HomeMy WebLinkAbout02. Bomber Heights Eng memo-w SWPPP excerpt & app comment letter 17.0443 Electronics Parkway, Liverpool, NY 13088·Office: 315-457-5200·Fax: 315-451-0052·BartonandLoguidice.com
August 19, 2026
Mr. Justin McNeal, Director of Engineering
Town Ithaca Engineering Department
114 Seven Mile Drive
Ithaca, New York 14850
Re: Bomber Heights Solar PV
Subj: Follow-up Engineering Review of SWPPP
File: 2071.015.001
Dear Mr. McNeal:
Barton & Loguidice, D.P.C. (B&L) has reviewed the Stormwater Pollution Prevention Plan
(SWPPP) prepared by LaBella Associates which was prepared on behalf of Nexamp, Inc.
(“Applicant”) for the above referenced project. The SWPPP document reviewed was last dated
July 2026.
Based on our follow-up engineering review of the SWPPP, we offer the following:
Based on the comment responses provided by the applicant to our engineering review
letter dated April 29, 2026, comments numbered 1-3, 5-6, 8-22, and 24-32 have been
addressed.
Comments numbered 4, 7, and 23 remain as they were not fully resolved by the
applicants response. These comments are shown below with additional information in
bold.
Our follow-up engineering review did identify additional comments what are shown
below and begin with number 33.
Suggestions and comments for the Town’s consideration:
Initial Review SWPPP Comments
4.Please provide correspondence with NYSDEC regarding the on-site Class A regulated
streams.It is anticipated that correspondence/permitting with NYSDEC for
disturbance of the streams will be needed, as the plans show the streams being
disturbed by the stormwater discharge locations and panels that extend over the
streams.
Mr. Justin McNeal, Director of Engineering
Town Ithaca Engineering Department
August 19, 2026
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7.Based on the topography of the site and the mapped DEC streams on and adjacent to
the site, it is anticipated that there may be 1-2 additional locations where channelized
water exits the site. Review and revise to ensure the design points are representative of
the discharge points from the site.Though all runoff from the site eventually enters the
Sixmile Creek downstream, the area between the property boundary of the site and
Sixmile Creek contains sensitive infrastructure that could be negatively impacted by
increased flows from the specific locations where runoff leaves the site. At a
minimum, the locations where mapped streams that convey runoff from the site
should be modeled as separate design points.
23.Please include a landscaping plan that details all proposed plantings.A specific
landscaping plan should be provided for the bioretention basin, with specific plantings
and on-center spacings to be utilized, rather than a seed mix. Refer to Chapter 11 of
the 2024 Stormwater Management Design Manual.
Additional Review SWPPP Comments
33.The post-development drainage map has not been updated with changes to the site
layout, review and revise.
34.Question 26 of the eNOI should be revised to specify the Sixmile Creek as the nearest
waterbody; questions 27 and 28 should be revised accordingly.
35.The SWPPP specifies that 1.40 acres of new impervious are being created, but only 1.18
acres are accounted for in the WQv calculation of the GI Worksheet. The plans specify
1.30 acres of new impervious. The HydroCAD model only includes 0.794 acres of
impervious area. Review and revise accordingly for consistency.
36.The GI Worksheet specifies that grass filter strips are being used to reduce runoff from
the access road and turnaround. Please provide these calculations in the GI Worksheets,
and call out the typical locations of the grass filter strips on the plans.
37.Some woods on site are modeled as “fair” and some as “poor” in the existing condition,
please confirm how these areas were differentiated. Additionally, the woods are
modeled as “good” in the proposed condition model. As the woods are not anticipated
to change as part of the project, they should remain the same as in the existing
condition.
38.The HydroCAD time of concentration path should be changed from shallow
concentrated flow to channelized flow when it intersects with an on-site stream.
Mr. Justin McNeal, Director of Engineering
Town Ithaca Engineering Department
August 19, 2026
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39.The existing condition sheet flow uses “Woods: Light Underbrush”, and the proposed
condition uses “Woods: Dense Underbrush”. As the woods are not anticipated to
change as part of the project, this should remain the same as in the existing condition.
40.The post-development HydroCAD model only includes the 100-year storm event, this
should be revised to include the 1-year and 10-year storm events.
41.The filter area in the GI Worksheets for the filtration bioretention basin (2,100 SF) does
not match the HydroCAD model (2,602 SF).
42.The silt socks should be placed parallel to contours, many of the silt socks shown are
shown crossing several contours.
43.The orange construction fencing to protect the wetlands and other sensitive
environmental features should be shown on the erosion and sediment control plan.
44.The elevations of the detention basin on the plans do not match that shown in the
HydroCAD model. Review and revise for consistency.
45.Please confirm if the proposed detention basin will be used as a sediment basin during
construction, and if so, please provide details and grading for the sediment basin if it will
differ from the detention basin.
46.Identify the Maintenance Access route for the bioretention area and stormwater pond.
47.Include Town inspection requirements from Chapter 228. Specifically, the rain
inspection requirement which is not already included in the SWPPP.
