Clean Water Act Residual Designation Determination for Certain Stormwater
Discharges in the Charles, Mystic, and Neponset River Watersheds, in
Massachusetts
The U.S. Environmental Protection Agency (EPA) Region 1 is exercising its discretionary Clean
Water Act (CWA) residual designation authority (RDA) under CWA § 402(p)(2)(E) and
implementing regulations to designate for National Pollutant Discharge Elimination System
(NPDES) permitting certain stormwater discharges from commercial, industrial, and institutional
properties1 with one acre or more of impervious surface2 in the Charles, Neponset, and Mystic
River watersheds in Massachusetts (See Attachment 1 for full list of communities). The
dischargers or categories of dischargers that this designation identifies do not have to apply for
individual permit coverage as EPA plans to issue one or more general permits for these
discharges, under which operators may seek coverage within defined deadlines in the general
permit(s).3 Moreover, "The question whether the initial designation was proper will remain open
for consideration during the public comment period under § 124.11 [for NPDES permits] and in
any subsequent hearing." 40 C.F.R. § 124.52(c).
I. Summary of Petitions
On May 9, 2019, the Conservation Law Foundation (CLF) and the Charles River watershed
Association (CRWA) submitted to the Regional Administrator of EPA Region 1 a "Petition for a
Determination that Certain Commercial, Industrial, Institutional, and Multi-Family Residential
Property Dischargers Contribute to Water Quality Standards Violations in the Charles River
1 For the purposes of this determination, "commercial parcels" are parcels with Massachusetts Department of
Revenue/Division of Local Services Property Type Classification Code 3; "industrial parcels" are parcels with
Massachusetts Department of Revenue/Division of Local Services Property Type Classification Code 4; and
"institutional parcels" are parcels with Massachusetts Department of Revenue/Division of Local Services Property
Type Classification Code 9 (Massachusetts Department of Revenue/Division of Local Services, June 2016); this
designation does not apply to any parcel owned or operated by an MS4 permit holder where the discharge of
stormwater from the parcel is subject to NPDES permitting.
2 For the purposes of this determination, "impervious surface" is defined as "any surface that prevents or
significantly impedes the infiltration of water into the underlying soil. This can include but is not limited to: roads,
driveways, parking areas and other areas created using non porous material; buildings, rooftops, structures, artificial
turf and compacted gravel or soil" (US EPA, 2016a). In this determination, EPA uses "impervious surface,"
"impervious area," and "impervious covef' interchangeably.
'J
EPA's regulations do not require public notice of a residual designation determination. Nonetheless, EPA has
made this determination available on its public website. When EPA issues a draft general NPDES permit(s) or any
individual NPDES permits to cover the discharges described in this determination, EPA will provide public notice in
accordance with 40 C.F.R. § 124.10. Note that 40 C.F.R. § 124.10(c)(2)(iv) deems posting of relevant material on
"the permitting authority's public website" to be sufficient for public notice purposes.
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watershed, Massachusetts, and that NPDES Permitting of Such Properties is Required."4 On
August 24, 2020, CLF followed this submission with two additional petitions requesting the
same residual designations for two other watersheds in Massachusetts: the Mystic River
watershed5 and the Neponset River watershed.6 The three petitions call for "a determination
pursuant to 40 C.F.R. § 122.26(f)(2) that discharges of storm water that are not currently subject
to direct permitting by EPA from privately owned commercial, industrial, institutional, and
multi-family residential real properties of one acre or greater" in the Charles River, Mystic River,
and Neponset River watersheds "contribute to violations of water quality standards" in (1) the
Charles River, (2) Boston Harbor, of which the Mystic River watershed is a sub-basin, and (3)
the Neponset River, "and require permits under the National Pollutant Discharge Elimination
System ('NPDES')"7
The petitions allege that urban stormwater discharges from non-permitted urban commercial,
industrial, and high-density residential areas with high levels of impervious surface "are a
primary cause of'8 or "significant contributor to"9 ongoing water quality standards violations in
the respective Massachusetts bodies of water and therefore should be designated and subjected to
NPDES permitting. To support these assertions, the petitions cite studies by EPA, Massachusetts
Department of Environmental Protection (MassDEP), and private entities; water quality
monitoring; and Total Maximum Daily Load reports (TMDLs) for the affected waters indicating
that they do not meet Massachusetts Water Quality Standards (WQS).10
Specifically, the Charles River Petition alleges that the high levels of impervious surface in
urbanized areas result in stormwater runoff discharging high levels of phosphorous and
pathogens into the Charles River.11 The petition further alleges that these high levels of
phosphorous trigger "excessive algae and aquatic plant growth and low and/or highly variable
dissolved oxygen levels."12 The petition cites the 2007 and 2011 Charles River TMDLs showing
that to attain water quality standards, phosphorous loading would have to be reduced "by 48
percent above the Watertown Dam and by 62 percent in each of the sub-watersheds draining to
the Lower Charles River" and by 51 percent in the Upper/Middle Charles River including by 65
percent "from all intense land uses (commercial, industrial, and high density residential sites)."13
4 Petition from Caitlin Peale Sloan, Senior Attorney, Conservation Law Found., to Deborah Szaro, Acting Reg'l
Adm'r, Envtl. Prot. Agency Region 1 (May 9, 2019) [hereinafter Charles River Petition], "Any person may petition
the Director to require a NPDES permit for a discharge which is composed entirely of storm water which contributes
to a violation of a water quality standard or is a significant contributor of pollutants to waters of the United States."
See 40 C.F.R. § 122.26(f)(2).
5 Petition from Caitlin Peale Sloan, Senior Attorney, Conservation Law Found., to Dennis Deziel, Acting Reg'l
Adm'r, Envtl. Prot. Agency Region 1 (Aug. 24, 2020) [hereinafter Mystic River Petition],
6 Petition from Caitlin Peale Sloan, Senior Attorney, Conservation Law Found., to Dennis Deziel, Acting Reg'l
Adm'r, Envtl. Prot. Agency Region 1 (Aug. 24, 2020) [hereinafter Neponset River Petition],
7 Charles River Petition at 1; Mystic River Petition at 1-2; Neponset River Petition at 1.
8 Charles River Petition at 5-7, 12-13.
9 Mystic River Petition at 5-6, 12-13; Neponset River Petition at 4-5, 10-11.
10 Charles River Petition at 4-7; Mystic River Petition at 6-7; Neponset River Petition at 4-5.
11 Charles River Petition at 5-7.
12 Id. at 5.
13 Id. at 7.
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The Mystic River and Neponset River petitions allege that "stormwater runoff is a significant
contributor" of pathogens and bacteria and that "most of the bacteria sources in the watershed[s]
are believed to be stormwater-related."14 The Mystic River Petition alleges that phosphorus loads
from stormwater sources would need to be reduced by as much as 67 percent to meet WQS
according to a 2020 alternative TMDL prepared by Eastern Research Group, Inc.15 The
Neponset River Petition cites a 2002 EPA and MassDEP TMDL indicating that the methods
employed to control bacterial pollution caused by stormwater were insufficient.16 The Petition
also states that the TMDL indicated that "concentrations of pollutants, particularly in the form of
fecal coliform and E. coli, have to be reduced by at a minimum 90 [percent] and in some places
up to 99 [percent] to comply with the TMDL" and meet the WQS.17
Since receiving the petitions, EPA has been in contact with CLF, CRWA, and other stakeholders
and has been gathering and analyzing additional evidence to help the Agency decide whether to
make a determination. For example, in 2020, EPA Region 1 staff conducted five focus group
sessions with Charles River watershed stakeholders to inform initial deliberations and discuss the
RDA concept generally.18
On July 14, 2022, EPA received a Notice of Intent to File Suit Under the Clean Water Act (NOI)
from CLF and CRWA.19 The NOI alleges that EPA failed "to perform an act or duty that is not
discretionary under Section 402(p)(2)(E), 33 U.S.C. § 1342(p)(2)(E)" based on EPA's failure to
make a final determination on CLF's and CRWA's petitions within the regulatory 90-day period.
40 C.F.R. § 122.26(f)(5).20 EPA is now acting on CLF's and CRWA's residual designation
petitions.
II. Residual Designation Legal Authority
In 1987, Congress amended the CWAto establish categories of industrial and municipal
stormwater point source discharges that require NPDES permits. See CWA § 402(p)(2)(B-E).
Congress instructed EPA to develop stormwater regulations in two phases. In the first phase,
Congress required EPA to develop regulations and NPDES permits for stormwater discharges
associated with industrial activity and discharges from municipal separate storm sewer systems
(MS4s) serving populations larger than 100,000 persons (i.e., large and medium MS4s). CWA §
402(p)(4)(A). In the second phase, Congress instructed EPA to study stormwater discharges from
small MS4s and other sources not covered by § 402(p)(4)(A) and report back to Congress on
14 Mystic River Petition at 6; Neponset River Petition at 4.
15 Mystic River Petition at 6-7.
16 Neponset River Petition at 5.
11 Id.
18 See Consensus Building Institute, "Charles River Stormwater Permitting: Residual Designation Authority Focus
Group Sessions Summary," Feb. 2021. (describes the information presented at the five focus group sessions and
then details the feedback received in each session).
19 Notice from Caitlin Peale Sloan, Senior Attorney, Conservation Law Found., to Michael S. Regan, Adm'r, Envtl.
Prot. Agency (July 14, 2022) [hereinafter NOI].
20 Id. at 2.
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how such stormwater discharges should be regulated. Congress also gave EPA "residual
designation authority" over a category of stormwater discharges that would be subject to NPDES
permit requirements only if EPA or a State "determines that the stormwater discharge contributes
to a violation of a water quality standard or is a significant contributor of pollutants to waters of
the United States." CWA § 402(p)(2)(E). Also, the CWA authorizes EPA to take action to
designate additional stormwater sources to be regulated to "protect water quality." CWA §
402(p)(6). EPA proceeded with two stormwater rulemaking phases. In the 1990 Phase I Rule,
EPA promulgated NPDES permit application regulations for large and medium MS4s and certain
industrial stormwater discharges (including large construction sites disturbing equal to or greater
than five acres). See 55 Fed. Reg. 47990 (Nov. 16, 1990). The 1999 Phase II Rule set forth
NPDES permitting requirements for discharges from certain small MS4s and from small
construction sites (disturbing equal to or greater than one acre and less than five acres) and
required NPDES permits for these discharges.21 See 64 Fed. Reg. 68722 (December 8, 1999).
CWA sections 402(p)(2)(E) and 402(p)(6) and implementing regulations provide that in states
where there is no approved state program,22 the EPA Regional Administrator may designate a
storm water discharge as requiring an NPDES permit where he/she determines that: " .. .(C)
storm water controls are needed for the discharge based on wasteload allocations that are part of
total maximum daily loads (TMDLs) that address the pollutants of concern, or (D) the discharge,
or category of discharges within a geographic area, contributes to a violation of a water quality
standard or is a significant contributor of pollutants to waters of the United States." 40 C.F.R. §§
122.26(a)(l)(v), 122.26(a)(9)(i)(C), (D). When it promulgated these regulations, EPA explained
that it "intend[ed] that the NPDES permitting authority have discretion in the matter of
designations based on TMDLs." 64 Fed. Reg. at 68,781. That discretion allows EPA (or a State)
to address "individual instances of storm water discharge" that "might warrant special
regulatory attention, but do not fall neatly into a discrete, predetermined category." Id. As these
regulations authorize and as supported by EPA's record in this matter, EPA is using its residual
designation authority to designate stormwater discharges from commercial, industrial, and
institutional properties with one acre or more of impervious surface in the Charles, Neponset,
and Mystic River watersheds for NPDES permitting. As this designation explains, such
stormwater discharges contribute to water quality standards violations,23 are significant
contributors of pollutants to waters of the United States, and need to be controlled based on
wasteload allocations that are part of the TMDLs that address phosphorus and/or bacteria.24
21 In limited circumstances, a prospective permittee may apply for and EPA may grant a waiver from stormwater
permitting requirements. See 40 C.F.R. §§ 122.32(c)-(e) (small MS4 waivers) and § 122.26(b)(15)(i) (waivers for
small construction activity).
22 EPA issues NPDES permits in Massachusetts. As of the date of this designation, Massachusetts is one of three
states (along with New Hampshire and New Mexico) that are not authorized to issue NPDES permits.
23 EPA views WQS "violations" to be the same as WQS "exceedances."
24 While any one of the factors in 40 C.F.R. § 122.26(a)(9)(i)(C), (D) are alone sufficient to support an RDA
determination, EPA demonstrates that all three factors are present for this RDA determination.
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EPA plans to implement this residual designation determination through one or more NPDES
general permits.25 The dischargers or categories of dischargers that this designation identifies
will not be required to obtain NPDES permit coverage until EPA issues a general permit(s) for
such discharges, under which operators may seek coverage within defined deadlines in the
general permit(s). Consistent with 40 C.F.R. § 124.52(c), "the question whether the initial
designation was proper will remain open for consideration during the [NPDES permit] public
comment period under § 124.11 and in any subsequent hearing."
III. Municipal Stormwater Permitting
a. This designation does not apply to discharges already authorized under the 2016
Massachusetts Small MS4 Permit.
On April 13, 2016, EPA issued a final NPDES general permit for discharges of stormwater from
small municipal separate storm sewer systems (MS4s) in Massachusetts (MA MS4 permit). The
2016 MA MS4 permit replaced the 2003 small MS4 permit.26 The MA MS4 permit took effect
on July 1, 2018, and EPA modified the permit on December 7, 2020. The MA MS4 permit
covers municipal stormwater discharges from (1) traditional cities and towns; (2) non-traditional
state, federal, county, and other publicly owned MS4s; and (3) non-traditional transportation
MS4s.
EPA wrote the MA MS4 permit to be consistent with CWA section 402(p)(3)(B) and the Phase
II stormwater rule, which requires small MS4 permits to include permit terms and conditions "to
"reduce the discharge of pollutants from the MS4 to the maximum extent practicable (MEP), to
protect water quality, and to satisfy the appropriate water quality requirements of the Clean
Water Act." See 40 C.F.R. §122.34(a); 81 Fed. Reg. 89320, 89349; 64 Fed. Reg. 68722, 68843;
see also 64 Fed. Reg. at 68752-53. The 2016 MA MS4 permit Part 2.3 requires small MS4s to
implement the following six minimum control measures: (1) public education and outreach on
stormwater impacts; (2) public involvement and participation; (3) illicit discharge detection and
elimination; (4) construction site stormwater runoff control; (5) post construction stormwater
management in new development and redevelopment; and (6) pollution prevention/good
housekeeping for municipal operations. In addition, 2016 MA MS4 permit parts 2.2.1 and 2.2.2
contain water quality-based requirements for those permittees subject to a TMDL or discharging
to a waterbody impaired for pollutants found in stormwater. The permit gives each permittee
flexibility to establish controls and measures applicable to their system to control stormwater
inputs into and discharges from their MS4 such that discharges from the permittee's small MS4
meet applicable water quality standards. The permit's Appendices F and H include compliance
timelines for addressing the requirements and assumptions of approved TMDLs and for
addressing complex or widespread sources of water quality impairments in the absence of a
25 EPA's regulations provide for the issuance of general permits to authorize one or more categories or subcategories
of discharges, including storm water point source discharges within a geographic area pursuant to 40 CFR
§ 122.28(a)(1) and (2)(i)).
26 The 2003 Small MS4 Permit covered small MS4s in Massachusetts and New Hampshire.
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TMDL, including specific requirements for MS4s discharging to waterbodies impaired for
phosphorus, nitrogen, and bacteria. The permit is consistent with the assumptions and
requirements of TMDLs that were approved as of the issuance date of the permit, including the
Upper and Lower Charles River TMDLs, and bacteria and pathogens TMDLs in the Charles
River and Neponset River watershed.
Currently, all communities in the Charles, Mystic, and Neponset River watersheds hold small
MS4 permit coverage under the MA MS4 permit. The City of Boston has an individual MS4
permit. In addition, there are multiple non-traditional permittees covered under the MA MS4
permit within all three watersheds (e.g., state and federal facilities and state colleges and
universities).27 As indicated above, the 2016 MA MS4 permit contains requirements specifically
targeting the reduction of nutrients and bacteria in stormwater from permittee-owned parcels;
therefore, this designation does not apply to any parcel subject to the 2016 MA MS4 permit that
is owned or operated by a current permittee under the 2016 MA MS4 permit.
b. This designation does not apply to discharges already authorized under the Boston
Individual MS4 Permit.
EPA issued an individual large MS4 permit to Boston Water and Sewer Commission (BWSC) in
1999 (NPDES No. MASO10001). This permit is a Phase IMS4 permit written in accordance
with 40 C.F.R. § 122.26. The permit expired October 30, 2004 and EPA administratively
continued the permit in accordance with 40 C.F.R. § 122.6. In 2012, BWSC entered into a
Consent Decree with EPA, MassDEP, and Conservation Law Foundation to address violations of
the 1999 BWSC permit and other CWA violations. The Consent Decree required BWSC to
address illicit connections to the MS4, reducing nutrient and bacteria discharges, as well as
comply with phosphorus reductions in stormwater sources consistent with the two Charles River
Phosphorus TMDLs. In 2016, BWSC completed an Implementation Plan consistent with the
Consent Decree and will implement this plan over a 30-year period ultimately resulting in the
removal of 7,362 pounds of phosphorus from stormwater per year by 2046 (CH2M Hill, 2016).
BWSC continues to undertake actions through its Implementation Plan to address the two
Charles River Phosphorus TMDLs as well as fully implement their MS4 permit; therefore, this
designation does not apply to any parcel owned or operated by the City of Boston or Boston
Water and Sewer Commission that is subject to NPDES permit MASO 10001.
c. This designation does not apply to parcels owned or operated by the Massachusetts
Department of Transportation, Highway Division (MassDOT) already subject to an
NPDES permit.
Massachusetts Department of Transportation, Highway Division (MassDOT) operates a
regulated MS4 in the Charles River, Mystic River, and Neponset River watersheds. Regulated
stormwater discharges from the MassDOT MS4 are currently covered under the 2003 MS4
general permit under permit number MA043025. The 2003 MS4 general permit was issued by
27 A list of 2016 MA MS4 permit holders can be found here: https://www.epa.gov/npdes-permits/regulated-ms4-
massachusetts-communities (Retrieved August 10, 2022).
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EPA Region 1 on May 1, 2003 and while the 2016 MA MS4 permit replaced the 2003 MS4
permit for most Massachusetts small MS4 permit holders, MassDOT communicated with EPA
during the 2003 permit term that based on the size and complexity of their MS4, along with the
stormwater management approach used under the 2003 permit, MassDOT would be better served
under an individual permit consistent with 40 CFR §122.34, rather than seeking coverage under a
re-issued MS4 general permit. This request was made in accordance with 40 C.F.R.
§ 122.28(b)(3). On September 25, 2018, EPA received a complete application for individual MS4
permit coverage from MassDOT. Regulated stormwater discharges from MassDOT remain
covered under the 2003 MS4 permit (permit number MA043025) until the effective date of a
new MassDOT individual permit, which EPA will draft to be consistent with 40 C.F.R. § 122.34.
During the 2003 permit term, MassDOT was required to update its stormwater management
program to address discharges to impaired waters as detailed in a letter from EPA dated April 22,
2010. As subsequently incorporated into a May 11, 2010 Order by the U.S. District Court of
Massachusetts in CLF v. DevalPatrick (No. 06-11295 WGY), EPA's April 22, 2010 letter
required MassDOT to immediately begin to identify control measures and BMPs for impaired
waters without TMDLs that will collectively control the discharge of pollutants of concern. EPA
also required MassDOT to propose schedules for implementation of identified BMPs as
expeditiously as possible, based on water quality considerations. MassDOT continues to
undertake actions through its Impaired Waters Program (MassDOT, 2022) to address discharges
to nutrient and bacteria impaired waterbodies as well as fully implement the 2003 MS4 permit;
therefore, this designation does not apply to any parcel owned or operated by MassDOT that is
subject to NPDES permit MA043025.
IV. Water Quality and TMDL Status
a. Applicable Massachusetts Water Quality Standards
Table 1 presents a summary of the Massachusetts water quality criteria applicable to the Charles
River, Mystic River, and Neponset River and pollutant loading from stormwater sources.
Massachusetts has established narrative but not numeric criteria for phosphorus and nitrogen.
Massachusetts does have, however, numeric criteria for pH, dissolved oxygen (DO), color and
turbidity and aesthetics. Excess phosphorus and nitrogen can cause a violation of these numeric
criteria and cause the narrative criteria to not be attained. In both marine and freshwater systems,
excess nutrients result in degraded water quality, adverse impacts to ecosystems, and limits on
the use of water resources (Center For Watershed Protection, 2003) (Shaver, Horner, Skupien,
May, & Ridley, 2007) (Howarth & Marino, 2006) (USEPA, 2000) (USEPA, 2001). The most
common forms of nutrient pollution are nitrogen and phosphorus. "When excessive levels of
these chemical nutrients are introduced into a water system, algae populations rapidly multiply to
nuisance levels. As populations 'bloom' and die-off in quick succession, dead algae accumulate
and decomposetheir nutrient-laden remains further enriching the immediate environment,
thereby perpetuating the eutrophication cycle. Increased rates of respiration and decomposition
deplete the available dissolved oxygen in the water, threatening other plant and animal life in the
system. When oxygen saturation levels drop below what is needed by fish and invertebrates to
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breathe, the waters become host to fish kills, red tides, and shellfish poisonings, events which
can pose threats to human health as well." Upper Blackstone Water Pollution Abatement Dist. v.
U.S. E.P.A., 690 F.3d 9, 11-12 (1st Cir. 2012).
Pollutant
Criteria
Source
Bacteria/Pathogens
for coir.
concentrations shall not exceed 126 colony-
forming units (cfu) per 100 mL, calculated as the
geometric mean of all samples collected within
any 90-day or smaller interval; and ii. no more
than 10% of all such samples shall exceed 410
cfu per 100 mL (a statistical threshold value); or
for enterococci: concentrations shall not exceed
35 cfu per 100 mL, calculated as the geometric
mean of all samples collected within any 90-day
or smaller interval; and
ii. no more than 10% of all such samples shall
exceed 130 cfu per 100 mL (the statistical
threshold value).
