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BMP 7R: TMDL Watershed Review
Where a Total Maximum Daily Load (“TMDL”) has been approved for a water body into which MassDOT’s
urbanized roadways discharges storm water, MassDOT will assess such TMDL reports in accordance with
Part I.D. of the NPDES Small MS4 Permit (the “Permit”).
As of April 30, 2010, the Massachusetts Department of Environmental Protection (“MassDEP”) has finalized
41 TMDL reports for impaired water bodies. MassDOT has conducted an initial review of these 41 final
TMDL reports to determine whether the TMDL includes a waste load allocation (WLA), BMP
recommendations, or other performance requirements for storm water discharges that are applicable to
MassDOT. MassDOT considers any general WLA for stormwater applicable to MassDOT as long as it is not
linked to a specific discharger other than MassDOT. If the TMDL does not contain an applicable WLA for
storm water from MassDOT, MassDOT has determined whether a Performance Agreement or
Memorandum of Understanding has been established with the EPA or MassDEP, which modifies the BMPs
or performance standards of the TMDL. MassDOT has compiled a summary of its initial review of the 41
final TMDL reports in Appendix K-1, along with an overview of the actions that MassDOT has taken or is
taking in response to the BMP recommendations or other performance requirements included in the TMDL
reports.
MassDOT will further assess its compliance with final TMDL reports under the steps described below.
MassDOT will separately assess, under BMP 7U, the need for additional control measures or other BMPs
for any impairments that are not covered by a TMDL. MassDOT will include any additional TMDLs finalized
after the date of this BMP in the assessment described below. MassDOT is committed to completing its
assessment of waters covered by the 41 final TMDL reports included in Appendix K-1 within a five-year
period, starting June 8, 2010. During this period, MassDOT will assess 20% of these waters each year.
Step 1. Identify TMDL Waters to Which MassDOT’s Urbanized Roadways May Potentially Discharge
Storm Water
MassDOT has initially identified the specific water bodies covered by TMDLs to which MassDOT’s
urbanized roadways may potentially discharge storm water, in order to define the scope of its review under
Part I.D. of the Permit. MassDOT identified such TMDL waters together with all impaired waters without
TMDLs as part of BMP 7U (Water Quality Impaired Waters Assessment and Mitigation Plan) (hereinafter,
“Impaired Waters Program”), as described below.
As set forth in BMP 7U, MassDOT identified a total of 684 impaired water bodies whose sub-basins contain
some portion of MassDOT’s urbanized area roadways (and therefore potentially receive discharges from
MassDOT outfalls); of this total number, 209 water bodies are covered by final TMDL reports (see revised
Appendix L-1 dated July 22, 2010, replacing prior Appendix K-2). Of the 209 TMDL waters listed in
Appendix L-1, 138 are covered by TMDL reports with WLAs that may be applicable to storm water
discharges from MassDOT. The remaining 71 waters covered by TMDLs do not have general stormwater
WLAs that are applicable (see Step 4 below).
Step 2. Conduct Desktop Review and Site Survey of TMDL Waters with Applicable WLAs
Final TMDLs with applicable WLAs will be assessed as described in this BMP. MassDOT initially will
perform a desk top review to determine the specific locations of MassDOT outfalls relative to the TMDL
waters. Where the desk top review indicates that MassDOT has potential to discharge to the water body
and may exceed the WLA, MassDOT will conduct a site survey and identify the surrounding drainage
infrastructure. The specific procedures for conducting this preliminary review are set forth in Steps 2 and 3
of BMP 7U. Appendix L-1 reflects the priority MassDOT places on assessing these waters; higher priority is
placed on waters lying within 500 feet of at least one MassDOT outfall.
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Step 3. Assess Whether WLAs for Storm Water Discharges Are Being Met
Where MassDOT discharges to a water body with an applicable WLA, MassDOT will assess whether the
WLA is being met through existing storm water control measure or if additional control measures may be
necessary. This assessment will be conducted using the steps outlined below.
Step 3a. Calculate the Relevant WLA
In virtually all cases, the WLAs in TMDL reports specify a single WLA for all storm water discharges or for
broad categories of storm water sources (such as “industrial” or “commercial” storm water sources). They
do not contain WLAs that are specific to MassDOT. Therefore, MassDOT will determine what portion of the
applicable WLA is relevant to storm water discharges from MassDOT. To do this, MassDOT will calculate
an areal WLA (e.g. lbs/acre) by dividing the applicable WLA by the area it applies to. The resulting areal
WLA will be multiplied by the area of MassDOT urban roadways that discharge into the TMDL water body to
calculate the WLA for MassDOT. This approach will assign a WLA that is proportional to the area MassDOT
operates that discharges to the water body.
For those TMDLs with WLAs expressed as concentrations (e.g. pathogen TMDLs) the areal WLA will be
calculated based on the concentration and the estimated runoff from impervious surface, where appropriate.
Step 3b. Calculate Loading from MassDOT Storm Water
MassDOT will estimate the loading of the pollutant of concern in storm water discharges from MassDOT into
the water body covered by a TMDL. MassDOT will rely on existing quantitative data (including data
provided by USGS to MassDOT in 2009, relating to pollutant loads in storm water from Massachusetts
highways) to estimate the approximate pollutant loads in highway runoff at particular sites where possible.