48.Please confirm where disposal of spoil materials hauled off site will occur. If disposal
will be at a site within the Town of Ithaca, a SWPPP and erosion control plan may need
to be prepared for the disposal site. If the disposal site will be outside of the Town of
Ithaca, we still will need to know the disposal location. This item should be coordinated
further with the Town Engineering Department.
49.Please confirm whether any Town roads will be utilized to haul materials to and from
the project site. If yes, and depending on the volume of vehicles, a roadway use
agreement with the Town Department of Public Works may be necessary. This item
should be coordinated further with the Town Engineering Department.
Mr. Justin McNeal, Director of Engineering
Town Ithaca Engineering Department
August 19, 2026
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At this time, we recommend that the Applicant address the engineering review comments
presented herein, and submit revised documents/additional information to the Town for
further review.
Please contact me if you have any questions or comments regarding our engineering review of
Bomber Heights Solar PV SWPPP.
Sincerely,
BARTON & LOGUIDICE, D.P.C.
Charles A. White, P.E., LEED AP
Vice President
CAW/jjb
cc: C.J. Randall, Director of Planning, Town of Ithaca
Stormwater Pollution Prevention Plan
Prepared for:
Nexamp, Inc.
101 Summer Street, 2nd. Floor
Boston, MA 02110
Submitted by:
LaBella Associates
300 State Street, Suite 201
Rochester, NY 14614
(585) 454-6110
Bomber Heights Solar PV
Town of Ithaca, Tompkins County, New York
Date: November 2025
Last revised: July 2026
Project No. 2240665-134393
PREPARER OF THE SWPPP
“I hereby certify that the Stormwater Pollution Prevention Plan (SWPPP) for this project has been
prepared in accordance with the terms and conditions of the GP-0-25-001. Furthermore, I understand
that certifying false, incorrect or inaccurate information is a violation of this permit and the laws of the
State of New York and could subject me to criminal, civil and/or administrative proceedings.”
Name and Title1: Mufuta Tshimanga
Date: Issued in June 2026
1 This is a signature of a New York State licensed Professional Engineer employed by LaBella Associates that is duly
authorized to sign and seal Stormwater Pollution Prevention Plans (SWPPPs), NOIs, and NOTs prepared under their direct
supervision. Refer to Appendix B for the SWPPP Preparer Certification Form, and Appendix I for the LaBella Certifying
Professionals Letter.
TABLE OF CONTENTS
1.0 EXECUTIVE SUMMARY .................................................................................................................... 1
1.1 Project Description ................................................................................................................... 1
1.2 Stormwater Pollution Controls ................................................................................................. 2
2.0 SITE CHARACTERISTICS .................................................................................................................. 2
2.1 Land Use and Topography ....................................................................................................... 2
2.2 Soils and Groundwater............................................................................................................. 3
2.3 Watershed Designation ........................................................................................................... 4
2.4 Receiving Water Bodies ........................................................................................................... 4
2.5 Aquifer Designation .................................................................................................................. 4
2.6 Wetlands ................................................................................................................................... 4
2.7 Flood Plains .............................................................................................................................. 4
2.8 Listed, Endangered, or Threatened Species .......................................................................... 5
2.9 Historic Places .......................................................................................................................... 5
2.10 Rainfall Data ........................................................................................................................... 5
2.11 Pre-development Watershed Conditions .............................................................................. 5
2.12 Post-development Watershed Conditions ............................................................................ 6
2.13 Description of Design Points ................................................................................................. 6
3.0 STORMWATER MANAGEMENT PLANNING .................................................................................... 6
3.1 STEP 1 – Site Planning ............................................................................................................ 7
3.2 STEP 2 – Calculate Water Quality Treatment Volume (WQv) ................................................ 7
3.3 STEP 3 – Apply RR Techniques and Standard SMPs with RRv Capacity to Reduce
Total WQv ......................................................................................................................................... 8