314 CMR 4.05(5)(f)
DO
Inland Waters. Shall not be less than 5.0 mg/L in
warm water fisheries unless background
conditions are lower; natural seasonal and daily
variations above these levels shall be maintained;
and levels shall not be below 60 percent of
saturation in warm water fisheries due to a
discharge.
Coastal and Marine Waters. Shall not be less than
5.0 mg/L. Where natural background conditions
are lower, DO shall not be less than natural
background. Natural seasonal and daily variations
that are necessary to protect existing and
designated uses shall be maintained.
314 CMR: 4.05:(3)(b)
1 and 314 CMR:
4.05:(4)(b) 1
pH
Shall be in the range of 6.5 - 8.3 standard units
and not more than 0.5 units outside of the
background range. There shall be no change from
background conditions that would impair any use
assigned to this Class.
314 CMR: 4.05 (3)(b)
3 and 314 CMR 4.05:
(4)(b) 3
Solids
These waters shall be free from floating,
suspended, and settleable solids in concentrations
and combinations that would impair any use
314 CMR: 4.05(3)(b)
5. And 314 CMR:
4.05(4)(b) 5.
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assigned to this Class, that would cause
aesthetically objectionable conditions, or that
would impair the benthic biota or degrade the
chemical composition of the bottom.
Color and Turbidity
These waters shall be free from color and
turbidity in concentrations or combinations that
are aesthetically objectionable or would impair
any use assigned to this Class.
314 CMR: 4.05(3)(b)
6 and 314 CMR:
4.05(4)(b) 6
Aesthetics
All surface waters shall be free from pollutants
in concentrations or combinations that settle to
form objectionable deposits; float as debris,
scum or other matter to form nuisances; produce
objectionable odor, color, taste or turbidity; or
produce undesirable or nuisance species of
aquatic life.
314 CMR: 4.05(5)(a)
Nutrients
Unless naturally occurring, all surface waters
shall be free from nutrients in concentrations that
would cause or contribute to impairment of
existing or designated uses and shall not exceed
the site specific criteria developed in a TMDL or
as otherwise established by the Department.
314 CMR: 4.05(5)(c)
Table 1: Relevant Massachusetts water quality standards
b. Charles River Watershed
The entire Charles River drains a watershed area of 310 square miles and encompasses at least
part of 36 communities. The Upper Charles River upstream of the Watertown Dam drains an
area of 268 square miles, while the Lower Charles River downstream from the Watertown Dam
to Boston Harbor drains an additional 42 square miles. Based on water quality data available for
the Charles River and applicable Massachusetts surface water quality standards for a Class B
surface water, MassDEP included many segments of the Charles River that are impaired due to
excess nutrients and bacteria on the State's 2002 Section 303(d) list, also known as the impaired
waters list. Throughout the years, including the latest EPA-approved Section 303(d) list in 2021
(2018/2021 303(d) list), MassDEP continues to indicate widespread impairments due to excess
nutrients and bacteria (Massachusetts Department of Environmental Protection, 2021) in the
Charles River System (see Attachment 2 for a full list of impairments in the Charles River
watershed based on the 2018/2021 303(d) list).
Phosphorus Impairments
Among the 303(d)-listed pollutants on the 2018/2020 Section 303(d) list are several related to
excessive phosphorus loading (see Attachment 2):
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Phosphorus
Low Dissolved Oxygen
Low Dissolved Oxygen Saturation
Algae
Harmful Algal Blooms
Chlorophyll-a
Nutrient/Eutrophication Biological Indicators
Aquatic Plants (Macrophytes)
Transparency/Clarity
The causal relationship between excessive phosphorus loads and water quality impairments is
well understood and is covered extensively in research literature.28 Analyses of water quality
data collected from the Charles River indicate that phosphorus is the key nutrient that controls
the amount of algal and aquatic plant growth during the middle to later summer period in the
Charles River when recreational use of the river peaks (Massachusetts Department of
Environmental Protection, 2011) (Massachusetts Department of Environmental Protection,
2007b). Excess phosphorus in the Charles River system leads to increased algal and aquatic plant
growth, which can lower dissolved oxygen in the water column, affect the pH of the water,
increase the turbidity in the water column, and decrease the clarity of the water (Massachusetts
Department of Environmental Protection, 2007b) (Massachusetts Department of Environmental
Protection, 2011).
As early as 2000, a MassDEP water quality assessment analysis indicated that phosphorus in
stormwater runoff is causing water quality impairments in almost all the Charles River segments
(Massachusetts Department of Environmental Protection, 2000). All segments of the Charles
River except the headwater segment are impaired, at least in part, because of elevated
phosphorus, excessive aquatic plant growth and/or algae.
In 2006, the Charles River Watershed Association (CRWA) and EPA began monitoring for the
presence of harmful algal blooms (HABs) and the presence of cyanobacteria, also known as
blue-green algae, in the lower Charles River basin. HABs in the lower Charles River basin
frequently contain cyanobacteria, which produce extremely dangerous toxins that have been
known to sicken or kill people and animals as well as cause low dissolved oxygen levels in the
water column, harming aquatic life. CRWA has documented the presence of cyanobacteria and
HABs in the lower basin every year since 2006 (Charles River Watershed Association, 2015),
with more than 150 days in 2020 (Charles River Watershed Association, 2021), severely
impacting public use of the river in the summer of 2020. In 2015 EPA began monitoring water
quality in the Charles River lower basin with a real-time buoy deployed during the summer
months and has monitored and tracked HABs every summer through the presence of
Phycocyanin and Chlorophyll in the water column (USEPA, 2022c).
28 See Part VII - References section of this document.
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The Charles River has two EPA-approved phosphorus TMDLs assigning waste load allocations
(WLAs) to phosphorus sources within the watershed. On October 17, 2007, EPA approved the
Final TMDL for Nutrients in the Lower Charles River Basin (Lower Charles TMDL)
(Massachusetts Department of Environmental Protection, 2007b) and on June 10, 2011 EPA
approved the Total Maximum Daily Loadfor Nutrients in the Upper/Middle Charles River
(Upper/Middle Charles TMDL) (Massachusetts Department of Environmental Protection, 2011).
The two phosphorus TMDLs address severe water quality impairments resulting from the
excessive algae growth caused by excessive amounts of phosphorus in discharges to the Charles
River system. The Lower Charles TMDL and the Upper/Middle Charles TMDL calculated the
baseline phosphorus load from stormwater sources as 87,432 pounds of total phosphorus per
year. Both TMDLs set WLAs that specify reductions for discharges of phosphorus throughout
the entire Charles River watershed from publicly owned treatment works, combined sewer
overflows, and stormwater discharges. According to the TMDLs, to meet TMDL goals, the more
developed lands (commercial, industrial, and high and medium density residential) need to
reduce total phosphorus loads in stormwater by 65% annually while the less developed, low
density residential lands need to reduce total phosphorus loads in stormwater by 45% annually.
The TMDLs set a watershed-wide stormwater phosphorus load reduction target of 47,347
pounds per year, bringing the overall phosphorus load from stormwater from a baseline of
87,432 pounds per year to a reduced load of 40,085 pounds per year of phosphorus from
stormwater sources. Overall, according to the TMDLs' analyses, the stormwater total phosphorus
load reduction would need to come from many private and public stormwater sources to meet
TMDL goals.29
Bacteria Impairments
The 2018/2020 EPA-approved 303(d) list indicates widespread impairments for bacteria,
including 25 segments of the Charles River that are impaired for E. coli or fecal coliform
(Massachusetts Department of Environmental Protection, 2021). The bacteria impairments have
been linked to stormwater discharges since 2000, where a MassDEP water quality assessment
analysis indicated that bacteria in stormwater is causing water quality impairments in many
segments of the Charles River (Massachusetts Department of Environmental Protection, 2000).
In addition, EPA has been assigning a "report card" grade for the lower Charles River since 1995
and multiple segments of the Charles River since 2019. EPA uses the Charles River Report Card
to measure and evaluate progress towards meeting the Massachusetts bacterial water quality
standards for swimming and boating as well as to assess general health of the watershed. The
2021 Report Card indicates that segments of the Charles River are meeting water quality
standards for swimming and boating based on bacteria concentrations ranging from 58.6% of the
time (Muddy River) to 94% of the time (Upper Middle Watershed) (USEPA, 2022f). While this
29 See Final TMDL for Nutrients in the Lower Charles River Basin (Massachusetts Department of Environmental
Protection, 2007b) pp 46-53 and Total Maximum Daily Load for Nutrients in the Upper/Middle Charles River
(Massachusetts Department of Environmental Protection, 2011) pp 46-51 and A Hydrodynamic and Water Quality
Model for the Lower Charles River Basin, Massachusetts (USEPA, 2005) pp 19-27.
11
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is a significant improvement since 1995, there are still yearly water quality standards violations
in the Charles River system due to excess bacteria, limiting recreational access to the river.
EPA approved a TMDL for pathogen indicators (e.g., fecal coliform, E. coli, and enterococcus
bacteria) in the Charles River watershed on May 22, 2007. (Massachusetts Department of
Environmental Protection, 2007a). The TMDL found that over 80% of the watershed segments
assessed were impaired due to bacteria or pathogens. The TMDL identified bacterial sources
such as failing septic systems, combined sewer overflows (CSO), sanitary sewer overflows
(SSO), sewer pipes connected to storm drains, certain recreational activities, wildlife (including
domestic pets), and direct storm water discharges. While the TMDL does not attempt to assign
specific WLAs or Load Allocations (LAs) to specific sources, it indicates that stormwater
sources of bacteria from direct runoff and discharges from storm sewer systems need to be
reduced to meet in stream water quality standards.30
c. Mystic River Watershed
The Mystic River watershed is a 76-square mile watershed that drains into Boston Harbor. It
encompasses all or portions of 21 urban and suburban communities. The outlet of Lower Mystic
Lake is recognized as the beginning of the Mystic River. Horn Pond Brook in Woburn, Mill
Brook in Arlington, and Alewife Brook in Cambridge contribute to the flows in the middle
Mystic River. The river flows southeast and joins the Maiden River. In 1966, the Amelia Earhart
Dam was built on the Mystic River just downstream from its confluence with the Maiden River.
This dam separates the estuarine and freshwater river portions. As described below, the
watershed faces multiple water quality impacts related to cultural eutrophication including
excessive algal growth, harmful cyanobacteria blooms, and invasive macrophyte growth. The
Mystic River watershed's pollution sources include stormwater runoff, combined sewer
overflows (CSO), sanitary sewer overflows (SSO), non-point source runoff, contaminated
sediment, and three Superfund sites (Massachusetts Department of Environmental Protection,
2006) (USEPA, 2020). The watershed suffers from many legacy pollutants as well as present day
pollutant loadings, as discussed below. Much of the basin is highly developed with considerable
industrial and commercial activity, and the watershed faces high development and re-
development pressure (Massachusetts Department of Environmental Protection, 2006) (USEPA,
2020).
Based on water quality data available for the Mystic River and applicable state surface water
quality standards for Class B and SB surface waters, MassDEP included many segments of the
Mystic River on the Massachusetts' 2002 303(d) impaired waters list. In the latest EPA-approved
303(d) list (the 2018/2021 303(d) list), MassDEP continues to indicate widespread impairments
due to excess nutrients and bacteria (Massachusetts Department of Environmental Protection,
30 See Final Pathogen TMDL for the Charles River Watershed (Massachusetts Department of Environmental
Protection, 2007a) pp 58-61.
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2021) in the Mystic River system (see Attachment 3 for a full list of impairments in the Mystic
River watershed based on the 2018/2021 303(d) list.
Nutrient Impairments
Among the 303(d)-listed pollutants on the 2018/2020 Section 303(d) list are several related to
excessive nutrient loading (see Attachment 3):
Phosphorus
Low Dissolved Oxygen
Low Dissolved Oxygen Saturation
Algae
Harmful Algal Blooms
Chlorophyll-a
Nutri ent/Eutrophi cati on B i ol ogi cal Indi cators
Transparency/Clarity
As indicated above for the Charles River, the causal relationship between excessive phosphorus
loads and water quality impairments is well understood and is covered extensively in research
literature. Similarly, the causal relationship between excess nitrogen and water quality
impairments in marine and estuarine systems is also well understood and is extensively covered
in literature.31 Excess phosphorus in the Mystic River system in the inland freshwater portions of
the Mystic River and excess nitrogen in the marine portions of the Mystic River lead to increased
algal and aquatic plant growth, which can lower dissolved oxygen in the water column, affect the
pH of the water, increase the turbidity in the water column, and decrease the clarity of the water.
The 2018/2020 Section 303(d) list indicate that 19 waterbody segments in the Mystic River
watershed are impaired due to excess nutrients.
As early as 2004, a MassDEP water quality assessment analysis indicated that nutrients in
stormwater are causing water quality impairments in the Mystic River watershed (Massachusetts
Department of Environmental Protection, 2010a).
Beginning in 2015, EPA deployed a real-time buoy during the summer months to monitor for the
presence of HABs and the presence of cyanobacteria, also known as blue-green algae, in the
Mystic River near the Blessing of the Bay (USEPA, 2022b). Like the Charles River, HABs in the
Mystic River frequently contain cyanobacteria, which produce extremely dangerous toxins that
have been known to sicken or kill people and animals as well as cause low dissolved oxygen
levels in the water column, harming aquatic life. Since deployment, EPA has tracked HABs
every summer through the presence of phycocyanin and chlorophyll in the water column
(USEPA, 2022b).
In 2020, EPA supported MassDEP in piloting an "Alternative TMDL" designed to address
nonattainment of nutrient related water quality standards over a period of time in the Mystic
River, consistent with the 2013 framework for prioritizing and implementing TMDLs and
31 See Part VII - References section of this document.
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pollution control strategies (USEPA, 2013). The Alternative TMDL, entitled "Mystic River
Watershed Alternative TMDL Development for Phosphorus Management - Final Report (Mystic
Alternative TMDL)," addresses impairments associated with excessive nutrient loading
including phosphorus, chlorophyll, dissolved oxygen, and secchi depth (water clarity). The
Mystic Alternative TMDL indicates that inadequately controlled stormwater runoff from
developed landscapes is the predominant source of nutrient loads to the surface waters of the
Mystic River watershed. Under existing conditions, the study estimated that to meet the selected
chlorophyll-a water quality target for attaining water quality standards in the most impacted
segment, the lower Mystic River above the Amelia Earhart Dam, will require a 67 percent
reduction of stormwater phosphorus loadings in the freshwater portion of the watershed and
assumes all reduction will be achieved through stormwater control measures.32 The Mystic
Alternative TMDL did not address the impairments in the estuarine portion of the watershed
(below the Amelia Earhart Dam) that are associated with excess nitrogen.
Bacteria Impairments
Similar to the Charles River, the 2018/2020 EPA-approved 303(d) list indicates widespread
bacteria impairments, including eleven segments of the Mystic River that are impaired for E. coli
or fecal coliform (Massachusetts Department of Environmental Protection, 2021). The bacteria
impairments have been linked to stormwater since a 2002 MassDEP water quality assessment
analysis indicated that bacteria in stormwater is a significant cause of water quality impairments
in many segments of the Mystic River (Massachusetts Department of Environmental Protection,
2010a). EPA has been assigning a "report card" grade for the Mystic River watershed since
2006. Prior to 2014, a single grade was assigned to the entire watershed; however, for the last
eight years, grades have been assigned to 14 individual stretches of the river and its tributaries.
The latest Report Card from 2021 indicates that the monitored segments of the Mystic River are
meeting water quality standards for swimming and boating based on bacteria concentrations
ranging from 30.2% of the time (Mill Creek) to 98.6% of the time (Upper Mystic Lake)
(USEPA, 2022d).
In 2018, EPA approved a TMDL for pathogen indicators (i.e., fecal coliform, Enterococci, and
E.coli) in the Mystic River watershed (Massachusetts Department of Environmental Protection,
2018). The TMDL found 24 river miles out of a total of 27.6 river miles in the watershed are
impaired due to bacteria and pathogens, including the Abeijona River, Alewife Brook, Maiden
River, Chelsea River, and the main stem of the Mystic River and four out of a total of five
estuaries are impaired for bacteria and pathogens. The TMDL identified bacterial sources such as
failing septic systems, CSOs, SSOs, sewer pipes connected to storm drains, certain recreational
activities, wildlife (including domestic pets), and storm water discharges. While the TMDL does
not attempt to assign specific WLAs or LAs to specific sources, it indicates that stormwater
sources of bacteria need to be reduced to meet in stream water quality standards.33
32 See Mystic River Watershed Alternative TMDL Development for Phosphorus Management - Final Report
(USEPA, 2020) p. 5 and pp. 48-56.
33See Final Pathogen TMDL for the Boston Harbor, Weymouth-Weir, and Mystic Watersheds (Massachusetts
Department of Environmental Protection, 2018) pp 66-67.
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d. Neponset River Watershed
The Neponset River watershed is located in eastern Massachusetts within the metropolitan
Boston area and encompasses all or portions of portions 14 communities. The Neponset River is
29.5 miles long and drains approximately 120 square miles. At its most downstream point, the
Neponset River is tidally influenced for three miles from Baker Dam in Milton to its confluence
with Dorchester Bay in Boston Harbor (Massachusetts Department of Environmental Protection,
2012). Since 1994, many waterbody segments within the Neponset River watershed have been
identified as impaired for bacteria and other impairments associated with excess nutrients
(Massachusetts Department of Environmental Protection, 1995) (Massachusetts Department of
Environmental Protection, 2010b). Based on water quality data available for the Neponset River
and applicable Massachusetts surface water quality standards for a Class B and SB surface water,
MassDEP included many segments of the Neponset River on the 2018/2021 303(d) list, where
MassDEP continues to indicate widespread impairments due to excess nutrients and bacteria in
the Neponset River watershed (Massachusetts Department of Environmental Protection, 2021)
(see Attachment 4 for a full list of impairments in the Neponset River watershed based on the
2018/2021 303(d) list).
Nutrient Impairments
Among the 303(d)-listed pollutants on the 2018/2020 Section 303(d) list are several related to
excessive nutrient loading (see Attachment 4):
Phosphorus
Low Dissolved Oxygen
Algae
Aquatic Plants (Macrophytes)
Nutri ent/Eutrophi cati on B i ol ogi cal Indi cators
Transparency/Clarity
Turbidity
Algae
As indicated above for the Charles River and the Mystic River, the causal relationship between
excessive phosphorus and nitrogen loads and water quality impairments is well understood.34
Excess phosphorus in the Neponset River system in the inland freshwater portions of the
Neponset River and excess nitrogen in the marine portions of the Neponset River lead to
increased algal and aquatic plant growth, which can lower dissolved oxygen in the water column,
affect the pH of the water, increase the turbidity in the water column, and decrease the clarity of
the water (Massachusetts Department of Environmental Protection, 2010b) (Massachusetts
Department of Environmental Protection, 2004). The current 2018/2020 Section 303(d) list
34 See Part VII - References.
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indicates 26 waterbody segments in the Neponset River watershed are impaired due to excess
nutrients in the waterbody.
A MassDEP 2004 assessment report found widespread impairments in the Neponset River
watershed due to excess nutrients with only one segment sampled between 2001 and 2003 found
to have no nutrient related problems (Massachusetts Department of Environmental Protection,
2004). Nutrient related issues throughout the Neponset River watershed have been linked to
stormwater sources since 1994.35
Bacteria Impairments
Similar to the Mystic River, the 2018/2020 EPA-approved 303(d) list indicates widespread
bacteria impairments, including 20 segments of the Neponset River that are impaired for E. coli,
enterococcus or fecal coliform (Massachusetts Department of Environmental Protection, 2021).
The bacteria impairments have been linked to stormwater since a 1994 MassDEP water quality
assessment analysis, which indicated that bacteria in stormwater is causing of water quality
impairments in many segments of the Neponset River (Massachusetts Department of
Environmental Protection, 1995) (Massachusetts Department of Environmental Protection, 2002)
(Massachusetts Department of Environmental Protection, 2004). EPA and the Neponset River
watershed Association have been assigning a "report card" grade for the Neponset River to
measure and evaluate progress towards meeting Massachusetts bacterial water quality standards
for swimming and boating as well as to assess general health of the watershed. The latest Report
Card from 2021 indicates that segments of the Neponset River are meeting water quality
standards for swimming and boating based on bacteria concentrations ranging from 25.1% of the
time (Meadows Brook) to 100% of the time (Crack Rock Pond). These 2021 grades in the
Neponset are similar to the 2020 report card grades (USEPA, 2022e).
In 2002, EPA approved a TMDL for pathogen indicators (e.g., fecal coliform and E.coli) in the
Neponset River watershed with an approved addendum in 2013 (Massachusetts Department of
Environmental Protection, 2002) (Massachusetts Department of Environmental Protection,
2012). The TMDL and associated addendum found that most of the Neponset River, and
tributaries, do not fully support the designated Class B or SB uses for primary and secondary
contact recreation, nor its class SB designated use of restricted shellfish harvesting due to excess
bacteria and pathogens. The TMDL identified bacterial sources such as failing septic systems,
CSOs, SSOs, sewer pipes connected to storm drains, certain recreational activities, wildlife
(including domestic pets), and stormwater. While the TMDL does not attempt to assign specific
35 See The Neponset River Watershed 1994 Resource Assessment Report (Massachusetts Department of
Environmental Protection, 1995) pp 8-1 through 8-10; Neponset River Watershed 2004 Water Quality Assessment
Report (Massachusetts Department of Environmental Protection, 2010b)p 10; Neponset River Estuary ACEC Water
Quality and Restoration Action Plan (Neponset River Watershed Association, 2014) pp 40-41.