Additionally, MassDOT will conduct a survey of any existing storm water BMPs or other structures that may
have the effect of reducing the pollutant of concern in storm water. Wherever possible, MassDOT will seek
to quantify the estimated pollutant removal efficiencies of existing BMPs (both structural and non-structural)
or structures, based on standard specifications for BMP designs set forth by the EPA and MassDEP
(Appendices L-2 to L-4). Based on this information, MassDOT will calculate the estimated loading of the
pollutant of concern from MassDOT.
Step 3c. Assess WLA Relative to Loading from MassDOT
MassDOT will compare the WLA calculated in Step 3a with the estimated load of the pollutant of concern
from MassDOT in Step 3b. If the estimated load from MassDOT storm water discharge into the TMDL
water is equal or lower than the WLA, then MassDOT will generally conclude that existing BMPs meet the
WLA. However, MassDOT will consider, in such instances, BMP recommendations or performance
requirements for highway dischargers listed in the TMDL report (or in other performance agreements or
memoranda of understanding) to assess whether additional measures may be warranted. As noted below,
MassDOT will also seek opportunities in pending construction projects to assess whether any structural
BMPs can be implemented to address the pollutant of concern as part of such projects.
If the estimated load from MassDOT is higher than the WLA, MassDOT will evaluate whether additional
BMPs may be required as described in Step 5. However, as noted below, EPA’s policy has recognized that
loading estimates from stormwater are imprecise. Therefore, the results of the comparison of the applicable
WLA and the estimated loading are not definitive. These estimates will be used to inform the evaluation of
appropriate BMPs.
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Step 4. Highlight Control Measures for Pollutants of Concern Listed in TMDL Reports that Do Not
Contain Storm Water WLAs
Of the 209 TMDL waters listed in Appendix L-1 (revised July 22, 2010), 71 are covered by TMDL reports
that do not specify WLAs for storm water discharges. Where a storm water WLA is not specified, MassDOT
will nevertheless review the TMDL report to assess the need for additional control measures to address the
pollutant(s) of concern listed in the TMDL report. For 43 of the 71 TMDL waters with no WLAs, the TMDL
report at issue is the Northeast Regional Mercury TMDL report, which expressly states that local sources of
mercury in storm water are de minimis. MassDOT will not implement any additional control measures with
respect to mercury for these TMDL waters. The remaining 28 waters do not have applicable WLAs, as
reported in the year seven annual report to the EPA.
For the remaining 28 TMDL waters where no WLA is specified, MassDOT will rely principally on the BMP
recommendations or performance requirements for highway dischargers listed in the TMDL report (or in
other performance agreements or memoranda of understanding) to determine whether the control
measures currently in place are adequate to control the relevant pollutant(s) of concern.
Step 5. Select, Design and Implement BMPs
Where existing BMPs may not meet the applicable WLA, MassDOT will further assess whether additional
BMPs are needed to meet the WLA. Where such BMPs are required, MassDOT will select, design, and
implement additional BMPs.
In a 2002 memorandum (the “2002 Memorandum”), the EPA stated that “EPA’s policy recognizes that
because storm water discharges are due to storm events that are highly variable in frequency and duration
and are not easily characterized, only in rare cases will it be feasible or appropriate to establish numeric
limits for municipal and small construction storm water discharges. The variability in the system and
minimal data generally available make it difficult to determine with precision or certainty actual and projected
loadings for individual dischargers or groups of dischargers. Therefore, EPA believes that in these
situations, permit limits typically can be expressed as BMPs, and that numeric limits will be used only in rare
instances.” EPA Memorandum, “Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations
(WLAs) for Stormwater Sources and NPDES Permit Requirements Based on Those WLAs” (Nov. 22, 2002).
The 2002 Memorandum affirmed an “iterative adaptive management” approach to selecting BMPs.
In light of the challenges of assessing pollutant loading quantitatively, MassDOT understands the Permit as
allowing an “iterative, adaptive management BMP approach” to assessing compliance with WLAs, rather
than requiring strict compliance with a numeric loading value (WLAs are typically expressed as a single
WLA for all stormwater dischargers or categories of dischargers).
Consistent with EPA’s policy, MassDOT will rely on its pollutant loading analysis (described in Step 3 above)
as a preliminary estimate of the total amount of pollutant reductions that may be required in particular cases.
However, MassDOT will also necessarily rely on other factors (as outlined below) to determine whether and
to what extent additional BMPs are warranted to comply with the specified WLA. For instance, the existing
data on bacteria concentrations in highway runoff are extremely variable, and therefore quantitative
assessments of the extent of pollutant reductions that may be required have limited value. In addition, site
constraints may limit the scope of retrofit projects within existing highway structures.
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Accordingly, MassDOT will consider, in addition to its quantitative calculations set forth in Step 3, a range of
other available information when selecting the appropriate BMPs for particular sites, including:

