use of all of the available data, comparisons to the water quality standards were made using all of the data.  Where available, dry and wet weather samples were compared separately.
   For the purposes of this TMDL, dry and wet weather samples are defined as:
   Dry weather sample: any sample collected on a day where no significant precipitation (<0.1 inch) was recorded in the previous 72 hours.   
   Wet weather sample:  any sample collected on a day where greater than 0.1 inches of rainfall was recorded.
   The sum of wet and dry samples at a given station does not always add up to the total number of samples.  This is related to the manner in which dry and wet weather sampling events are defined.  The approach used leaves some samples undefined.  For example, if a sample was collected on a day where precipitation was zero, it was not defined as a dry weather sample if the sum of precipitation on the three preceding days was >0.1 inches.  This same sample would not be defined as a wet weather sample either because there was no precipitation on that day.  The results collected on such a day are included in the calculation of the overall statistics, but are not included
in the wet weather or dry weather summary statistics. 
   Table 3 presents total precipitation for the years during which monitoring occurred, and a comparison to the average precipitation for the Bedford station.  As shown in this table, 1989 was the closest to an average year in terms of precipitation totals, while 1996 and 1998 were significantly wetter than average.  1995 and 1997 were drier than average years.

Table  SEQ Table \* ARABIC 3.  Precipitation Analysis

Year

Total precipitation (in)

% difference from average1

Monitoring conducted
1989
44.7
2%

Dry weather only
1995
41.0
-10%

Dry weather only
1996
61.5
35%

Wet and dry weather
1997
39.7
13%

Wet and dry weather
1998
55.9
23%

Dry weather only
1Average total precipitation = 45.5 inches

Data Analysis

Tables 4 through 8 present the calculated geometric means and percent of samples exceeding 400 organisms per 100 ml for each location in 1989, 1995-96, 1996, 1997 and 1998.  Geometric means were calculated using all data collected by either the MDEP or the MRWC within each of the time periods just presented.  Consistent with the Water Quality Standards for fecal coliform, data are summarized and presented in terms of a geometric mean and also in terms of percent of samples that exceed 400 organisms/100 ml.  In instances where both wet and dry weather samples were collected, results are presented for both conditions as well as for the entire data set.
   An analysis of all data collected by MDEP and the MRWC between 1989 and 1998 is presented in Table 9.  Consistent with the Water Quality Standards for fecal coliform, data are summarized and presented in terms of a geometric mean and also in terms of percent of samples that exceed 400 organisms/100 ml.  In instances where both wet and dry weather samples were collected, results are presented for both conditions as well as for the entire data set.  Data for MDEP and MRWC stations are reported separately because it was difficult to determine if stations established by these different entities coincided.
   Review of fecal coliform data clearly illustrates the extent of the bacteria violations throughout the Shawsheen River Basin.  Violations of the bacteria standard are regularly observed during wet and dry weather events in all four of the waterbodies listed for pathogens on the 303(d) list: Shawsheen River, Elm Brook, Rogerís Brook and Vine Brook.  These four waterbodies have violated water quality standards during every period in which data are available.  This TMDL applies not only to those segments within the Shawsheen River basin that appear on the 1998 303(d) list for pathogen violations, but also to all segments in this basin that are identified as being impaired by pathogens through the evaluation of water quality monitoring data as presented in this report. 
   Further illustrating the extent of the bacteria problem in the Shawsheen River watershed are the number of other tributaries in which violations of the bacteria standard are regularly or recently observed.  These include: Content Brook, Kiln Brook, North Lexington Brook, Sutton Brook, Sandy Brook, Long Meadow Brook, Clark Brook, Clark Pond, Pinnacle Brook, Meadow Brook, Strong Water Brook, Tributary from Fosterís Pond/Fosterís Brook, Elm Brook Tributary, Kiln Brook Tributary, Little Content Brook Tributary, Tributary to Content Brook, Pompís Pond Outlet and Spring Brook.
   Exceedingly high bacteria concentrations (>5,000 #/100ml) were observed in Vine Brook (1995-96, 1997, 1998), Strong Water Brook (1996), Rogerís Brook (1996), Content Brook (1996), Elm Brook (1997), North Lexington Brook (1997), several locations along the Shawsheen River (1997, 1998), Kiln Brook (1998) and Pinnacle Brook (1998).  In 1997, bacteria concentrations as high as 375,000 #/100ml, 26,000 #/100ml and 25,000 #/100ml were observed in the Shawsheen River, Elm Brook and Vine Brook, respectively.  In 1998, bacteria concentrations as high as 112,000 #/100ml and 20,000 #/100ml were observed in the Shawsheen River and Pinnacle Brook, respectively.  The high concentrations observed in the Shawsheen River were collected from the same station in 1997 and 1998.
   Forty-five percent of the existing data represent dry weather conditions (as defined in Section 5.2.1).  These data are valuable for identifying dry weather sources of bacteria such as leaking sewers and illicit sewer connections, but are of limited utility for assessing wet weather impacts.  Nineteen percent of the data were collected during wet weather conditions.  Wet weather samples were collected by the MRWC in 1996 and 1997.  Recall that the 1996 MRWC data were not collected under a QAPP.  There are no wet weather samples in either of the MDEP datasets or in the 1998 MRWC dataset (as defined in Section 5.2.1).  To illustrate the relative magnitudes of dry and wet weather bacteria levels, Tables 6 and 7 provide separate geometric means for dry and wet weather conditions for the 1996 MRWC and 1997 MRWC datasets, respectively.  The 1996 wet weather geometric means are consistently higher than the dry weather geometric means in Table 6 (1996 MRWC dataset).  However, violations of the water quality standard are observed during both dry and wet weather.  Similarly, 1997 wet weather fecal coliform geometric means are frequently higher than the dry weather geometric means (Table 7, 1997 MRWC dataset).  Violations of the water quality standard are observed during both dry and wet weather.  At several stations along Vine Brook, Elm Brook, and the Shawsheen River, the wet weather geometric mean is lower than the dry weather geometric mean.  This may indicate a dilution effect, however, it may also be related to the timing of sample collection in relationship to peak storm runoff.  Without additional wet weather data collection it is difficult to determine the cause for this.
   A comparison of 1997 and 1998 dry weather geometric means for stations that were sampled during both of these years shows that, in general, dry weather geometric means are higher in 1998 than in 1997.  Figure 2 shows the percent difference in 1998 dry weather geometric means at each station, as compared to 1997 results.  The stations are not shown in any particular order.

MDEP ID

Station Description

No. of Samples Collected1

Geometric Mean

% of Samples > 400

No. of Dry Weather Samples

Dry Weather Geometric Mean% of Dry Samples > 400 Elm BrookEB02Grant Road bridge, Bedford2188501800ShawsheenSH010.2 mi downstream of confluence w/ Kiln Brook (Off Westview St., Bedford).  26935012400ShawsheenSH01AWhere river emerges from underground at Hanscom Field in Bedford24565014000ShawsheenSH020.4 mi downstream of confluence with Elm Brook.  Page Rd. Bridge, Bedford21,1831001700100ShawsheenSH06Route 38 Bridge, Tewksbury Just downstream of marshy reach.2139011600ShawsheenSH06ABurlington water supply intake - located in swampy reach that begins 3.7 mi upstream of station (at Route 62) 2173501600100ShawsheenSH08Located in the middle of an impounded area.  Andover St. bridge at Ballardvale, Andover.  2268011800ShawsheenSH09Horn Bridge, Andover212001900ShawsheenSH11Route 114 bridge, South Lawrence. 2268012400Vine BrookVB01Route 62 culvert, Bedford285810014601001No wet weather samples were collected.Table  SEQ Table \* ARABIC 5.  1995-96 MDEP Fecal Coliform Data for the Shawsheen River Basin (#/100ml)

