Conservation Commission Agenda (linked)

Docusign Envelope ID: 8F3BBD48-0039-435A-B02C-D2C36B54505A
TOWN OF WATERFORD
Application for Inland Wetland / Watercourse Permit
Type of Application: Agency Use:
Permitted Use, Section 4.1 Date Received:
Unregulated Activities, Section 4.2 _ Received By:
Regulated Activities, Section 6 Va Fee: il Application Number: C- aL = aj ms
1. Applicant: Connecticut College Arboretum Phone: | ss
Address: State: CT Zip: P|
2. Owner: Connecticut College Phone:
Fax: E-Mail:
3. Agent: GreenVest, LLC c/o Graham Boardman Pl»:
4. Property Address: 435 Mohegan Ave Pkwy
5. Abutting Property Owners — Complete Attached Form Attached
6. Activity to be Reviewed and / or Licensed (attach sheet if necessary): Stream stabilization, Stream
restoration; Non-native, invasive species management (see attached cover letter and design
report.)
7. Description of Proposed Activity (attach sheet if necessary): See attached cover letter and design report
8. Purpose of Activity (attach sheet if necessary): See attached cover letter and design report
9a. Acreage of Property: 54.10 9b. Acreage of Wetlands: 3.07
(2.25 tidal; 0.82 inland)
10. Acreage of Wetlands Altered: 0.70
11. Wetland Mitigation Proposed: 0.75
12. Section 7 and sections 8.1 & 8.2 of the Town of Waterford “Inland Wetlands and Watercourse Regulations”
have been complied with: (Review attached check list) Yes: x No:
The applicant / owner hereby gives the Commission, its agent and consultants the right of free access to any part of the property under
consideration. The undersigned warrants the truth of all statements contained herein and in all supporting documents according to the best of
his / her knowledge, information and belief. — —
Applicant: } YAIR Riife— DIEASEw Wi id Ny Date: 2/12/26
Owner: Loan Congr ooo oavere Date: 2/13/26
2/16/2026
Agent: [vin Cramer FEB 2? 4 7096 Date:
DeSOCH NOLO
Planning & Development
Town of Waterford, CT

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Residential Improvements, Additions & New Structures: $110.00
Residential Subdivision, 3 or more Lots: $160.00
Commercial/Industrial Development: $160.00
TOWN OF WATERFORD
Instruction Guide for Inland Wetland / Watercourse Permit
Application Fees: All Application fees include $60.00 for the State of Connecticut.
Permit Extension/Modification: $ 110.00
Permitted Use: No Fee
Unregulated Activity: No Fee
Major or Significant Impact Activity: $360.00
Public Hearing Fee: $400.00
All applications shall include a completed original application and 14 copies to be submitted to the
Conservation Commission office. The wetlands application checklist is for your convenience, it is not necessary
to submit this document with your application. Incomplete applications will not be completed by staff, they will
be returned.
9a.
9b.
10.
li.
12.
Applicant
Owner
Agent
Address
List of Abutters
Activity to Be
Reviewed
Description of
Proposed Activity
Purpose of Activity
Acreage of Property
Area of Wetlands and
Watercourses
Wetlands Altered
Wetland Mitigation
Regulations
Include the full name, address, zip code and telephone number of the applicant(s).
Include the name(s) of the owner(s) of record as it appears on the land records (deed) of the
Town of Waterford. The owners’ complete address, zip code and telephone number are
required.
Include the full name, address, zip code, and telephone number of the agent. An agent
prepares the application for submission or will represent the owner / applicant at a meeting.
Provide street name and number of subject property.
Complete the attached form with the name, address, and assessor’s map and parcel numbers
for all adjacent properties.
Briefly describe the type or nature of permit requested. Attach additional sheet(s) if
necessary.
Describe in detail all proposed work. Scope of ali work shall be included. Attach
additional sheet(s) if necessary.
Describe in detail the purpose of the permit request. Attach additional sheet(s) if necessary.
Provide the size of the subject parcel and the area of all wetlands on site.
[Note: one acre = 43,560 square feet.]
Provide the area of all wetlands on the site in acres, [Note: one acre = 43,560 square feet.]
Indicate the area of the wetlands to be altered by proposed activity.
Describe measures incorporated in the plan to mitigate the wetland impacts associated with
the proposed activity, including restoration, enhancement or creation of wetland area.
Indicate you have reviewed the “Waterford Inland Wetlands and Watercourses
Regulations” and have complied with the application requirements.

Biohabitats
NORTHEAST HIGHLANDS & COASTAL BIGREGION
Biohabitats.com
February 17, 2026
Waterford Conservation Commission
c/o Maureen FitzGerald
15 Rope Ferry Road
Waterford, CT 06385
Re.; Mamacoke Brook Outfall Channel Stabilization & Restoration
Dear Ms. FitzGerald:
Connecticut College received grant funding to stabilize and restore Mamacoke Brook, a
coastal lowland stream located on Connecticut College Arboretum property between
Mohegan Avenue (Route 32) and the Thames River, north of Benham Avenue. The
principal investigator at Connecticut College is Ms. Maria Rosa, with technical support
from Dr. Doug Thompson, Connecticut College and Ms. Maggie Redfern, the Director of
Connecticut College Arboretum. For the design team, GreenvVest, LLC is the College's
implementation partner for the broader Mamacoke Island Aquatic Habitat Resilience
(MIAHR) initiative and Biohabitats is the project ecological and engineering lead
The project site, located at 435 Mohegan Avenue Parkway, is 54.10 wooded acres and
contains approximately 0.82 acres of inland wetlands and watercourses and 2.25 acres
of tidal wetlands. The proposed project intends to restore 0.27 acres of wetland and
watercourse and enhance 0.47 acres of wetlands and watercourse.
A detailed assessment of the project site and Mamacoke Brook is discussed in the
attached design report. This includes assessments of watershed characteristics,
geology, soil, wetlands and watercourses, hydrology, vegetation and ecological
communities, listed species, and cultural resources. These existing condition are
accounted for in the design approach discussed in the report as well as depicted in the
design plans. Below is a summary of design report and plans, specifically the project
need, objectives and approach.
Mamacoke Brook currently exhibits substantial instability, including bank erosion and
channel incision, producing excessive sediment that is transported downstream into
Mamacoke Cove and ultimately the Thames River. Primary drivers include concentrated
stormwater outfails, a steep flow path, and reduced riparian vegetation in portions of
the corridor. To reduce erosion and improve hydrologic and ecosystem function, the
Mamacoke Brook restoration projected intends to:
Restore the Earth and inspire ecological stewardship.