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WLAs or LAs to specific sources, it indicates that stormwater sources of bacteria need to be
reduced in order to meet in-stream water quality standards.36
V. Analysis of Petitions and Designation
a. Water Quality Progress in the Charles River, Mystic River, Neponset River, and Boston
Harbor
For decades, EPA, CLF, the Commonwealth of Massachusetts, the Massachusetts Water
Resources Authority (MWRA), the Boston Water and Sewer Commission (BWSC), and many
municipalities and watershed groups have played important roles in improving water quality in
Boston Harbor and its tributaries. A landmark effort to clean up Boston Harbor began in earnest
in 1983 when CLF filed a suit against the sewage authority at the time, the Metropolitan District
Commission (MDC),37 and EPA alleging that the discharge of untreated sewage into Boston
Harbor violated the CWA. In 1985, EPA filed suit against a newly created sewage authority,
MWRA, and the cases were consolidated. The complex federal litigation included a key 1985
ruling setting forth a schedule with mandatory construction and operation deadlines for new
sewage treatment infrastructure and facilities.38 It resulted in the construction of a new
wastewater treatment facility at Deer Island in Boston Harbor which became operational in
phases between 1995 and the early 2000s; sewage sludge processing facilities in Quincy; a
tunnel from Nut Island to Deer Island allowing the closure of the old Nut Island wastewater
treatment facility; and a 9.5-mile outfall tunnel to discharge treated effluent offshore in
Massachusetts Bay. These four major construction projects were designed to deal with the
problem of untreated and poorly treated sewage that had been dumped into Boston Harbor for
decades. The offshore outfall significantly reduced the nutrient and bacteria load in Boston
Harbor (Massachusetts Department of Environmental Protection, 2018). Deer Island's expanded
capacity also reduced SSOs and backups in communities surrounding Boston Harbor that were
once caused by an overloaded sewer system (Massachusetts Department of Environmental
Protection, 2018).
In 1995, EPA launched an additional effort to make the Charles River fishable and swimmable.
This effort included work that would impact areas throughout the Boston Harbor watershed,
reducing nutrients and bacteria in all waterways and improving water quality. Since then,
BWSC, MWRA, and other municipalities have made significant progress towards improving
water quality by reducing illicit sewage discharges to storm drain systems and CSOs. The work
by BWSC, MWRA, and municipalities within the Charles River, Neponset River, and Mystic
River watersheds has reduced CSO discharges to the Charles River by over 95% (USEPA,
2022f); eliminated all CSO discharges to the Neponset River (Massachusetts Water Resources
36 Total Maximum Daily Loads of Bacteria for Neponset River Basin (Massachusetts Department of Environmental
Protection, 2002) pp 31-37.
37 The State of Massachusetts legislature created the Massachusetts Water Resources Authority (MWRA) in 1984.
MWRA is the successor entity to the MDC.
38 U.S. etal. v. Metropolitan Dist. Comm1985 WL 9071 (Sept. 5, 1985).
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Authority, 2022); and significantly reduced the CSO events in the Mystic River watershed
(Massachusetts Water Resources Authority, 2022). In addition, targeted enforcement by EPA
and MassDEP focused on removing illicit sewage connections to MS4 systems in the Boston
Harbor watershed, including many enforcement actions in the Charles, Mystic, and Neponset
River watersheds, have reduced the amount of nutrients and bacteria entering local waterways
(Massachusetts Department of Environmental Protection, 2018) (USEPA, 2020) (USEPA,
2022a) (USEPA, 2022f). While significant progress has occurred since 1995, recent water
quality data collected by the Charles River Watershed Association, Mystic River Watershed
Association, the Neponset River watershed Association, MWRA, EPA and MassDEP continue to
indicate widespread impairments caused by nutrients and bacteria in each system as described in
Part IV of this document.
Since at least 2004, MassDEP has indicated that stormwater discharges are a source of nutrients
and bacteria causing impairments in the three watersheds. However, the priorities for the past
three decades were to focus on wastewater treatment plant upgrades and CSO reductions to
remove the largest sources of nutrients and bacteria in each watershed, and eventually Boston
Harbor. As work finishes on MWRA's Long-Term Control Plan for CSO discharges
(Massachusetts Water Resources Authority, 2022) and because Deer Island has been operating
since 2000, energy and resources are now focused on the remaining sources of nutrients and
bacteria that continue to degrade water quality in each watershed, including stormwater
discharges that are not currently regulated.
Recent studies in all three watersheds indicate that stormwater is the current leading cause of
water quality issues. See Part IV of this document. These studies include TMDLs in the Charles
River watershed and an Alternative TMDL in the Mystic River watershed that both indicate that
water quality standards and TMDL targets can only be achieved with a reduction of phosphorus
in stormwater discharges from both public and private developed lands. The most recent Three
Rivers Report Card (USEPA, 2022f) (USEPA, 2022d) (USEPA, 2022e) underscores the
importance of stormwater controls in achieving bacteria water quality standards in all three
watersheds (CRWA, MyRWA, NepRWA, 2022). In EPA's technical and scientific judgment,
based on careful consideration of record information, controlling nutrients and bacteria in
stormwater discharges from developed lands in all three watersheds is necessary to meet water
quality standards and TMDL WLAs. Whereas the 2016 MA Small MS4 permit, Boston
individual MS4 permit, and MassDOT MS4 permit regulate stormwater discharges from most
publicly owned parcels in the three watersheds, EPA has concluded based on the available
evidence in the record before it that more must be done to control stormwater discharges from
commercial, industrial, and institutional parcels to meet WQS and TMDL WLAs which is why
EPA is designating these sites for NPDES permitting.
b. Environmental Justice and Climate Change
EPA is making this residual designation determination now because of the urgent need to make
progress toward regulating currently unregulated stormwater discharges in these highly
populated urban and suburban areas. In addition to the overall environmental and human health
18
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reasons described above, EPA has determined it must act expeditiously because these watersheds
include communities with environmental justice concerns. EPA recognizes that the burdens of
environmental pollution disproportionately fall on population groups of concern (e.g., minority,
low income, and indigenous populations as specified in Executive Order 128 98).39 EPA also
recognizes that climate change is impacting stormwater pollution and management in many
Massachusetts communities and ecosystems,40 and typically has a disproportionate adverse
impact on communities with environmental justice concerns.4142
EPA has defined environmental justice as the "fair treatment and meaningful involvement of all
people regardless of race, color, national origin, or income with respect to the development,
implementation and enforcement of environmental laws, regulations and policies."43 In May
2022, EPA published EPA Legal Tools to Advance Environmental Justice and identified RDA as
a potential method for addressing environmental justice concerns.44 EPA expects that
designating stormwater sources for permitting that are (1) not currently regulated but that
contribute to water quality standards exceedances, (2) are significant contributors of pollutants to
waters of the U.S., and/or (3) that need to be controlled to meet TMDL WLAs, is likely to
improve water quality in many communities, including communities with environmental justice
concerns. "These [stormwater] controls could result in healthier urban streams, thereby providing
benefits not only to the ecosystem itself, but also to the surrounding communities. Stormwater
controls may also yield the additional benefit of transforming gray urban environments into more
inviting green spaces, enhancing recreational opportunities and quality of life. They may also
help to address bigger and more frequent storms caused by climate change."45
Wet weather and heavy precipitation can have a significant effect on communities, especially in
areas with high amounts of impervious cover, and climate change augments those effects.
Increased (or decreased) flows of stormwater from climate change will likely lead to increased
pollution, either from additional loads (from increased flows), or greater concentration (from
decreased flows).46
39 Executive Order 12898 (59 Fed. Reg. 7629, February 16, 1994).
411 Massachusetts Department of Environmental Protection Assessment of Climate Change Impacts on Stormwater
BMPs and Recommended BMP Design Considerations in Coastal Communities (Dec. 2015).
41 U.S. EPA, Climate Adaptation Action Plan (October 2021), at 2-3, a\'ailable at
https://www.epa.gov/system/files/documents/2021-09/epa-climate-adaptation-plan-pdf-version.pdf;jSee also U.S.
EPA, EPA 43-R-21-003, Climate Change and Social Vulnerability in the United States: A Focus on Six Impacts
(2021), available at Climate Change and Social Vulnerability in the United States: A Focus on Six Impacts
(epa.gov) (analyzing six categories of climate change impacts on four socially vulnerable groups and finding that
minorities and low-income individuals are more likely to currently live in areas with the highest projected climate
change impacts compared to reference populations of people not included in those groups).
42 See Mystic River Watershed Association, "Sewage: An Enviromnental Justice Tragedy," blog post, Feb. 5, 2021.
43 See https:// www.epa.gov/enviromnentaljustice/learn-aboutenvironmental-justice.
44 See U.S. EPA, EPA Legal Tools to Advance Enviromnental Justice (May 2022).
45 Mat 81.
46 See U.S. EPA, Climate Adaptation Action Plan 5 (Oct. 2021) (noting that climate change impacts, "if combined
with sufficiently high nutrient levels and temperatures, [can lead to] more harmful algal blooms, pathogens, and
water related illnesses"); see also U.S. EPA, Climate Change and Harmful Algal Blooms,
https://www.epa.gov/nutrientpollution/climate-change-and-liarmful-algal-
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In the Charles, Mystic, and Neponset River watersheds, the farthest downstream segments are
generally the most impaired (Massachusetts Department of Environmental Protection, 2021) due
to the accumulation of pollutants (specifically nutrients) in these downstream reaches. Moreover,
in all three watersheds, communities with environmental justice concerns are concentrated in
these same lower watershed reaches with the highest degree of impairment in all three
watersheds. In addition, these same areas are also closest to Boston Harbor, at the lowest
elevation in the watersheds, likely making them the most prone to sea level rise and other effects
of climate change (See Attachment 5 for maps of the three watersheds and EJ communities and
Attachments 2-4 for list of impaired waters in each watershed).
While this residual designation determination does not impose immediate permitting
requirements or obligations on the owners or operators of the sources of the designated
discharges, it will ultimately improve environmental conditions in communities with
environmental justice concerns by improving water quality in nearby waterways, which may
include creating more green infrastructure in these areas. EPA will follow this residual
designation determination with one or more draft NPDES general permits that will offer
coverage for eligible operators of designated sources, spell out the specific requirements and
obligations for the operators of the sources of the designated discharges, and offer an opportunity
to comment on the residual designation determination and EPA's proposed general permit(s).
EPA recognizes that these permits may impact owners and operators of facilities in communities
with environmental justice concerns (as well as other parts of the watersheds); when issuing the
draft permits, EPA will provide an analysis of environmental justice and climate change
considerations, and provide an opportunity to comment on those issues as well as any other
aspect of the permits.
c. Nutrients and Bacteria in New England Stormwater
Nutrients
EPA, states, and the scientific community have effective tools for characterizing the mass load of
nutrients in stormwater. As discussed in more detail below, nutrient loading to waterbodies is
often characterized not only through event mean concentrations (EMCs) but also through export
coefficients (i.e., export rates) from land uses with similar characteristics in areas with similar
rainfall patterns which represents the total amount (expressed in pounds) of either nitrogen or
phosphorus delivered annually to a system from a defined area (expressed in acres). Annual
export coefficients for nutrients are particularly useful at characterizing stormwater because of
the cumulative effects nutrients have on receiving water bodies, including effects on downstream
receiving waters. Receiving waters respond to the overall annual load of nutrients they receive,
not just a snapshot in time of the stormwater nutrient concentration. The results of this can be
blooms#:~:text=Warmer%20temperatures%20prevent%20water%20from.warmer%20and%20promoting%20more
%20blooms.
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seen in the impairments in each watershed, with downstream reaches exhibiting the higher levels
of degradation due to excess nutrients which accumulate as the tributaries in each watershed
deliver nutrient loads to the main stem of each river (Massachusetts Department of
Environmental Protection, 2021). Below is a further explanation of nitrogen and phosphorus in
stormwater in New England.
Nitrogen
The primary sources of nitrogen in stormwater are (See, e.g., (Carpenter, et al., 1998) (Chen,
Theller, Gitau, Engel, & Harbor, 2017) (Jani, Jang, Lusk, & Toor, 2020) (Moore, Johnston,
Smith, & Milstead, 2011) (Shaver, Horner, Skupien, May, & Ridley, 2007) (Driscoll, et al.,
2003) (National Research Council, 2000)):
Atmospheric deposition including mobile source deposition (deposition from
combustion engines);
Wash-off of fertilizers;
Nitrogen attached to eroded soils and stream banks;
Organic matter (such as pollen and leaves) and pet wastes that are deposited on
impervious surfaces; and
Leaching of nitrate from functioning septic systems.
The median nutrient concentration of total nitrogen seen in stormwater is 2.0 mg/L across the
New England region, based on the data available in NSQD (USEPA, 2014) (Pitt, Maestre, &
Morquecho, 2004). Similar levels of total nitrogen were seen in stormwater discharges in the
Chesapeake region (Schueler, 2011) as well as across the nation, with Lin reporting a national
average EMC of 2.415 mg/L for nitrogen (TKN +NO2 and NO3) (Lin, 2004). While the
concentrations of nitrogen in stormwater may appear low when compared to other sources (e.g.,
sewage overflow), it has been shown that stormwater from impervious surfaces, particularly
from roads, is the main source of nitrogen delivered to urban streams due to the large amounts of
pollutants transported by the significant stormwater volume that would otherwise be infiltrated.
See, e.g., (Wang, Ma, Zhang, & Shen, 2022) (Jacobson, 2011) (Jani, Jang, Lusk, & Toor, 2020).
While EMC data are important in characterizing nitrogen concentrations in stormwater derived
from different land uses, it is more useful to define the impacts of stormwater discharges in terms
of average annual load given the cumulative impacts of nutrients on downstream waterbody
segments. The total nitrogen load delivered from stormwater sources in any given area is
controlled by the precipitation patterns, the amount of impervious surface in that drainage area,
and the land use type of that drainage area. Table 2 below displays the average annual total
nitrogen export from different land use classes and land cover types for New England. Annual
export coefficients for total nitrogen from developed lands is controlled by precipitation patterns,
land use within the drainage area, and the amount of impervious surface in the drainage area. In
New England, the average annual nitrogen loading (export coefficient/rate) from impervious
surfaces ranges from 10.5 and 17 pounds per acre per year depending on land use type and 0.3
and 3.6 pounds per acre per year from pervious areas depending on the infiltration rate of the
pervious area (US EPA, 2016a).
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Nitrogen Source Category
by Land Use
Land Surface
Cover
N Load Export
Rate,
lbs./acre/year
Commercial and Industrial
Directly connected
impervious
15.0
All Residential
Directly connected
impervious
14.1
Highway
Directly connected
impervious
10.5
Forest Agriculture and Open
Land
Directly connected
impervious
11.3
Developed Land Pervious-
HSG A
Pervious
0.3
Developed Land Pervious -
HSGB
Pervious
1.2
Developed Land Pervious-
HSGC
Pervious
2.4
Developed Land Pervious-
HSGC/D
Pervious
3.1
Developed Land Pervious-
HSGD
Pervious
3.6
Table 2: Average annual distinct nitrogen (N) load export rates for use
in estimating N load reduction credits in the 2016 MA MS4 permit (US
EPA, 2016a). The Commercial and Industrial export rate would also
apply to institutional lands. HSG stands for Hydrologic Soil Group
Phosphorus
The primary sources of phosphorus in stormwater are (See e.g. (Carpenter, et al., 1998) (Lin,
2004) (Massachusetts Department of Environmental Protection, 2007b) (Massachusetts
Department of Environmental Protection, 2011) (Waschbusch, 2000) (Mattson & Isaac, 1999):
Wash-off of phosphorus-based lawn fertilizers used in residential areas, parks,
cemeteries, and golf courses and fertilizers used by agriculture;
Wash-off of organic matter (such as pollen and leaves) and pet wastes that are
deposited on impervious surfaces;
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Atmospheric deposition;
Soil erosion; and
Leaching from failed or inadequate septic systems.
The median nutrient concentration of total phosphorus in stormwater is 0.25 mg/L across the
New England region, based on data available in NSQD (USEPA, 2014) (Pitt, Maestre, &
Morquecho, 2004). An analysis of data nationwide found the concentration of phosphorus during
storms is very consistent with a mean EMC of 0.30 mg/L (Center For Watershed Protection,
2003). Like total nitrogen, while EMCs of phosphorus in stormwater are important, it is more
useful to define the impacts of stormwater discharges in terms of average annual load given the
cumulative impacts of nutrients on downstream waterbody segments. Also, like total nitrogen,
the total phosphorus load delivered from stormwater sources in any given area is controlled by
the precipitation patterns, the amount of impervious surface in that drainage area, and the land
use type of that drainage area. Table 3 below displays the average annual total phosphorus export
rates from different land use classes and land cover types for the New England region. In New
England, average annual phosphorus loading (export coefficient/rate) from impervious cover
ranges from between 1.34 and 2.32 pounds per acre per year of total phosphorus based on land
use type, and 0.03 and 0.37 pounds per acre per year from pervious areas depending on
infiltration rate of the pervious area (US EPA, 2016a) (USEPA, 2016b).
Phosphorus Source Category
by Land Use
Land Surface Cover
P Load Export
Rate,
lbs/acre/year
Commercial and Industrial
Directly connected
impervious
1.78
Multi-Family and High-Density
Residential
Directly connected
impervious
2.32
Medium -Density Residential
Directly connected
impervious
1.96
Low Density Residential
Directly connected
impervious
1.52
Highway
Directly connected
impervious
1.34
Forest Agriculture and Open
Land
Directly connected
impervious
1.52
Developed Land Pervious -
HSG A
Pervious
0.03
23
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Developed Land Pervious -
HSGB
Pervious
0.12
Developed Land Pervious -
HSG C
Pervious
0.21
Developed Land Pervious -
HSG C/D
Pervious
0.29
Developed Land Pervious -
HSGD
Pervious
0.37
Table 3: Average annual distinct phosphorus load export rates for use in estimating
phosphorus load reduction credits in the 2016 MA MS4 permit (US EPA, 2016a).
The Commercial and Industrial export rate would also apply to Institutional lands.
HSG stands for Hydrologic Soil Group
Bacteria/Pathogens
Stormwater discharged to recreational waters such as beaches and lakes or stormwater that
comes into contact with shellfish beds can impair the water's designated uses, which may
include swimming, boating, and shellfish propagation. Bacteria in stormwater also poses a public
health risk from exposure to pathogen contamination. Several indicator organisms may be used
to evaluate the presence of harmful pathogens in stormwater: fecal coliform, E. coli,
streptococci, and enterococci (US EPA, 1999). Primary sources of pathogens in stormwater
runoff are (See e.g. (Massachusetts Department of Environmental Protection, 2018)
(Massachusetts Department of Environmental Protection, 2002) (Massachusetts Department of
Environmental Protection, 2007a) (Lin, 2004)):
Leaky sanitary sewer lines,
Sanitary sewer cross-connections,
Wash-off of wildlife and pet excrement, and
Failing septic systems.
Bacteria and pathogen concentrations in stormwater vary greatly with total E. coli concentrations
ranging from 10 colonies per 100 ml to 35,000 colonies per 100 ml across the New England
Region, based on data available in NSQD (USEPA, 2014) (Pitt, Maestre, & Morquecho, 2004).
As a point of reference, to meet water quality standards, Massachusetts Class B waters cannot
exceed 235 colonies per 100 ml during the bathing season due to the threat to human health.
Generally, bacteria and pathogen concentrations increase with increased impervious surface and
increased urbanization (Mallin, Johnson, & Ensign, 2009). Bacteria concentrate on impervious
surfaces during dry weather and are readily washed off into receiving waterbodies during storm
events, a process that would otherwise not occur if the land was pervious instead of impervious.
24
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d. Selection of Designation Sites
Selection of Land Use Categories
Table 4 below contains the land use breakdown by land area for the Charles River, Mystic River,
and Neponset River watersheds. As Table 4 demonstrates, residential land use (single and multi-
family) is the dominant land use in all three watersheds with 41% of the total area in the Charles
River watershed, 35% of the Mystic River watershed, and 39% of the Neponset River watershed
classified as residential land area. While residential land use represents the dominant land use in
all three watersheds, EPA's data analysis for the Charles River watershed47 indicates that the
average multi-family and single-family parcel discharges approximately six times less
phosphorus in stormwater than the average commercial, industrial, or institutional parcel. Given
EPA's understanding of the similar pattern of increasing impact with increasing proportion of
impervious surface on a parcel and the consistency of pollutant loading in New England from
stormwater discharged from developed lands, in EPA's technical judgment, the same pattern
seen in phosphorus in stormwater would also be seen in nitrogen and bacteria contributions.
EPA's data analysis for the Charles River watershed also indicates that, generally, residential
parcels have a smaller water quality impact from stormwater discharges on a per-parcel basis
compared to commercial, industrial, and institutional parcels. Similarly, given the similarities in
land use in all three watersheds (Table 4), EPA can reasonably apply this information to all three
watersheds, not just the Charles River watershed.
Therefore, EPA is choosing to focus this designation on commercial, industrial, and institutional
parcels48 and focus on permitting such stormwater discharges given their greater pollutant
loading impact on a per parcel basis, as opposed to residential parcels. At the same time, EPA
explicitly considered whether to designate residential properties and the adaptive methodology it
adopted for the purpose of this RDA accounts for the possibility of extending the RDA to
encompass certain of those sources in the future, should the facts and circumstances on the
ground warrant such an action. In other words, the question of whether to designate certain
residential properties is integral to EPA's ongoing evaluation of the RDA implementation using
an adaptive management model. Depending in part on the progress that occurs as a result of this
designation and ensuing permit action(s), and on an evaluation of data and other analysis
resulting from those actions, EPA may designate multi-family parcels in the future. EPA also
intends to conduct further analysis on the impact permitting multi-family parcels will have on
receiving water quality and an analysis of environmental justice considerations such an action
may have. This approach will also allow MS4 permit holders in each watershed to focus efforts
on residential properties in their communities as they see fit to meet MS4 permit obligations.
Overall, in EPA's judgment, this stepwise, adaptive approach will (1) avoid duplicative or
potentially conflicting regulatory mandates on residential parcels,49 and (2) will enable EPA to
47 See Attachment 6, Charles River Watershed Stormwater Total Phosphorus Analysis.
48 Id
49 A related benefit of this iterative approach that EPA also factored into its decision making is that reliance on
existing MS4 implementation activity with respect to residential properties will reduce the administrative burden on
EPA associated with regulating those sources. Logistically and administratively, municipal governments are better
25
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pursue any necessary incremental reductions from residential parcels in a more targeted,
impactful, and cost-effective manner, as decisions can be made with the benefit of more detailed
information and more extensive implementation experience. EPA's objective is to evaluate
options for maximizing stormwater pollution reductions as efficiently as possible (i.e., fewest
necessary stormwater controls installed to fully address the problem). This approach is consistent
with how courts have construed agency action that is at once compelled by a sense of urgency
given the gravity of the problem from the standpoint of human health and the environment but is
also calibrated and measured. The U.S. Court of Appeals for the D.C. Circuit has held that
"agencies have great discretion to treat a problem partially." City of Las Vegas v. Lujan, 891 F.2d
927 (D.C. Cir. 1989) ("we [shjould not strike down [a regulation] if it [is] a first step toward a
complete solution."). In sum, the methodology here is designed to ensure EPA neither over nor
underregulates in its attempts to solve an indisputably complex environmental problem. This
adaptive approach to managing stormwater in these watersheds is also appropriate given EPA's
decision to act with dispatch based on the best information reasonably available and without
awaiting the development of costly water quality and land use models. "As in many science-
based policymaking contexts, under the CWA the EPA is required to exercise its judgment even
in the face of some scientific uncertainty." Upper Blackstone Water Pollution Abatement Dist. v.