StreamMDEP IDStation DescriptionNo. of Samples Collected1Geometric Mean% of Samples > 400 No. of Dry Weather SamplesDry Weather Geometric Mean% of Dry Samples > 400Elm Brook EB02At Great Rd., Routes 4 & 225, Bedford5310403363 33 Elm Brook EB03At South Rd, Bedford16000Kiln Brook KB01At Hartwell Ave., Lexington18000Rogers Brook RB01200ft from confluence w/Shawsheen5198210031,887 100 Rogers Brook RB02Off Chestnut St. near headwaters, Andover5208403150 33 Shawsheen SH12At Merrimack St., Lawrence long rope to sample side of river approx. 30-40 feet above right where river goes underground58448031,141 100 Shawsheen SH11ALoring St., Lawrence4479753388 67 Shawsheen SH07AAt Route 38, Tewksbury5217203272 33 Shawsheen SH07At USGS gage (Salem Rd/Rte 129 (Shawsheen Avenue)).  Billerica/Wilmington off bridge downstream side512203168 Shawsheen SH06AAt Burlington water intake - behind school at Alexander Road, Billerica brick building pump station cement pontoon on river at intake413603146 Shawsheen SH06At Route 3A, Billerica off bridge downstream side5246203384 33 Shawsheen SH11At Route 114, Salem Turnpike5430803482 100 Shawsheen SH02At Page Rd, Bedford upstream from center cement bridge structure5313403315 33 Shawsheen SH01At Summer St., Bedford, north side of road downstream 5139403141 33 Shawsheen SH01A-MADrainage culvert from below runway (Massport side), Bedford- discharges to Shawsheen R. from 6th pipe from left side of pipe array4390348 Shawsheen SH01A-USDrainage culvert from Hanscom AFB Bedford 3 pipes sampled from left pipe but all connected to same D box4301253335 33 Shawsheen SH01BAt Hanscom School - Hanscom Air Force Base, Lincoln (from footbridge at school upstream - miles calculated from straight line SH01AUS to school.5181203126 Shawsheen SH10At Route 28, Andover517503197 Shawsheen SH09ABrook St. (near Shawsheen Rd) Andover5100203127 33 Shawsheen SH09At Central Street, Andover5900378 Shawsheen SH08Above Ballardvale Dam, Andover510303124 Spring Brook SH03Off downstream side of bridge on Rt. 62, Bedford2280140 Strong Water BrookSW01~100 feet from confluence, at Shawsheen St., Tewksbury511103156 Vine Brook VB01At Route 62, Bedford5219203352 33 Vine BrookVB02AAt Terrace Hall Ave near pump station, Burlington116000Vine Brook VB02At East St., near Grant Street, Lexington14000Vine Brook VB0At emergence of underground culvert at Grant St., Lexington1630010001No wet weather samples were collected.

Table  SEQ Table \* ARABIC 6.  1996 Merrimack River Watershed Council Fecal Coliform Data for the Shawsheen River Basin (#/100ml)

StreamMRWC IDStation DescriptionDry Weather Geometric MeanNumber of Dry SamplesWet Weather Geometric MeanNo. of Wet SamplesTotal Number SamplesOverall Geometric MeanOverall % of Samples > 400 Content BrookCOB 1.7At Gray Street in Billerica321212504856250Content BrookCOB 2.0Whipple Street250223484896463Content BrookCOB 3.5At Shawsheen33925964844225Tributary to Content BrookCOBT 0.0Ý75279485125Tributary to Content BrookCOBT 1.0Ý1522165481350Elm Brook EB 0.5On North side of Route 2A crossing, Lincoln, just before Concord line9226244823838Elm BrookEB 2.0Ý21523324820825Elm BrookEB 4.0At Great Road (62) crossing, Bedford13024634819838Foster's PondFPR 1.4Foster's Pond on pond side of the dam3221448220Tributary from Foster's Pond/ Foster's BrookFPR 2.1At River St. culvert in Andover13027748900Tributary from Foster's  Pond/ Foster's BrookFPR 2.4RR bridge just before Shawsheen enters Ballardvale Mill Pond8723794828438Kiln BrookKB 0.5Before landfill13017703535340Kiln BrookKB 0.8After leaving landfill28014333535540Meadow BrookMDB 1.2At culvert under Kendall Road, near Ames pond 080011800100Meadow BrookMDB 2.6By Canalas Waste property, Pinnacle Road crossover, Tewksbury (US of SWB)13418001331133Pomp's Pond PP 0.0On beachhead in Andover2832949310Pomp's Pond outletPP 0.5Pond outlet9335024914922Roger's BrookROB 0.0At Highland Ave, Phillips academy121235502642050Roger's BrookROB 1.0School ball field before river is culverted66324460261,47783Roger's BrookROB 1.5Upstream of confluence w/ Shawsheen R.63525126261,912100Shawsheen River SH 1.0Where Kiln Brook meets the Shawsheen7018001223750Shawsheen RiverSH 12.3Below Ballardvale dam - near pipe discharging brown scum.  9011900Shawsheen RiverSH 12.35At outfall pipe from Pomp's Pond22332464925633Shawsheen RiverSH 2.2At Cedar Ridge Terrace, Bedford3018001215550Strong Water BrookSWB 0.6Where Strong Water Brook crosses Lee St. near Tewksbury cemetery02846332,846100Strong Water BrookSWB 1.0At culvert under East St. , near Tewksbury Cemetery36337904980089Strong Water BrookSWB 2.0Crossover at East St./Maple St. intersection near state hospital, Tewksbury2533114917233Strong Water BrookSWB 3.0At end of Algonquin Dr.7531214911611Strong Water BrookSWB 3.3Just before confluence with Shawsheen8422964720529Vine BrookVB 1.8Just upstream of Butters-worth Pond, below bridge on North St., Lexington39026403650267Vine Brook (Pond)VB 2.9Butterfield Pond - near spillway where Vine Brook exits6326854728243Long Meadow Brook (trib to VB)VB 4.0Before Long Meadow Brook enters Vine Brook9227184734957Vine BrookVB 4.3By Lexington St., Burlington 12322674720643Vine BrookVB 5.0At Terrace Hall Road, Burlington8034544917622Vine BrookVB 5.3Middlesex Turnpike, Burlington8636692715629Vine BrookVB 6.3South side of Route 62 overpass near on/off ramp for route 3 south, Bedford8533854918033

Table  SEQ Table \* ARABIC 8.  1998 Merrimack River Watershed Council Fecal Coliform Data for the Shawsheen River Basin