February 17, 2026
Re.: Mamacoke Brook Outfall Channel Stabilization & Restoration
Page 2 of 5
a
Improve geomorphic function to promote long-term bed and bank stability
Reduce sediment transport downstream
Attenuate stormwater flows from concentrated sources by increasing
infiltration/ groundwater recharge where feasible, and reduce nonpoint source
pollutants (e.g., roadway contaminants and fertilizers)
Enhance ecological functions and stream habitat quality
Maximize reuse of onsite native rock and wood in restoration features
Control invasive species and improve riparian vegetation conditions through
treatment and native plantings
The design prioritizes long-term stability, floodplain reconnection, and water quality
improvement while accommodating constraints such as steep terrain, limited
construction access in forested reaches, and avoidance of significant impacts on
Connecticut Department of Transportation (CTDOT) right-of-way. The project is divided
into three segments based on field conditions and the related the design approach.
Upstream Restoration Reach - Although a reinforced plunge pool and outfall
energy dissipation could reduce erosive power, this approach is not feasible
under current constraints (e.g, pipe elevations, access limitations, and CTDOT
right-of-way impacts). Instead, restoration in the upstream reach focuses on
limited, low-impact measures to increase sediment trapping and habitat
complexity. This approach uses wood augmentation, including Post-Assisted Log
Structures (PALS) where feasible and/or strategic use of existing fallen trees. This
is expected to provide modest functional uplift given the high-gradient
environment and limited upstream wood recruitment potential (culvert
constraints).
Middle Restoration Reach - The middle reach is identified as the most actively
enlarging and degrading portion of the system. The proposed design will restore
stability in a steep intermittent channel (~8-10% siope) using a series of cascade
grade control structures spaced roughly every 70-100 feet, over a total length of
approximately 560 feet to the more stable downstream reach.
Key elements of the proposed design include:
e Cascade structures that provide ~3—4 feet of vertical drop over short
distances using large subangular boulders sized for stability during the 100-
year storm, with plunge pools for energy dissipation.
Restore the earth and inspire ecological stewardship.

February 17, 2026
Re: Mamacoke Brook Outfall Channel Stabilization & Restoration
Page 3 of 5
* Between cascades, the restored channel bed is set higher (within ~1-2 feet of
top-of-bank) and designed at ~5% slope to support riffle/pool formation and
wood retention.
¢ Two complementary restoration techniques are incorporated to encourage
geomorphic/habitat diversity and support adaptive learning:
o Regenerative Stormwater Conveyance (RSC) riffle/pool step-pool
approach, with riffles sized to convey approximately the 5-year storm
(10 ft wide by I ft deep), plus shaliow pools enhanced with woody
material for roughness and habitat.
© Dynamic bouider cluster / woody streambed approach to partially fill
incised sections and promote a roughened bed surface that may
evolve toward multi-threaded flow patterns (with performance
standards acknowledging material sorting and wood decay over
time).
¢ Because there are known sensitive archaeological resources within the
project area, specific steps have been taken to avoid or limit ground
disturbance that is otherwise not necessary or associated with the
restoration of the stream channel through this reach.
3. Downstream Restoration Reach - Downstream, where the stream slope softens,
the valley widens, and stability is greater, a Stage 0, full-valley restoration
concept is proposed to maximize floodplain reconnection, wetland function, and
water quality benefits. In this reach, design intent is to restore the wetland/valley
complex with multiple anabranching flow paths, high habitat diversity, and
enhanced sediment/nutrient retention across the floodplain.
Because this downstream reach includes dense stands of Phragmites australis,
an integrated management approach (i.e, timed chemical treatment combined
with biomass removal) will be coordinated with the Arboretum’s policies and
long-term stewardship capacity. Additionally, because there are known
sensitive archaeological resources within the project area, specific steps have
been taken to avoid or limit ground disturbance that is otherwise not necessary
or associated with the enhancement through this reach.
When implemented as designed, the project is expected to:
¢ Reduce active erosion and sediment delivery to the salt pond and Thames River
through grade control, raised bed profiles, and floodplain reconnection
Restore the earth and inspire ecological stewardship.

