Facts & Figures


To gain some idea how dominant the effluent flow of the Brockton Waste Water Treatment Plant is in the upper Taunton River we have provided the figures below. The plant according to (CDM, the cities engineering firm) discharges an average of 21.5 million gallons of effluent per day into the Salisbury Plain River. We will use a figure of 20 million gallons per day (MGD) for our purposes because the flow does fluctuate, and sometimes goes down to 17 or 18 MGD.

{NOTE}  The Salisbury Plain drains into the Matfield River which in turn joins the Town River to become the Taunton River above Rt. 104 in Bridgewater. It is important to note that during low summertime flows (below 100cfs at Titicut St) the Salisbury Plain and Matfield Rivers are little more than sluiceways filled with effluent from the Brockton Sewer Treatment Plant. During these low flows there is very little water coming into these streams to buffer or dilute the effluent. In fact it would not be inaccurate to say that when flows are less than 100 cfs at Titicut St, the Matfield, where it joins with the Town River to form the Taunton River is so dominated by effluent that it, for all practical purposes becomes the direct discharge point for the Brockton Sewer Treatment Plant.

{NOTE 1} The 7Q10 at the Titicut St gauging station is 24.6 cfs according to Ma DEP. At this flow the Upper Taunton River would be little more than a river of effluent.

 What is the 7Q10? (Courtesy of Ma Riverways)

The 7Q10 refers to the lowest consecutive 7 day streamflow that is likely to occur in a ten year period. It is used by many states and the federal government in setting discharge limits in National Pollutant Discharge Elimination System (NPDES) water quality permits. A permit will only be granted if the proposed amount of pollutant that will be discharged into a river will not significantly impair the designated uses, such as drinking or swimming, when the streamflow falls to the 7Q10 level. In other words, NPDES permit holders are restricted from discharging pollutants that would cause pollutant concentrations in the receiving water to exceed permit limits, even at very low (i.e. 7Q10) streamflow levels. Although such a low streamflow value, roughly equivalent to a ten-year drought, is appropriately used in the context of limiting pollution discharges, the 7Q10 flow statistic is sometimes inappropriately claimed to represent an adequate streamflow for maintaining a healthy aquatic ecosystem, when in fact much higher streamflow levels are required.

We have used the 7Q10 figures for these tributary streams which were calculated by  the United States Geological Survey to demonstrate how dominant the Brockton Sewer Plant is in the Salisbury Plain, Matfield and Upper Taunton River.

The 7Q10 flow above the Brockton Sewer Treatment Plant on the Salisbury Plain River is 0.6 cfs or 927 thousand gallons of water per day (to convert cfs to gallons per day you divide .647 the conversion factor by 0.6). Therefore at the outfall of the plant the mix is 20 million gallons effluent to 927 thousand gallons river water.

The next significant downstream tributary is Beaver Brook. At the confluence of Beaver Brook and the Salisbury Plain River the Matfield begins. Beaver Brooks 7Q10 flow is .3 cfs or 463 thousand gallons per day. Therefore where the Matfield begins the water to effluent ratio is 1.4 mgd (million gallons per day) river water to 20 mgd effluent.

The next significant downstream tributary to the Matfield is Satucket River which is below Rt. 18 in East Bridgewater. Satuckets 7Q10 flow is  1.3 cfs or 2mgd. Therefore at Satucket the ratio of river water to effluent is 3.4 mgd river water to 20 mgd effluent.

Below here approximately 8 miles below the Brockton Sewer Plant the Matfield River meets the Town River above Rt. 104 in Bridgewater to become the Taunton River. The Town River 7Q10 flow is 2.7 cfs or 4.1 mgd. Therefore where the Taunton River begins the ratio of river water to effluent is 7.4 mgd river water to 20 million mgd effluent.

While this is a simplified example of the dilution or lack of dilution, it is instructive and provides a good example of how dominant the effluent flow of the Brockton Sewer Plant is in the Taunton, Matfield and Salisbury Plain Rivers.

It's also worth noting that these 7Q10 figures for the tributaries were calculated in the 1950's and 1960's when water demands were much lower than they are today. In a study performed on the Matfield watershed in the summer of 2002 Beaver Brooks flow was recorded as 0 on one sampling day.

As examples we can look at the Nemasket River and the Middleboro Sewer Plant. the Middleboro plant discharges approximately 1.3 mgd of effluent into the Nemasket River. Nemasket's 7Q10 flow is 4.2 cfs or 6.5 mgd. Therefore the Nemasket at the plants discharge point has a ratio of 1.3 mgd effluent to 6.5 mgd river water.

Another good example is the Town River in Bridgewater. Bridgewater's plant discharges about 700 thousand gallons per day into the Town River. The Town River's 7Q10 is 2.7 cfs or 4.1 mgd. Therefore the Town River has a ratio at the plants discharge point of 4.1 mgd river water to 700 thousand gallons per day of effluent.