U.S. E.P.A., 690 F.3d 9, 23 (1st Cir. 2012), accord City of Taunton, Massachusetts v. United
States Env't Prot. Agency, 895 F.3d 120, 135 (1st Cir. 2018) and American Iron and Steel
Institute v. EPA, 151 F.3d 979, 1004 (D.C. Cir. 1997).
Charles
Mystic
Neponset
River
River
River
Land Use
Watershed
Watershed
Watershed
Percent of
Percent of
Percent of
Total Land
Total Land
Total Land
Area
Area
Area
Commercial
4%
6%
6%
Industrial
3%
4%
4%
Institutional
20%
17%
16%
Residential - single-
34%
23%
33%
family
Residential - multi-
7%
12%
6%
family + other
Mixed Use
3%
1%
1%
Other
29%
37%
34%
Table 4: Land Use comparison Charles River, Mystic River and
Neponset River Watersheds. All Data based on MassGIS 2016 Land
situated to interact with residential property owners than EPA. Prior to assuming an administrative burden of that
magnitude, EPA concluded that it made sense to determine whether the controls contemplated by this action were
sufficient to achieve its intended aim of restoring and maintaining designated uses in the Charles, Mystic and
Neponset Rivers.
26
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Use/Land Cover dataset (MassGIS, 2016). "Other" includes
unknown, open land, forest, agriculture, recreation, right of way, and
water land use categories. "Institutional" land use is renamed from
"Tax Exempt"
Selection of Size Threshold
In general, the amount of impervious surface50 on a property increases the volume of stormwater
discharged from that property or land use class, which increases the loading of pollutants to
waters of the U.S., including phosphorus, nitrogen, and bacteria. (Shaver, Horner, Skupien, May,
& Ridley, 2007) (Center For Watershed Protection, 2003) (Schueler, 2011) (Chen, Theller,
Gitau, Engel, & Harbor, 2017). All three watersheds contain a significant amount of impervious
surface with 23 percent of the land area in the Charles River watershed mapped as impervious,
41 percent of the land area in the Mystic River watershed mapped as impervious, and 21 percent
of the land area in the Neponset River watershed mapped as impervious (MassGIS, 2016). All
three watersheds contain impervious surface totals over thresholds (e.g. greater than ten percent
impervious surface) that have been linked to water quality impairments due to stormwater
discharges (Center For Watershed Protection, 2003) (King, Maker, Kazyak, & Weller, 2011)
(Jacobson, 2011) (Roy & Schuster, 2009) (National Research Council, 2008). As Table 2 and
Table 3 above demonstrate, impervious surfaces can deliver up to ten times the annual load of
phosphorus and nitrogen via stormwater as opposed to pervious areas. In addition, bacteria in
stormwater increases with increasing impervious surface in a drainage area. Parcels can also
contain both impervious and pervious surfaces. For these reasons, this designation focuses on the
amount of impervious surface contained on a parcel instead of the overall size of the parcel, as
requested by the petitioners51. All three petitions contain detailed information about the impact
of impervious cover on water quality, and this designation criteria is consistent with that finding.
Data analysis52 for the Charles River watershed examined phosphorus inputs from private
parcels to the Charles River and indicates that stormwater from private parcels is contributing the
majority of phosphorus to the Charles River system. However, the analysis also shows that not
all parcels will need to reduce phosphorus in stormwater discharges to meet WQS and TMDL
goals. The analysis53 suggests that WQS and TMDL goals can be met through a combination of
actions by municipalities as required by the 2016 MA MS4 permit as well as actions on private
parcels containing the largest amount of impervious surface (the parcels with the largest relative
contribution of pollutants via stormwater) but cannot be met by municipalities' actions alone.
EPA can reasonably assume that bacteria and nitrogen would show similar patterns of increasing
impact with increasing proportion of impervious surface because of New England's consistent
stormwater pollutant loading patterns described above. Where there are impairments due to
excess nitrogen in the tidal portions of all three watersheds, stormwater that reaches surface
waters from parcels with a large amount of impervious surface is contributing a large amount of
50 See Attachment 6, Charles River Watershed Stormwater Total Phosphorus Analysis
51 see Part I Summary of Petitions
52 See Attachment 6, Charles River Watershed Stormwater Total Phosphorus Analysis
53 Id.
27
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nitrogen to the receiving waterbodies and all downstream waterbodies, thus contributing to the
impairments, i.e., WQS violations. Similarly, where there are impairments due to excess
phosphorus in freshwater portions of all three watersheds, stormwater that reaches surface waters
from parcels with a large amount of impervious surface is contributing a large amount of
phosphorus to the receiving waterbody and all downstream waterbodies, contributing to the
impairments, i.e., WQS violations. Bacteria impairments are ubiquitous throughout the Charles,
Mystic, and Neponset watersheds, and stormwater that reaches an impaired surface water from
parcels with a large amount of impervious surface contributes a large amount of bacteria to the
receiving waterbody, thus contributing to the impairments, i.e., WQS violations.
As EPA continues to implement the 2016 MA MS4 permit, municipal permittees in all three
watersheds are likely to make significant improvements in reducing total nitrogen, total
phosphorus, and bacteria discharges in stormwater. However, municipalities largely lack the
authority to control existing private commercial, industrial, and institutional parcels' direct
stormwater discharges to waterbodies. As to indirect stormwater discharges through
municipalities' MS4 systems, it may be challenging for municipalities to adequately address the
water quality impacts of properties with the largest amount of impervious surface. As discussed
above, without action on private parcels within all three watersheds specifically targeting the
reduction of pollutants in stormwater from those parcels with the largest amount of impervious
surface, WQS and TMDL targets cannot be met.
Data analysis54 for the Charles River watershed indicates that that there are approximately
14,800 private commercial, industrial, and institutional parcels within the Charles River
watershed, 12% of which have one acre or more of impervious surface. These parcels contribute
approximately 70% of the overall phosphorus load from all commercial, industrial, and
institutional parcels within the watershed. The relative proportion is also applicable to nitrogen
and bacteria loads based on the impact of impervious surface, and is likely similar in all three
watersheds based on similarities in land use distribution (see Table 4) and impervious surface
percentage in all three watersheds. The focus of this determination is therefore on those
commercial, industrial, and institutional properties with greater than or equal to one acre of
impervious surface within these three watersheds. This designation targets parcels with a large
amount of impervious surface and the majority of phosphorus, nitrogen, and bacteria loads from
these land use classes, resulting in reduced nutrient and bacteria inputs to MS4 systems and
directly to waterbodies in all three watersheds. In addition, this designation's focus on parcels
with a large amount of impervious surface will alleviate some MA MS4 permit requirements for
municipalities and allow municipalities the flexibility to address smaller parcels within their
jurisdiction as they see fit to meet MA MS4 permit requirements.
e. Designation Determination
Pursuant to the discretionary authority provided under CWA § 402(p)(2)(E) and 40 C.F.R. §
122.26(a)(9)(i), EPA is designating for NPDES permitting certain stormwater discharges from
commercial, industrial, and institutional properties55 with one acre or more of impervious
54 Id
55 See footnote 1.
28
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surface56 in the Charles, Mystic, and Neponset River watersheds.57 EPA finds that the designated
stormwater discharges contribute to violations of water quality standards; are significant
contributors of pollutants to waters of the United States; and require stormwater controls based
on wasteload allocations that are part of TMDLs that address phosphorus, nitrogen, and/or
bacteria. Each of these bases is sufficient on its own to designate under the applicable
regulations at 40 C.F.R. § 122.26(a)(9)(i)(C) and (D). This designation includes contiguous
commercial, industrial, or institutional properties with the same owner or operator where the
combined land area contains one acre or greater of impervious surface. This designation does not
apply to any parcel subject to the 2016 MA MS4 permit that is owned or operated by a current
permittee under the 2016 MA MS4 permit; any parcel owned or operated by the City of Boston
or BWSC that is subject to NPDES permit MASO10001; or any parcel owned or operated by
MassDOT that is subject to NPDES permit MA043025. Consistent with 40 C.F.R. § 124.52(c),
"the question whether the initial designation was proper will remain open for consideration
during the [NPDES permit] public comment period under § 124.11 and in any subsequent
hearing."
DAVID
CASH
Digitally signed by DAVID
CASH
Date: 2022.09.14
07:41:21 -04'00'
David W. Cash
Regional Administrator, EPA Region 1
56 See footnote 2.
57 See Attachment 1: List of Communities Included in the Clean Water Act Residual Designation Determination for
Certain Stormwater Discharges in the Charles, Mystic, and Neponset River Watersheds, in Massachusetts.
29
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VI. References
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(1998). Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological
Applications, 559-568.
Center For Watershed Protection. (2003). Impacts of Impervious Cover on Aquatic Systems.
Ellicott City, MD: Center For Watershed Protection.
CH2MHill. (2016). Stormwater Best Management Practices Recommendations Report. Prepared
For Boston Water and Sewer Comission.
Charles River Watershed Association. (2015). Cyanobacteria in the Charles River Lower Basin
2006-2014 Monitoring Report.
Charles River Watershed Association. (2021). 2020 Annual Water Quality Report.
Chen, J., Theller, L., Gitau, M. W., Engel, B. A., & Harbor, J. M. (2017). Ubranization Impacts
on Surface Runoff of the Contiguous United States. Journal of Environmental
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CRWA, MyRWA, NepRWA. (2022). Three Rivers Report Card.
Driscoll, C. T., Whitall, D., Aber, J., Boyer, E., Castro, M., Cronan, C., . . . Ollinger, S. (2003).
Nitrogen Pollution in the Northeastern United States: Sources, Effects, and Management
Options. BioScience, 357-374.
Howarth, R., & Marino, R. (2006). Nitrogen as the limiting nutrient for eutrophication in coastal
marine ecosystems: Evolving views over three decades. Limnology and Oceanography,
364-376.
Jacobson, C. R. (2011). Identification and quantification of the hydrological impacts of
imperviousness in urban catchments: a review. Journal of Environmental Management,
1438-1448.
Jani, J., Jang, Y.-Y., Lusk, M., & Toor, G. (2020). Composition of nitrogen in urban residential
stormwater runoff: Concentrations, loads, and source characterization of nitrate and
organic nitrogen. PLoS ONE, e0229715.
King, B. S., Maker, M. E., Kazyak, P. F., & Weller, D. E. (2011). How Novel is Too Novel?
Stream Community Thresholds at Exceptionally Low Levels of Catchment Urbanization.
Ecological Applications, 21, 1659-1678.
Lin, J. P. (2004). Review of Published Export Coefficient and Event Mean Concentration (EMC)
Data. Vicksburg, MS: U.S. Army Engineer Reserach and Development Center.
Mallin, M. A., Johnson, V. L., & Ensign, S. H. (2009). Comparative impacts of Stormwater
Runoff on Water Quality of an Urban, a Suburban, and a Rural Stream. EnvirnMonit
Assess, 159, 475-491.
30
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Massachusetts Department of Environmental Protection. (1995). The Neponset River Watershed
1994 Resource Assessment Report.
Massachusetts Department of Environmental Protection. (2000). Charles River Watershed
1997/1998 Water Quality Assessment Report. Retrieved January 18, 2022, from
https://www.mass.gov/doc/charles-river-basin-watershed-19971998-water-quality-
assessment-report-section-iii/download
Massachusetts Department of Environmental Protection. (2002). Total Maximum Daily Loads of
Bacteria for Neponset River Basin.
Massachusetts Department of Environmental Protection. (2004). Boston Harbor South
Watersheds 2004 Assessment Report.
Massachusetts Department of Environmental Protection. (2006). Mystic River Watershed
Assessment and Action Plan.
Massachusetts Department of Environmental Protection. (2007a). Final Pathogen TMDL for the
Charles River Watershed.
Massachusetts Department of Environmental Protection. (2007b). Final TMDL for Nutrients in
the Lower Charles River Basin.
Massachusetts Department of Environmental Protection. (2009). Northeast Region Bacteria
Source Tracking 2008 Results.
Massachusetts Department of Environmental Protection. (2010a). Mystic River Watershed and
Coastal Drainage Area 2004 -2008 Water Quality Assessment Report.
Massachusetts Department of Environmental Protection. (2010b). Neponset River Watershed
2004 Water Quality Assessment Report.
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Nutrients in the Upper/Middle Charles River Basin, Massachusetts.
Massachusetts Department of Environmental Protection. (2012). Addendum: Final Total
Maximum Daily Loads of Bacteria for Neponset River Basin.
Massachusetts Department of Environmental Protection. (2018). Final Pathogen TMDL for the
Boston Harbor, Weymouth-Weir, and Mystic Watersheds.
Massachusetts Department of Environmental Protection. (2021). Final Massachusetts Integrated
List of Waters for the Clean Water Act 2018/2020 Reporting Cycle.
Massachusetts Department of Revenue/Division of Local Services. (June 2016). Property Type
Classification Codes, Non-Arm's Length Codes and Sales Report Spreadsheet
Specifications.
Massachusetts Water Resources Authority. (2022). Combined Sewer Overflows (CSOs).
Retrieved from https://www.mwra.com/03sewer/html/sewcso.htm
31
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MassDOT. (2022, August). MassDOTHighway Impaired Waters Program. Retrieved from
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Mattson, M. D., & Isaac, R. A. (1999). Calibration of Phosphorus Export Coefficients for Total
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Moore, R. B., Johnston, C. M., Smith, R. A., & Milstead, B. (2011). Source and delivery of
nutrients to receiving waters in the Northeastern and Mid-Atlantic Regions of the United
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National Research Council. (2000). Clean Coastal Waters: Understanding and Reducing the
Effects of Nutrient Pollution. Washington, D.C.: National Academies Press.
National Research Council. (2008). Urban Stormwater Management in the United States.
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Neponset River Watershed Association. (2014). Neponset River Estuary ACEC Water Quality
and Restoration Action Plan.
Neponset River Watershed Association. (2017). Hotspot Monitoring 2017 Report.
Pitt, R., Maestre, A., & Morquecho, R. (2004). The National Stormwater Quality Database
(NSQD, Version 1.1).
Roy, A. H., & Schuster, W. D. (2009). Assessing Impervious Surface Connectivity and
Applications for Watershed Management. Journal of the American Water Resource
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Runoff Management: Technical and Institutional Issues. Madison, WI: North American
Lake Management Society.
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amended). Retrieved August 10, 2022, from https://www.epa.gov/npdes-
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USEPA. (2001). Nutrient Criteria Technical Guidance Manual -Esturine and Coastal Marine
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Clean Water Act Section 303(d) Program.
USEPA. (2014). Fact Sheet to the 2014 Draft MA Small MS4 Permit.
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for Use in Fulfilling Phosphorus Load Reduction Requirements in EPA Region 1
Stormwater Permits.
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https://www.epa.gov/mysticriver/live-water-quality-data-mystic-river
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https://www.epa.gov/charlesriver/live-water-quality-data-lower-charles-river
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https://www.epa.gov/neponsetriver
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https://www.epa.gov/charlesriver/charles-river-initiative
Wang, S., Ma, Y., Zhang, X., & Shen, Z. (2022). Transport and sources of nitrogen in
stormwater runoff at the urban catchment scale. Science of the Total Environment,
150281.
Waschbusch, R. J. (2000). Sources of Phosphorus in Stormwater and Street Dirt from two Urban
Residential Basins in Madison, Wisconsin, 1994-1995. National conference on Tools for
Urban Water Resource Management and Protection (pp. 15-55). US EPA.
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ATTACHMENT 1 - RDA Charles, Mystic, Neponset 2022
ATTACHMENT 1
Clean Water Act Residual Designation Determination for Certain Stormwater Discharges in the
Charles, Mystic, and Neponset River Watersheds, in Massachusetts
List of Communities Included in this Residual Designation
Charles River Watershed
Mystic River Watershed
Neponset River Watershed
Arlington
Arlington
Quincy
Ashland
Belmont
Boston
Bellingham
Boston
Milton
Belmont
Burlington
Dedham
Boston
Cambridge
Westwood
Brookline
Chelsea
Dover
Cambridge
Everett
Medfield
Dedham
Lexington
Walpole
Dover
Maiden
Foxborough
Foxborough
Medford
Sharon
Franklin
Melrose
Stoughton
Holliston
Reading
Canton
Hopedale
Revere
Norwood
Hopkinton
Somerville
Randolph
Lexington
Stoneham
Lincoln
Wakefield
Medfield
Watertown
Medway
Wilmington
Mendon
Winchester
Milford
Winthrop
Millis
Woburn
Natick
Needham
Newton
Norfolk
Somerville
Sherborn
Walpole
Waltham
Watertown
Wayland
Wellesley
Weston
Page 1 of 2
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ATTACHMENT 1 - RDA Charles, Mystic, Neponset 2022
Westwood
Wrentham
Page 2 of 2
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ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
ATTACHMENT 2
Clean Water Act Residual Designation Determination for Certain Stormwater Discharges in the
Charles, Mystic, and Neponset River Watersheds, in Massachusetts
Charles River Watershed Impairments Based on Final Massachusetts Integrated List of Waters for the
Clean Water Act 2018/2020 Reporting Cycle
Waterbody
AUJD
Description
Impairment
Charles: Alder Brook
MA72-22
Headwaters, perennial portion
northwest of the Route 135 and
South Street intersection,
Needham to mouth at confluence
with the Charles River, Needham.
Benthic Macroinvertebrates;
Nutrient/Eutrophication Biological
Indicators
Charles: Beaver Brook
MA72-12
Headwaters, outlet Beaver Pond,
Bellingham to mouth at
confluence with the Charles
River, Bellingham.
Escherichia Coli (E. Coli)
Charles: Beaver Brook
MA72-28
Headwaters, perennial portion
north of Route 2, Lexington to
mouth at confluence with the
Charles River, Waltham (one
culverted portion approximately
2900 feet (0.55mile)).
(Flow Regime Modification*); (Non-
Native Aquatic Plants*); (Other
anthropogenic substrate
alterations*); (Water Chestnut*);
Algae; Chloride; Dissolved Oxygen;
Escherichia Coli (E. Coli); Organic
Enrichment (Sewage) Biological
Indicators; Phosphorus, Total;
Sedimentation/Siltation
Charles: Beaver Pond
MA72004
Bellingham/Milford.
Mercury in Fish Tissue
Charles: Beaver Pond
MA72006
Franklin.
(Fanwort*); (Non-Native Aquatic
Plants*)
Charles: Bogastow Brook
MA72-16
Headwaters, outlet Factory Pond,
Holliston to mouth at inlet South
End Pond, Millis.
(Dewatering*); Escherichia Coli (E.
Coli); Fecal Coliform
Charles: Brookline
Reservoir
MA72010
Brookline.
Charles: Bulloughs Pond
MA72011
Newton.
Algae; Nutrient/Eutrophication
Biological Indicators
Charles: Cambridge
Reservoir
MA72014
Waltham/Lincoln/Lexington.
Chloride
Charles: Cambridge
Reservoir, Upper Basin
MA72156
Lincoln/Lexington.
Aquatic Plants (Macrophytes);
Chloride; Turbidity
Page 1 of 11
-------
ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: Cedar Swamp
Pond
MA72016
locally known as "Milford Pond",
Milford.
(Eurasian Water Milfoil,
Myriophyllum Spicatum*); (Non-
Native Aquatic Plants*); Dissolved
Oxygen; Mercury in Fish Tissue
Charles: Chandler Pond
MA72017
Boston.
Algae; Nutrient/Eutrophication
Biological Indicators; Phosphorus,
Total; Transparency / Clarity
Charles: Charles River
MA72-01
Headwaters, outlet Echo Lake,
Hopkinton to Dilla Street (just
upstream of Cedar Swamp Pond),
Milford.
(Dewatering*); (Flow Regime
Modification*); Dissolved Oxygen
Charles: Charles River
MA72-03
From Milford WWTF discharge
(NPDES: MA0100579), Hopedale
to outlet Box Pond, Bellingham
(through former 2006 segment:
Box Pond MA72008).
Algae; DDT in Fish Tissue; Dissolved
Oxygen Supersaturation;
Escherichia Coli (E. Coli); Organic
Enrichment (Sewage) Biological
Indicators; Phosphorus, Total
Charles: Charles River
MA72-04
From outlet Box Pond,
Bellingham to inlet Populatic
Pond, Norfolk/Medway (one
culverted portion approximately
350 feet (0.07mile)).
(Flow Regime Modification*);
Ambient Bioassays - Chronic
Aquatic Toxicity; Chlordane in Fish
Tissue; DDT in Fish Tissue;
Escherichia Coli (E. Coli); Fish
Bioassessments; Mercury in Fish
Tissue; Nutrient/Eutrophication
Biological Indicators; Phosphorus,
Total; Temperature
Charles: Charles River
MA72-05
From outlet Populatic Pond,
Norfolk/Medway to South Natick
Dam (NATID: MA00341), Natick.
(Fanwort*); (Non-Native Aquatic
Plants*); (Water Chestnut*); Algae;
Benthic Macroinvertebrates;
Chlordane in Fish Tissue; DDT in
Fish Tissue; Dissolved Oxygen;
Dissolved Oxygen Supersaturation;
Mercury in Fish Tissue;
Nutrient/Eutrophication Biological
Indicators; Phosphorus, Total;
Turbidity
Page 2 of 11
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ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: Charles River
MA72-06
From South Natick Dam (NATID:
MA00341), Natick to Chestnut
Street, Needham/Dover.
(Eurasian Water Milfoil,
Myriophyllum Spicatum*);
(Fanwort*); (Flow Regime
Modification*); (Non-Native
Aquatic Plants*); (Water
Chestnut*); Algae; Cause Unknown
[Fish Population Imbalance]; DDT in
Fish Tissue; Fish Bioassessments;
Nutrient/Eutrophication Biological
Indicators; PCBs in Fish Tissue;
Phosphorus, Total
Charles: Charles River
MA72-07
From Chestnut Street,
Needham/Dover to Watertown
Dam (NATID: MA00456),
Watertown.