February 17, 2026
Re: Mamacoke Brook Outfall Channel Stabilization & Restoration
Page 4 of 5
° Improve stormwater attenuation, infiltration opportunities, and pollutant
processing by re-establishing floodpiain and wetland function—especially within
the Stage 0 restoration area
¢ Increase habitat complexity and ecological function through wood structures,
dynamic bed features, invasive species management, and native plant
community restoration
« Avoid and minimize impacts, to the greatest extent practicable, to trees along
the restoration reach
e Protect known and potential areas of archaeological resources
« Preserve and avoid potential areas of state-listed species.
« Provide a high-value, long-term teaching and research opportunities for
Connecticut College students, staff and partners
While the proposed project will result in 0.74 acres of direct wetland impacts, we believe
that this restoration activity is not a significant impact.
* Deposition and/or removal of material will have substantial long-term benefits
to the watercourse and overwheim any potential negative short-term effects
related to construction. Construction will include an erosion and sediment
control plan consistent with CTDEEP guidelines that will minimize impacts to
downstream wetlands and watercourses.
e The natural channel has been greatly impacted by erosion associated with
increased runoff from Mohegan Avenue Parkway. Natural dynamics of the
watercourse will be reintroduced through the construction of a natural channel
to the extent practicable based on current climatic and land use conditions.
e The project will not diminish but rather enhance the watercourses’ ability to:
support aquatic life and wildlife; reduce flooding in established areas by
reconnecting existing floodplains; promote improved water quality; and
enhance recreational opportunities and safety at the site.
« Water quality will be further improved by reestablishing a riparian buffer within
the upland review area and improving groundwater connections. Reducing
erosion also decreases water turbidity and establishing a canopy will address
increased water temperature relative to solar energy input.
e The project will be conducted during a period of low-flow when the Mamacoke
Brook is typically dry. Turbidity, siltation, and sedimentation will be addressed
during construction by using established erosion and sediment control
techniques. Over the long-term, the proposed restoration will reduce turbidity,
siltation, and sedimentation.
Restore the earth and inspire ecological stewardship,
é

February 17, 2026
Re.: Mamacoke Brook Outfali Channel Stabilization & Restoration
Page 5 of 5
* The proposed restoration includes educational and scientific benefits by
allowing students and faculty of Connecticut College to support the assessment
and design process, observe construction, and complete monitoring to
document project outcomes along with adaptive management if needed.
A detailed assessment of the project site and Mamacoke Brook and the resultant design
are discussed in the attached design report and depicted in the attached design plans.
It is anticipated that the project will begin during the low-flow period (summer) and
take approximately 3 months to complete. Plantings will be installed immediately
following construction, but no later than October 31.
Should you have any questions about the proposed project, please do not hesitate to
contact me directly at 860.968.2738 or jwilson@biohabitats.com.
Sincerely,
Biohabitats, inc.
Me bf
shua H. Wilson, PWS
Sr. Ecologist
Enclosures
Restore the earth and inspire ecological stewardship.

Mamacoke Brook Outfall Channel Stabilization and
Restoration Project
Mamacoke Island Aquatic Habitat Resilience Project
New London County — Thames River Watershed
Design Report
January a
Me Biohabitats GreenVest
NORTHEAST HIGHLANDS & COASTAL BIOREGION SIMON AESEFONH ANCE BESO CONNECTICUT
COLLEGE

Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
Table of Contents
TINTPOCAUCTION oo. cece tcce rene tetetetsenesesesentessesescasneesecseeceestsssnenesenavensasacasseneeeesssersasinetetatees 1
1 Project Are ANd BACKGPOUNG...... cece cece essences tse serevenseesasecaeseseeesesteeeatanenes 1
12 Project Goals ONd Objectives... cence tes tec cseerenseeaestatsiseesenenensnnensees 2
2 Environmental RESOUFCES INVENOTY oo. ceesetceccseeeetenereeesencacsesesesessessesatuseeassesseeseatenseasens 3
2.1 Overview of ASSeSSMENt Methods oa... ccc eseeeeeseenssecsceneeseneasensesseneseeneneasaeess 4
2.2 Watershed Characterization... ccc scence eenseeeseetseesseesseenensneaeiesnereneseeaeenenenecess 4
2.3 GEOIOGY AN SOI oo. ee eects eeererseseneseaneetenenenseesansesanesaesesesenantsetetversreassuanseatee 5
2.4 Wetlands and Surface WALETS 0... ee esceeseteserersentacuserterecsesenssevesetariversenerensenees 6
2.5 HYCFOlOGY ....sescscesceeeereseenesessssseteeneeessesescessscersneaseteasseessneaceceseasasiuenseseeearensieenensatenseneens 8
2.6 Vegetative Community Assessment & Tree SUIVEY oo. eecccceesssseeseeeererteretseseneatees 12
2.7 LISTED SPOCIOS...... cece cee eee res eersssecsseeeeneseersseseeesececeseasacetsscatsvsesaeastaeensseaneenvacsnsaees
2.8 Cultural Resources
3 Site CONSENS... eects eee este cesescasecasessesensnessitanseaecsesssasenseenecensnsasieetaeenerseersneeeas 17
3.1 Existing Utilities and InfrostrUCtUre cress cscs cseceneeneneaseseeenesensseessensieetensees 17
3.2 Property Ownership and EASeMents 0... ecceeee es eeseeeneeeeeeesceessseatineesereeasssanseesaese
3.3 Regulated Floodplain and Hydrologic Trespass
3.4 Stream ANd Wetland IMPACtS 0... ce ceceseesesseeeescensennsetsesserseeenestanerenesneenseraeenes 19
3.5 Cultural RESOUrCE IMPACtsS ue cece eee eee sete entsesssesetsessneesiceceeseseeeesiautecenecnteets 20
4 Existing Stream Conditions... cesses eseereeeseeneseseesescsnenensaneseansneaserenseesesaeaeseaeevense 20
4 Site Assessment
4.2 Stream GEOMOrPholOGY oo... cece eeeneserseetscanenesseeseeenersasaeacssecseetenseeneeaeaeeees 20
4.3 Habitat ASSESSMENE we cect rence reneeesecunstrerersenetsavseseasensassessimneesesatasasaaeneesess 28
4.4 Bank Stability Analysis and Erosion Estimate oo... eseeeereeseserenseeneteeeeeeinteeres 29
5 Stream Restoration DESIGN oo... eee ssc eeeeeensestetevsreneteesasacaeevesettneterseeensaesseseaes 31
5.1 Overall Restoration APPrOdch uu... cesses ceesseresneasescicseseseeestsnssesesesnessstersacssenneees 31
5.2 Landscape INStAllation ces eeeseneesseeeeeeerscnesenseensenesesensessseatistererseseesaeeseenene 38
5.3 Construction Access and Erosion and Sediment Control.......cccseeeceeecetensensenee 38
5.4 Existing and Proposed HYCrQuliCs oo. cee enseseseecsecsersnecsneneneeeteneessesteeneseneneass 40
6 REPEFEN CES... eeeececeece cece esesseeeaeseeeereneseeustsnsensecenseeseesescisensessoetaveasisaeseaseneceuenecetenteeaeaeese 42

Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
Appendix A: Wetland Delineation Report
Appendix B: Hydrology
Appendix C: Natural Diversity Data Base (NDDB)Request Response
Appendix D: Archaeological and Cultural Resource Inventory Consultation Report
Appendix E: Existing Stream Condition Documentation
Appendix F: Stream Design Supporting Computations
Appendix H: Semi-Final Design Plans
Appendix H: Hydraulics

Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
T INTRODUCTION
1.1 Project Area and Background
Connecticut College received grant funding for the stabilization and restoration of
the Mamacoke Brook, which is located on Connecticut College Arboretum property
between Route 32 and the Thames River. GreenVest (GV) is the College’s
implementation partner. The Brook will be stabilized and restored as part of the
Mamacoke Island Aquatic Habitat Resilience (MIAHR) Project, which also includes
tidal marsh restoration along the Thames River. The Brook is laterally and vertically
unstable, with eroded banks 4-6 feet in height and deep channel incision along
portions of its approximate 1,500-foot length. This instability is likely caused by
concentrated stormwater flow contributions, a steeply sloped flow path, and a
reduction in vegetation along portions of the channel. Consequently, this has
resulted in channel enlargement and excessive sediment generation due to bank
erosion. The proposed stream restoration will stabilize the flowpath, enhance the
overall health and stability of the stream system, and reduce pollutant loading into
the Thames River.
Key Partners and Stakeholders involved in the project include Connecticut College as
landowner, and who will act as the Administrator, Community Engagement Lead and
provide technical assistance. GreenVest, Connecticut College’s resiliency
implementation partner, is managing the full delivery of the MIAHR project, including
design, permitting, and eventual construction. Community stakeholders include the
City of New London, Town of Waterford, and the Mohegan Tribe.
Connecticut College is committed to leveraging the MIAHR as a significant
educational asset. The Project will serve as an instructional platform for students
from high school to undergraduate and, through collaborations with regional
universities, for graduate scholars as well.
The Mamacoke Stream restoration project area included in this report and
associated design drawings are shown in Figure 1 below.
© Biohabitats, Inc ]

Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
N
1,000 Feet A
Figure 1: Project Area Map
1.2 Project Goals and Objectives
The Mamacoke Stream Restoration project (the Project) entails an environmental
resource inventory, field surveys, schematic and final design, permitting, and
construction implementation. The overall project goals for the Project are to improve
the overall stability and habitat condition/diversity of the coastal lowland stream.
Specific goals include:
1.
Improve geomorphic function of the stream channel to promote long-term
bed and bank stability. This will reduce sediment transport into Mamacoke
Cove and the Thames River, improving water quality and habitat in the
downstream restoration areas.
Attenuate/slow the delivery of stormwater flows originating from the
concentrated flow sources at the upstream limit of the project to the salt pond
and cove at the downstream limit of the project. Maximize the conversion of
surface water to groundwater, assisting with the improvement in
physicochemical functions and water quality. This will also decrease the non-
© Biohabitats, Inc 2

Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
point source pollution carried by the stormwater discharges (such as
petroleum products and trash from the roadway, and fertilizers from
contributing land use) that degrade downstream water quality.
Create and enhance the ecological functions of existing stream habitats.
4. Where feasible, maximize the reuse of onsite native rock and wood throughout
the restoration.
5, Control non-native and invasive species, including the vines pulling down the
existing canopy in the riparian buffer, through chemical and physical
treatment and planting of native trees and shrubs.
oe
2 ENVIRONMENTAL RESOURCES INVENTORY
Understanding the existing conditions within a stream and its watershed is critical for
providing context for project work, identifying determinant physical processes,
characterizing specific stream stability issues, and formulating an appropriate
restoration strategy.
This section briefly describes assessment methods and results related to the
physical setting, geology, soils, land cover, land use, and hydrology within the
watershed. As described below, this information was compiled from existing
Geographic Information System (GIS) layers, orthophotography, field run
topographic survey, and field observations.
Prior to the development within the watershed, this channel likely did not receive
concentrated storm flows and was a likely a wider, shallower vegetated flowpath.
The Mamacoke Brook watershed and the surrounding area have undergone land use
changes following the establishment of Connecticut College in the early 1900s.
Review of historical maps and aerial imagery show that the roadway (Route 32) and
railroad that serve as the bounding limits for the project were in place in the 1890s.
The 1950s saw the construction of a residential neighborhood at the upper limits of
the watershed. This watershed development resulted in increased impervious
surfaces and installation of storm drain conveyance systems that increased the
volume and rate of stormwater being delivered to the steeply sloped channel. Site
history reviewed for this project confirms that a portion of the land surrounding the
channel was converted from forest to meadow in 2005. These land use changes
throughout the watershed, as well as increases in rainfall intensity and frequency of
storm events driven by climate change, are causing impacts to the stream network
© Biohabitats, inc 3

Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
within the project area. Stream conditions throughout the project area are variable
and described on a reach-by-reach basis later in this report.
2.1 Overview of Assessment Methods
Desktop analyses primarily used orthophotography, existing geographic information
system (GIS), and other watershed data available from various sources. GIS data for
the full watershed area including natural watershed boundaries, hydrography,
geology, roads, land cover, and LiDAR-derived topography, were downloaded online
from the University of Connecticut Center for Land Use Education and Research
(CLEAR) and the Connecticut Department of Energy and Environmental Protect
(CTDEEP). Local utility data, notably stormwater infrastructure, was downloaded from
the Town of Waterford and the Connecticut Department of Transportation
(ConnDOT). Soils data were obtained from the Natural Resource Conservation
Service’s (NRCS) Web Soil Survey available online.
Base mapping for the project area was created for the immediate stream corridor
using dedicated LiDAR-derived topography collected by Whiteout Solutions in
October 2024. Field run topographic survey was conducted in the Summer of 2025 by
Martinez Couch & Associates, LLC. Additional data was added by Biohabitats from
follow-up field survey efforts. GIS data was used for basemapping purposes outside
of the stream valley.
Field investigations were conducted by Biohabitats staff during the summer and fall
of 2025. Investigations within the project area included a general reconnaissance, a
limited geomorphic channel assessment, and characterization of bank conditions,
wetland delineation, and a vegetative inventory. Wetland boundary locations were
collected by Biohabitats.
Each assessment is discussed and summarized in the sections that follow. Mapping
showing existing conditions through the project area is included in the Schematic
Design plans, with more detailed information about the mapped features included
throughout this report.
2.2 Watershed Characterization
The Project originates at a confluence of stormwater pipes at Mohegan Avenue
Parkway (Route 32) and flows east through Connecticut College Arboretum property
(the George S. Avery Tract and the Katherine Matthies Tract) to its terminus at a
small pond (“Salt Pond”) which is bounded to the east by an elevated private
© Biohabitats, Inc 4

Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
railroad. The Salt Pond is connected by a box culvert to the South Cove of Mamacoke
Island, a tidal bay along the Thames River.
The project drainage area is in Waterford, New London County and a drainage area
map is included in Section 2.5 below. The drainage area is generally of steep
topographic relief that slopes east, rapidly becoming lowland terrain near the
confluence with the Salt Pond. The upstream portion of the watershed consists of
residential properties, Route 32 runoff, and undeveloped wooded areas which drain
towards the wooded upland College Arboretum before continuing downstream
where the valley widens to a maintained meadow area with scattered trees.
2.3 Geology and Soil
Geology within the project area consists of the Mamacoke Formation (Zwm). This
formation consists of interlayered light- to dark-gray, medium-grained gneiss from
the Neoproterozoic geologic age (USGS).
A soil survey using the Natural Resource Conservation Service (NRCS) soil web map
was completed to evaluate the major soil components within the project area. The
soil resource report equips field investigators and designers with information about
soil properties and land classifications that supports a better understanding of the
behavioral characteristics of a proposed project. “The objective of soil mapping is
not to delineate pure map unit components; the objective is to separate the
landscape into landforms or landform segments that have similar use and
management requirements. Each map unit is defined by a unique combination of
soil components and/or miscellaneous areas in predictable proportions. Some
components may be highly contrasting to the other components of the map unit.
The presence of minor components in a map unit in no way diminishes the
usefulness or accuracy of the data. The delineation of such landforms and landform
segments on the map provides sufficient information for the development of
resource plans.” (NRCS).
© Biohabitats, Inc 5

Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
= Soil Map—State of Connecticut, Eastern Part '
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Figure 2: NRCS Soil Resource Report Soil Map
The upstream limits of the project area are classified as Canton and Charlton soils
(60D), a steep-sloped, well-drained soil. The majority of soils within the project area
are classified as Sutton fine sandy loams (50B), which is a moderately well-drained
soil typically found on hillslopes and classified as having high runoff potential. The
northern side and downstream limits of the project area are Charlton-Chatfield
complex (73), a very rocky, well-drained soil found on 15 to 45 percent slopes. All of
these soil classes are derived from granite, gneiss, and/or schist.
2.4 Wetlands and Surface Waters
A wetland delineation was completed by Biohabitats staff in September 2025. The
Project is located on a 54.1 acres parcel, which contains 3.07 acres of wetlands — 2.25
acres tidal, 0.82 acres inland. An inland scrub-shrub wetland totaling 0.48 acres was
identified within the project area along with 0.34 acres of inland watercourse. The
majority of the 1,500 linear feet of inland watercourse channel within the project area
was determined to be intermittent, approximately 1,200 linear feet originating from
the Rt 32 culvert. There is short section of perennial channel below the confluence
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
with spring fed tributary near the downstream end, approximately 300 linear feet.
The channels and wetlands are depicted on the design plan sheets, below is a
summary of methodology.
2.4.1 Federal Jurisdictional Wetlands
In support of the Project, the wetland and waters of the U.S. (WUS) boundaries were
identified, flagged and survey located. Biohabitats identified, delineated, and
documented nontidal wetlands and WUS within the project limits in compliance with
applicable State and Federal regulations. The delineation was performed using the
three parameter approach - wetland hydrology, hydrophytic vegetation, and hydric
soils — in accordance with the 1987 Corps of Engineers Wetlands Delineation Manual -
Technical Report 87-1 (USACE, 1987) and the Regional Supplement to the Corps of
Engineers Wetland Delineation Manual: Northcentral and Northeast Region - Version
2.0 (USACE, 2012). The existing hydrology was evaluated at each sample location by
documenting the presence of primary and secondary hydrologic indicators, which
provide evidence as to whether a site has a continual wetland hydrologic regime. For
the hydrophytic vegetation determination, the abundance of each species within five
strata — tree stratum, sapling stratum, shrub stratum, herb stratum, and woody vines
- was sampled. The vegetative sample plots had a 26.3-ft radius, according to
standard USDA forest inventory methods. A wetland indicator status was applied to
each identified plant species per the 2014 National Wetland Plant List (NWPL) (Lichvar
et. al, 2014). To determine if hydric soils were present, the soil profile at each sample
location was characterized, focusing on the presence/absence of redoximorphic
features to a depth of 12 to 18 inches using an auger and/or spade. Upon assessment
of the three parameters, wetland area boundaries were flagged and plotted with
sequentially numbered flagging. In depth discussion of the findings of the wetland
delineation can be found in the wetland delineation memo (Appendix A).
2.4.2 Connecticut Jurisdictional Wetlands
Inland, non-tidal wetlands are regulated under the Connecticut Inland Wetland and
Watercourses Act. In general, wetlands are defined as a soil that is saturated to
within 20 inches of the surface during a portion of the growing season. These soils
have redoximorphic features, a deficiency of oxygen near the surface, and/or
ponded water during the growing season. They are poorly drained, very poorly
drained, alluvial, or fluvial as specified by the USDA Natural Resource Conservation
Service (NRCS). Depth to seasonal high water table is determined by low-chroma
mottling or wetness indicators.
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
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Inland, non-tidal watercourses are also regulated under the Connecticut Inland
Wetland and Watercourses Act. Watercourses are rivers, streams, brooks,
waterways, lakes, ponds, marshes, swamps, bogs, and all other bodies of water
including natural or artificial, vernal or intermittent, public or private. A defined
permanent channel and bank, and the occurrence of two or more of the following
characteristics delineate intermittent watercourses:
e Evidence of scour or deposits of recent alluvium or detritus
e Presence of standing or flowing water for a duration longer than a particular
storm incident
e Presence of hydrophytic vegetation
2.5 Hydrology
Biohabitats identified and evaluated two delineation points and three sub-
watersheds for hydrologic analysis throughout the project reach. The overall
drainage area includes portions of the Connecticut College Arboretum, residential
neighborhoods and College properties west of Route 32, an undeveloped portion of
the watershed immediately west of Route 32, and a segment of Route 32 itself. A
drainage area map showing the three sub-watersheds is shown below in Figure 3.
The watershed contains 14.2% impervious surfaces.
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
Biohabitats collected inputs from available LIDAR and GIS data from New London
County, Connecticut and site-specific LIDAR. The available GIS data was utilized to
determine time of concentration paths and weighted curve numbers for the overall
project drainage area. Weighted curve numbers are based on hydrologic soil group
(NRCS Web Soil Survey) as well as land use (NOAA) to reflect current existing
conditions. Maps showing the drainage area’s soil and land use are shown below in
Figures 4 and 5.
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
The County’s zoning indicates that the entire drainage area could be developed as
medium density residential (R-20), however given the fact that the majority
(approximately 70%) of the watershed is within the arboretum, it is assumed this
area is protected from future development and will not be developed.
\ Hydrologic Soil