STREAMMRWC IDNo. of Samples Collected1Geometric Mean% of Samples > 400

(cfu/100 ml)No. of Dry Weather SamplesDry Weather Geometric Mean% of Dry Samples >400 (cfu/100ml)Unnamed streamBM 0.359404730Clark BrookCB 0.412,00010012,000100Clark PondCB 0.7824838531040Content BrookCOB 1.77133144860Content BrookCOB 2.872771452130Darby BrookDAB 2.061751741340Elm BrookEB 0.572031441700Elm BrookEB 1.5779144430Elm BrookEB 2.564804330Elm BrookEB 3.3645733337633Elm BrookEB 3.4646750443150Elm BrookEB 4.07590864535100Tributary from Foster's Pond/ Foster's BrookFPR 2.175305590Heath BrookHB 1.0597041060Heath BrookHB 1.972171441520Hussey BrookHP 1.3811705940Kiln BrookKB 0.6846450520520Kiln Brook tributaryKBT 0.2845450533740Little Content BrookLCB 1.0382021230Little Content Brook TributaryLCB 2.0320333219150Meadow BrookMDB 2.67122145550North Lexington Brook (Pond) tributary To Kiln BrookNL 0.352402021000Pinnacle BrookPB 1.378,72610056,262100PBR 0.22160160Pinnacle Brook TributaryPBT 0.42268501360Pomp's PondPP 0.081605390Roger's BrookROB 0.0831725527320Roger's BrookROB 1.5823138511520Spring BrookSB 0.8742043436150Spring BrookSB 2.365803160Shawsheen RSH 0.381731351340Shawsheen RSH 0.6840750531940Shawsheen RSH 1.86100320Shawsheen RSH 11.48178051420Shawsheen RSH 12.2710505940Shawsheen RSH 12.36155041330Shawsheen RSH 13.47159041290Shawsheen RSH 14.47215041870Shawsheen RSH 14.567704430Shawsheen RSH 14.6652267460875Shawsheen RSH 15.5617517518620Shawsheen RSH 17.37112145730Shawsheen RSH 18.2572221451300Shawsheen RSH 2.3613104820Shawsheen RSH 3.153484032910Shawsheen RSH 3.7633233343733Shawsheen RSH 3.8743729432525Shawsheen RSH 4.2710,986100412,775100Shawsheen RSH 5.0722514421025Shawsheen RSH 5.5534980432375Shawsheen RSH 6.12325013200Shawsheen RSH 7.162341731710Shawsheen RSH 8.5717529410225Shawsheen RSH 9.06122174740Shawsheen RSH 9.581441351150Shawsheen RSHT 0.5521220422625Sutton BrookSTB 0.372602951570Sutton BrookSTB 0.764705400Strong Water BrookSWB 2.0733729523320Strong Water BrookSWB 3.3827525520820Vine BrookVB 1.0667450443350Vine BrookVB 1.1680174420Vine BrookVB 1.5798386461375Vine BrookVB 2.3637650433050Vine Brook (Pond)VB 2.9666174420Vine BrookVB 4.3733129425725Vine BrookVB 5.0715614414725Vine BrookVB 6.57150041670Webb BrookWB 1321133113201No wet weather samples were collected.

(cfu/100 ml)Dry Weather Geometric MeanWet Weather  Geometric MeanElm BrookElm Brook 0.02MDEP31040%363Elm BrookElm Brook 0.2MDEP18850%80Elm BrookElm Brook 0.9MDEP600%Kiln BrookKiln Brook 0.4MDEP800%Rogers BrookRogers Brook 0.1MDEP1982100%1887Rogers BrookRogers Brook 1.1MDEP20840%150Shawsheen R.Shawsheen 0.3MDEP84480%1141Shawsheen R.Shawsheen 0.8MDEP47975%388Shawsheen R.Shawsheen 13.8MDEP1390%160Shawsheen R.Shawsheen 13.9MDEP21720%272Shawsheen R.Shawsheen 16.2MDEP1220%168Shawsheen R.Shawsheen 17.5MDEP17350%600Shawsheen R.Shawsheen 18MDEP1360%146Shawsheen R.Shawsheen 19.6MDEP24620%384Shawsheen R.Shawsheen 2.3MDEP2680%240Shawsheen R.Shawsheen 2.7MDEP43080%482Shawsheen R.Shawsheen 23.4MDEP1183100%700Shawsheen R.Shawsheen 23.5MDEP31340%315Shawsheen R.Shawsheen 25MDEP22043%161Shawsheen R.Shawsheen 25.6MDEP45650%400Shawsheen R.Shawsheen 25.99MDEP390%48Shawsheen R.Shawsheen 26MDEP30125%335Shawsheen R.Shawsheen 26.6MDEP18120%126Shawsheen R.Shawsheen 4.8MDEP1750%197Shawsheen R.Shawsheen 5.3MDEP10020%127Shawsheen R.Shawsheen 5.9MDEP1200%90Shawsheen R.Shawsheen 6.2MDEP900%78Shawsheen R.Shawsheen 8MDEP2680%180Shawsheen R.Shawsheen 8.2MDEP1030%124Spring BrookSpring Brook 0.2MDEP280%40Strong Water BrookStrong Water Brook 0.01MDEP1110%156Vine BrookVine Brook 0.6MDEP32443%376Vine BrookVine Brook 2MDEP1600%Vine BrookVine Brook 6MDEP400%Vine BrookVine Brook 6.1MDEP6300100%Unnamed streamBM 0.3MRWC1090%9590Unnamed streamBM 0.7MRWC680%20200Pond in Baker's MeadowBM 0.8MRWC120%255Clark BrookCB 0.4MRWC2000100%2000Clark PondCB 0.7MRWC24838%310Content BrookCOB 1.7MRWC27833%1171260Content BrookCOB 2.0MRWC96463%2502348Content BrookCOB 2.8MRWC30317%256Content BrookCOB 3.5MRWC44225%339596Tributary to Content BrookCOBT 0.0MRWC5125%7579Tributary to Content BrookCOBT 1.0MRWC1350%152165Darby BrookDAB 2.0MRWC17517%134Elm BrookEB 0.5MRWC21625%163302Elm BrookEB 1.5MRWC829%5450Elm BrookEB 2.0MRWC20825%215332Elm BrookEB 2.5MRWC829%71128Elm BrookEB 3.3MRWC50758%421770Elm BrookEB 3.4MRWC46750%431Elm BrookEB 4.0MRWC49963%520800Elm Brook TributaryEBT 0.2MRWC37150%522134Foster's PondFPR 1.0MRWC30%62Foster's PondFPR 1.4MRWC140%2118Foster's PondFPR 1.6MRWC930%117380Tributary from Foster's Pond/Foster's BrookFPR 2.1MRWC630%7264Tributary from Foster's Pond/Foster's BrookFPR 2.4MRWC28438%87379Heath BrookHB 1.0MRWC970%106Heath BrookHB 1.75MRWC1030%103400Heath BrookHB 1.9MRWC21714%152Hussey BrookHP 1.3MRWC949%492700Hussey PondHP 1.8MRWC980%120300Kiln BrookKB 0.5MRWC35340%130770Kiln BrookKB 0.6MRWC33243%234252Kiln BrookKB 0.8MRWC35540%280433Kiln Brook TributaryKBT 0.2MRWC45450%337Little Content BrookLCB 1.0MRWC600%67100Little Content Brook TributaryLCB 2.0MRWC15511%22694Long Meadow BrookLMB 0.7MRWC68267%2000440McKee BrookMC 0.3MRWC4217%2618Meadow BrookMDB 1.2MRWC800100%800Meadow BrookMDB 2.6MRWC12613%60566North Lexington BrookNL 0.3MRWC31633%159789Pinnacle BrookPB 1.3MRWC8726100%6262ÝPBR 0.2MRWC160%6Pinnacle Brook TributaryPBT 0.4MRWC26850%36Pomp's PondPP 0.0MRWC190%2530Pomp's Pond outletPP 0.5MRWC14922%93502Roger's BrookROB 0.0MRWC35836%2163550Roger's BrookROB 1.0MRWC147783%6634460Roger's BrookROB 1.5MRWC57164%1885126Sandy BrookSB 0.6MRWC61275%360698Spring BrookSB 0.8MRWC94960%8223800Spring BrookSB 2.3MRWC580%16Shawsheen R.SH 0.0MRWC124363%12101000Shawsheen R.SH 0.3MRWC38531%2551000Shawsheen R.SH 0.6MRWC40750%319Shawsheen R.SH 1.0MRWC23750%70800Shawsheen R.SH 1.8MRWC2214%22100Shawsheen R.SH 10.6MRWC20017%740295Shawsheen R.SH 11.0MRWC49067%2000950Shawsheen R.SH 11.4MRWC1780%142Shawsheen R.SH 12.2MRWC1050%94Shawsheen R.SH 12.3MRWC1808%127219Shawsheen R.SH 12.35MRWC21127%217181Shawsheen R.SH 13.3MRWC930%18077Shawsheen R.SH 13.4MRWC1310%96Shawsheen R.SH 14.2MRWC1160%106173Shawsheen R.SH 14.4MRWC16814%68693Shawsheen R.SH 14.45MRWC19429%122894Shawsheen R.SH 14.5MRWC15423%63300Shawsheen R.SH 14.55MRWC24629%157219Shawsheen R.SH 14.6MRWC50062%4751470Shawsheen R.SH 14.9MRWC24120%358173Shawsheen R.SH 15.5MRWC33338%240424Shawsheen R.SH 15.7MRWC66457%452424Shawsheen R.SH 15.8MRWC112250%14000Shawsheen R.SH 16.6MRWC36814%400358Shawsheen R.SH 17.3MRWC11214%73Shawsheen R.SH 17.8MRWC69883%6451196Shawsheen R.SH 18.25MRWC33538%1692491Shawsheen R.SH 2.2MRWC15550%30800Shawsheen R.SH 2.3MRWC18210%104550Shawsheen R.SH 2.6MRWC42150%360810Shawsheen R.SH 3.1MRWC34840%291Shawsheen R.SH 3.7MRWC31729%437240Shawsheen R.SH 3.8MRWC20021%199223Shawsheen R.SH 4.2MRWC20853100%1500832863Shawsheen R.SH 5.0MRWC978%13270Shawsheen R.SH 5.5MRWC28250%279Shawsheen R.SH 6.1MRWC1780%199290Shawsheen R.SH 7.1MRWC1219%127100Shawsheen R.SH 7.5MRWC1160%66220Shawsheen R.SH 8.5MRWC11615%96104Shawsheen R.SH 9.0MRWC12217%74Shawsheen R.SH 9.5MRWC14413%115Shawsheen R.SHT 0.0MRWC310%1094Shawsheen R.SHT 0.5MRWC22530%173221Sutton BrookSTB 0.3MRWC18223%12899Sutton BrookSTB 0.7MRWC1008%63308Strong Water BrookSWB 0.6MRWC2846100%2846Strong Water BrookSWB 1.0MRWC80089%363790Strong Water BrookSWB 2.0MRWC16523%81276Strong Water BrookSWB 3.0MRWC11611%75121Strong Water BrookSWB 3.3MRWC17318%133257Strong Water BrookSWB 3.6MRWC1020%76204Vine BrookVB 1.0MRWC107267%932770Vine BrookVB 1.1MRWC8017%42Vine BrookVB 1.5MRWC173692%8892700Vine BrookVB 1.8MRWC50267%390640Vine BrookVB 2.3MRWC61775%529740Vine BrookVB 2.9MRWC9325%32249Vine BrookVB 4.0MRWC34957%92718Vine BrookVB 4.3MRWC26137%280228Vine BrookVB 5.0MRWC16019%99398Vine BrookVB 5.3MRWC15629%86669Vine BrookVB 5.8MRWC820%12842Vine BrookVB 6.3MRWC8717%42299Vine BrookVB 6.5MRWC1500%167Webb BrookWB 1MRWC21133%132