3.4 STEP 4 – Calculate the Minimum RRv Required..................... Error! Bookmark not defined.
3.5 STEP 5 – Apply Standard SMPs to Address Remaining Water Quality Volume .................... 9
3.6 STEP 6 - Apply Volume and Peak Rate Control .................................................................... 10
3.7 Deviations from NYSDEC Requirements............................................................................... 11
4.0 CONSTRUCTION SEQUENCE ......................................................................................................... 12
5.0 CONSTRUCTION-PHASE POLLUTION CONTROL ........................................................................... 13
5.1 Temporary Erosion and Sediment Control Measures .......................................................... 13
5.2 Permanent Erosion and Sediment Control Measures ......................................................... 14
5.3 Other Pollutant Controls......................................................................................................... 15
5.4 Construction Housekeeping Practices .................................................................................. 17
6.0 INSPECTIONS, MAINTENANCE, AND REPORTING ....................................................................... 18
6.1 Inspection and Maintenance Requirements ........................................................................ 18
6.2 Reporting Requirements ........................................................................................................ 20
7.0 SWPPP IMPLEMENTATION RESPONSIBILITIES ........................................................................... 22
7.1 Owner’s/Operator's Responsibilities ..................................................................................... 22
7.2 Owner’s/Operator’s Engineer’s Responsibilities .................................................................. 25
7.3 Contractor's Responsibilities ................................................................................................. 26
7.4 Qualified Inspector’s/Qualified Professional’s Responsibilities ......................................... 27
7.5 SWPPP Participants ............................................................................................................... 29
LIST OF TABLES
Table 1: USDA Soil Data .............................................................................................................................. 3
Table 2: Project Site HSG Data ................................................................................................................... 3
Table 3: Rainfall Data .................................................................................................................................. 5
Table 4: Required WQv Summary ............................................................................................................... 7
Table 5: Summary of Standard SMPs with RRv Capacity being Applied .................................................. 8
Table 6: RRv Summary ................................................................................................................................ 9
Table 7: Minimum RRv Summary ............................................................................................................... 9
Table 8: Summary of WQv Provided ......................................................................................................... 10
Table 9: Design Events .............................................................................................................................. 11
Table 10: Summary of Pre- and Post-Development Peak Discharge Rates ........................................... 12
Table 11: Common Construction Pollutants ............................................................................................ 16
APPENDICES
Appendix A: Figures
• A-1: Site Location Map
• A-2: Soils Map
• A-3: Historic Places Screening Map
• A-4: Environmental Resource Map
• A-5: FEMA Firm Map
• A-6: Pre-Development Watershed Delineation Map
• A-7: Post-Development Watershed Delineation Map
Appendix B: Forms
• Notice of Intent (NOI)
• SWPPP Preparer Certification Form
• Owner/Operator Certification Form
• Contractor and Subcontractor Certification Forms
• Notice of Termination (NOT)
Appendix C: Project Evaluation and Design Calculations
Appendix D: Pre-Development Stormwater Modeling
Appendix E: Post-Development Stormwater Modeling
Appendix F: SWPPP Inspection Report (Sample Form)
Appendix G: Post-Construction Inspections and Maintenance
Appendix H: NYSDEC “Deep-Ripping and Decompaction,” April 2008
Appendix I: LaBella Certifying Professionals Letter
Appendix J: NYSDEC SPDES General Permit GP-0-25-001
Appendix K: Geotechnical Documentation
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1.0 EXECUTIVE SUMMARY
This Stormwater Pollution Prevention Plan (SWPPP) has been prepared for major activities associated
with construction of 5-MW solar array in the Town of Ithaca. This SWPPP includes the elements necessary
to comply with the national baseline general permit for construction activities enacted by the U.S.
Environmental Protection Agency (EPA) under the National Pollutant Discharge Elimination System
(NPDES) program and all local governing agency requirements. This SWPPP must be executed, and
permit coverage must be obtained prior to the commencement of construction activity.
This SWPPP has been developed in accordance with the “New York State Department of Environmental
Conservation (NYSDEC) State Pollutant Discharge Elimination System (SPDES) General Permit for
Stormwater Discharges from Construction Activity,” Permit No. GP-0-25-001, effective January 29, 2025
through January 28, 2030. The SWPPP and accompanying plans identify and detail stormwater
management, pollution prevention, and erosion and sediment control measures necessary during and
following completion of construction.
This SWPPP and the accompanying plans entitled “Bomber Heights Solar” have been submitted as a
set. These engineering drawings are considered an integral part of this SWPPP. Therefore, this SWPPP
is not considered complete without them. References made herein to “the plans” or to a specific “sheet”
refer to these drawings.
This report considers the impacts associated with the intended development with the purpose of:
1. Maintaining existing drainage patterns as much as possible while continuing the conveyance of
upland watershed runoff;
2. Controlling increases in the rate of stormwater runoff resulting from the proposed development
so as not to adversely alter downstream conditions; and
3. Mitigating potential stormwater quality impacts and preventing soil erosion and sedimentation
resulting from stormwater runoff generated both during and after construction.
The analysis and design completed and documented in this report is intended to be part of the
application made for a solar development project completed on behalf of the Owner/Operator.
1.1 Project Description
Nexamp, Inc. is proposing development project, to include 5.0-MW solar array to be installed on one
parcel totaling approximately 62 acres located at an unaddressed property along Troy Road, town of
Ithaca, Tompkins County, New York 147750 (tax parcel ID: 49.00-1-26.2). Activities include the
installation of a ground-mounted solar energy system of freestanding modules/panels, new electrical
equipment, and accessories including fencing, under and aboveground electrical lines, access roads,
and inverter/transformer equipment pads.
The total project area of disturbance proposed is approximately ±40.8 acres. The project will disturb
one (1) or more acres and as such, preparation of this SWPPP is required under GP-0-25-001. A Site
Location Map has been provided in Appendix A, as Figure A-1.
This type of project is included in Table 2 of Appendix B of GP-0-25-001; and the project site is not
located in one of the watersheds listed in Appendix C of GP-0-25-001. Therefore, this SWPPP includes
post-construction stormwater management practices, as well as erosion and sediment controls.