Group (HSG)
GollegesCl
Figure 4: Hydrologic Soil Groups within the drainage area
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
Side}Swale)
Land Cover Class
f | Impervious
Surface
Open Space
Developed
(098 Mixed Forest
{_) Grassland
BS Estuarine Scrub
Shrub Wetland
| Bare Land
‘ 1 { | Open Water
LP # G ‘ | ‘ \ "J |) Scrub Shrub
- q - r \" = | fay UNconsolidated
© j=. , F t. 4 Shore
u a l= uw ae = a
Figure 5: Land Use within the drainage area
NRCS hydrologic modeling was performed in HydroCAD Version 10.00, a hydrologic
modeling software, to calculate the peak discharges for the I-year, 2-year, 5-year,
10-year, 25-year, 50-year, and 100-year storm events. For this analysis, the runoff
method was SCS TR-20, rainfall distribution was 24-hour NOAA D and rainfall depths
were pulled from NOAA Atlas 14, Volume 10, Version 3. All hydrologic modeling for this
project was performed in accordance with the Connecticut Stormwater Quality
Manual. The full hydrologic modeling results can be found attached in Appendix B.
Summaries of the hydrologic analysis are shown in Tables 1 through 4 below.
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
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Table 1: 24-hour Rainfall Depths (inches)
I-year | 2.89
2-year (3.45
5-year 4.36
10-year 5.11
25-year 6.15,
50-year 6.93
100-year (7.76
Table 2: Hydrology Summary
Drainage Area (ac) |76.6
Impervious Area (ac) 10.9 (14.2%)
Weighted CN |70
I-year peak (cfs) 23.82
2-year peak (cfs) | 37.92
5-year peak (cfs) 64.38
10-year peak (cfs) | 88.39
25-year peak (cfs) 123.84
50-year peak (cfs) /151.59
100-year peak (cfs) '181.90
Table 3: Sub- Watershed Hydrologic Summary
Sub-Watershed ID Area [AC] RCN Te [hr]
Mamacoke Stream | 53.26 73 0.577
Side Swale | 10.99 61 0.525
Salt Pond | 12.40 60 0.665
Table 4: Peak Flows by Sub-Watershed
Peak Flows [cfs]
Sub-Watershed ID 100-
1-Year 2-Year 5-Year 10-Year 25-Year 50-Year
a | ; Year _
Mamacoke Stream | 21.95 33.37 53.89 72.09 98.53 18.98 141.12
Side Swale | 1.17 2.60 5.69 8.70 13.37 17.14 21.35
Salt Pond 1.02 2.31 5.21 8.10 12.61 16.28 20.41
2.6 Vegetative Community Assessment & Tree Survey
A vegetation inventory was completed by Biohabitats staff in September 2025. Four
main vegetative communities were identified on-site: Mature Mixed Deciduous-
Coniferous Upland Forest, Deciduous Hedgerow, Scrub-shrub Wetland and Dry
Meadow. Each of these communities contain a diverse mix of native species and
non-native invasive vegetation including multiple stands of non-native Phragmites
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
New London County, Connecticut
australis located within the identified wetland. These communities are mapped and
included in the Schematic Design plans. Below is a brief summary of the vegetation
communities identified within the project area.
Mature Mixed Deciduous-Coniferous Upland Forest is the primary forest type that
surrounds the project area and occurs primarily on the hillslopes. The mature
canopy of red/black and white oak, sweet birch, red maple, American beech and
white pine that are over 18” in diameter at breast height (dbh) dominates over the
6"-12" doh American beech, sweet birch, mockernut hickory and sugar/Norway
maple of the sub canopy. The understory is dense within the project area containing
primarily non-native shrub species including barberry, burning bush, multiflora rose,
wineberry, Tartarian honeysuckle among the native maple-leaved viburnum,
sassafras and arrowwood. The typical sparse groundcover layer of vegetation
occurs in this forest which contains a mix of wintergreen, white wood aster, garlic
mustard, burnweed, and woodland sedge with poison ivy, Japanese honeysuckle
and Asiatic honeysuckle vines growing where canopy gaps have allowed for more
sunlight.
The upstream 500’ of the project area contains numerous dead standing trees and
multiple blowdowns that have created gaps in the canopy allowing the growth of a
large stand of tree of heaven and other non-native invasive species in this upland
forest community along the stream channel.
Dry Meadow
The vegetation community within the large open areas along the lower half of the
project site include a variety of native grasses and forbs with an occasional woody
trees or shrub. Dominant herbaceous species present in this community include
grass leaved goldenrod, showy goldenrod, wrinkleleaf goldenrod, spotted joe-pye
weed, big bluestem, New England aster, hairy aster, butterfly weed, bracken fern,
mugwort, common milkweed, and late boneset. Observed trees and shrubs include
Eastern red cedar and winged sumac. The Dry Meadow area was forested until 2005,
when the woody vegetation was cleared and converted into meadow habitat. This
was done with the intent of creating early-successional habitat for floral and faunal
species that depend on open canopies.
Deciduous Hedgerow is the dense vegetation community type that is in between the
open dry meadow areas, relic agriculture fields and roadways within and
surrounding the project area, This community is composed of a few tree species
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
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such as crabapple, young black oak, northern catalpa, black cherry, winged sumac
and sassafras but generally dominated by shrub and vine species. These include
autumn olive, multiflora rose, shrub honeysuckle, burning bush, barberry, privet,
porcelainberry, Japanese honeysuckle, Asiatic bittersweet, poison ivy, greenbriar,
and fox grape.
Scrub-shrub Wetland Two stands of common reed occupy a large portion of this
vegetation community and porcelainberry is growing in from the periphery, but there
are numerous native shrub and herbaceous species present between the non-
native invasives. Shrubs are dominated by spicebush and gray alder with some
privet present in lower numbers. Dominant herbaceous species include arrowhead,
tickseed, water plantain, false nettle, greenbriar, clearweed, smartweed, skunk
cabbage, white snakeroot, soft rush, narrowleaf cattail, giant goldenrod and
jewelweed.
All trees greater than 6” in diameter at breast height (DBH) within the possible
project limits of disturbance (LOD) were considered “significant” and identified to
species and evaluated for their general condition (Good, Fair, Poor). Each tree was