Figure  SEQ Figure \* ARABIC 2.  Percent Difference in Dry Weather Geometric Mean Bacteria Concentrations Between 1997 and 1998Identification of Fecal Coliform Bacteria Sources

This TMDL applies not only to those segments within the Shawsheen River basin that appear on the 1998 303(d) list for pathogen violations, but also to all segments in this basin that are identified as being impaired by pathogens through the evaluation of water quality monitoring data as presented in this report.  As such, this TMDL evaluation examined all known potential sources of fecal coliform bacteria in the Shawsheen River watershed using all available information.  Direct measurements were unavailable for many sources; however, through the evaluation of water quality monitoring data, investigations by the MRWC and MDEP, as well as through analysis of land uses within the watershed and literature values for typical stormwater concentrations, it was possible to perform an initial evaluation of bacteria sources.

Table 10 summarizes the 303(d) listed river segments that are impaired due to measured fecal coliform contamination and identifies suspected and known sources to these segments and their tributaries, as identified by the MRWC (Mattei et al., 1999) and by the MDEP (MDEP, 1996).  Table 10 also includes all tributaries to the Shawsheen River that have been identified as being impaired through analysis of fecal coliform bacteria collected between 1989 and 1998, but which were not included on the 1998 303(d) list.

The MRWC has effectively used information and data collected through its monitoring program to target known and/or suspected bacteria sources.  For example, a broken sewage pipe was discovered to be leaking raw sewage directly into the Shawsheen River.  This problem was fixed and bacteria levels quickly returned to normal (Mattei et al., 1999).  Another example is the ìalarmingly highî bacteria levels on the Shawsheen River at Dunham Road (SH 4.2).  The high bacteria levels at this site are due to raw sewage coming from a storm drainpipe at an industrial park on Dunham Road.  High bacteria levels were also found behind Shawsheen Technical High School at site SH 6.1.  Volunteers suspect a sewage leak.  Volunteers have brought the problem of high bacteria levels at Dunham Road (site SH 4.2) to the attention of the Board of Health and local Department of Public Works.  Steps are being taken to try and rectify this situation.  The town of Billerica is requiring that all of the businesses in the industrial park tie into the public sewer system.  The Billerica Board of Health is also investigating a suspected sewage leak which volunteers found near site SH 6.1 behind Shawsheen Technical High Schoolî (Mattei et al., 1999).

Because violations of the bacteria water quality standard occur during dry and wet weather, the discussion that follows addresses both continuous (dry weather) and wet weather bacteria sources, as identified in Table 10.  Continuous source categories evaluated include: point sources, broken sewer lines, illicit disposal to storm drains, poorly performing septic systems and direct wildlife.  Wet weather source categories that were evaluated include: urban stormwater runoff and pump station overflows.  Data analysis and comparison of data to suspected or known sources identified by the MRWC (Mattei et al., 1999) shows that illicit connections and sewer breaks are the most important sources during dry weather.  Urban stormwater is the largest potential wet weather source of bacteria to the Shawsheen River.  Other wet weather sources include illicit storm sewer connections and sewer breaks which are expected to be a source of bacteria not only during dry weather, but also during wet weather.

Table  SEQ Table \* ARABIC 10.  Summary of Fecal Coliform Contamination in the Shawsheen River Watershed within 303(d) Listed Segments and Other Tributaries Identified Through Water Quality Data Analysis as Being Impaired

Location1Known and Suspected SourcesUpper Shawsheen River (including tributary impacts)2Broken sewage pipe (fixed); Stormwater runoff; Failing septic systemsMiddle Shawsheen River (including tributary impacts)2Illicit connection to storm drainpipe; Sewage leak; Stormwater runoff, farm (piggery); Failing septic systemsLower Shawsheen River (including tributary impacts)2Stormwater runoff; Failing septic systems; Dry weather discharges; Wildlife; possible sewer leakElm Brook2Leaking septic systems; Stormwater runoff; possible sewer leakVine Brook2Burlington Sewer Overflow (documented wet weather overflows); Manure piles near stream; possible sewer leaks; Stormwater runoffRogers Brook2Pipes discharging during dry periods (possible sewer line leak); Stormwater runoff; Failing septic systemsClark BrookUnknownClark PondUnknownContent BrookUnknownElm Brook TributaryUnknownKiln BrookUnknownKiln Brook Tributary (KBT 0.2)UnknownLittle Content Brook Tributary (LCB 2.0)UnknownLong Meadow BrookUnknownMeadow BrookUnknownNorth Lexington BrookUnknownPinnacle BrookUnknownPompís Pond OutletUnknownSandy BrookUnknownSpring BrookUnknownStrong Water BrookUnknownSutton BrookUnknownTributary to Content Brook (COBT 0.0)UnknownTributary from Fosterís Pond/Fosterís Brook (FPR 2.4)Unknown1MRWC Station ID is in parentheses, when waterbody name is ambiguous

2Appears on the Massachusetts 303(d) list for pathogen violationsThis source assessment is divided into two sections:

Potential dry weather/continuous sources

Potential wet weather sources

Potential Dry Weather/Continuous Sources

Based on a review of NPDES permitted point sources in the watershed, information on the areas of the watershed serviced by septic systems and a review of the Shawsheen River Watershed 1996-1998 Volunteer Monitoring Report as well as the 1996 MDEP Shawsheen Assessment Summary Report, potential dry weather sources were identified.  These sources, which are all continuous, even during wet weather events, include:

point sources,

sewer line breaks/leaks,

illicit sewer connections,

poorly performing septic systems,

direct wildfowl, and

livestock

Dry weather sources of fecal coliform within the Shawsheen River watershed are discussed below.