(Curly-leaf Pondweed*); (Eurasian
Water Milfoil, Myriophyllum
Spicatum*); (Fish Passage Barrier*);
(Flow Regime Modification*); (Non-
Native Aquatic Plants*); (Water
Chestnut*); Benthic
Macroinvertebrates; DDT in Fish
Tissue; Escherichia Coli (E. Coli);
Fish Bioassessments; Harmful Algal
Blooms; Nutrient/Eutrophication
Biological Indicators; PCBs in Fish
Tissue; Phosphorus, Total;
Temperature
Charles: Charles River
MA72-33
From outlet Cedar Swamp Pond,
Milford to the Milford WWTF
discharge (NPDES: MA0100579),
Hopedale (formerly part of 2006
segment: Charles River MA72-02)
(two culverted portions totaling
approximately 1100 feet
(0.21mile) (as of 2008 excluding
the approximately 0.8 mile
through segment: Cedar Swam
(Physical substrate habitat
alterations*); Escherichia Coli (E.
Coli); Nutrient/Eutrophication
Biological Indicators
Page 3 of 11
-------
ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: Charles River
MA72-36
From Watertown Dam (NATID:
MA00456), Watertown to the
Boston University Bridge,
Boston/Cambridge (formerly part
of 2006 segment: Charles River
MA72-08).
(Fish Passage Barrier*); (Flow
Regime Modification*); (Non-
Native Aquatic Plants*); (Non-
Native
Fish/Shellfish/Zooplankton*);
(Water Chestnut*); Chlorophyll-a;
DDT in Fish Tissue; Dissolved
Oxygen; Escherichia Coli (E. Coli);
Fish Bioassessments; Harmful Algal
Blooms; Nutrient/Eutrophication
Biological Indicators; Oil and
Grease; PCBs in Fish Tissue; pH,
High; Phosphorus, Total; Sediment
Bioassay [Acute Toxicity
Freshwater]; T ransparency / Clarity;
Unspecified Metals in Sediment
Charles: Charles River
MA72-38
From Boston University Bridge,
Boston/Cambridge to mouth at
the New Charles River Dam
(NATID: MA01092), Boston
(formerly part of 2006 segment:
Charles River MA72-08).
(Fish Passage Barrier*); (Flow
Regime Modification*); Cause
Unknown [Sediment Screening
Value (Exceedance)]; Chlorophyll-a;
Combined Biota/Habitat
Bioassessments; DDT in Fish Tissue;
Dissolved Oxygen; Dissolved
Oxygen Supersaturation;
Escherichia Coli (E. Coli); Harmful
Algal Blooms;
Nutrient/Eutrophication Biological
Indicators; Odor; Oil and Grease;
PCBs in Fish Tissue; Phosphorus,
Total; Salinity; Temperature;
Transparency / Clarity
Charles: Cheese Cake
Brook
MA72-29
Emerges south of Route 16,
Newton to mouth at confluence
with the Charles River, Newton.
(Alteration in stream-side or littoral
vegetative covers*); (Other
anthropogenic substrate
alterations*); Algae; Dissolved
Oxygen Supersaturation;
Escherichia Coli (E. Coli); Fish
Bioassessments; Phosphorus, Total
Charles: Chestnut Hill
Reservoir
MA72023
Boston.
Page 4 of 11
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ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: Chicken Brook
MA72-34
Source, outlet Waseeka
Sanctuary Pond, Holliston to
mouth at confluence with the
Charles River, Medway.
Escherichia Coli (E. Coli)
Charles: Crystal Lake
MA72030
Newton.
Harmful Algal Blooms
Charles: Dopping Brook
MA72-40
Headwater outlet small unnamed
pond on Holliston/Sherborn
border to mouth at confluence
with Bogastow Brook,
Holliston/Sherborn.
Charles: Dug Pond
MA72034
Natick.
(Curly-leaf Pondweed*); (Non-
Native Aquatic Plants*)
Charles: Echo Lake
MA72035
Milford/Hopkinton.
Mercury in Fish Tissue
Charles: Factory Pond
MA72037
Holliston.
(Non-Native Aquatic Plants*);
Aquatic Plants (Macrophytes)
Charles: Farm Pond
MA72039
Sherborn.
-
Charles: Franklin
Reservoir Northeast
MA72095
Franklin.
(Water Chestnut*); Aquatic Plants
(Macrophytes); Turbidity
Charles: Franklin
Reservoir Southwest
MA72032
Franklin.
Aquatic Plants (Macrophytes);
Turbidity
Charles: Fuller Brook
MA72-18
Headwater south of Route 135,
Needham to mouth at confluence
with Waban Brook, Wellesley
(one culverted portion
approximately 360 feet
(0.07mile)).
(Physical substrate habitat
alterations*); Escherichia Coli (E.
Coli); Nutrient/Eutrophication
Biological Indicators;
Sedimentation/Siltation
Charles: Godfrey Brook
MA72-51
Perennial portion, South Main
Street, Milford to mouth at
confluence with the Charles
River, Milford.
Charles: Halls Pond
MA72043
Brookline.
-
Charles: Hammond Pond
MA72044
Newton.
-
Charles: Hardys Pond
MA72045
Waltham.
(Non-Native Aquatic Plants*);
(Water Chestnut*); Algae;
Phosphorus, Total; Turbidity
Charles: Hobbs Brook
MA72-45
Headwaters west of Bedford
Road, Lincoln to inlet Cambridge
Reservoir, Upper Basin, Lincoln
Chloride
Page 5 of 11
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ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: Hobbs Brook
MA72-46
From outlet Cambridge Reservoir,
Waltham to mouth at confluence
with Stony Brook, Weston.
Chloride
Charles: Hopping Brook
MA72-35
Source in Cedar Swamp, Holliston
to mouth at confluence with the
Charles River,
Bellingham/Medway.
Escherichia Coli (E. Coli)
Charles: Houghton Pond
MA72050
Holliston.
(Non-Native Aquatic Plants*);
Algae; Turbidity
Charles: Jamaica Pond
MA72052
Boston.
(Eurasian Water Milfoil,
Myriophyllum Spicatum*);
Dissolved Oxygen; Phosphorus,
Total
Charles: Jennings Pond
MA72053
Natick.
-
Charles: Kendrick Street
Pond
MA72055
Needham.
Turbidity
Charles: Kingsbury Pond
MA72056
Norfolk.
(Dewatering*)
Charles: Lake Archer
MA72002
Wrentham.
(Non-Native Aquatic Plants*)
Charles: Lake Pearl
MA72092
Wrentham.
(Eurasian Water Milfoil,
Myriophyllum Spicatum*); (Non-
Native Aquatic Plants*); Dissolved
Oxygen
Charles: Lake Waban
MA72125
Wellesley.
(Eurasian Water Milfoil,
Myriophyllum Spicatum*);
(Fanwort*); (Non-Native Aquatic
Plants*)
Charles: Lake Winthrop
MA72140
Holliston.
(Fanwort*); (Non-Native Aquatic
Plants*); 2,3,7,8-
Tetrachlorodibenzo-p-dioxin;
Aquatic Plants (Macrophytes)
Charles: Linden Pond
MA72063
Holliston.
Aquatic Plants (Macrophytes);
Turbidity
Charles: Little Farm Pond
MA72064
Sherborn.
-
Charles: Louisa Lake
MA72068
Milford.
(Non-Native Aquatic Plants*)
Charles: Lymans Pond
MA72070
Dover.
Aquatic Plants (Macrophytes);
Turbidity
Charles: Mill Brook
MA72-39
Source wetlands, Pine Street,
Medfield to mouth at confluence
with the Charles River, Medfield.
Page 6 of 11
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ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: Mill River
MA72-15
Headwaters, outlet Bush Pond,
Norfolk to mouth at confluence
with the Charles River, Norfolk.
(Curly-leaf Pondweed*); (Non-
Native Aquatic Plants*);
Temperature
Charles: Mine Brook
MA72-14
Headwaters in Franklin State
Forest, Franklin to mouth at
confluence with the Charles
River, Franklin (through former
2006 segment: Mine Brook Pond
MA72077) (HQW applies
upstream of former Franklin
WWTP discharge, approximately
4 miles upstream of mouth (note:
Franklin WWTP tied into Medway
(CRWPCD) on
(Habitat Assessment*); Escherichia
Coli (E. Coli); Temperature
Charles: Mirror Lake
MA72078
Wrentham/Norfolk.
(Curly-leaf Pondweed*); (Non-
Native Aquatic Plants*);
Nutrient/Eutrophication Biological
Indicators; Phosphorus, Total;
Transparency / Clarity
Charles: Morses Pond
MA72079
Wellesley/Natick.
(Eurasian Water Milfoil,
Myriophyllum Spicatum*);
(Fanwort*); (Non-Native Aquatic
Plants*)
Charles: Muddy River
MA72-11
Headwaters, outlet Ward Pond in
Olmstead Park, Boston through
Leverett Pond, Boston/Brookline
to confluence with Charles River,
Boston (four culverted portions
totaling approximately 2200 feet
(0.42mile)).
(Bottom Deposits*); (Flow Regime
Modification*); (Non-Native
Aquatic Plants*); (Physical
substrate habitat alterations*); DDT
in Fish Tissue; Dissolved Oxygen;
Escherichia Coli (E. Coli); Odor; Oil
and Grease; PCBs in Fish Tissue;
Phosphorus, Total; Turbidity;
Unspecified Metals in Sediment
Charles: Noannet Pond
MA72084
Westwood/Dover.
(Non-Native Aquatic Plants*)
Charles: Nonesuch Pond
MA72085
Natick/Weston.
(Curly-leaf Pondweed*); (Non-
Native Aquatic Plants*)
Charles: Norumbega
Reservoir
MA72086
[North Basin] Weston.
Charles: Norumbega
Reservoir
MA72087
[South Basin] Weston.
Page 7 of 11
-------
ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: Populatic Pond
MA72096
Norfolk.
Algae; Chlordane in Fish Tissue;
DDT in Fish Tissue; Dissolved
Oxygen; Dissolved Oxygen
Supersaturation; Mercury in Fish
Tissue; Nutrient/Eutrophication
Biological Indicators
Charles: Powissett Brook
MA72-20
Headwaters, outlet Noannet
Pond, Westwood to mouth at
confluence with the Charles
River, Dover.
Combined Biota/Habitat
Bioassessments
Charles: Rock Meadow
Brook
MA72-21
Headwaters, Fisher Meadow,
Westwood to mouth at
confluence with the Charles
River, Dedham.
Algae; Benthic Macroinvertebrates;
Dissolved Oxygen;
Nutrient/Eutrophication Biological
Indicators; Organic Enrichment
(Sewage) Biological Indicators;
Phosphorus, Total
Charles: Rosemary Brook
MA72-25
Headwaters, outlet Rosemary
Lake, Needham to mouth at
confluence with the Charles
River, Wellesley.
Dissolved Oxygen; Phosphorus,
Total
Charles: Sandy Pond
MA72105
Lincoln.
-
Charles: Sawmill Brook
MA72-23
Headwaters, Newton to mouth at
confluence with the Charles
River, Boston.
Chloride; Dissolved Oxygen;
Escherichia Coli (E. Co 1 i); Organic
Enrichment (Sewage) Biological
Indicators; Phosphorus, Total
Charles: Scarboro Golf
Course Pond
MA72107
Boston.
(Non-Native Aquatic Plants*)
Charles: Seaverns Brook
MA72-44
Headwaters outlet Norumbega
Reservoir, Weston to mouth at
confluence with the Charles
River, Weston.
Escherichia Coli (E. Coli)
Charles: Sewall Brook
MA72-49
Headwaters outlet Washington
Street Pond, south off Route 16
(Washington Street), Sherborn to
mouth at confluence with Charles
River, Sherborn.
Charles: Shepards Brook
MA72-50
Perennial portion, north of Brook
Street, Franklin to mouth at
confluence with Charles River,
Franklin.
Charles: South End Pond
MA72109
Millis.
--
Page 8 of 11
-------
ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: South Meadow
Brook
MA72-24
From emergence west of Parker
Street, Newton to mouth at
confluence with the Charles
River, Newton (three culverted
portions totaling approximately
2870 feet (0.54mile)).
(Bottom Deposits*); (Debris*);
(Physical substrate habitat
alterations*); Dissolved Oxygen;
Escherichia Coli (E. Coli); Fish
Bioassessments; Phosphorus, Total;
Trash; Turbidity
Charles: Stony Brook
MA72-26
Headwaters, outlet Beaver Pond,
Lincoln to mouth at inlet Stony
Brook Reservoir,
Waltham/Weston (mileage
includes length of braid).
Temperature
Charles: Stony Brook
MA72-37
Headwaters, outlet Turtle Pond,
Boston to culvert entrance,
Boston (two culverted portions
totaling approximately 740 feet
(0.14mile)).
Charles: Stony Brook
Reservoir
MA72114
Waltham/Weston.
Charles: Stop River
MA72-09
Headwaters south of Route 1A,
Wrentham to Norfolk-Walpole
MCI discharge (NPDES:
MA0102253), Norfolk (through
former 2006 segment: Highland
Lake MA72047).
Ambient Bioassays - Chronic
Aquatic Toxicity; Dissolved Oxygen;
Phosphorus, Total
Charles: Stop River
MA72-10
From Norfolk-Walpole MCI
discharge, Norfolk to confluence
with Charles River, Medfield.
Organic Enrichment (Sewage)
Biological Indicators; Phosphorus,
Total; Temperature
Charles: Todd Pond
MA72117
Lincoln.
-
Charles: Trout Brook
MA72-19
Headwaters, outlet Channings
Pond, Dover to mouth at
confluence with the Charles
River, Dover.
Nutrient/Eutrophication Biological
Indicators; Temperature
Charles: Uncas Pond
MA72122
Franklin.
(Non-Native Aquatic Plants*);
Dissolved Oxygen
Charles: Unnamed
Tributary
MA72-27
Headwaters, outlet Stony Brook
Reservoir, Waltham/Weston to
mouth at confluence with the
Charles River, Waltham/Weston.
(Dewatering*); (Flow Regime
Modification*)
Page 9 of 11
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ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: Unnamed
Tributary
MA72-30
Locally known as "Laundry Brook"
- emerges north of California
Street, Watertown to mouth at
confluence with the Charles
River, Watertown (stream not
depicted on 1987 Newton USGS
map).
(Physical substrate habitat
alterations*); Enterococcus;
Escherichia Coli (E. Coli); Odor;
Phosphorus, Total; Total Suspended
Solids (TSS); Turbidity
Charles: Unnamed
Tributary
MA72-31
Locally known as "Millers River" -
from emergence near Route 93,
Cambridge/Boston to mouth at
confluence with the Charles
River, Cambridge.
(Bottom Deposits*); (Debris*);
(Habitat Assessment*); Flocculant
Masses; Metals; Odor; Oil and
Grease; Petroleum Hydrocarbons;
Polychlorinated Biphenyls (PCBs);
Polycyclic Aromatic Hydrocarbons
(PAHs) (Aquatic Ecosystems);
Scum/Foam;
Sedimentation/Siltation; Trash;
Turbidity; Unspecified Metals in
Sediment
Charles: Unnamed
Tributary
MA72-32
Locally known as "Sawins Brook" -
emerges east of Elm Street,
Watertown to mouth at
confluence with the Charles
River, Watertown (one culverted
portion approximately 360 feet
(0.07mile)).
Escherichia Coli (E. Coli)
Charles: Unnamed
Tributary
MA72-41
Unnamed tributary to the Charles
River, outlet Lymans Pond, Dover
to mouth at confluence with the
Charles River, Dover.
Escherichia Coli (E. Coli)
Charles: Unnamed
Tributary
MA72-42
Unnamed tributary to the Charles
River, from outlet unnamed pond
north of South Street, Natick to
mouth at confluence with the
Charles River, Natick.
Benthic Macroinvertebrates
Charles: Unnamed
Tributary
MA72-43
Unnamed tributary to Morses
Pond, headwaters outlet Reeds
Pond, Wellesley to mouth at
confluence with Morses Pond,
Wellesley.
Escherichia Coli (E. Coli)
Page 10 of 11
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ATTACHMENT 2 - RDA Charles, Mystic, Neponset 2022
Charles: Unnamed
Tributary
MA72-47
Headwaters west of Forbes Road,
Lexington to mouth at confluence
with Hobbs Brook, Lincoln.
Chloride
Charles: Unnamed
Tributary
MA72-48
Headwaters northeast of the
Trapelo Road/Smith Street
intersection, Waltham to mouth
at inlet Cambridge Reservoir,
Lexington.
Chloride
Charles: Waban Brook
MA72-17
Headwaters, outlet Lake Waban,
Wellesleyto mouth at confluence
with the Charles River, Wellesley.
Temperature
Charles: Walker Pond
MA72126
Millis.
-
Charles: Waseeka
Sanctuary Pond
MA72155
Holliston.
Charles: Weld Pond
MA72131
Dedham.
-
Charles: Weston
Reservoir
MA72134
Weston.
Charles: Weston Station
Pond
MA72135
Weston.
Page 11 of 11
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ATTACHMENT 3 - RDA Charles, Mystic, Neponset 2022
ATTACHMENT 3
Clean Water Act Residual Designation Determination for Certain Stormwater Discharges in the
Charles, Mystic, and Neponset River Watersheds, in Massachusetts
Mystic River Watershed Impairments Based on Final Massachusetts Integrated List of Waters for the
Clean Water Act 2018/2020 Reporting Cycle
Waterbody
AUJD
Description
Impairment
Boston Harbor:
Mystic: Aberjona River
MA71-01
Source just south of Birch Meadow
Drive, Reading to inlet Upper Mystic
Lake at Mystic Valley Parkway,
Winchester (portion culverted
underground), (through former 2010
segments: Judkins Pond MA71021
and Mill Pond MA71031).
(Physical substrate habitat alterations*);
Ammonia, Un-ionized; Arsenic; Arsenic
in Sediment; Benthic
Macroinvertebrates; Chloride; Dissolved
Oxygen; Escherichia Coli (E. Coli); Fish
Bioassessments; Phosphorus, Total;
Sediment Bioassay [Chronic Toxicity
Freshwater]
Boston Harbor:
Mystic: Alewife Brook
MA71-20
From emergence north of
Cambridgepark Drive, Cambridge to
mouth at confluence with Mystic
River, Arlington/Somerville (formerly
part of 2016 segment: Alewife Brook
MA71-04).
(Debris*); (Water Chestnut*); Chloride;
Copper; Copper in Sediment; Dissolved
Oxygen; Escherichia Coli (E. Coli);
Flocculant Masses; Lead; Lead in
Sediment; Odor; Oil and Grease; PCBs in
Fish Tissue; Phosphorus, Total;
Scum/Foam; Sediment Bioassay [Chronic
Toxicity Freshwater]; Transparency/
Clarity; Trash
Boston Harbor:
Mystic: Belle Isle Inlet
MA71-14
From tidegate at Bennington Street,
Boston/Revere to confluence with
Winthrop Bay, Boston/Winthrop.
Cause Unknown [Contaminants in Fish
and/or Shellfish]; Fecal Coliform; PCBs in
Fish Tissue
Boston Harbor:
Mystic: Bellevue Pond
MA71004
Medford.
Boston Harbor:
Mystic: Blacks Nook
MA71005
Cambridge.
(Non-Native Aquatic Plants*); (Water
Chestnut*); Nutrient/Eutrophication
Biological Indicators; Transparency /
Clarity
Page 1 of 5
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ATTACHMENT 3 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
Mystic: Chelsea River
MA71-06
From confluence with Mill Creek,
Chelsea/Revere to confluence with
Boston Inner Harbor, Chelsea/East
Boston.
(Debris*); Ammonia, Un-ionized; Cause
Unknown [Contaminants in Fish and/or
Shellfish; Sediment Screening Value
(Exceedance)]; Dissolved Oxygen; Fecal
Coliform; Odor; PCBs in Fish Tissue;
Petroleum Hydrocarbons; Trash;
Turbidity
Boston Harbor:
Mystic: Clay Pit Pond
MA71011
Belmont.
Chlordane in Fish Tissue
Boston Harbor:
Mystic: Cummings
Brook
MA71-10
Headwaters east of Wright Street,
Woburn to confluence with Fowle
Brook, Woburn.
Escherichia Coli (E. Coli)
Boston Harbor:
Mystic: Ell Pond
MA71014
Melrose.
Chlorophyll-a; Fecal Coliform; Harmful
Algal Blooms; Phosphorus, Total; Total
Suspended Solids (TSS); Transparency /
Clarity
Boston Harbor:
Mystic: Fellsmere
Pond
MA71016
Maiden.
Harmful Algal Blooms
Boston Harbor:
Mystic: Hills Pond
MA71018
Arlington.
(Eurasian Water Milfoil, Myriophyllum
Spicatum*)
Boston Harbor:
Mystic: Horn Pond
MA71019
Woburn.
(Curly-leaf Pondweed*); (Fish Passage
Barrier*); (Non-Native Aquatic Plants*);
DDT in Fish Tissue; Dissolved Oxygen;
Harmful Algal Blooms; Phosphorus, Total
Boston Harbor:
Mystic: Little Pond
MA71024
Belmont.
(Water Chestnut*); Harmful Algal
Blooms
Boston Harbor:
Mystic: Little River
MA71-21
Headwaters, outlet Little Pond,
Belmont to MWRA CSO outfall
(MWR003) approximately 150 feet
upstream of mouth at the confluence
with Alewife Brook, Cambridge
(formerly part of 2016 segment:
Alewife Brook MA71-04).
(Debris*); (Water Chestnut*); Chloride;
Copper; Copper in Sediment; Dissolved
Oxygen; Escherichia Coli (E. Coli);
Flocculant Masses; Lead; Lead in
Sediment; Odor; Oil and Grease; PCBs in
Fish Tissue; Phosphorus, Total;
Scum/Foam; Sediment Bioassay;
Transparency / Clarity; Trash
Boston Harbor:
Mystic: Little River
MA71-22
From MWRA CSO outfall (MWR003,
approximately 150 feet upstream of
mouth), Cambridge to mouth at
confluence with Alewife Brook,
Cambridge (formerly part of 2016
segment: Alewife Brook MA71-04).