The table below shows flow figures at Titicut St. for the summer of 2002.

Glossary of commonly used terms (courtesy of Ma Riverways)


The following link provides a series of photo's showing the difference in flows of the Matfield and Town Rivers.

Click Here


We provide a link to this site in our good eggs section on our home page, it's a great resource.





LOCATION.--Lat 41o56'02", long 70o57'25", Plymouth County, Hydrologic Unit 01090004, on right bank at bridge on Titicut Road, 1 mi upstream from Sawmill Brook, 3.5 mi northwest of Middleboro, and 4.0 mi southeast of Bridgewater.
DRAINAGE AREA.--258 mi2.
PERIOD OF RECORD.--October 1929 to April 1976, April 1985 to May 1988, October 1996 to current year. Published as "at State Farm" October 1929 to September 1969, and as "at State Farm near Bridgewater" October 1969 to April 1976.
REVISED RECORDS.--WSP 781: 1934. WSP 1051: 1933. WSP 1201: 1931. WSP 1301: 1930(M), 1933(M), 1935(M). WDR MA-RI-84-1: Drainage area.
GAGE.--Water stage recorder. Datum of gage is 9.61 ft above sea level. Prior to October 1996, at sites 40 ft apart about 600 ft upstream: October 1929 to Sept. 30, 1931, inverted nonrecording gage with zero of gage at 10.02 ft; Oct. 1, 1931, to June 8, 1934, nonrecording gage, and June 9, 1934, to April 1976, April 1985 to May 1988, water-stage recorders, at present datum.
REMARKS.--Records good except those for estimated daily discharge, which are fair. Flow affected by diversions to and from basin for municipal supplies. Flow regulated by reservoirs and, prior to about 1975, by powerplants upstream. Satellite gage-height telemeter at station.
COOPERATION BY.-- Department of Environmental Management, Office of Water Resources and Department of Environmental Protection, Office of Watershed Management.



JULY 01 2002 TO DECEMBER 14 2002,
1 126 48.0 50.0 87.0 161 430
2 113 45.0 52.0 79.0 145 394
3 101 47.0 99.0 72.0 131 368
4 95.0 46.0 89.0 67.0 120 320
5 87.0 42.0 75.0 65.0 113 298
6 80.0 40.0 68.0 62.0 132 282
7 77.0 40.0 63.0 58.0 209 268
8 74.0 39.0 60.0 56.0 200 267
9 71.0 39.0 56.0 54.0 195 258
10 89.0 39.0 53.0 54.0 186 245
11 82.0 37.0 51.0 59.0 191 237
12 72.0 36.0 47.0 63.0 208 601
13 66.0 37.0 47.0 77.0 397 859
14 63.0 36.0 47.0 88.0 583 894
15 60.0 35.0 47.0 87.0 494  
16 61.0 36.0 103 92.0 429  
17 64.0 36.0 178 192 790  
18 61.0 36.0 103 155 1,170  
19 59.0 35.0 81.0 136 1,150  
20 58.0 41.0 74.0 123 954  
21 57.0 68.0 68.0 109 764  
22 54.0 50.0 64.0 97.0 706  
23 52.0 50.0 168 90.0 748  
24 57.0 53.0 207 88.0 649  
25 55.0 51.0 155 83.0 568  
26 51.0 51.0 136 119 505  
27 48.0 48.0 140 338 474  
28 50.0 45.0 154 268 489  
29 54.0 45.0 130 236 446  
30 57.0 54.0 107 209 433  
31 52.0 56.0   182    
COUNT 31 31 30 31 30 14
MAX 126 68.0 207 338 1,170 894
MIN 48.0 35.0 47.0 54.0 113 237


The following is from the EPA ECHO ( Environment and Compliance History on Line) website. It lists the permit violations that have taken place at the Brockton plant in the past two years. Below this table is a detailed description of how to interpret the figures provided.


CWA/NPDES Compliance Status
Statute:Source ID
Facility Level Status   E(EffViol) E(EffViol) E(EffViol) E(EffViol) E(EffViol) E(EffViol) E(EffViol) E(EffViol)  
Effluent Violations by NPDES Parameter:
Discharge point:001
LC50 STAT 48HR ACU CERIODAPHNIA Neither               30%  
NOEL STATRE 7DAY CHR CERIODAPHNIA Neither               49%  
OXYGEN, DISSOLVED (DO) Neither     3%            
PH Neither 5%   5% 8% 3% 5%      
SOLIDS, TOTAL SUSPENDED Mthly     125% 70% 86%     699%  
  NMth     272% 129% 25%     1068%  
NITROGEN, AMMONIA TOTAL (AS N) Mthly       131% 220% 62% 40% 1066%  
  NMth       232% 480% 87%   1020%  
PHOSPHORUS, TOTAL (AS P) Mthly         20%     124%  
  NMth         70% 10%   309%  
COPPER, TOTAL (AS CU) Mthly 221% 240% 266% 279% 77% 151% 108% 796%  
  NMth 130% 143% 162% 172% 27% 80% 49% 542%  
COLIFORM, FECAL GENERAL Mthly               32%  
  NMth       2000% 300%     1483%  
BOD, CARBONACEOUS 05 DAY, 20C Mthly     97% 2%       179%  
  NMth     264% 129%       223%  
SOLIDS, SUSPENDED PERCENT REMOVAL Mthly     7%         33%  
Compliance Schedule Violations:
ACHIEVED LATE;SUBMIT PART 503 ANNUAL RPT #3               02/2002    
NOT RECEIVED ;SUBMIT I/I REPORT #3               02/2002 >>>>>>>>  