Point Sources

The greatest potential source of human fecal coliform from point sources is raw sewage.  Ten NPDES permitted point sources are known to discharge in the Shawsheen River watershed; however, only the Battle Road Wastewater Plant  (NPDES ID MA0031658) receives sanitary sewage and has a fecal coliform limit specified within its permit.  Point sources without bacteria limits specified in their permits are not considered to be significant contributors of bacteria and are not discussed in this document.

The Battle Road Wastewater Plant discharges to an unnamed tributary to the Shawsheen River.  Monthly operating report records obtained for this facility indicate that this facility did not violate its permit limit between April 1997 through May 1998 and is not likely to be a significant source of bacteria to the Shawsheen River.  The permit limits along with monthly operating report data from April 1997 through May 1998 are summarized in Tables 11 and 12 below:

Table  SEQ Table \* ARABIC 11.  Battle Road Wastewater Plant Discharge Limit

Permit NumberFlow

(MGD)Fecal coliform permit limit(#/100 ml)Average MonthlyDaily MaximumMA00316580.033200400

Fecal Coliform (#/100 ml)Average MonthlyMaximum MonthlyApril 199742392May 1997518.492June 1997440.5154July 199751252August 1997N/A1N/AN/ASeptember 1997416.566October 1997438November 19974312December 1997500January 1998400February 199842392March 1998400April 1998545.6208May 19984291081N/A = Not available.

Sewer Line Breaks/Leaks

Raw sewage, although not usually discharged intentionally, can reach waterbodies through leaks in sanitary sewer systems, overflows from surcharged sanitary sewers (sanitary sewer overflows), illicit connections of sanitary sewers to storm sewer collection systems, or unidentified broken sanitary sewer lines.  According to the Center for Watershed Protection (CWP, 1999), "in some communities, as many as 10 percent of all pipe outfalls have dry weather flow.  Even if only a few of these flows contain sewage, they can produce very high bacteria concentrations because of low instream flow."  Typical values of fecal coliform in untreated domestic wastewater range from 106 to 107 MPN/100 ml (Metcalf and Eddy, 1991).

The Merrimack River Watershed Council volunteers have discovered suspected sewer line breaks and leaks within three tributary subwatersheds to the Shawsheen River which appear on the 303(d) list (Rogers Brook, Elm Brook and Vine Brook) as well as near several Shawsheen River sampling stations.  Within the Rogers Brook watershed, two locations were noted by volunteers.  The first location consisted of observed dry weather discharge to Rogers Brook.  Second, a sewer overflow in Andover was discovered.  Within the Vine Brook watershed, possible sewer breaks were noted to be affecting stations VB 1.0 and VB 1.5.  Within the Elm Brook subwatershed, a possible sewer break was noted near station EB 4.0.  Finally, several sewer line breaks/leaks were discovered to be directly affecting the Shawsheen River.  A broken sewage main was discovered at the Hanscom Air Force Base near the headwaters of the Shawsheen River (Shawsheen Stations SH 0.0 and SH 0.3).  In North Andover, near Mass Ave/Glenwood (Shawsheen River station SH 17.8), a sewage smell was reported by volunteers (p. 97 Mattei et al., 1999).

A dry weather violation of fecal coliform water quality standards was observed at each of the stations identified in the discussion above.  The sewer break noted on Elm Brook may also explain the increase in bacteria levels downstream of the Elm Brook confluence with the Shawsheen River (downstream of station SH 1.8).  Likewise, the high bacteria levels in Vine Brook during dry weather, caused by possible sewer breaks, may explain the increase in low-flow concentrations in the Shawsheen River downstream of station SHÝ3.1.

Illicit Sewer Connections

Illicit disposal of sewage to storm drains results in direct discharges of sewage to receiving waters through storm drainage system outfalls.  Illicit sewer connections can have as large an impact as broken or leaking sewer pipes.  The Merrimack River Watershed Council volunteers discovered that some businesses were improperly discharging sewage and were not hooked up to the sewer system near Shawsheen River station SH 4.2.  This is likely the cause of the excessive fecal coliform concentrations at this station.

Illicit sewer connections represent a direct threat to public health since they result in discharges of partially treated or untreated human wastes.  Quantifying this source is extremely speculative without direct monitoring of the source because the magnitude is directly proportional to the volume of the sources and its proximity to the surface water.  Typical values of fecal coliform in untreated domestic wastewater range from 106 to 107 MPN/100 ml (Metcalf and Eddy, 1991).

Poorly Performing Septic Systems

Septic systems designed, installed and maintained in accordance with 310 CMR 15.000: Title 5, are not significant sources of fecal coliform bacteria.  ìFor the most part, properly sited and maintained septic systems can treat wastewater effectively and not threaten water quality.  However, the effectiveness of septic systems strongly depends on site conditions and timely inspection and maintenanceî (Schueler and Holland, 2000).  Failing septic systems hold the potential to deliver bacteria to surface waters due to failure of the system to provide adequate treatment due to malfunctions. ìThe causes of septic system failure are numerous: inadequate soils, poor design, siting, testing or inspection, hydraulic overloading, tree growth in the drain field, old age and failure to clean out.î (Center for Watershed Protection, 1999). Typical values for fecal coliform in untreated domestic wastewater range from 106 to 107 MPN/100 ml (Metcalf and Eddy, 1991).

No information was available on the specific locations of septic systems, septic tank densities or failure rates in the Shawsheen River watershed.  However, the Merrimack River Watershed Council (personal communication w/ Michelle Carley) surveyed each of the towns in the watershed to get an estimate of the percent of sewered versus non-sewered area of each town.  This survey indicated that most of the Shawsheen River watershed is serviced by sewer lines, with only portions of the towns of Bedford, Andover, Billerica and Tewksbury serviced by septic systems.  Using 1990 census data (Massachusetts Department of Housing and Community Affairs website) for each of the towns to estimate the number of homes and assuming a failure rate of 3%, the number of failing systems can be estimated for the portion of each town within the watershed (TableÝ13).

Table  SEQ Table \* ARABIC 13.  Summary of % of Each Town Serviced by Sewer

Town% Sewered# Single Unit Homes in Watershed1# Septic Systems2# Failing systems3Tributaries w/in Town BoundariesAndover903,96339612Baker's Meadow, Content Brook, Roger's Brook, Hussey PondBedford942,5111515Spring Brook, Elm BrookBillerica704,6071,38241Content Brook, McKee, Web and Jones Brooks  Burlington100Lawrence100North Andover100Tewksbury455,6293,09693Strongwater Brook, Sutton Brook, Content Brook, Heath Brook1 Number of single unit homes per 1990 U.S. Census * % of town in watershed

2 Number of homes on septic systems in the watershed, assuming one septic system per home

3 Number of homes with failing septic systems based on 3% national failure rate

Almost the entire length of the Shawsheen River (Shawsheen River stations SH 0.0 - SH 15.8) falls with the town boundaries of Bedford, Billerica, Tewksbury and Andover.  Therefore, septic systems are a potential source of bacteria for much of the Shawsheen River, and also for the following tributaries: Baker's Meadow, Content Brook, Roger's Brook, Hussey Pond, Spring Brook, Elm Brook, McKee, Webb and Jones Brooks, Strongwater Brook, Sutton Brook and Heath Brook.

According to information obtained in the Shawsheen River Watershed 1996-98 Volunteer Monitoring Report (Mattei et al., 1999), septic systems are a suspect source of fecal coliform in the Vine Brook watershed (potentially outdated septic (VB 1.0)).  However, this source is probably a minor impact on the Vine Brook system, since according to the survey results, the Vine Brook watershed is 100% sewered, being located in the towns of Lexington and Burlington.  It would be prudent to more closely examine the number of septic systems in the watershed to verify that they are not a dry weather source to Vine Brook.