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This project is located within the town of Ithaca, regulated, traditional land use control Municipal
Separate Stormwater Sewer System (MS4). Therefore, an MS4 SWPPP Acceptance Form is required to
accompany NOIs submitted to the NYSDEC.
Runoff from the project site will discharge to Sixmile Creek, which is not included in the list of Section
303(d) water bodies included in Appendix D of GP-0-25-001.
Project construction activities will consist primarily of the installation of solar facility and the necessary
infrastructure. Construction phase pollutant sources anticipated at the site are disturbed (exposed) soil,
vehicle fuels and lubricants, chemicals associated with building construction, and building materials.
Without adequate control there is the potential for each type of pollutant to be transported by
stormwater.
1.2 Stormwater Pollution Controls
The stormwater pollution controls outlined herein have been designed and evaluated in accordance with
the following standards and guidelines:
• New York State Stormwater Management Design Manual, dated July 31, 2024 (Design Manual).
• New York State Standards and Specifications for Erosion and Sediment Control, dated November
2016 (SSESC).
Stormwater quality will be enhanced through the implementation of temporary and permanent erosion
and sediment control measures, the proposed stormwater management practice(s), and other
construction-phase pollution controls outlined herein.
The proposed stormwater management approach consisting of on-site stormwater management
practices will adequately collect, treat, and convey the stormwater runoff.
Pre- and post-development surface runoff rates have been evaluated for the 1-, 10-, and 100-year 24-
hour storm events. Comparison of pre- and post-development watershed conditions demonstrates that
the peak rate of runoff from the project site will not be increased.
The post-construction stormwater management practice(s) will be owned by Bomber Heights Solar PV.
Policy and procedures will be in place, which ensure operation and maintenance of the practice(s) in
accordance with the operation and maintenance plan.
2.0 SITE CHARACTERISTICS
2.1 State Environmental Quality Review
The construction activity is subject to State Environmental Quality Review (SEQR). The project is
considered a Type I action. As such, SEQR coordination has been initiated A copy of the SEQR
documentation, in accordance with Part I.A.5. of GP-0-25-001.
2.2 Land Use and Topography
The project site is located within the low Density Residential (LDR) zoning district. The proposed solar
project is permitted use within this district.
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The overall site is slightly sloping, with slopes ranging from 3 to 15 percent. Site elevations range from
approximately 1,000 feet above mean sea level (MSL) to 1166 feet MSL. The site is gradually sloping to
the northeast.
2.3 Soils and Groundwater
The US Department of Agriculture (USDA) Web Soil Survey (http://websoilsurvey.nrcs.usda.gov/app/)
was used to obtain surficial soil conditions for the study area, as follows:
Table 1: USDA Soil Data
Map Symbol & Description Hydrologic Soil
Group
Permeability
(inches/hour)
Erosion
Factor K
Depth to
Water Table
(feet)
Depth to
Bedrock
(feet)
BgC- Bath and Valois, 5 to 15
percent slopes C 0.01- 0.14 0.32 2.0- 3.0 >5.0
BgD- Bath and Valois soils, 15
to 25 percent slopes, eroded C 0.01-0.14 0.37 2.0- 3.0 >5.0
EbB- Erie channery silt loam, 3
to 8 percent slopes D 0.01-0.14 0.37 0.6-1.2 >5.0
EbC- Erie channery silt loam, 8
to 15 percent slopes D 0.01-0.14 0.37 0.6-1.2 >5.0
EbC3- Erie channery silt loam, 8
to 15 percent slopes, eroded D 0.01-0.14 0.43 0.6-1.2 >5.0
EcA - Chippewa and Alden soils,
0 to 8 percent slopes D 0.06-0.57 0.32 0.0-0.5 >5.0
LnD - Lordstown channery silt
loam, 15 to 25 percent slopes C 0.14-1.42 0.32 <6.6 >5.0
Upon review of the soil data presented in Table 1, the project site does not contain soils with a soil slope
phase of D with a map unit name that inclusive of slopes greater than 25%, and does not contain soils
with a soil slope phase of E or F.
The project site is composed of HSG A soils, HSG B soils, HSG C soils, and HSG D soils, as shown in the
table below.
Table 2: Project Site HSG Data
HSG A HSG B HSG C HSG D
0% 0% 23% 77%
• Type C Soils: Soils having a low infiltration rate when thoroughly wet and consisting chiefly of
soils with a layer that impedes downward movement of water and soils with moderately fine-to-
fine texture. These soils have a low rate of water transmission.
• Type D Soils: Soils having a very low infiltration rate and high runoff potential when thoroughly
wet. These soils consist chiefly of clays that have high shrink-swell potential, soils that have a
permanent high water table, soils that have a clay pan or clay layer at or near the surface, and
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soils that are shallow over nearly impervious material. These soils have a very low rate of water
transmission.
An on-site geotechnical investigation was performed by Terraconon 06/12/2026 an 06/16/2026. 11
test pits were performed on the project site to obtain representative subsurface information within the
limits of the proposed disturbance. For detailed geotechnical information, refer to the Geotechnical
Interpretive Report in Appendix K, entitled, “Bomber Heights Solar”.