Effluent violations are displayed as highest percentage by which the permit limit was exceeded for the quarter. Bold, largeprint indicates Significant Noncompliance (SNC) effluent violations.Shaded boxes indicate unresolved SNC violations.

Effluent violations are indicated by displaying the highest percentage by which the permit limit was exceeded for the quarter. Bold, large print indicates Significant Noncompliance (SNC) effluent violations. For unresolved SNC violations (e.g., violations with no government action against the facility), the table cell is shaded gray. It is possible for a facility to have effluent violations but not be out of compliance at the permit level. This occurs if the exceedances are not significantly over permit limits.

To the right of each parameter/chemical shown with a discharge violation, there is an indicator of what type of measurement was used to determine the violation. "Mnthly" stands for monthly. This means that the exceedance shown in that row was based upon a monthly average of readings submitted by the permittee. EPA generally believes that monthly averages are the most important, because the exceedance represents an average of many readings. "NMth" stands for non-monthly. This is generally a "maximum" amount read during the reporting period (and could indicate a spike that is not continuous). "Neither" denotes other measurements such as a minimum (e.g. pH could be in violation if below the permitted level). Please note that the exceedances shown in the table are the "worst" value within the quarter. Generally the permittee will report three times within the quarter (each month).

The following codes are used on the Quarterly Noncompliance Report (QNCR) to indicate compliance status at the facility level. If more than one code applies to a facility, a prioritization is used to determine which codes appears. The order of precedence from most to least important is as follows:

S = SNC - an enforcement action has been issued, and the facility is not meeting its compliance schedule

E = SNC - effluent violations of monthly average limits (TRC and chronic)

X = SNC - effluent violations of non-monthly average limits (TRC and chronic)

T = SNC - compliance schedule reporting violation

D = SNC - reporting violation - non-receipt of DMR

N = RNC - Reportable non-compliance

P = Compliance - an enforcement action has been issued, and facility compliance with the action is pending final completion

R = Compliance - an enforcement action has been issued, and the facility has completed all requirements of the action

C = Compliance - manual override of non-compliance data by state or EPA Region. This manual override status is also indicated by a superscripted "m".

Blank = Compliance

SNC categories are shown in RED, Reportable Non-compliance (RNC) categories are shown in ORANGE, On Schedule categories are shown in BLUE, and Compliance categories are shown in GREEN.

The quarterly compliance status for a NPDES permit (under the CWA) is based on two sets of compliance variables in PCS. The first set of variables is automatically generated by PCS. The second set is manually entered into PCS and covers the same eight quarters. Manually entered data values exist in the case of a Single Event Violation. A Single Event Violation is a violation which cannot be classified as a compliance schedule violation or an effluent violation. For example, an unexplained fish kill in a river often results in Single Event Violations for those regulated facilities which release into the river. Manually entered compliance data, if present, override machine-generated compliance data.

A CWA permit is considered non-compliant in a given quarter if a D, E, S, T, X, or N is presented in the Historical Non-Compliance field. A code of C, P, or R indicates compliance (in addition to the automatically generated blank field).

Compliance Schedule Violations
If a facility has been issued an enforcement action and is on a compliance schedule, all non-compliance events related to violations of that schedule in the past two years are listed under the Compliance Schedule Violations section. Text descriptions of the violation(s) are presented below the section heading (e.g., ACHIEVED LATE; NOTICE OF VIOLATION). If the facility is not on such a schedule or is on a compliance schedule but has no schedule violations, this section is not presented. Schedule violations are listed with the beginning and return-to-compliance dates across the eight quarters. If the report shows a right arrow with no closing date, that means that the violation has not been resolved and continues to be active in the data system. If the violation started before the last two years of data and continues into the last two years, the beginning date is listed in QTR1.

Single Event Violations
If the facility is identified as being in violation of CWA requirements not related to their established permit requirements or a compliance schedule, these violations are presented in the section titled Single Event Violations. Text descriptions of the violation(s) are presented below the section heading (e.g., DISCHARGE WITHOUT A VALID PERMIT). If the facility has no single event violations in the past two years, this section is not presented. The date of each single event violation is listed in the table.