Direct Wildfowl

Animals that are not pets can be a potential source of fecal coliform, even in an urban environment.  "Geese, gulls and ducks are speculated to be a major bacterial source in urban areas, particularly at lakes and stormwater ponds where large resident populations have become established.  However, relatively little data are available to quantify whether geese and ducks are a major source of fecal coliforms." (CWP, 1999).  Wildfowl are of particular concern in the following subwatersheds:  Pinnacle Brook, Strong Water Brook, Foster's Pond and Baker's Meadow (Mattei et al., 1999) due in part to the undeveloped land adjacent to some of these waterways.  Of these tributaries, dry weather fecal coliform water quality violations were only observed at the mouth of Strong Water Brook.  Therefore, it is unlikely that wildfowl are a significant source of fecal coliform bacteria violations.

Livestock

A farm located on the banks of Pinnacle Brook, a tributary to Strong Water Brook, is a suspected source for the fecal coliform levels observed at PB 1.3 (Mattei et al., 1999).  The dry weather geometric mean at PB 1.3 was 6,262 in 1998.  Pinnacle Brook may contribute to the water quality violations observed at the mouth of Strong Water Brook.

Potential Wet Weather Sources

Potential sources for wet weather violations of fecal coliform standards were identified from an analysis of land use patterns, a literature review and a review of the Shawsheen River Watershed 1996-1998 Volunteer Monitoring Report.  Potential wet weather sources include:

High stormwater runoff loads of bacteria are more likely to be caused by bacteria from domestic animals rather than from livestock and wildlife.  This is based on an analysis of fecal coliform violations at stations downstream of areas with higher concentrations of livestock and wildlife.

Stormwater Runoff

With over half of the watershed developed with either urban or residential land use, the potential for conversion of precipitation to significant amounts of stormwater runoff exists.  Stormwater runoff may carry fecal coliform from pets, livestock and wildlife to the Shawsheen River and its tributaries.  Urban stormwater runoff appears to be a significant wet weather source of bacteria not only to the Shawsheen River, but also to its tributaries.  In several tributary watersheds, including Vine Brook and Elm Brook, an apparent correlation has been noted (Mattei et al., 1999) between the highly developed lower sections with high bacteria levels, in addition to an apparent correlation between high turbidity and fecal coliform levels.  In Elm Brook, runoff is suspected of contributing fecal coliform since most Bedford residents are on the town sewer system, although it should be remembered that a possible sewer leak was also noted in the Elm Brook subwatershed near station EB 4.0.

The concentration of bacteria in stormwater runoff can vary widely.  Typical stormwater event mean concentrations derived from studies in Marquette, MI and Madison, WI are presented in Table 14.  As shown in this table, event mean concentrations may vary depending on land use.  Additionally, event mean concentrations may vary depending on location so it is preferable to collect site-specific stormwater data to most accurately characterize bacteria concentrations in runoff.  Sources contributing to fecal coliform in stormwater runoff are discussed below.

Table  SEQ Table \* ARABIC 14.  Concentrations (Geometric Mean Colonies/100ml) of Fecal Coliforms from Urban Source Areas

Land UseMarquette, MIMadison, WINo. of storms sampled129Commercial parking lot4,2001,758High traffic street1,9009,627Medium traffic street2,40056,554Low traffic street28092,061Commercial rooftop301,117Residential rooftop2,200294Residential driveway1,90034,294Residential lawns4,70042,093Steuer et al., 1997; Bannerman et al., 1993 as cited in Schueler and Holland, 2000

Domestic animals

One source of bacteria in stormwater runoff in urban areas like the Shawsheen River watershed, is the feces from household pets such as cats and dogs, which comprise a large potential source of bacteria (~23,000,000 #/gm (CWP, 1999)).  A rule of thumb estimate for the number of dogs is ~1 dog per 10 people producing an estimated 0.5 pound of feces per dog per day.  This translates to an estimated 10,700 dogs in the watershed producing 5,400 pounds of feces per day (personal communication, Don Waye).  Unless this waste is picked up and properly disposed, runoff flushes the bacteria from the parks and yards where pets are walked, into nearby waterways.

Livestock

In rural areas, runoff from livestock areas may be a source of bacteria.  Within the Shawsheen River Watershed, only 1% of the watershed area is classified as pasture land, and the tributary watersheds with the highest percentage of pasture land are Sutton Brook and Strong Water Brook, with 13% and 5% respectively, of their areas being classified as such.  Sutton Brook only slightly violated water quality standards at its mouth during dry weather (geometric mean=203 in 1997) and wet weather (geometric mean=308 in 1997), indicating that stormwater runoff of livestock waste is likely not a significant problem in this watershed.

Wildlife

Rural wildlife can also contribute to stormwater loads of bacteria.  Wildfowl are noted to be of particular concern in the following subwatersheds:  Pinnacle Brook, Strong Water Brook, Foster's Pond and Baker's Meadow (Mattei et al., 1999) due in part to the undeveloped land adjacent to some of these waterways.  Of these tributaries, wet weather fecal coliform water quality violations were observed at the mouth of Strong Water Brook and Foster's Pond.  These exceedances may be due to the runoff of bacteria from deposits left by wildlife, although their contribution is difficult to quantify.

Although there are no known combined sewers in the watershed, there was a pumping station overflow noted on Terrace Hall Road  (VB 6.5) where the sewer overflows into Vine Brook (MRWC hot spot results, 1999).  Pump station by-passes may contribute fecal coliform concentrations which are likely to be similar to those from combined sewer overflows.  "Fecal coliform bacteria concentrations from combined sewer overflows are on the order of 104 - 107 counts/100 ml (CWP, 1999)."  While fecal coliform concentrations are expected to be very high in these overflows, the total fecal load delivered to Vine Brook depends upon the quantity of water that is discharged.

Total Maximum Daily Load Development

Section 303(d) of the Federal Clean Water Act (CWA) requires states to place waterbodies that do not meet the water quality standards on a list of impaired waterbodies.  The CWA requires each state to establish Total Maximum Daily Loads (TMDLs) for listed waters and the pollutant contributing to the impairments.  TMDLs determine the amount of a pollutant that a waterbody can safely assimilate without violating the water quality standards.

Total Maximum Daily Loads (TMDLs) are comprised of the sum of individual waste load allocations (WLAs) for point sources and load allocations (LAs) for non-point sources and natural background levels.  In addition, the TMDL must include a Margin of Safety (MOS), either implicitly or explicitly, that accounts for uncertainty in the relationship between pollutant loads and the quality of the receiving water body.  Conceptually, this definition is denoted by equation 1.

LC = TMDL = S?WLAs + S?LAs + MOSEquation 1.

The term LC represents the loading capacity, or maximum loading that can be assimilated by the receiving water while still achieving water quality standards.  The overall loading capacity is subsequently allocated into the TMDL components of Waste Load Allocations (WLAs) for point sources, Load Allocations (LAs) for non-point sources, and the Margin of Safety (MOS).

Fecal Coliform TMDL

Loading Capacity

The pollutant loading that a waterbody can safely assimilate is expressed as either mass per time, toxicity or some other appropriate measure (40 C.F.R. Section 130.2(i)).  Typically, TMDLs are expressed as total maximum daily loads.  However, MDEP believes it is appropriate to express bacterial TMDLs in terms of concentration because the fecal coliform standard is also expressed in terms of the concentrations of organisms per 100 ml.  Since source concentrations may not be directly added, the previous equation does not apply.  To ensure attainment with Massachusettsí water quality standards for bacteria, all sources (at their point of discharge to the receiving water) must be equal to or less than the standard.  Expressing the TMDL in terms of daily loads is difficult to interpret given that the very high numbers of bacteria and the magnitude of the allowable load are dependent on flow conditions and, therefore, will vary as flow rates change.  For example, a very high number of bacteria is allowable if the volume of water that transports the bacteria is high too.  Conversely, a relatively low number of bacteria may exceed water quality standards if flow rates are low.  For all the above reasons, the TMDL is simply set equal to the standard and may be expressed as follows (Equation 2):

TMDL = Fecal coliform standard = WLA(p1) = LA(n1) =WLA(p2) = etc.    Equation 2.