(Debris*); Copper; Copper in Sediment;
Dissolved Oxygen; Escherichia Coli (E.
Coli); Flocculant Masses; Lead; Lead in
Sediment; Odor; Oil and Grease; PCBs in
Fish Tissue; Phosphorus, Total;
Scum/Foam; Sediment Bioassay;
Transparency / Clarity; Trash
Page 2 of 5
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ATTACHMENT 3 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
Mystic: Lower Mystic
Lake
MA71027
Arlington/Medford.
DDT in Fish Tissue; Dissolved Oxygen;
Hydrogen Sulfide; PCBs in Fish Tissue;
Salinity; Sediment Bioassay [Chronic
Toxicity Freshwater]
Boston Harbor:
Mystic: Maiden River
MA71-05
From culverted portion south of
Charles Street, Maiden to confluence
with Mystic River, Everett/Medford.
(Debris*); (Water Chestnut*); Chlordane
in Fish Tissue; DDT in Fish Tissue;
Dissolved Oxygen; Dissolved Oxygen
Supersaturation; Escherichia Coli (E.
Coli); Fecal Coliform; Flocculant Masses;
Odor; Oil and Grease; PCBs in Fish
Tissue; pH, High; Phosphorus, Total;
Scum/Foam; Sediment Bioassay [Chronic
Toxicity Freshwater]; Temperature; Total
Suspended Solids (TSS); Transparency /
Clarity; Trash
Boston Harbor:
Mystic: Mill Brook
MA71-07
Headwaters south of Massachusetts
Avenue, Lexington to inlet of Lower
Mystic Lake, Arlington (portions
culverted underground).
(Physical substrate habitat alterations*);
Benthic Macroinvertebrates; Escherichia
Coli (E. Coli)
Boston Harbor:
Mystic: Mill Creek
MA71-08
From Route 1, Chelsea/Revere to
confluence with Chelsea River,
Chelsea/Revere.
Cause Unknown [Contaminants in Fish
and/or Shellfish]; Fecal Coliform; PCBs in
Fish Tissue
Boston Harbor:
Mystic: Munroe Brook
MA71-15
Headwaters, north of Solomon Pierce
Road, Lexington to the mouth at inlet
Arlington Reservoir, Lexington
(includes culverted portion).
Escherichia Coli (E. Coli)
Boston Harbor:
Mystic: Mystic River
MA71-02
Outlet Lower Mystic Lake,
Arlington/Medford to Amelia Earhart
Dam, Somerville/Everett.
(Eurasian Water Milfoil, Myriophyllum
Spicatum*); (Fish Passage Barrier*);
(Non-Native Aquatic Plants*); (Water
Chestnut*); Arsenic; Chlordane in Fish
Tissue; Chlorophyll-a; DDT in Fish Tissue;
Dissolved Oxygen; Dissolved Oxygen
Supersaturation; Escherichia Coli (E.
Coli); PCBs in Fish Tissue; pH, High;
Phosphorus, Total; Sediment Bioassay
[Chronic Toxicity Freshwater];
Transparency / Clarity
Page 3 of 5
-------
ATTACHMENT 3 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
MA71-03
Amelia Earhart Dam,
Ammonia, Un-ionized; Cause Unknown
Mystic: Mystic River
Somerville/Everett to confluence with
Boston Inner Harbor,
Chelsea/Charlestown (Includes Island
End River).
[Contaminants in Fish and/or Shellfish;
Sediment Screening Value
(Exceedance)]; Dissolved Oxygen; Fecal
Coliform; Flocculant Masses;
Nutrient/Eutrophication Biological
Indicators; Odor; Oil and Grease; PCBs in
Fish Tissue; Petroleum Hydrocarbons;
Scum/Foam
Headwaters, outlet Horn Pond,
Boston Harbor:
Woburn to mouth at inlet Wedge
(Fish Passage Barrier*); Benthic
Mystic: Pond Brook
MA71-16
Pond, Winchester.
Macroinvertebrates
Headwaters near Route 145, Revere
to Bennington Street
Boston Harbor:
tidegate/confluence with Belle Isle
Mystic: Sales Creek
MA71-12
Inlet, Boston/Revere.
--
Headwaters, west of Dix Road
Boston Harbor:
Extention, Woburn to confluence with
Mystic: Shaker Glen
Fowle Brook, Woburn (portion
Brook
MA71-11
culverted underground).
Escherichia Coli (E. Coli)
Boston Harbor:
Mystic: Spot Pond
MA71039
Stoneham/Medford.
--
Headwaters outlet Spot Pond,
Stoneham to mouth at confluence
Boston Harbor:
with Maiden River, south of Charles
Mystic: Spot Pond
Street, Maiden (approximately 55%
Brook
MA71-17
culverted).
--
(Curly-leaf Pondweed*); (Eurasian Water
Milfoil, Myriophyllum Spicatum*);
(Water Chestnut*); Chlordane in Fish
Tissue; DDT in Fish Tissue; Dissolved
Boston Harbor:
Oxygen; Harmful Algal Blooms;
Mystic: Spy Pond
MA71040
Arlington.
Phosphorus, Total
Unnamed tributary locally known as
'Meetinghouse Brook', from
emergence south of Route 16/east of
Winthrop Street, Medford to
confluence with the Mystic River,
Medford. (brook not apparent on
Boston Harbor:
1985 Boston North USGS quad - 2005
Mystic: Unnamed
orthophotos used to delineate
Tributary
MA71-13
stream).
Escherichia Coli (E. Coli)
Page 4 of 5
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ATTACHMENT 3 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
Mystic: Unnamed
Tributary
MA71-19
Unnamed tributary to Little River
(locally known as 'Wellington Brook'),
headwaters south of Trapelo Road,
Belmont to inlet Claypit Pond,
Belmont (portions culverted
underground) (1893 Boston USGS
quad used to delineate stream).
Benthic Macroinvertebrates
Boston Harbor:
Mystic: Upper Mystic
Lake
MA71043
Winchester/Arlington/Medford.
(Curly-leaf Pondweed*); (Non-Native
Aquatic Plants*); Dissolved Oxygen;
Dissolved Oxygen Supersaturation;
Enterococcus
Boston Harbor:
Mystic: Wedge Pond
MA71045
Winchester.
Dissolved Oxygen; Harmful Algal Blooms;
Phosphorus, Total
Boston Harbor:
Mystic: Winn Brook
MA71-09
Headwaters near Juniper Road and
the Belmont Hill School, Belmont to
confluence with Little Pond, Belmont
(portions culverted underground).
(Physical substrate habitat alterations*);
Escherichia Coli (E. Coli)
Boston Harbor:
Mystic: Winter Pond
MA71047
Winchester.
(Non-Native Aquatic Plants*);
Nutrient/Eutrophication Biological
Indicators
Page 5 of 5
-------
ATTACHMENT 4 - RDA Charles, Mystic, Neponset 2022
ATTACHMENT 4
Clean Water Act Residual Designation Determination for Certain Stormwater Discharges in the
Charles, Mystic, and Neponset River Watersheds, in Massachusetts
Mystic River Watershed Impairments Based on Final Massachusetts Integrated List of Waters for the
Clean Water Act 2018/2020 Reporting Cycle
Waterbody
AUJD
Description
Impairment
Boston Harbor:
Neponset: Beaver
Brook
MA73-19
Headwaters (perennial portion),
near Moose Hill Street, Sharon
through Sawmill Pond to mouth at
confluence with Massapoag Brook,
Sharon.
Benthic Macroinvertebrates;
Dissolved Oxygen
Boston Harbor:
Neponset: Beaver
Meadow Brook
MA73-20
Headwaters, outlet of Glenn Echo
Pond, Stoughton, to mouth at inlet
of Bolivar Pond, Canton.
Dissolved Oxygen; Escherichia Coli
(E. Coli)
Boston Harbor:
Neponset: Billings
Street/East Street
Pond
MA73065
Sharon.
(Non-Native Aquatic Plants*)
Boston Harbor:
Neponset: Blue Hills
Reservoir
MA73004
Quincy.
Boston Harbor:
Neponset: Bolivar
Pond
MA73005
Canton.
(Fanwort*); (Non-Native Aquatic
Plants*); Turbidity
Boston Harbor:
Neponset: Bubbling
Brook
MA73-11
Headwaters (perennial portion),
near North Street, Walpole to mouth
at inlet Pettee Pond,
Walpole/Westwood border.
Benthic Macroinvertebrates; Fish
Bioassessments
Boston Harbor:
Neponset: Buckmaster
Pond
MA73006
Westwood.
Boston Harbor:
Neponset: Clark Pond
MA73008
Walpole.
(Non-Native Aquatic Plants*);
(Water Chestnut*)
Page 1 of 7
-------
ATTACHMENT 4 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
Neponset: Cobbs Pond
MA73009
Walpole.
(Non-Native Aquatic Plants*);
Dissolved Oxygen;
Nutrient/Eutrophication Biological
Indicators; Transparency / Clarity
Boston Harbor:
Neponset: East Branch
MA73-05
East Branch Neponset River -
Headwaters, outlet of Forge Pond,
Canton through East Branch Pond to
mouth at confluence with Neponset
River, Canton (locally known as
Canton River).
(Dewatering*); (Flow Regime
Modification*); Benthic
Macroinvertebrates; DDT in Fish
Tissue; Dissolved Oxygen;
Escherichia Coli (E. Coli); Fecal
Coliform; Metals; PCBs in Fish
Tissue; Temperature; Unspecified
Metals in Sediment
Boston Harbor:
Neponset: Ellis Pond
MA73018
Norwood.
(Fanwort*); (Non-Native Aquatic
Plants*)
Boston Harbor:
Neponset: Farrington
Pond
MA73040
Stoughton.
(Non-Native Aquatic Plants*)
Boston Harbor:
Neponset: Flynns
Pond
MA73019
Medfield.
Boston Harbor:
Neponset: Forge Pond
MA73020
Canton.
Turbidity
Boston Harbor:
Neponset: Ganawatte
Farm Pond
MA73037
Walpole/Sharon/Foxborough.
Aquatic Plants (Macrophytes);
Dissolved Oxygen; Transparency /
Clarity
Boston Harbor:
Neponset: Germany
Brook
MA73-15
Headwaters, east of Winter Street,
Norwood to inlet of Ellis Pond,
Norwood.
Escherichia Coli (E. Coli); Fecal
Coliform; pH, High; Phosphorus,
Total
Boston Harbor:
Neponset: Glen Echo
Pond
MA73022
Canton/Stoughton.
(Non-Native Aquatic Plants*)
Boston Harbor:
Neponset: Gulliver
Creek
MA73-30
From confluence Unquity Brook,
Milton to confluence Neponset
River, Milton (Note: Unquity Brook
culverted, confluence not visible on
quad).
Cause Unknown [Contaminants in
Fish and/or Shellfish]; Fecal
Coliform; PCBs in Fish Tissue
Boston Harbor:
Neponset: Hammer
Shop Pond
MA73023
Sharon.
Page 2 of 7
-------
ATTACHMENT 4 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
Neponset: Hawes
Brook
MA73-16
Headwaters, outlet of Ellis Pond,
Norwood to mouth at confluence
with Neponset River, Norwood.
Escherichia Coli (E. Coli); Fecal
Coliform; Odor
Boston Harbor:
Neponset: Jewells
Pond
MA73026
Medfield.
(Non-Native Aquatic Plants*)
Boston Harbor:
Neponset: Lymans
Pond
MA73021
Westwood.
Boston Harbor:
Neponset: Massapoag
Brook
MA73-21
Headwaters, outlet Hammer Shop
Pond, Sharon to mouth at inlet Forge
Pond, Canton (through former 2010
segment: Manns Pond MA73028).
(Curly-leaf Pondweed*);
(Fanwort*); (Non-Native Aquatic
Plants*); Benthic
Macroinvertebrates; Phosphorus,
Total
Boston Harbor:
Neponset: Massapoag
Lake
MA73030
Sharon.
(Non-Native Aquatic Plants*);
Mercury in Fish Tissue
Boston Harbor:
Neponset: Memorial
Pond
MA73012
Walpole.
Aquatic Plants (Macrophytes);
Turbidity
Boston Harbor:
Neponset: Mill Brook
MA73-08
From headwaters (perennial portion)
north of Hartford Street, Medfield to
mouth at inlet of Jewells Pond,
Medfield.
(Dewatering*); Benthic
Macroinvertebrates; Dissolved
Oxygen; Temperature
Boston Harbor:
Neponset: Mill Brook
MA73-12
Source northeast of Ledgewood
Drive, Dover to inlet of Pettee Pond,
Westwood.
Boston Harbor:
Neponset: Mine Brook
MA73-09
Headwaters, outlet of Jewells Pond,
Medfield, to the inlet of Turner
Pond, Walpole.
Dissolved Oxygen
Boston Harbor:
Neponset: Mother
Brook
MA73-28
Headwaters at the Charles River
Diversion control structure, Dedham
to mouth at confluence with
Neponset River, Boston [Reported as
MA72-13 until May 3, 2000],
(Debris*); (Dewatering*); (Flow
Regime Modification*); Color; DDT
in Fish Tissue; Dissolved Oxygen;
Escherichia Coli (E. Coli); Fecal
Coliform; Mercury in Fish Tissue;
Odor; PCBs in Fish Tissue;
Phosphorus, Total; Trash
Page 3 of 7
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ATTACHMENT 4 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
Neponset: Neponset
Reservoir
MA73034
Foxborough.
(Fanwort*); (Non-Native Aquatic
Plants*); Algae; Turbidity
Boston Harbor:
Neponset: Neponset
River
MA73-01
Outlet of Neponset Reservoir,
Foxborough to confluence with East
Branch, Canton (through former
2010 segments: Crackrock Pond
MA73010 and Bird Pond MA73002)
(HQW qualifer applies upstream of
Crackrock Pond Dam (NATID:
MA00816)) (SARIS note: the upper
portion of segment between
Neponset Reservoir Dam
(Curly-leaf Pondweed*); (Fish
Passage Barrier*); (Non-Native
Aquatic Plants*); Cadmium; DDT in
Fish Tissue; Dissolved Oxygen;
Escherichia Coli (E. Coli); Metals;
Nutrient/Eutrophication Biological
Indicators; PCBs in Fish Tissue;
Phosphorus, Total; Unspecified
Metals in Sediment
Boston Harbor:
Neponset: Neponset
River
MA73-02
Confluence with East Branch, Canton
to confluence with Mother Brook,
Boston.
(Debris*); (Fish Passage Barrier*);
DDT in Fish Tissue; Dissolved
Oxygen; Escherichia Coli (E. Coli);
Fecal Coliform; Flocculant Masses;
Metals; Oil and Grease; PCBs in Fish
Tissue; Scum/Foam; Trash;
Turbidity; Unspecified Metals in
Sediment
Boston Harbor:
Neponset: Neponset
River
MA73-03
Confluence with Mother Brook,
Boston to Neponset River Baker
Chocolate Dam (NATID: MA01093),
Milton/Boston.
(Curly-leaf Pondweed*); (Debris*);
(Fish Passage Barrier*); DDT in Fish
Tissue; Dissolved Oxygen;
Enterococcus; Escherichia Coli (E.
Coli); Fecal Coliform; Flocculant
Masses; Metals; Oil and Grease;
PCBs in Fish Tissue; PCBs in
Sediment; Polychlorinated
Biphenyls (PCBs); Scum/Foam;
Trash; Unspecified Metals in
Sediment
Boston Harbor:
Neponset: Neponset
River
MA73-04
Milton Lower Falls Dam (Neponset
River Baker Chocolate Dam, NAT ID:
MA01093), Milton/Boston to mouth
at Dorchester Bay, Boston/Quincy.
(Debris*); Cause Unknown
[Contaminants in Fish and/or
Shellfish]; Dissolved Oxygen;
Enterococcus; Fecal Coliform; PCBs
in Fish Tissue; Trash; Turbidity
Boston Harbor:
Neponset: Pecunit
Brook
MA73-25
Headwaters east of Carey Circle and
west of Pecunit Street, Canton to
mouth at confluence with Neponset
River, Canton.
Benthic Macroinvertebrates;
Escherichia Coli (E. Coli)
Page 4 of 7
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ATTACHMENT 4 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
Neponset: Pequid
Brook
MA73-22
Headwaters east of York Street,
Canton to mouth at inlet of Forge
Pond, Canton (excluding the
approximately 1.3 miles through
Reservoir Pond, segment MA73048).
Dissolved Oxygen
Boston Harbor:
Neponset: Pettee
Pond
MA73036
Walpole/Westwood.
Mercury in Fish Tissue
Boston Harbor:
Neponset: PineTree
Brook
MA73-29
Headwaters, outlet Hillside Pond,
Milton to mouth at confluence with
the Neponset River, Milton (through
former 2010 segment: Pope's Pond
MA73044).
(Physical substrate habitat
alterations*); Aquatic Plants
(Macrophytes); Dissolved Oxygen;
Escherichia Coli (E. Coli); Fecal
Coliform; Turbidity
Boston Harbor:
Neponset: Pinewood
Pond
MA73039
Stoughton.
(Aquatic Plants (Macrophytes)*);
(Non-Native Aquatic Plants*)
Boston Harbor:
Neponset:
Plantingfield Brook
MA73-23
Headwaters east of Thatcher Street,
Westwood, to mouth at confluence
with Purgatory Brook, Norwood
(portion culverted).
(Dewatering*); Escherichia Coli (E.
Coli)
Boston Harbor:
Neponset: Ponkapoag
Pond
MA73043
Canton/Randolph.
(Eurasian Water Milfoil,
Myriophyllum Spicatum*);
(Fanwort*); (Non-Native Aquatic
Plants*); Mercury in Fish Tissue
Boston Harbor:
Neponset: Ponkapog
Brook
MA73-27
Headwaters, outlet of Ponkapoag
Pond, Canton to confluence with
Neponset River, Canton.
Escherichia Coli (E. Coli); Fecal
Coliform
Boston Harbor:
Neponset: Purgatory
Brook
MA73-24
Headwaters east of Farm Lane,
Westwood to confluence with
Neponset River, Norwood.
(Debris*); Escherichia Coli (E. Coli);
Fecal Coliform; Trash
Boston Harbor:
Neponset: Reservoir
Pond
MA73048
Canton.
(Eurasian Water Milfoil,
Myriophyllum Spicatum*);
(Fanwort*); (Non-Native Aquatic
Plants*); Mercury in Fish Tissue
Boston Harbor:
Neponset: Russell
Pond
MA73003
Milton.
(Curly-leaf Pondweed*); (Non-
Native Aquatic Plants*); Turbidity
Page 5 of 7
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ATTACHMENT 4 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
Neponset: Sprague
Pond
MA73053
Boston/Dedham.
Boston Harbor:
Neponset: Steep Hill
Brook
MA73-18
Headwaters, outlet of Pinewood
Pond, Stoughton, to mouth at inlet
of Bolivar Pond, Canton.
Escherichia Coli (E. Coli)
Boston Harbor:
Neponset: Town Pond
MA73056
Stoughton.
(Fanwort*); (Non-Native Aquatic
Plants*)
Boston Harbor:
Neponset: Tubwreck
Brook
MA73-07
Headwaters - small unnamed pond
southeast of Powissett Street, Dover
to confluence with Mill Brook just
southwest of Dover/Medfield
border.
Boston Harbor:
Neponset: Turner
Pond
MA73058
Walpole.
(Fanwort*); (Non-Native Aquatic
Plants*)
Boston Harbor:
Neponset: Turners
Pond
MA73059
Milton.
Dissolved Oxygen;
Nutrient/Eutrophication Biological
Indicators; Turbidity
Boston Harbor:
Neponset: Unnamed
Tributary
MA73-10
Headwaters, outlet Turner Pond,
Walpole to confluence with
Neponset River, Walpole.
Boston Harbor:
Neponset: Unnamed
Tributary
MA73-14
Headwaters, outlet Willet Pond,
Walpole/Norwood, to inlet Ellis
Pond, Norwood.
Boston Harbor:
Neponset: Unnamed
Tributary
MA73-31
Headwaters, outlet of Massapoag
Lake, Sharon to mouth at inlet of
Hammer Shop Pond, Sharon (not
depicted on 1987 Mansfield USGS
quad).
Fecal Coliform
Boston Harbor:
Neponset: Unnamed
Tributary
MA73-32
From the outlet of Town Pond,
Stoughton to mouth at confluence
with Steep Hill Brook, Stoughton.
Benthic Macroinvertebrates;
Escherichia Coli (E. Coli); pH, Low;
Phosphorus, Total
Page 6 of 7
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ATTACHMENT 4 - RDA Charles, Mystic, Neponset 2022
Boston Harbor:
Neponset: Unnamed
Tributary
MA73-33
Locally known as "Meadow Brook" -
From where the
underground/culverted stream
emerges east of Pleasant Street,
Norwood to confluence with
Neponset River, Norwood.
Benthic Macroinvertebrates;
Escherichia Coli (E. Coli);
Phosphorus, Total
Boston Harbor:
Neponset: Unnamed
Tributary
MA73-34
Headwaters, outlet Clark Pond,
Walpole to confluence with
Neponset River, Walpole (locally
considered part of Spring Brook)
(excluding the approximately 0.2
miles through Diamond Pond and
the approximately 0.2 miles through
Memorial Pond segment MA73012).
(Debris*); Benthic
Macroinvertebrates; Trash
Boston Harbor:
Neponset: Unnamed
Tributary
MA73-35
Unnamed tributary to Beaver Brook,
headwaters outlet small unnamed
pond east of Moose Hill Street,
Sharon to mouth at confluence with
Beaver Brook, Sharon.
Boston Harbor:
Neponset: Unquity
Brook
MA73-26
Isolated (urban): Headwaters
(perennial portion) near Randolph
Avenue, Milton to mouth at
confluence with Gulliver Creek,
Milton (Note: culverted portions of
segment total approximately 1/3 of
segment length, or 0.5 miles).
(Dewatering*); (Physical substrate
habitat alterations*); Dissolved
Oxygen; Escherichia Coli (E. Coli);
Fecal Coliform; Fish
Bioassessments; pH, Low;
Phosphorus, Total;
Sedimentation/Siltation
Boston Harbor:
Neponset: Willet Pond
MA73062
Walpole/Westwood/Norwood (at
northern end, includes former 2008
segment: Unnamed Tributary MA73-
13).