The geotechnical evaluation found that the soils on-site classify as variations of sandy, silty, clay, lean
classifications in the Unified Soil Classification System, with varied rock fragments across the site. The
depth to bedrock was observed at minimum 3.6 feet below current grade of the site. It was reported that
the weathered bedrock will affect the project where pre-drilling is required. The testing determined that
groundwater was not observed at the test pit locations.
The soils map for the study area is presented in Appendix A, as Figure A-2.
2.4 Watershed Designation
The project site is not located in a restricted watershed identified in Appendix C of GP-0-25-001.
2.5 Receiving Water Bodies
The nearest natural classified water body into which runoff from the project site will discharge is Sixmile
Creek. The Sixmile Creek is classified by NYSDEC as a Class A water body, and is not included in the
Section 303(d) list of impaired waters found in Appendix D of GP-0-25-001.
2.6 Aquifer Designation
The project site is not located over a US EPA designated Sole Source aquifer; nor is it located over a
Primary or Principal aquifer listed in the NYSDEC Technical and Operational Guidance Series (TOGS)
2.1.3 (1980).
2.7 Wetlands
Wetlands depicted on the accompanying plan set were delineated by GZA Geoenvironmental of New
York in October 2023, March and May 2026. The wetland boundary was surveyed by GZA on January 2,
2024 and presented on a map entitled “Figure 3”. At the time of application to the NYSDEC, the revised
2025 regulations were still in effect and a site visit was coordinated to address NYSDEC jurisdictional
wetlands and streams on-site. After the conclusion of the site visit in May 2025, a non-jurisdictional
notice was issued stating that there were no NYSDEC wetlands or “adjacent regulated areas” on the
site.
2.8 Flood Plains
According to the National Flood Insurance Program Flood Insurance Rate Map (FIRM), Town of Ithaca
New York, Community Panel Numbers 36109C0211D & 36109C0213 D. The project site lies within
Flood Zone D, areas determined to be outside 500-year floodplain The FEMA Flood Map has been
provided in Appendix A, as Figure A-5.
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2.9 Listed, Endangered, or Threatened Species
An ecological assessment report dated 02/20/2024, as prepared by Labella Associates, DPC,
indicates that the project will not have a significant adverse impact on any listed, endangered, or
threatened species, or on any critical habitat. An Environmental Resource Map has been provided in
Appendix A, as Figure A-4.
2.10 Historic Places
A search on the New York State Cultural Resource Information System (CRIS) database, performed on
October 29, 2025, revealed that the construction activity is not within an archaeological buffer area
indicated on the sensitivity map, and that the construction activity is not located on or immediately
adjacent to a property listed or determined to be eligible for listing on the National or State Registers of
Historic Places. The project does propose a new permanent building on the construction site within 20
feet from a building, structure, or object that is more than 50 years, however NYS Office of Parks,
Recreation and Historic Preservation (OPRHP) has determined that the building, structure, or object
more than 50 years old is not historically/archaeologically significant in accordance with Part I.A.4 of
GP-0-25-001. A printout of the historic places screening map is presented in Appendix A, as Figure A-3.
.
2.11 Rainfall Data
Rainfall data utilized in the modeling and analysis was obtained from the Cornell University online
Extreme Precipitation in New York & New England website (http://precip.eas.cornell.edu/). A local IDF
file was imported, and specific mass curves were generated, in HydroCAD to evaluate the pre- and post-
development stormwater runoff characteristics. Rainfall data specific to the portion of Tompkins County
under consideration, for various 24-hour storm events, is presented in the following Table:
Table 3: Rainfall Data
Storm Event
Return Period
24-Hour Rainfall
(inches)
1-year 2.01
10-year 3.43
100-year 5.94
2.12 Pre-development Watershed Conditions
The pre-development project site is covered predominantly by woods and agricultural fields. Analysis of
pre-development conditions considered existing drainage patterns, soil types, ground cover, and
topography. The Pre-Development Watershed Delineation Map has been provided in Appendix A, as
Figure A-6.
The results of the computer modeling used to analyze the overall watershed under pre-development
conditions are presented in Appendix D. A summary of the pre-development watershed runoff rates at
each Design Point is presented in Table 10.
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Subcatchment ES-1 is a 62.0± acre watershed consisting of agricultural fields and woods Runoff flows
in a direction overland via sheet and shallow concentrated toward the northeast.
2.13 Post-development Watershed Conditions
The post-development project site is covered predominantly by meadow, woods, and impervious
pavement. The analysis of post-development conditions considered existing drainage patterns, soil
types, ground cover to remain, planned site development, site grading, and stormwater management
facilities proposed as part of site improvements. The Post-Development Watershed Delineation Map has
been provided in Appendix A, as Figure A-7.
The results of the computer modeling used to analyze the overall watershed under post-development
conditions are presented in Appendix D. A summary of the post-development watershed runoff rates at
each Design Point is presented in Table 11.