Where:

WLA(p1)  = allowable concentration for point source category (1)

LA(n1)    = allowable concentration for nonpoint source category (1)

WLA(p2)  = allowable concentration for point source category (2), etc.

For Class B surface waters the fecal coliform TMDL includes two components: (1) the geometric mean of a representative set of fecal coliform samples shall not exceed 200 organisms per 100 ml; and (2) no more than 10% of the samples shall exceed 400 organisms per 100 ml.  The Shawsheen River and its tributaries are all Class B waters.

The goal to attain water quality standards at the point of discharge is environmentally protective, and offers a practical means to identify and evaluate the effectiveness of control measures.  In addition, this approach establishes clear objectives that can easily be understood by the public and individuals responsible for monitoring activities.  Also, the goal of attaining standards at the point of discharge minimizes human health risks associated with exposure to pathogens because it does not consider losses due to die-off and settling that are known to occur.

Wasteload Allocations and Load Allocations

There is only one permitted point source discharger of fecal coliform within the Shawsheen River Basin.  The fecal coliform permit limits for this discharger are: an average monthly concentration of 200 #/100 ml and a daily maximum concentration of 400 #/100 ml.  A WLA set equal to the fecal coliform standard will be assigned to the Battle Road Wastewater Plant discharge.  Based on a review of recent monthly operating reports, it appears that this facility is in compliance with its permit limits and also in compliance with the fecal coliform water quality standard.

Direct storm water discharges of fecal coliform from storm drainage systems also occur within the Shawsheen River Basin.  Piped dischargers are, by definition, point sources regardless of whether they are currently subject to the requirements of NPDES permits.  Therefore, a WLA set equal to the fecal coliform standard will be assigned to the portion of the storm water that discharges to surface waters via storm drains.

WLAs and LAs are identified for all known source categories including both dry and wet weather sources for all Class B segments within the Shawsheen River Basin.  Establishing WLAs and LAs that only address dry weather bacteria sources would not ensure attainment of standards because of the significant contribution of wet weather bacteria sources to fecal coliform criteria exceedences.  Leaking sewer lines and illicit sewer connections represent the primary dry weather point sources of bacteria, while failing septic systems represent the nonpoint sources.  Wet weather point sources include discharges from storm water drainage systems, and pump station overflows.

Table 15 presents the fecal coliform bacteria WLAs and LAs for each of the source categories.  Source categories representing discharges of untreated sanitary sewage to receiving waters are prohibited, and therefore assigned WLAs and LAs equal to zero.  The WLA and LA for stormwater discharging to the Shawsheen River and its tributaries are set equal to the fecal coliform standard for Class B waters.

Table  SEQ Table \* ARABIC 15.  Fecal Coliform Wasteload Allocations (WLAs) and Load Allocations (LAs) for the Shawsheen River and Identified Tributary Streams

Bacteria Source CategoryWLA (organisms/100ml)LA (organisms/100ml)Point SourceGeomean < 200

10% < 400Sewer leaks00Sanitary Sewer Overflow00Illicit Sewer Connections0Failing Septic Systems00Direct WildlifeGeomean < 200

10% < 400Urban Stormwater RunoffGeomean < 200

10% < 400Geomean < 200

10% < 400The TMDL should provide a discussion of the magnitudes of the pollutant reductions needed to attain the goals of the TMDL.  Since accurate estimates of existing source contributions are generally unavailable, it is difficult to estimate the pollutant reductions for specific sources.  For the illicit sources, the goal is complete elimination (100% reduction).  However, overall wet weather bacteria load reductions can be estimated using typical storm water bacteria concentrations, as presented in Table 14, and the magnitude of the wet weather data observed in the Shawsheen Basin.  This information indicates that 1 to 2 orders of magnitude reductions in stormwater fecal coliform loadings will be necessary.

In addition, overall reductions needed to attain water quality standards can be estimated using the extensive ambient fecal coliform data that are available for the Shawsheen Basin.  Using ambient data is beneficial because it provides more realistic estimates of existing conditions and the magnitude of cumulative loading to the surface waters.  Reductions are calculated using data from both wet weather conditions and combined wet and dry conditions and are presented in Table 16.

Stations selected for presentation in Table 16 include those that are located on 303(d) listed segments and also which have both wet and dry weather monitoring data available.  Stations were selected where violations of bacteria standard were observed.  Both Stations ROB 1.5 and SH 18.25 are the most downstream stations on Rogers Brook and the Shawsheen River, respectively.  Shawsheen River station 4.2 was selected for inclusion in Table 16 due to its location downstream of an illicit sewer connection, to highlight the need for elimination of illicit sources.

Data from 1997 were used preferentially in Table 16 because these data were collected using a QAPP, the sampling included wet and dry weather data collection, and this data set is the most recent data set with both wet and dry data.  Data collected in 1996 by the MRWC were used for Rogers Brook because Rogers Brook was not monitored in 1997.

Examination of wet weather data separately provides estimates of magnitudes of reductions from all sources during wet weather conditions.  As indicated in Table 16, bacteria reductions of 1 to 2 orders of magnitude (e.g., 2,000 to 200 (1 order of magnitude); 20,000 to 200 (2 orders of magnitude)) are needed to attain water quality standards.  For example, when viewing the data in Table 16 at station EB 3.3, a reduction of 74% is needed to reduce fecal coliform levels to meet water quality standards during wet weather conditions.  The 90% observation listed in the table means that 90% of the samples collected at this station fall below the value of 760 organisms per 100ml.  That value would have to be reduced to 400 organisms per 100 ml to meet water quality criteria.  This translates to a 47.4% reduction.

Table  SEQ Table \* ARABIC 16.  Estimates of Fecal Coliform Loading Reductions to the Shawsheen River and Tributaries

StationEB 3.3VB 1.5ROB 1.5SH 4.2SH 18.25 Wet weather Geo. Mean

  % Reduction1770

74.02,700

92.65,126

96.132,863

99.42,491

92.0 Overall Geo. Mean

  % Reduction1563

64.53,851

94.81,912

89.544,041

99.5542

63.1 90% Observation

 % Reduction2760

47.45,200

92.37,100

94.454,000

99.3660

Margin of Safety

This section addresses the incorporation of a Margin of Safety (MOS) in the TMDL analysis.  The MOS accounts for any uncertainty or lack of knowledge concerning the relationship between pollutant loading and water quality.  The MOS can either be implicit (e.g., incorporated into the TMDL analysis through conservative assumptions) or explicit (e.g., expressed in the TMDL as a portion of the loadings).  This TMDL uses an implicit MOS, through inclusion of two conservative assumptions.  First, the TMDL does not account for mixing in the receiving waters and assumes that zero dilution is available.  Realistically, influent water will mix with the receiving water and become diluted below the water quality standard, provided that the influent water concentration does not exceed the TMDL concentration.  Second, the goal of attaining standards at the point of discharge does not account for losses due to die-off and settling that are known to occur.

Seasonal Variability

In addition to a Margin of Safety, TMDLs must also account for seasonal variability.   Bacteria sources to the Shawsheen River arise from a mixture of continuous and wet weather-driven sources, and there may be no single critical condition that is protective for all other conditions.  For example, leaking septic system contributions are assumed to be relatively constant over time, and their control will be most critical during drought conditions.  Urban runoff, on the other hand, will be most critical during wet weather periods.  This TMDL has set WLAs and LAs for all known and suspected source categories equal to the fecal coliform criteria independent of seasonal and climatic conditions.  This will ensure the attainment of water quality standards regardless of seasonal and climatic conditions.  Any controls that are necessary will be in place throughout the year, and therefore, will be protective of water quality at all times.