Mercury in Fish Tissue
Boston Harbor:
Neponset: Woods
Pond
MA73055
Stoughton.
(Non-Native Aquatic Plants*)
Page 7 of 7
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ATTACHMENT 5 - RDA Charles, Mystic, Neponset 2022
ATTACHMENT 5
Clean Water Act Residual Designation Determination for Certain Stormwater Discharges in the
Charles, Mystic, and Neponset River Watersheds, in Massachusetts
Watershed Maps Including Communities with EJ Concerns
-------
Charles River
Watershed
Great
Meadows
Nat'l
Wildlife
Refuge
Woburn
HERA
Scale 1 : 225,000
when printed at 81A x 11"
0 1 2 3 4 5 Kilometers
LllllI I I I I
I" " " IJ
1 1
4 5 Miles
Water Features: National Hydrography Dataset
Basemap: ESRI, USGS, NOAA, IMPS,
DeLorme and the GIS User Community.
US EPA R1 GIS Center Map #13732, 9/13/2022
Iborough
Sudbury
Reservoir
Cordaville
Melrose
Maiden
Medford
(Everett Rever
.Chelsea;
tf>n (Airpo
Framingham
Center
quant
Wollastor
Qu
Blue Hills
Reservation
Moose Hill
ildlift
Stoughton
Foxboroi
Communities with EJ Concerns
This map highlights U.S. Census
block groups that have at least one
of the 12 EJ Indexes at or above the
80th percentile in the nation (using
EJScreen 2021 data):
Woonsocket
1 - 5 Indexes
6-9 Indexes
10-12 Indexes
(9,420
Acres
Total)
-------
Mystic River
Watershed
&EPA
Scale 1:112,000
when printed at 8V2 x 11"
0 1
2 Kilometers
_l
I I I I I I
0 1
2 Miles
Water Features: National Hydrography Dataset
Basemap: ESRI, USGS, NOAA, IMPS,
DeLorme and the GIS User Community.
US EPA R1 GIS Center Map #13732, 9/13/2022
Hundred
Acre
Meadow
Communities with EJ Concerns
This map highlights U S Census
block groups that have at least one
of the 12 EJ Indexes at or above the
80th percentile in the nation (using
EJScreen 2021 data):
1 - 5 Indexes
6-9 Indexes
10-12 Indexes
(7,709
Acres
Total)
Ced
Swamp
West
Peabody
Breakheart
Reservation
Lynn Woods
Reservation
West Lynn
Point of
Pines
Broad
Sound
-------
Neponset River
Watershed
&EPA
Scale 1:120,000
when printed at 81A x 11"
0 1 2 Kilometers
1 i i I I I I
I l l l l I 1
0 1 2 Miles
Water Features: National Hydrography Dataset
Basemap: ESRI, USGS, NOAA, NPS,
DeLorme and the GIS User Community.
US EPA R1 GIS Center Map #13732, 9/13/2022
Grove Halt
I
'IS
Bellevue
Clarendc
Hills,
iiNepxinset
%r State
ield
Pondville
Randolph
J \
Borderland
State Park
Foxborough
F. Gilbert
Hills State
Forest
Whiteville
East
w7!
V3'
\ "V Squantu
&
\iVolTarfeJ
Sou
Quir
Holb
Brook
Montellc
Brockto
Communities with EJ Concerns
This map highlights U.S. Census block groups with at
least one of the 12 EJ Indexes at or above the 80th
percentile in the nation (using EJScreen 2021 data):
1 - 5 Indexes
6-9 Indexes
10-12 Indexes
(6,552
Acres
Total)
-------
ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
ATTACHMENT 6
Clean Water Act Residual Designation Determination for Certain Stormwater Discharges in the
Charles, Mystic, and Neponset River Watersheds, in Massachusetts
Charles River Watershed Stormwater Total Phosphorus Analysis
INTRODUCTION
On May 19, 2019, the Conservation Law Foundation (CLF) and the Charles River Watershed Association
(CRWA) petitioned EPA to use its Clean Water Act residual designation authority to designate
commercial, industrial, institutional, and multi-family residential properties greater than 1 acre in size in
the Charles River Watershed (CRW) as needing National Pollutant Discharge Elimination System (NPDES)
permits for stormwater discharges that significantly contribute pollutants to waters of the U.S.,
contribute to water quality standards violations, and/or that need to be controlled in order to meet
Total Maximum Daily Load (TMDL) wasteload allocations (WLAs). EPA then undertook an analysis to
quantify the total phosphorus (TP) loading from all private properties in the CRW. The goal of this
analysis was to determine whether stormwater discharges from private properties were contributing to
violations of water quality standards in the Charles River and required NPDES permit coverage. In
addition, this analysis set out to identify which land use classes were contributing the most phosphorus
to the Charles River through stormwater and to identify and evaluate options for maximizing
phosphorus reductions efficiently (i.e., fewest stormwater controls installed). The results of the analysis
can be used to better understand the potential magnitude of impact on TP loads from private
properties, as well as understand the TP reductions in the CRW necessary to meet water quality
standards that would result from designation and permitting actions. As described below, the analysis
resulted in the following broad conclusions:
1. Private properties in the CRW generate approximately 50,738 pounds of TP per year from
stormwater, which is 58% of the baseline TP load from stormwater sources identified in the
Charles River TMDLs.
2. Without stormwater controls on some private properties in the CRW, the burden of phosphorus
reduction falls completely on municipalities and this burden makes achieving the TMDL goals
and water quality standards in the Charles River unlikely if not infeasible.
3. The greater the percent impervious cover (IC) on a property, the greater the mass load of
phosphorus in stormwater from that property compared to other properties of similar size.
4. Of private properties in the CRW, commercial, industrial, and institutional classifications have
the highest percentage of impervious cover per property.
5. Over 50% of the IC in the CRW is located on a subset of commercial, industrial, institutional, and
multi-family residential properties, all of which contain greater than 1 acre of IC.
6. The most efficient way to reduce TP discharges from private properties is to target stormwater
controls on properties based on the amount of IC on the properties (which is proportional to the
amount of TP generated) and based on property types (which also affects amount of TP
Page 1 of 2
-------
ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
generated), thereby maximizing TP reduction while minimizing the number of properties
installing controls.
II. METHODS
To quantify TP loads in stormwater derived from private properties within the CRW, the first step was to
identify the private properties within the watershed, identify the land use of each property, and
calculate the area of IC on each property. To accomplish this, the following data files were used:
Files obtained from MassGIS:
o Municipal Boundaries Shapefile - provides town name and town boundary
o Tax Assessors Parcels Shapefile - provides location, parcel ID (LocJD), and area
of each parcel (property)
o Assessors Table L3 - provides use code, site address, owner information, and
year built
o Land Cover Land Use Shapefile - provides land cover name and generalized use
name
o Land Use Table L3 - provides type code and a code description
o UC Land Use Table L3 - provides use code and use code description
o 2005 Impervious Cover Raster File - provides location and area of 2005 IC
o 2016 Impervious Cover Shapefile - provides location and area of 2016 IC
Files obtained from EPA:
o MS4 Boundary- provides location and area covered under the MS4
o CRW Boundary - provides location and area of the CRW
o CSA Boundary - provides location and area of communities with Combined
Sewer Systems (CSSs)
A Geographic Information System (GIS) model was used to create a data file that calculated the property
area, the associated land use, and the amount of IC on each property in the watershed (USEPA, 2022).
Extensive quality assurance and quality control was completed on the resulting dataset to ensure proper
classification of property information and to correct any errors in the underlying dataset (USEPA, 2022).
From this data file, EPA identified or quantified the following for each individual property: size (acres),
land use classification, ownership information, location, and area (acres) and percent of impervious
cover, pervious cover, forest, and wetlands.
The dataset was then used to calculate the TP generated from each property in pounds per year using
the Phosphorus Load Export Rates (PLERs) documented in the MA MS4 Permit. This parcel loading
analysis was accomplished by applying stormwater PLERs to land surface areas with differing land use
and cover types such as commercial, industrial, high-density residential uses with impervious cover (IC)
and pervious grassed and landscaped cover (i.e., developed land pervious). The PLERs provide estimates
of the average annual phosphorus load export delivered by untreated stormwater from areas with
distinct cover and use types for the same climatic conditions as used in the development of the Charles
River phosphorus TMDLs. In general, the amount of impervious cover on a property increases the
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
volume of stormwater derived from that property or land use class, which increases the loading of
pollutants found in stormwater, including phosphorus. (Shaver, Horner, Skupien, May, & Ridley, 2007)
(Center For Watershed Protection, 2003) (Schueler, 2011) (Chen, Theller, Gitau, Engel, & Harbor, 2017).
Multiplying the area of interest by the distinct PLER provides an estimate of the average annual
phosphorus loading rate. For example, one (1) acre of impervious cover in commercial use is estimated
to deliver 1.78 lbs of phosphorus per year (e.g., 1.0 acre of commercial IC X 1/78 Ibs/acre/yr = 1.78
Ib/yr). Attachment 1 to Appendix F of the 2016 Massachusetts MS4 Permit includes a detailed
description of assigning PLERs to different land use classes in the CRW (USEPA, 2016) and this is also
summarized in the MEMORANDUM- Charles River Watershed Private Parcel Analysis GIS Methods
(USEPA, 2022). These specific PLERs create a comprehensive methodology for calculating phosphorus
load reductions and increases based on land use information for projects and properties in the CRW.
Table 1 below displays the land use classifications used in this analysis and the associated PLERs for
impervious cover and pervious cover for the given land use. As seen in Table 1, the amount of
phosphorus generated by a land use type increases with the increased human utilization of that land
use. For instance, the forest land use has a phosphorus loading rate of 1.52 Ib/acre/year of TP for
impervious areas within the forested area, while Commercial areas have a phosphorus loading rate of
1.78 Ib/acre/year of TP for impervious areas. In addition, as seen in Table 1, impervious cover generates
up to, and in excess of, 10 times the annual phosphorus load compared to pervious areas on that same
land use class due to the increase in stormwater generated by impervious cover compared to previous
cover (USEPA, 2016). For a detailed description of PLER and land use classes used for this analysis see
MEMORANDUM- Charles River Watershed Private Parcel Analysis GIS Methods (USEPA, 2022).
PLER - Developed Land
PLER Aggregate Land Use
PLER Impervious Cover
Pervious Area (e.g.,
Category
(Ibs/acre/year)
landscaped area)
(Ibs/acre/year)
Commercial/Industrial
1.78
0.207
Multi Family/High Density
Residential
2.32
0.207
Single Family/Medium Density
Residential
1.96
0.207
Forest/Agriculture
1.52
0.207
Table 1 : PLERs used to calculate annual phosphorus load from properties in the CRW. PLERs for
Developed Land Pervious Area do not include forested or wetland areas
a. Limitations
This analysis used the Massachusetts Tax Assessors Database to assign land uses to properties and
calculate impervious cover contained on each property. The Massachusetts Tax Assessors Database and
the 2016 Impervious Cover Shapefile does not contain information for public roads, highways, and right
of ways, and therefore, the analysis did not capture all the impervious cover and phosphorus loading
from all land area in the CRW. However, this analysis focuses on total phosphorus load in stormwater
from private properties, not from public parcels already regulated under the 2016 MA MS4 permit, the
Boston Individual MS4 Permit, or to parcels owned or operated by the Massachusetts Department of
Transportation already subject to an NPDES permit.
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
For the purposes of this analysis, EPA excluded privately owned roads and properties on the border of
the watershed where less than 50% of the property is in the watershed. Applying this exclusion to the
analysis resulted in less than 1% of the total land area (2.5 square miles) of the private properties in the
CRW being omitted from the analysis (USEPA, 2022). Given the low number of missing properties in the
dataset, it is not expected that the overall watershed loading analysis and comparison of phosphorus
loading from different sources is impacted.
The analysis does not attempt to estimate or calculate the connectedness (i.e., how much stormwater is
delivered directly to nearby waterbodies) of any property identified in the analysis. The values in Table 1
represent the delivery of phosphorus from an area that is directly connected to a waterbody or
municipal stormwater system. In addition, the pervious annual phosphorus loading rate was set at the
weighted average of pervious area estimated loading rate based on soil type distribution in the CRW.
Given the significantly lower contribution of phosphorus from pervious areas (approximately 25% of the
stormwater phosphorus load in the CRW (USEPA, 2016)) this value is meant to approximate the impact
of pervious cover stormwater without having site specific soil type data. Therefore, all phosphorus
loading estimates in the property analysis should be considered conservative for the property or land
use classification identified. This removes assumptions necessary for stormwater delivery and focuses
on phosphorus generated at the source on each property, allowing for a more direct comparison of
potential magnitude of impact.
This analysis does not contain calculations of phosphorus export from public lands. Given the limitations
contained in the 2016 Land Cover Dataset and Impervious Cover Dataset from MassGIS, accurate
calculation of phosphorus loading from public lands (primarily roadways and rights-of-way) is not
feasible. However, given this analysis focuses on phosphorus export stormwater from private
properties, the exclusion of public land does not affect the analysis.
b. Other Relevant Information for this Analysis
Massachusetts Department of Environmental Protection (MassDEP) established two Total Maximum
Daily Loads (TMDLs) for the CRW. On October 17, 2007, EPA approved the Final TMDL for Nutrients in
the Lower Charles River Basin (Lower Charles TMDL) (Massachusetts Department of Environmental
Protection , 2007) and on June 10, 2011 EPA approved the Total Maximum Daily Load for Nutrients in
the Upper/Middle Charles River (Upper/Middle Charles TMDL) (Massachusetts Department of
Environmental Protection, 2011). The Lower Charles TMDL and the Upper/Middle Charles TMDL
baseline phosphorus load from stormwater sources was calculated at 87,432 pounds of total
phosphorus per year. Both TMDLs set Waste Load Allocations (WLAs) that specify reductions for
discharges of phosphorus throughout the entire CRW from publicly owned treatment works, combined
sewer overflows and stormwater discharges. To meet TMDL goals, the more developed lands
(Commercial, Industrial, and High and Medium Density Residential) need to reduce total phosphorus
loads by 65% annually while the less developed, low density residential lands need to reduce total
phosphorus loads by 45% annually. While the TMDLs did not consider land classified as "institutional" as
its own category, this analysis included a 65% reduction requirement for this classification, which is
consistent with the other similarly developed land use categories. The TMDLs set a watershed-wide
stormwater phosphorus load reduction requirement of 47,347 pounds per year, bringing the overall
phosphorus load from stormwater from a baseline of 87,432 pounds per year to an allowable load of
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
40,085 pounds per year of phosphorus from stormwater sources. Overall, the stormwater TP load
reduction will need to come from multiple stormwater sources; this analysis does not attempt to
partition this overall stormwater TP required reduction between private and public properties. The
47,347 pounds per year TP reduction is referenced in this analysis as the stormwater required TP
reduction from all stormwater sources in the CRW.
III. RESULTS AND DISCUSSION
a. Current Charles River Watershed Characterization
Based on the analysis described above, EPA identified 196,645 properties in the CRW. These properties
comprise a total of 166,703 acres or 84% of the entire watershed. These properties are primarily single
family residential (36%), institutional (20%), commercial (10.5%), open land (8.6%), multi-family
residential (5.4%) Industrial (2.6%) and Agricultural (1.2%) (Figure 1). The remaining 16% of the
watershed is comprised of waterbodies, public roads, and rights-of-way without tax codes in the Tax
Assessors Parcels Shapefile (indicated as "other" in Figure 1). Figure 2 displays a map of the Charles
River Watershed and 2016 land use classifications. In total, the CRW is approximately 40% public land
(Institutional Federal, Institutional State, Institutional Local, Open Land and "Other" land use categories)
and 60% private land (all other land use categories displayed in Figure 1).
35.6%
Figure 1: Acres of CRW Property by Classifications*
*The "Other" category accounts for land not in the property analysis, including waterbodies, public
roads, and rights-of-way.
Commercial, 10.5%
Open Land, 8.6%
Institutional Local, 11.6%
Other, 15.9%
Institutional Federal,
2 Family Residential, 1.
Multi-Family Residential,
Industrial, 2.6%
Institutional State, 2.
Institutional Private, 4.
Single Family Residential,
Agriculture, 1.2%
Multi-Residential >8,0.5%
3 Family Residential, 0.4%
Multi-Residential 4-8,0.3%
Page 5 of 5
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
Land Use Classifications for the
Charles River Watershed
Legend
Charles River
Water Bodies
Charles River Watershed
Classification
Agriculture
Single Family Residential
Commercial
| Multi-Family Residential
| Public Institutional
Private Institutional
I Industrial
Land
|o
1 2
4
CT>
. 00
1 ¦ m iviiiesi
Figure 2: Land Use Classifications in the Charles River Watershed. Land
Use data from MassGIS 2016 Land Cover Land Use Shapefile
b. Private Properties
Since stormwater discharges from most of the public land area (state and federal roads, public
institutions, state and locally owned open space, etc.) in the CRW are currently regulated by the 2016
Massachusetts MS4 Permit, the Boston Individual MS4 Permit, or are on parcels owned or operated by
the Massachusetts Department of Transportation already subject to an NPDES permit, this analysis
focuses on phosphorus loads from private property including commercial, industrial, private
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
institutional, single family residential, and multi-family residential properties.1 In addition, there are
13,635 properties located in areas served by combined sewers; these properties were removed from
this analysis as the stormwater is delivered to the Deer Island Wastewater Treatment Plant. Agricultural
land was also excluded from the analysis due to the low number of properties (208) and relatively low
phosphorus load compared to the other private property land uses (approximately 0.5% of the overall
TP load). Therefore, this analysis focused on 166,489 private commercial, industrial, institutional, and
residential properties in the CRW which comprise 114,298 acres (Table 2). As demonstrated in Table 1,
the phosphorus loading rate of IC is approximately 10 times that of developed, pervious cover (e.g. for
commercial/industrial the load is 1.78 Ibs/acre/year for impervious vs 0.207 Ibs/acre/year for pervious).
Therefore, EPA's analysis of phosphorus load included a parcel-by-parcel calculation of the amount of IC
land area and pervious land area. The appropriate PLERs (Impervious vs Pervious) were then applied on
a parcel-by-parcel basis in accordance with its designated the land use (USEPA, 2022). From this parcel-
by-parcel analysis, EPA determined that the stormwater runoff from private commercial, industrial,
institutional, and residential properties identified in the analysis generate 50,738 pounds (43,787+6,951)
of total phosphorus per year. In addition, EPA also determined that while impervious cover comprises
about 20% of the total land area from these properties (22,424/114,298 acres), it actually contributes
86% of the total phosphorus load from these properties (43,787/50,738 lbs/year) (Table 2). While
pervious areas, such as lawns and other various covers, generate stormwater runoff and contribute to
the overall phosphorus loading, the load from these areas is much less than the load from impervious
cover.
Classification
#
Properties
Acres
ICArea
(Acres)
%IC
ICTP
Load
(Ibs/yr)
Pervious
TP Load
(Ibs/yr)*
Average
TP Load
per
Property
(Ibs/yr/pr
operty)
Commercial
9,548
20,120
5,657
28%
10,102
1,273
1.19
Industrial
1,000
5,016
1,468
29%
2,609
330
2.94
Institutional Private
4,255
8,986
1,412
16%
2,446
416
0.67
Multi-Family Residential
33,412
9,870
3,987
40%
9,223
428
0.29
Single Family Residential
118,274
70,307
9,900
14%
19,407
4,504
0.20
TOTAL
166,489
114,298
22,424
43,787
6,951
Table 2: Private Properties
*Pervious load does not include TP loads from forest or wetland areas on private properties
1 The GIS dataset contained several different designations for multi-family residential (see Figure 1). For this
analysis, EPA combined all residential properties with two or more families into one category called "multi-family
residential."
Page 7 of 7
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
Impervious Cover on Private Properties
in the Charles River Watershed
Legend
Charles River
| Private IC
Watershed
Miles
Figure 3: Impervious cover on private property in the Charles River Watershed.
Data from MassGIS 2016 Impervious Cover Layer
Based on the analysis and as shown in Table 2, the estimated overall TP generated by private properties
in the CRW is substantial and could be as much as 50,738 pounds per year (43,787+6,951), which is 58%
(50,738/87,432) of the baseline stormwater load estimated by the TMDL analysis.
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
If all 166,489 private properties were to install stormwater controls on their properties to reduce TP in
stormwater discharges by 65% on Commercial, Industrial, Institutional and Multi-family properties and
by 45% from single family homes (as suggested by the Lower and Upper/Middle Charles TMDLs), the
overall TP reduction from stormwater sources could be up to 28,197 pounds of phosphorus per year, or
approximately 60% of the required watershed reduction in TP from the TMDLs (28,197/47,347).
However, requiring all private properties to take action on their properties presents several challenges
and may not be necessary to meet TMDL reduction goals. For instance, if we assume the public
properties in the CRW contribute 36,694 pounds of phosphorus per year (baseline loading from the
TMDL [87,432]- calculated load from private property [50,738]) and all public properties were able to
reduce this load by 65%, the resulting reduction in TP load would be 23,851 pounds of phosphorus per
year, or approximately 50% of the required reduction from the TMDL (23,851/47,347). These scenarios
added together would equal a reduction of 52,048 (28,197+23,851) pounds of phosphorus per year
removed, which would be greater than the TMDL target reduction of 47,347 pounds of phosphorus per
year. While simplified, this indicates that there has to be a mix of actions on public and private land in
order to meet TMDL goals and also highlights the fact that no one group can meet the TMDL goals alone
(e.g. if no actions were taken on private property to reduce phosphorus in stormwater discharges the
TMDL goals cannot be met).
c. Single Family Properties
There are approximately 118,274 single family residential properties in the watershed that consist of
approximately 70,307 acres (Table 2 and Figure 5). Single family residential land use accounts for the
highest number and acreage of properties; however, just 14% of its acreage (10,114 acres) is
impervious. Therefore, the resulting phosphorus load for single family residential land use is distributed
over many properties making the contribution from any one property relatively low (0.20
Ibs/year/property) compared to other land use types (Figure 4).