Stormwater discharge from the project site is controlled by a single stormwater management practice.
It has been designed to provide the above quantity controls by attenuating stormwater runoff and
releasing runoff to off-site locations at a rate equal to or less than that which existed prior to
development of the site. The design is detailed on the accompanying plans. A Post-Development
Watershed Delineation Map, with the tributary areas to each stormwater management practice
proposed, has been provided in Appendix A, as Figure A-7.
2.14 Description of Design Points
The study area consists of an overall watershed that encompasses approximately 62.0 acres, including
±41-acre area of disturbance. The overall watershed encompasses the entire project area; therefore,
discharge from the project site was evaluated at one design point (DP). A description of the design point
is provided below.
• Off-site discharge to low area located northeast of the project area.
3.0 STORMWATER MANAGEMENT PLANNING
Chapter 3 of the Design Manual outlines a six-step planning process for site planning and selection of
stormwater management practices that must be implemented for both new development and
redevelopment projects. This process is intended to develop a design that maintains pre-construction
hydrologic conditions through the application of environmentally sound development principles, as well
as treatment and control of runoff discharges from the site. The following sections outline the step-by-
step process and how it has been applied to this project.
The goals of this Stormwater Management Plan are to analyze the peak rate of runoff under pre- and
post-development conditions, to maintain the pre-development rate of runoff in order to minimize
impacts to adjacent or downstream properties, and to minimize the impact to the quality of runoff exiting
the site.
The Design Manual provides both water quality and water quantity objectives to be met by projects
requiring a “Full SWPPP”. These objectives will be met by applying stormwater control practices to limit
peak runoff rates and improve the quality of runoff leaving the developed site.
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3.1 STEP 1 – Site Planning
During the Site Planning process, the project site is evaluated for implementation of the green
infrastructure planning measures identified in Table 3.1 of the Design Manual, in order to preserve
natural resources and reduce impervious cover. Appendix C provides a description of each green
infrastructure planning measure, along with a project specific evaluation.
3.2 STEP 2 – Calculate Water Quality Treatment Volume (WQv)
Stormwater runoff from impervious surfaces is recognized as a significant contributor of pollution that
can adversely affect the quality of receiving water bodies. Therefore, treatment of stormwater runoff is
important since most runoff related water quality contaminants are transported from land, particularly
the impervious surfaces, during the initial stages of storm events.
3.2.1 NYSDEC Requirements for Water Quality Volume
The Design Manual requires that water quality treatment be provided for the initial flush of runoff from
every storm. The NYSDEC refers to the amount of runoff to be treated as the “Water Quality Volume”
(WQv). Section 4.2 of the Design Manual defines the Water Quality Volume as follows:
WQv = ()()()[]
12
ARPV
Where: P = 90% Rainfall Event Number (per DEC 1.0 inch
minimum)
Rv = 0.05 + 0.009 (I)
I = Impervious Cover (Percent)
A = Contributing Area in Acres
This definition ensures that, all other things being equal, the Water Quality Volume will increase along
with the impervious cover percentage.
3.2.2 Methodology for New Development
The Water Quality Volume equation has been applied to the drainage area tributary to each of the
stormwater quality practices proposed for this project. The practices have been sized to accommodate
the Water Quality Volume, as per the performance criteria presented in Chapter 5 and/or Chapter 6 of
the Design Manual. Water quality volume calculations for each of the proposed practices are presented
in Appendix C.
Table 4: Required WQv Summary
Required WQv
4260 cf 0.098 af
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3.3 STEP 3 – Apply RR Techniques and Standard SMPs with RRv Capacity to Reduce Total
WQv
Land use change and development in the watershed increases the volume of runoff. As such, reductions
in the amount of runoff from new development, accomplished through the implementation of a
stormwater management plan for the site, will play an important role in the success or failure of the
watershed-wide stormwater management plan. Runoff reduction techniques can be applied to manage,
reduce, and treat stormwater, while maintaining and restoring natural hydrology through infiltration,
evapo-transpiration, and the capture and reuse of stormwater. Volume reduction techniques by
themselves typically are not sufficient to provide adequate attenuation of stormwater runoff, but they
can decrease the size of the peak runoff rate reduction facilities.
3.3.1 NYSDEC Requirements for New Development
The Design Manual states that runoff reduction shall be achieved through infiltration, groundwater
recharge, reuse, recycle, and/or evaporation/evapotranspiration of 100-percent of the post-
development water quality volume to replicate pre-development hydrology. Runoff control techniques
provide treatment in a distributed manner before runoff reaches the collection system, by maintaining
pre-construction infiltration, peak runoff flow, discharge volume, as well as minimizing concentrated
flow. This can be accomplished by applying a combination of Runoff Reduction Techniques, standard
Stormwater Management Practices (SMPs) with RRv capacity, and good operation and maintenance.