marked with a sequentially numbered round aluminum tag that was affixed to the
tree using an aluminum nail at approximately eye level, generally located on the side
of the trunk facing the stream channel. Pink survey flagging tape was also attached
to the tag for improved visibility in locating each tag, and to keep track of the survey
completion allowing the survey crew to remove as they survey trees. The DBH of each
tree was estimated and occasionally measured using a DBH measuring tape as
calibration to maintain accurate estimates. Trees with multiple trunks were treated
as a single tree for survey purposes but the DBH of each stem was recorded and a
composite DBH was calculated using the following root sum squared formula:
J (dbhi?+dbh2?+..tdbhn’). A total of 76 significant trees were located and tagged, 8 of
which were specimen trees with greater than 24” DBH (Table 5). Located trees are
included in the plan set basemapping and shown on the existing and proposed
conditions sheets (Appendix F).
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
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Table 5: Mamacoke Tree Survey — September 2025
Tree
Number Species DBH (inches) | Condition Notes
] Red Oak 28" Good
2 Sweet Birch 18° Good _ Multistem 13, 13
3 Sweet Birch 7" Good _
4 Sweet Birch 19" Good -
5 Sweet Birch 14" Good
6 Hackberry 12 Poor
7 American Beech Tv Poor
8 Hackberry e" Poor
9 American Beech T Poor
10 American Beech 28" Poor
fi _ Sweet Birch 19" Poor -
12 Sweet Birch 1 Good -
13 Sweet Birch 12" Good
i Sweet Birch T Good
ie) Sweet Birch 8 Good Multistem 6, 6
16 Black Cherry s Good
17 Sweet Birch e" Good ~
18 Sweet Birch 12" Good
19 Red Oak 32" Good
20 Willow 14" Good ___ Muttistem 11, 8
21 White Pine 23" Good
22 Catalpa 10" Good Multistem 8, 6
23 Sweet Birch T Good
| 24 Unknown 12" Dead
25 Sweet Birch 15" Good undercut bank
26 Hickory 19" Good
27 Black Oak 18" Fair
28 Black Oak 3r Good
29 Black Oak 24" Good
30 Black Oak 24° Good
31 Ash 7 Good
32 Red Maple 6" Fair Poor Form
33 Red Mapie 26" Poor
34 Red Maple 19” Poor
35 Norway Maple 12" NNI
36 Unknown Dead 8-ft snag & 15-ft snag
37 Unknown 36" Dead Multistem 18, 18, 18, 18
38 Tree Of Heaven T NNI
39 Norway Maple 4 NNi
40 Unknown 20" Dead 40-ft snag
41 Elm 9" Poor
42 Hackberry s Good
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project
New London County, Connecticut
Design Report
Tree
| Number Species DBH (inches) | Condition Notes es
44 Unknown | 23" Dead Multistem 16, 16; 15-ft snag & 40-ft snag
45 Norway Maple Te _ _ NNI |
46 Norway Maple 9° _ _ NNI
47 Unknown 18" Dead 40-ft snag
48 | Norway Maple 12" NNI
49 Cherry 6" Poor |
50 | Red Maple 8 Poor 7 ee _ _|
sl Black Oak 22" "Good _
52. Elm 6" Good
53 Elm 6" Good
54 Red Maple 12" Good
55 Red Maple 12" Good
56 Unknown 20" Dead 20-ft snag
57 Black Oak 26" Poor ___Multistem 14, 22
58 Elm 7 Good
59 Red Maple 8" Poor
60 Unknown 20" Dead
61 Red Maple 6" Good
62 Unknown 20" Dead
63 Black Oak 23" Poor
64 Elm 1" Good
65 Norway Maple 8" NNI
66 Elm 6 Good
67 Norway Maple 10" NNI
68 Norway Maple 1" NNI
69 Elm 1" Poor
70 Unknown 24" Dead 50-ft snag
72 Norway Maple 12" NNI
73 Norway Maple 6" NNI
74 Norway Maple 16" NNI
75 Red Maple 12" Good
76 Tree Of Heaven 10" NNI
2.7 Listed Species
The proposed project limits are located within a designated Natural Diversity Data
Base (NDDB) area. This would indicate that there is or historically has been observed
instances of a state-listed endangered, threatened, or special concern species.
Based on discussion with the College, there is one known instance of historical
documentation of the special concern plant species Bolboschoenus maritimus ssp.
paludosus (saltmarsh bulrush). This species, which was last documented in 2006,
was observed in the tidal scrub-shrub wetland area where a significant stand of
common reed is currently found.
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
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An NDDB request was filed with the Connecticut Department of Energy and
Environmental Protection (CTDEEP) and a response was received on December 5,
2025 (Appendix C). In accordance with the recommendation from CTDEEP, a
botanical survey will be conducted to confirm and the presence or absence of this
species in or near the project area. Alterations to the design plans or inclusion of best
management practice will be incorporated based on the findings of the botanical
survey and coordination with CTDEEP.
2.8 Cultural Resources
An archaeological and cultural resource inventory was performed by Dr. Anthony
Graesch, Ph.D Associate Professor of Anthropology at Connecticut College. See
Appendix D for full report. Recommendations from this report were considered when
developing the proposed design and continued coordination will be required as the
design progresses.
3 SITE CONSTRAINTS
3.1 Existing Utilities and Infrastructure
Based on site observations and survey, the following utility and infrastructure
constraints have been identified within the project limits:
e Stormwater Infrastructure
o Mohegan Avenue Parkway (Route 32)
» A 48" RCP conveys the primary channel underneath Mohegan
Ave, tied into concrete headwalls on both sides of the road.
= Numerous drop culverts along the roadway convey water to the
upstream limits of the project reach, there are 4 culvert pipes
which discharge into multiple headwalls at the upstream limits of
the project.
o Stream Culvert
» A 24" RCP is located in the middle of the project channel, timbers
are placed to span this culvert. This culvert was recently
damaged during a storm event and replaced in its current
configuration as a temporary measure.
o Railroad Culvert
» An aging4’ W x 2’ H concrete box culvert that is likely nearing the
end of its service life (visual observations noted possible
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Mamacoke Brook Outfall Channel Stabilization and Restoration Project Design Report
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blockage or partial collapse within it) crosses underneath the
railroad embankment at the downstream limit of the salt pond.
e Electrical Infrastructure
o Overhead power lines run along Mohegan Avenue Parkway as well as
Benham Avenue.
e Sewer Infrastructure
o No sanitary sewer infrastructure was observed on sit