The estimated pollutant reduction efficiencies for structural BMPs based on standard specifications
for BMP designs set forth by the EPA and MassDEP (Appendices L-2 to L-4);

Where obtainable, specific input from the EPA on what BMPs are appropriate;

BMP recommendations or performance requirements for highway dischargers listed in the TMDL
report (or in other performance agreements or memoranda of understanding);

The specific potential sources of certain pollutants;

The nature and extent of site constraints that may limit the scope of retrofit projects;

Any existing literature regarding appropriate BMPs for the pollutant(s) at issue, including any
guidance issued by the EPA or MassDEP; and

The overall magnitude of MassDOT’s stormwater discharges and the degree to which its estimated
pollutant loads deviate from the WLAs.
Based on this information, MassDOT will select appropriate BMPs (both structural and non-structural) that
are intended to achieve the WLA, and will document the basis for the selection. MassDOT will create
conceptual designs of structural BMPs and develop or confirm protocols for the implementation of nonstructural BMPs. If EPA later determines that the BMPs selected by MassDOT are not sufficient, MassDOT
will re-assess the water body and consider additional BMPs.
Consistent with its prior practice, MassDOT will continue to seek opportunities in pending construction
projects to implement any structural BMPs that would be impracticable as stand-alone (retrofit) projects. In
the context of such construction projects, MassDOT will, wherever possible, seek to reduce the loading of
the pollutant of concern to a greater extent than may be possible with retrofits.
MassDOT plans to implement BMPs, including structural BMPs, on a rolling basis as the need is identified
and funding is secured. A more detailed implementation schedule is set forth in Appendix L-5 of BMP 7U.
Step 6. Document Results of Assessment and Progress on Implementation
As described in BMP 7U, MassDOT will include in its reports to the EPA updates on its progress in
assessing and mitigating 303(d) impaired waters, including TMDL waters. MassDOT will provide quarterly
reports to the EPA during the first year of the Impaired Waters Program (BMP 7U) and BMP 7R, and semiannual reports thereafter.
For TMDL waters reviewed under BMP 7R, MassDOT will document the results of its assessment in a
standardized format, which includes the name of the TMDL water body; the underlying pollutant(s) of
concern; the applicable WLA; the estimated load from MassDOT; any BMP recommendations, performance
requirements, or other Performance Agreement or Memorandum of Understanding applicable to the TMDL;
a summary of MassDOT’s assessment and/or mitigation plan; and a report on the status of any planned
implementation of additional control measures or BMPs. Any relevant “calculations, maintenance log books,
or other appropriate controls” will be included in MassDOT’s documentation or otherwise kept on file and
made readily available for inspection by the EPA. MassDOT’s reports to the EPA will clearly document the
basis of any conclusions reached by MassDOT regarding the need or lack of need for BMPs at specific
sites.
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Measurable Goals:
1) Assess all TMDL waters listed in Appendix L-1 using the process described in BMP 7R within
five years (20% per year) from June 8, 2010.
2) Assess at least 25 water bodies (both TMDL and non-TMDL waters) within the first quarter of
the Impaired Waters Program (BMP 7U) and BMP 7R. 3)
Submit annual reports to EPA containing the documentation described in Step 6. 4) Submit quarterly progress reports to EPA during the first year of the Impaired Waters Program (BMP 7U) and BMP 7R and semi-annually thereafter, including reports on TMDL waters. 3-15(5)
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