3.3.2 Application of Standard Stormwater Management Practices (SMPs) with RRv Capacity
The following Table demonstrates a summary of the standard SMP(s) with RRv capacity that have
been incorporated into the stormwater management plan for this project. The standard SMP(s) with
RRv capacity have been designed in accordance with Chapter 6 of the Design Manual. Refer to the
contract drawings for practice dimensions, material specifications, and installation details. Practice
specific calculations are presented in Appendix C.
Table 5: Summary of Standard SMPs with RRv Capacity being Applied
Standard
SMP with
RRv Capacity
Design
Variant
Pretreatment
Volume
Required
(% of WQv)
Pretreatment
Volume
Provided (CF)
RRv
Capacity
WQv
Required
(CF)
WQv
Reduced
/RRv
Provided
(CF)
WQv
Treated1
(CF)
Total WQv
Provided2
(CF)
Filtration
Bioretention F-5 25 690 40% 2,571 2,016 555 2,571
Dry Swale
(HSG C & D) O-1 10 170 20% 1,689 338 1,351 1,689
Standard SMP with RRv Capacity Totals 4,260 2,354 1,906 4,260
Footnotes:
1WQv Treated = WQV Required - RRv Provided
2Total WQv Provided = WQV Treated + RRv Provided
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3.3.3 RRv Performance Summary
A summary of the RRv provided is presented in the following table:
Table 6: RRv Summary
WQv Required (CF)
(increase in impervious cover)
RRv Provided
WQv Reduced (CF)
% RRv Provided/
WQv Reduced
4,260 2,354 55%
As indicated in the above table, the RRv provided/WQv reduced is not greater than or equal to the WQv
required for the project site. The remaining WQv will be treated on-site using standard SMPs with RRv
capacity as shown below.
3.4 STEP 4 – Calculate the Minimum RRv Required
Projects that cannot achieve 100% of the runoff reduction requirement due to site limitations, shall
provide a minimum runoff reduction volume as calculated by the following equation:
RRvmin = ()()()()[]
12
AicRPV S∗
Where: RRvmin = Runoff Reduction Volume (in acre-feet)
P = 90% Rainfall Event Number
Aic = Total area of new impervious cover (acres)
Rv* = 0.05+0.009(I), where I is 100% impervious
S = Hydrologic Soil Group (HSG) Specific
Reduction Factor where:
HSG A = 0.55 HSG C = 0.30
HSG B = 0.40 HSG D = 0.20
Based upon the soil survey data, the site consists of soils having a hydrologic soil type of D. As such, a
specific reduction factor of 0.20 has been applied. Calculation of the required minimum RRv is
presented in Appendix C.
Table 7: Minimum RRv Summary
Minimum RRv Required (CF) RRv Provided/
WQv Reduced (CF)
% of Minimum
RRv Provided
958 2,354 246%
As indicated in the above table, the RRv provided is greater than the minimum RRv required for the
project site. Therefore, the runoff reduction volume criteria has been met for the project and the design
can proceed to Step 5.
3.5 STEP 5 – Apply Standard SMPs to Address Remaining Water Quality Volume
If the entire Water Quality Volume is not treated through implementation of RR techniques and standard
SMPs with RRv capacity, then the design must achieve the remaining WQv through the standard SMPs
listed in Table 3.3 of the Design Manual.
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Table 8: Summary of WQv Provided
Step 2
WQv Required (CF)
Step 3
WQv Reduction by RR
Techniques & Standard
SMPs w/ RRv Capacity
(CF)1
Step 5
Reduced WQv to be
Treated by Standard
SMPs (CF)2 Redevelopment
WQv
New
Development
WQv
0 4,260 2,354 1,906
Footnotes:
1Step 3: WQv Reduction = RRv Provided + WQv Treated by Standard SMP with RRv Capacity
2Step 5: Reduced WQv to be Treated = WQv Required – WQv Reduced
Based upon the results listed in the above Table, the entire WQv has been treated by application of RR
techniques and standard SMPs with RRv capacity.
3.6 STEP 6 - Apply Volume and Peak Rate Control
This report presents the pre-development and post-development features and conditions associated
with the rate of surface water runoff within the study area. For both cases, the drainage patterns,
drainage structures, soil types, and ground cover types are considered in this study.
3.6.1 NYSDEC Requirements for New Development
Chapter 4 of the Design Manual requires that projects meet three separate stormwater quantity criteria:
1. The Channel Protection (CPv) requirement is designed to protect stream channels from erosion.
This is accomplished by providing 24 hours of extended detention for the 1-year, 24-hour storm
event. The Manual defines the CPv detention time as the center of mass detention time through
each stormwater management practice.
2. The Overbank Flood Control (Qp) requirement is designed to prevent an increase in the frequency
and magnitude of flow events that exceed the bank-full capacity of a channel, and therefore
must spill over into the floodplain. This is accomplished by providing detention storage to ensure
that, at each Design Point, the post-development 10-year 24-hour peak discharge rate does not
exceed the corresponding pre-development rate.