Implementation Activities and Future Monitoring

The Shawsheen River TMDL site data indicate that bacteria enter the Shawsheen River from a number of contributing sources, under a number of conditions.  This section describes activities that are currently ongoing and/or planned, designed to ensure that the TMDL can be implemented.  It is divided into separate sections describing:

Control of point sources

Septic tank controls

Urban runoff

Additional monitoring

Control of Point Sources

The Battle Road treatment plant is not a source of bacteria that needs to be further controlled, although existing permitted effluent concentrations must be maintained.  However, other point sources including pump station bypasses, illicit connections to storm drains and sewer line breaks should all be addressed. 

Many of these sources are either already under control or are in the process of being addressed.  The pump station bypass on Vine Brook will be addressed within the next 5-10 years when an interceptor line is built.  The illicit disposal of sewage discovered near Shawsheen River station 4.2 is currently being addressed.  Additionally, the sewer overflow in Andover, impacting Roger's Brook, is currently being addressed by the Massachusetts DEP.  Finally, a broken sewage main discovered at the Hanscom Air Force Base was fixed in 1997. Further examination of the sewer lines should be conducted to identify any additional leaks or breaks. 

It is strongly recommended that communities in the Shawsheen Basin implement an illegal connection identification and removal program, especially in those areas that are known to be in violation of the bacteria standard during dry weather based on the sampling results.  This may be the single most important implementation activity that takes place in the Basin.  Such initiatives have been shown to have dramatic benefits in the Charles Basin.  Information on techniques to accomplish this is available.  As a result of an MWI grant, MRWC has recently created a GIS data layer of all pipes along the mainstem of the Shawsheen, with information that notes the presence of any discharge (during dry weather) and the characteristics of the discharge, all of which will help focus efforts.

Septic Tank Controls

Septic system bacteria contributions to the Shawsheen River may be reduced in the future through septic system replacement that is currently occurring in the lower Shawsheen basin.  Additionally, the implementation of Title V, which requires inspection of private sewage disposal systems before the sale, expansion or change in use of properties where they are present, will aid in the discovery of poorly operating or failing systems.  Because systems which fail must be repaired or upgraded, it is expected that the bacteria load from septic systems will be significantly reduced in the future.

From the Massachusetts DEP website, several steps which can be taken to maintain a properly operating septic system include:

(Website address    http://www.magnet.state.ma.us/dep/brp/files/yoursyst.htm))

DO have your tank pumped out and system inspected every 3 to 5 years by a licensed septic contractor (listed in the yellow pages).

DO keep a record of pumping, inspections, and other maintenance. Use the back page of this brochure to record maintenance dates.

DO practice water conservation. Repair dripping faucets and leaking toilets, run washing machines and dishwashers only when full, avoid long showers, and use water-saving features in faucets, shower heads and toilets.

DO learn the location of your septic system and drainfield. Keep a sketch of it handy for service visits. If your system has a flow diversion valve, learn its location, and turn it once a year. Flow diverters can add many years to the life of your system.

DO divert roof drains and surface water from driveways and hillsides away from the septic system. Keep sump pumps and house footing drains away from the septic system as well.

DO take leftover hazardous household chemicals to your approved hazardous waste collection center for disposal. Use bleach, disinfectants, and drain and toilet bowl cleaners sparingly and in accordance with product labels.

DON'T allow anyone to drive or park over any part of the system. The area over the drainfield should be left undisturbed with only a mowed grass cover. Roots from nearby trees or shrubs may clog and damage your drain lines.

DON'T make or allow repairs to your septic system without obtaining the required health department permit. Use professional licensed septic contractors when needed.

DON'T use commercial septic tank additives. These products usually do not help and some may hurt your system in the long run.

DON'T use your toilet as a trash can by dumping nondegradables down your toilet or drains. Also, don't poison your septic system and the groundwater by pouring harmful chemicals down the drain. They can kill the beneficial bacteria that treat your wastewater. Keep the following materials out of your septic system:

NONDEGRADABLES: grease, disposable diapers, plastics, etc.

POISONS: gasoline, oil, paint, paint thinner, pesticides, antifreeze, etc

Urban Runoff

"Bacteria levels in urban stormwater are so high that watershed practices will need to be exceptionally efficient to meet current fecal coliform standards during wet weather conditions (CWP, 1999)".  The recommended plan of action for the Shawsheen River is to collect additional monitoring data to isolate sources prior to designing an implementation plan for structural controls.  Watershed managers should be aware that urban runoff has been listed by TMDL Federal Advisory Committee as an extremely difficult problem worthy of a long implementation schedule.  Furthermore, it should be noted that it may be very difficult to reduce urban stormwater fecal coliform concentrations such that water quality standards are met.  A review by the Center for Watershed Protection concludes that "current stormwater practices, stream buffers and source controls have a modest potential to reduce fecal coliform levels, but cannot reduce them far enough to meet water quality standards in most urban settings (CWP, 1999)."  Therefore, more intensive ìgood housekeepingî practices, such as proper pet waste removal, street sweeping and reductions in impervious areas, are likely to be necessary, at a minimum, to increase reductions of stormwater bacteria loadings.

 Additional Monitoring

Additional data are recommended in two areas as part of the TMDL implementation plan to identify sources and assess water quality standards attainment in response to implementation activities.  These areas are: wet weather sources and instream conditions.

Wet Weather Sources

Wet weather monitoring will need to be conducted in order to isolate wet weather sources and assist in identifying those sources which are most easily controllable.  Monitoring of runoff from a variety of different land uses (parks, residential, commercial, industrial, forest and agriculture) will assist in identifying those land uses which are likely to contribute higher loads of fecal coliform to the Shawsheen River.

Instream Conditions

Future data collection in the Shawsheen River systems will be useful in order to monitor trends in bacteria concentration and verify that implementation of controls is leading to compliance with water quality standards.  This monitoring could be conducted on a seasonal (e.g. quarterly) basis, and should be structured to include at least one high flow and one low flow period.

References

Carley, M., 1999. Merrimack River Watershed Council.  Personal communication. 

Center for Watershed Protection,  1999.  Watershed Protection Techniques. Vol. 3, No. 1.

Department of Environmental Protection, Massachusetts Division of Water Pollution Control.  1990.  Shawsheen River 1989 Water Quality Survey Data and Water Quality Analysis.  Publication No. 16, 483-25-25-10-90-CR.

Johnson, A.  1999. Massachusetts Department of Environmental Protection, Division of Watershed Management.  Personal communication.

Laffin, C., J. Goodno, R. Baillargeon, and K. Lawrence,  1998.  Shawsheen River Watershed 1997 Aquatic Habitat Assessment Report.  Produced by the Merrimack River Watershed Council.

Massachusetts Department of Environmental Protection.  1996.  1996 Shawsheen Assessment Summary Report.

Massachusetts Department of Environmental Protection (MDEP), 1999.  Massachusetts Section 303(d) List of Waters - 1998.

Massachusetts Department of Housing and Community Affairs.  Web site address: http://www.magnet.state.ma.us/dhcd/iprofile/locate.htm

Mattei, L., M. Carley, T. Long, 1999.  Shawsheen River Watershed 1996-1998 Volunteer Monitoring Report.   Produced by the Merrimack River Watershed Council.

Merrimack River Watershed Council, 1999.  Hot Spots Results.

Metcalf & Eddy, 1991.  Wastewater Engineering: Treatment, Disposal, Reuse.  Third Edition. p. 110.

Schueler, T.R. and H.K. Holland.  2000.  The Practice of Watershed Protection.  Center for Watershed Protection, Ellicott City, MD.

USEPA, 1999.  Draft Guidance for Water Quality-based Decisions: The TMDL Process (Second Edition).  EPA 841-D-99-001, Office of Water (4503F), Washington, DC.

Waye, D.  1999.  Northern Virginia Planning District Commission.  Personal communication.

Draft Total Maximum Daily Loads of Bacteria for the Shawsheen River BasinFebruary 7, 2002

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Draft Total Maximum Daily Loads of Bacteria for the Shawsheen River BasinFebruary 7,2002

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