From a phosphorus reduction perspective, this suggests that focusing efforts on other property types
would lead to larger reductions while also requiring stormwater controls on fewer properties. For
instance, if all single-family homes implemented structural controls to treat phosphorus on their
properties and achieved a 45% reduction in TP generated per year in stormwater as required by the
TMDL, the watershed would see an approximate reduction of 10,760 pounds of TP per year for the
implementation of 118,274 individual structural practices, or 0.09 pounds of TP reduced per year per
property. If, however, a 65% reduction as required by the TMDL was applied to commercial properties,
the watershed would see an approximate reduction of 7,394 pounds per year of TP for the
implementation of 9,548 structural practices, or 0.77 pounds of TP reduced per year per property. This
example indicates an increase in efficiency of 8.6 times if controls were focused on commercial property
instead of single-family residential properties. This efficiency is primarily driven by the amount of IC in
the different land use classes. Looking at Table 2, it is evident that the phosphorus load from IC is larger
than the phosphorus load from pervious cover on private properties. Single family residential properties
have an average of 7.4 times less IC per property when compared to commercial properties in the CRW,
indicating that structural controls would be needed on over seven single family properties to achieve the
same amount of phosphorus reduction that could be achieved by placing controls on one commercial
property.
Page 9 of 9
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
Acres of Property Phosphorus Load per Property
80,000 3.50
70'000 H 3.00
60,000 / \
/ \ I 50
50,000 / \
/ \ ¦ 200
40,000 / \
/ \ ¦
30,000 / \
\
20,000 \
10,000 ¦ °-50
¦ ¦ ¦ ¦ ¦
Commercial Industrial Institutional Multi-Family Single Family
Private Residential Residential
Property Type
Figure 4: Acres of Commercial, Industrial, Private Institutional, Multi-Family Residential and
Single Family Residential are in the CRW with associated phosphorus load generated by each land
use
Page 10 of 10
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
Figure 5: Acres of Private Properties by Classification and the Associated Impervious Cover (IC)
(Acres) of Each Classification
d. Other Private Properties
When single family residential properties are removed from the dataset, the annual total phosphorus
load from commercial, industrial, institutional, and multi-family residential (CIIM) properties is 26,827
pounds per year (Table 3 and Table 4), including 24,380 pounds per year (91%) generated from IC. A
65% reduction in the total load from CIIM properties as suggested by the TMDL would result in a
potential reduction of 17,437 pounds per year. This reduction amounts to approximately 37% of the
47,347 pounds per year stormwater TP reduction required by the TMDL for the CRW. This reduction
would require stormwater controls on 48,215 properties (i.e. the total number of CIIM properties in the
CRW).
Page 11 of 11
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
While it may be possible to achieve 37% of the overall TP reduction needed through practices on all
48,215 CIIM properties, it likely is not the most efficient way to reduce TP in stormwater from CIIM
properties in the watershed. To identify a more efficient way to target properties for stormwater
controls, EPA compared the impact of requiring controls on properties based on property size versus
requiring controls based on the amount of impervious cover. As shown in Figure 6, there are 4,728 CIIM
properties >1 acre in property size. These properties generate around 18,476 pounds of TP per year.
There are 2,257 CIIM properties with >1 acre of IC, which generate around 15,048 pounds of TP per
year. Comparatively, the properties >1 acre in size generate on average about 3.9 pounds of TP per
property per year, while the properties with IC >1 acre generate approximately 6.7 pounds of TP per
property per year. Overall, targeting phosphorus reduction actions on properties with larger IC instead
of overall property size is more effective to reduce the phosphorus load. In this example it would require
stormwater controls on approximately half the number of properties while achieving only a slight
decline in TP reduction.
Page 12 of 12
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
Property Size
Acres
ICArea
(Acres)
# Properties
% of Total
CRW CIIM
IC
TP Load
(Ibs/yr)
Annual TP Load
Reduction
Assuming 65%
Removal (Ibs/yr)
% of Total
Reduction
Required in
Watershed
# Properties
per % of Total
Reduction
Required
Average IC
Acres/Property
All Properties*
43,991
12,524
48,215
100%
26,827
17,437
36.8
1,309.2
0.26
>0.1 Acre
43,091
11,851
35,193
95%
25,339
16,471
34.8
1,011.7
0.34
>0.25 Acre
39,629
9,757
12,354
78%
20,635
13,412
28.3
436.1
0.79
>0.5 Acre
37,793
8,792
7,016
70%
18,611
12,097
25.6
274.6
1.25
>1 Acre
36,045
7,845
4,519
63%
16,737
10,879
23.0
196.7
1.74
>2 Acres
33,640
6,619
2,797
53%
14,353
9,329
19.7
141.9
2.37
>3 Acres
31,953
5,882
2,107
47%
12,910
8,391
17.7
118.9
2.79
>4 Acres
30,711
5,405
1,749
43%
11,959
7,774
16.4
106.5
3.09
>5 Acres
29,534
4,970
1,487
40%
11,090
7,209
15.2
97.7
3.34
>6 Acres
28,451
4,567
1,288
36%
10,295
6,692
14.1
91.1
3.55
>7 Acres
27,292
4,231
1,109
34%
9,606
6,244
13.2
84.1
3.81
>8 Acres
26,425
3,961
994
32%
9,047
5,880
12.4
80.0
3.99
>9 Acres
25,644
3,754
902
30%
8,619
5,602
11.8
76.2
4.16
>10 Acres
24,870
3,558
820
28%
8,214
5,339
11.3
72.7
4.34
>11 Acres
24,095
3,382
746
27%
7,845
5,099
10.8
69.3
4.53
>12 Acres
23,141
3,073
663
25%
7,225
4,696
9.9
66.8
4.63
>13 Acres
22,405
2,947
604
24%
6,946
4,515
9.5
63.3
4.88
>14 Acres
21,944
2,865
570
23%
6,762
4,395
9.3
61.4
5.03
>15 Acres
21,219
2,673
520
21%
6,361
4,135
8.7
59.5
5.14
>16 Acres
20,773
2,530
491
20%
6,076
3,949
8.3
58.9
5.15
>17 Acres
20,181
2,378
455
19%
5,749
3,737
7.9
57.6
5.23
>18 Acres
19,726
2,272
429
18%
5,529
3,594
7.6
56.5
5.30
>19 Acres
19,301
2,169
406
17%
5,310
3,452
7.3
55.7
5.34
>20 Acres
18,634
2,039
372
16%
5,015
3,260
6.9
54.0
5.48
Table 3: Commercial, Industrial, Institutional, and Multi-Family Residential Properties Based on Property Size.
Page 13 of 14
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
Impervious
Cover Size
Acres
ICArea
(Acres)
# Properties
% of Total
CRW CIIM
IC
TP Load
(Ibs/yr)
Annual TP Load
Reduction
Assuming 65%
removal (Ibs/yr)
% of Total
Reduction
Required in
Watershed
# Properties
per % ofTotal
Reduction
Required
Average IC
Acres/Property
All Properties
43,991
12,524
48,215
100%
26,827
17,437
36.8
1,309.2
0.26
>0.1 Acre
31,240
10,660
17,238
85%
21,908
14,240
30.1
573.2
0.62
>0.25 Acre
26,955
9,119
6,320
73%
18,439
11,985
25.3
249.7
1.44
>0.5 Acre
23,013
8,230
3,808
66%
16,477
10,710
22.6
168.3
2.16
>1 Acre
19,721
7,041
2,120
56%
14,091
9,159
19.3
109.6
3.32
>2 Acres
15,252
5,540
1,048
44%
11,033
7,171
15.1
69.2
5.29
>3 Acres
12,206
4,592
658
37%
9,121
5,929
12.5
52.5
6.98
>4 Acres
10,097
3,919
463
31%
7,782
5,059
10.7
43.3
8.46
>5 Acres
8,274
3,358
337
27%
6,642
4,317
9.1
37.0
9.97
>6 Acres
7,198
2,917
256
23%
5,747
3,736
7.9
32.4
11.39
>7 Acres
6,195
2,545
199
20%
5,008
3,255
6.9
28.9
12.79
>8 Acres
5,505
2,267
162
18%
4,461
2,900
6.1
26.5
14.00
>9 Acres
4,984
2,020
133
16%
3,986
2,591
5.5
24.3
15.19
>10 Acres
4,436
1,757
105
14%
3,474
2,258
4.8
22.0
16.74
>11 Acres
4,042
1,570
87
13%
3,120
2,028
4.3
20.3
18.05
>12 Acres
3,488
1,397
72
11%
2,761
1,795
3.8
19.0
19.40
>13 Acres
3,002
1,248
60
10%
2,439
1,586
3.3
17.9
20.80
>14 Acres
2,496
1,099
49
9%
2,132
1,386
2.9
16.7
22.42
>15 Acres
2,391
1,041
45
8%
2,016
1,310
2.8
16.3
23.14
>16 Acres
2,300
995
42
8%
1,930
1,254
2.6
15.9
23.69
>17 Acres
2,066
880
35
7%
1,709
1,111
2.3
14.9
25.14
>18 Acres
1,881
811
31
6%
1,563
1,016
2.1
14.4
26.15
>19 Acres
1,777
755
28
6%
1,462
950
2.0
14.0
26.98
>20 Acres
1,610
659
23
5%
1,273
828
1.7
13.2
28.64
Table 4: Commercial, Industrial, Institutional, and Multi-Family Residential Properties Based on Impervious Cover Size
Page 14 of 15
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
i onnn
lOUUU
16000
a a r\r\r\
_
2257
14UUU
12000
10000
8000
dr\r\r\
2710
1823
2385
8913
7562
DUUU
4000
2000
594
2267
811
2857
2320
1176
335
- 315
u
# Properties Total Phosphorus Load
(Ibs/yr)
Properties >1 Acre
# Properties Total Phosphorus Load
(Ibs/yr)
Properties with >1 Acre IC
¦ Multi-Family Residential ¦Commercial 1 Industrial ¦ Institutional Private
Figure 6: Number of Properties and Total Phosphorus Load by Property Classifications for Both
Properties >1 Acre and Properties with IC >1 Acre
To further refine this evaluation, EPA evaluated the optimum size of ICthat would most effectively
capture the largest load reduction over the fewest number of properties. The private properties in the
CRW were first broken up into groups based on the amount of IC contained on the property. Figure 7
displays the potential TP reduction (assuming a 65% reduction from the total load) from CIIM properties
and the number of properties where the reduction would occur. The trendline in Figure 7 provides
insight on the size of IC area that would result in optimizing the tradeoff between TP reduction and
number of properties installing controls. Ultimately the optimal implementation scenario would lie
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
where the trendline is "curving" or moving from high slope to low slope. In Figure 7, this optimal zone is
highlighted in light orange and lies between properties with >0.25 acres and >5 acres of IC.2
LO
-Q
20,000
18,000
16,000
14,000
12,000
3 10,000
~o
0.25 Acres ...
*ic>0.5 Acr
es
? IC>1 Acres
w
1*
L IC>5 Acres
*
|
10,000 20,000 30,000 40,000
Number of Properties
50,000
60,000
Figure 7: TP Load Reduction Assuming 65% Reduction vs. Number of Properties for CUM
Properties. The light orange represents a potential optimal IC size for stormwater control
implementation
To understand the potential TP reductions from stormwater controls on properties at different IC
thresholds, thresholds between 0.5 acres of IC and 5 acres of IC, were evaluated more closely.
Specifically, thresholds of >0.5, 1.0, 2.0, and 5.0 acres of IC are discussed in further detail below.
An IC size of > 0.5 acre includes 3,808 CIIM properties and contributes a TP load of approximately 16,477
pounds per year (Table 5). Approximately 93% of the TP load is generated from IC on these properties.
Of the 3,808 properties, 2,151 are commercial, 632 are multi-family residential, 517 are industrial, and
508 are institutional. The average IC per property ranges from 1.85 acres to 2.69 acres with multi-family
residential as the lowest and industrial as the highest. Reducing TP from these properties by 65% has the
2 While Figure 7 provides a tool for visualizing one way to optimize implementation, it should not be interpreted
without taking into account other factors for efficiency of stormwater control sighting within the watershed,
namely targeting those properties with the greatest proportion of IC and targeting those land use classes
contributing the largest amount of TP proportionally (Figure 4).
Page 16 of 17
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
potential TP reduction of 10,710 pounds per year, which equates to 22.6% of the reduction needed in
the CRW (Table 4).
ICArea
ICTP Load
Pervious TP
TP Load
Average IC Area
Classification
# Properties
Acres
(Acres)
(Ibs/yr)
Load (Ibs/yr)*
(Ibs/yr)
(Acres)/Property
Commercial
2151
12,234
4,592
8,199
669
8,868
2.13
Industrial
517
3,280
1,389
2,470
168
2,638
2.69
Institutional Private
508
3,789
1,083
1,902
204
2,107
2.13
Multi-Family Residential
632
3,711
1,167
2,688
177
2,864
1.85
TOTAL
3,808
23,013
8,230
15,259
1,218
16,477
Table 5: Commercial, Industrial, Institutional, and Multi-Family Residential Properties with >0.5 Acre
Impervious Cover
*Pervious load does not include TP loads from forest or wetland areas on private properties
An IC size of > 1.0 acre includes 2,120 CIIM properties and contributes a TP load of approximately 14,091
pounds per year (Table 6). Around 92% of the phosphorus load is generated from IC. Of the 2,120
properties, 1,176 are commercial, 335 are industrial, 315 are multi-family residential and 294 are
institutional properties, and the TP load from each property type follows the same order. They include
56% of the total impervious cover from all CIIM properties. The average IC area per property ranges
from 3.01 to 3.74 acres with multi-family residential as the lowest and industrial as the highest (Table 6).
Reducing the phosphorus load from these properties by 65% has the potential TP reduction of 9,159
pounds per year, which equates to 19% of the reduction needed in the CRW (Table 4).
ICArea
ICTP Load
Pervious TP
TP Load
Average IC Area
Classification
# Properties
Acres
(Acres)
(Ibs/yr)
Load (Ibs/yr)
(Ibs/yr)
(Acres)/Property
Commercial
1,176
10,500
3,903
6,969
593
7,562
3.32
Industrial
335
2,957
1,254
2,230
156
2,385
3.74
Institutional Private
294
3,330
937
1,648
175
1,823
3.19
Multi-Family Residential
315
2,934
947
2,181
139
2,320
3.01
TOTAL
2,120
19,721
7,041
13,028
1,063
14,091
Table 6: Commercial, Industrial, Institutional, and Multi-Family Residential Properties with >1 Acre
Impervious Cover
*Pervious load does not include TP loads from forest or wetland areas on private properties
An IC size > 2.0 acres includes 1,048 CIIM properties and contributes a phosphorus load of
approximately 10,242 pounds per year (Table 7). They include 44% of the total impervious cover from all
CIIM properties. The average IC per property ranges from 4.74 acres for multi-family residential to 5.42
acres for commercial properties, which indicates that many properties have more than 2 acres IC (Table
7). Reducing the phosphorus load from these properties by 65% has the potential TP reduction of 7,171
pounds per year, which equates to 15% of the reduction needed CRW (Table 4).
Page 17 of 17
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
ICArea
ICTP Load
Pervious TP
TP Load
Average IC Area
Classification
# Properties
Acres
(Acres)
(Ibs/yr)
Load (Ibs/yr)*
(Ibs/yr)
(Acres)/Property
Commercial
561
7,865
3,043
5,432
430
5,861
5.42
Industrial
199
2,471
1,064
1,892
127
2,019
5.35
Institutional Private
137
2,581
717
1,268
126
1,394
5.23
Multi-Family Residential
151
2,334
716
1,651
108
1,759
4.74
TOTAL
1,048
15,252
5,540
10,242
790
11,033
Table 7: Commercial, Industrial, Institutional, and Multi-Family Residential Properties with >2 Acres
Impervious Cover
*Pervious load does not include TP loads from forest or wetland areas on private properties
An IC size > 5.0 acres includes 337 CIIM properties where 188 are commercial, 71 are industrial, 45 are
multi-family residential and 33 are institutional and the phosphorus load from each property type
follows the same order (Table 8). These properties include 27% of the impervious cover of all CIIM
properties. The average IC area per property ranges from 8.65 to 12.14 acres with multi-family
residential as the lowest and institutional as the highest (Table 8). These values are much higher than
the 5-acre threshold, indicating that some properties likely have more than 5 acres IC. These properties
generate 6,642 pounds of TP per year and reducing the load by 65% has the potential TP reduction of
4,317 pounds per year, which equates to 9% of the reduction needed in the CRW (Table 4).
ICArea
ICTP Load
Pervious TP
TP Load
Average IC Area
Classification
# Properties
Acres
(Acres)
(Ibs/yr)
Load (Ibs/yr)*
(Ibs/yr)
(Acres)/Property
Commercial
188
4,393
1,908
3,407
258
3,665
10.15
Industrial
71
1,393
661
1,173
72
1,246
9.31
Institutional Private
33
1,171
401
718
55
773
12.14
Multi-Family Residential
45
1,317
389
900
57
958
8.65
TOTAL
337
8,274
3,358
6,199
443
6,642
Table 8: Commercial, Industrial, Institutional, and Multi-Family Residential Properties with >5 Acres
Impervious Cover
*Pervious load does not include TP loads from forest or wetland areas on private properties
Figure 8 displays the potential TP reduction realized for each land use type assuming the CIIM properties
in the scenarios described above were required to achieve a 65% reduction in TP in stormwater
discharges called for in the TMDL WLAs. Commercial properties have the largest phosphorus reduction
potential for all IC sizes. While multi-family residential properties have the second highest phosphorus
reduction potential when looking at CIIM properties with any IC size (all properties), the proportion of
total reduction from Multi-family residential properties in each scenario decreases as the IC threshold
increases (Figure 6) due to the fact that Multi-family residential properties have the lowest amount of IC
per property in each scenario (Table 5-Table 8).
Page 18 of 17
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
>
to
_Q
C
o
u
¦a
(D
cc
20,000
18,000
16,000
14,000
12,000
LO
M 10,000
8,000
c
o
+J
u
3
T3
QJ
CC
Q.
6,000
4,000
2,000
36.8% of
required
reduction
All Properties
22.6% of
required
reduction
19.3% of
required
reduction
15.1% of
required
reduction
>0.5 Acre >1 Acre >2 Acres
Amount of IC on Property
9.1% of
required
reduction
>5 Acres
I Commercial ¦ Institutional ¦ Industrial
Multi-Family Residential
Figure 8: TP Reduction Assuming a 65% Reduction for CUM Properties Based on Impervious
Cover Size on Properties
IV. CONCLUSION
Stormwater systems in general, and in the highly-developed Charles River Watershed in particular, are
complex, comprising different stormwater flow paths based on soils, slope, road design, piped network
design, among other factors. This analysis does not attempt to reproduce stormwater flow paths from
any property or land use group and focuses solely on the potential phosphorus in stormwater that could
be discharged off any given property. It analyzes stormwater impacts and assesses the need for their
reduction on a gross, aggregate scale, as EPA is entitled to do. Natural Resources Defense CouncilInc. v.
Costle. 568 F.2d 1369. 1380 (D.C. Cir. 1977) (emphasis added). ("EPA may issue permits with conditions
designed to reduce the level of effluent discharges to acceptable levels. This may well mean opting for a
gross reduction in pollutant discharge rather than the fine-tuning suggested by numerical
limitations. But this ambitious statute is not hospitable to the concept that the appropriate response to a
difficult pollution problem is not to try at all."). The analysis demonstrated that private properties make
up most of the phosphorus load in stormwater (over 60% of the baseline phosphorus load) in this
watershed and that load is contributing to the Charles River not meeting water quality standards.
Therefore, reducing the phosphorus in stormwater discharges from private properties is necessary to
meet TMDL goals and water quality standards. While some action must be taken on private properties,
it may be beneficial to target certain private properties for stormwater controls over others. It is likely
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
that most of the discharges from private properties is discharged through the local community's
municipal separate storm sewer system (MS4), making that municipality ultimately responsible for the
phosphorus load coming off all private properties tied into their systems and regulated in the 2016 MA
MS4 Permit. Municipalities will therefore likely be responsible for the majority of the phosphorus
reductions in the CRW. However, placing the entire burden of phosphorus reductions on municipalities
will likely not result in sufficient reduction to reach TMDL goals and WQS, indicating that designating
stormwater discharges from certain classes of private properties for NPDES permits is required. In any
scenario, municipalities will still need to engage the private property owners with smaller property size
or IC size in order to eventually meet TMDL goals and WQS, but requiring action on private properties
with larger amounts of IC now through NPDES permitting provides greater flexibility to the communities
in deciding which private properties to target to meet their own MS4 permit obligations. Requiring
actions through NPDES permitting on those properties with larger IC sizes reduces the burden on the
community that holds an MS4 permit, targets those properties generating the largest amount of
phosphorus in stormwater on a per-property scale, and makes meeting TMDL goals and water quality
standards possible.
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ATTACHMENT 6 - RDA Charles, Mystic, Neponset 2022
V. REFERENCES
Center For Watershed Protection. (2003). Impacts of Impervious Cover on Aquatic Systems. Ellicott City,
MD: Center For Watershed Protection.
Chen, J., Theller, L., Gitau, M. W., Engel, B. A., & Harbor, J. M. (2017). Ubranization Impacts on Surface
Runoff of the Contiguous United States. Journal of Environmental Management, 187, 470-481.
Massachusetts Department of Environmental Protection . (2007). Final TMDLfor Nutrients in the Lower
Charles River Basin.
Massachusetts Department of Environmental Protection. (2011). Total Maximum Daily Load for
Nutrients in the Upper/Middle Charles River Basin, Massachusetts.
MassGIS. (2016). Full documentation for MassGIS' 2016 Land Use/Land Cover Data.
MassGIS. (2022). MassGIS Data: Property Tax Parcels. Retrieved January 2022, from
https://www.mass.gov/info-details/massgis-data-property-tax-parcels
Schueler, T. (2011). Technical Bulletin No. 9: Nutrient Accounting Methods to Document Local
Stormwater Load Reduction in the Chesapeake Bay Watershed REVIEW DRAFT. Chesapeak
Stormwater Network.
Shaver, E., Horner, R., Skupien, J., May, C., & Ridley, G. (2007). Fundamentals of Urban Runoff
Management: Technical and Institutional Issues. Madison, Wl: North American Lake
Management Society.
USEPA. (2016). MEMORANDUM - Annual Average Phosphorus Load Export Rates (PLERs)for Use in
Fulfilling Phosphorus Load Reduction Requirements in EPA Region 1 Stormwater Permits.
USEPA. (2022). MEMORANDUM- Charles River Watershed Private Parcel Analysis GIS Methods.
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