3. The Extreme Flood Control (Qf) requirement is designed to prevent the increased risk of flood
damage from large storm events, to maintain the boundaries of the pre-development 100-year
floodplain, and to protect the physical integrity of stormwater management practices. This is
accomplished by providing detention storage to ensure that, at each Design Point, the post-
development 100-year 24-hour peak discharge rate does not exceed the corresponding pre-
development rate.
3.6.2 Methodology
In order to demonstrate that the NYSDEC detention requirements are being met, the Design Manual
requires that a hydrologic and hydraulic analysis of the pre- and post-development conditions be
performed using the Natural Resources Conservation Service Technical Release 20 (TR-20) and
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Technical Release 55 (TR-55) methodologies. HydroCAD, developed by HydroCAD Software Solutions
LLC of Tamworth, New Hampshire, is a Computer-Aided-Design (CAD) program for analyzing the
hydrologic and hydraulic characteristics of a given watershed and associated stormwater management
facilities. HydroCAD uses the TR-20 algorithms and TR-55 methods to create and route runoff
hydrographs.
HydroCAD has the capability of computing hydrographs (which represent discharge rates characteristic
of specified watershed conditions, precipitation, and geologic factors) combining hydrographs and
routing flows though pipes, streams and ponds. HydroCAD can also calculate the center of mass
detention time for various hydraulic features. Documentation for HydroCAD can be found on their
website: http://www.hydrocad.net/.
For this analysis, the watershed and drainage system was broken down into a network consisting of
three types of components as described below:
1. Subcatchment: A relatively homogeneous area of land, which produces a volume and rate of
runoff unique to that area.
2. Reach: Uniform streams, channels, or pipes that convey stormwater from one point to another.
3. Pond: Natural or man-made impoundment, which temporarily stores stormwater runoff and
empties in a manner determined by its geometry and the hydraulic structure located at its
outlets.
Subcatchments, reaches, and ponds and links are represented by hexagons, squares, and triangles, and
broken boxes respectively, on the watershed routing diagrams provided with the computations included
in Appendix D and Appendix E.
The analysis of hydrologic and hydraulic conditions and proposed stormwater management facilities,
servicing the study area, was performed by dividing the tributary watershed into relatively homogeneous
subcatchments. The separation of the watershed into subcatchments was dictated by watershed
conditions, methods of collection, conveyance, and points of discharge. Watershed characteristics for
each subcatchment were then assessed from United States Geological Service (USGS) 7.5-minute
topographic maps, aerial photographs, a topographical survey, soil surveys, site investigations, and land
use maps.
Proposed stormwater management practices were designed and evaluated in accordance with the
Design Manual and local regulatory requirements. A local IDF file was imported, and specific mass curves
were generated, in HydroCAD to evaluate the pre- and post-development stormwater runoff
characteristics for various 24-hour storm events identified in the following Table.
Table 9: Design Events
Facility 24-hour Storm Event
Storm Sewer 10- or 25-year
Stormwater Management Practice(s)
1-year
10-year
100-year
Flood Conditions 100-year
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3.6.3 Performance Summary
Per Section 4.6 of the Design Manual , the CPv requirement does not apply as the reduction of the entire
CPv is achieved by application of runoff reduction techniques or infiltration systems.
A comparison of the pre- and post-development watershed conditions was performed for all Design
Points and storm events evaluated herein. For all Design Points and design storms, this comparison
demonstrates that the peak rate of runoff will not be increased. Therefore, the project will not have a
significant adverse impact on the adjacent or downstream properties or receiving water courses.
The results of the computer modeling used to analyze the pre- and post-development watersheds are
presented in Appendix D and Appendix E, respectively. The following Table summarizes the results of
this analysis.
Table 10: Summary of Pre- and Post-Development Peak Discharge Rates
Pre- vs. Post-Development Discharge Rate (cfs)
Design Point
(AP)
10-year 24-hour storm event 100-year 24-hour storm event
Pre Post Pre Post
1 82.04 52.47 204.80 152.60
Total 82.04 52.47 204.80 152.60
3.7 Climate Change Consideration
This report presents the consideration for future physical risks due to climate change, in accordance
with Part III.A.2 of the permit. Overall site planning, control measures and practices, conveyance systems
and detention systems were evaluated against the seven (7) physical risks identified by NYSDEC due to
climate change pursuant to the Community Risk and Resiliency Act (CRRA), 6 NYCRR 490, and
associated guidance. Appendix C provides a description of each consideration, specific to the project.
• NOAA Sea Level Rise Mapper
4.0 CONSTRUCTION SEQUENCE
This project has not received written approval from NYSDEC the Town of Ithaca allowing the disturbance
of more than five acres of land at any one time. Therefore, if the Contractor’s construction sequence
requires the disturbance of more than five acres at any one time, written approval must be obtained
from written approval from NYSDEC the Town of Ithaca prior to disturbing more than five acres at once.
The “Erosion and Sediment Control Plan” and the “Erosion and Sediment Control Plan Prior to
Construction” in the accompanying drawings and waiver request identifies the major construction
activities that are the subject of this SWPPP. The order (or sequence) in which the major activities are
expected to begin is presented on the accompanying drawings, though each activity will not necessarily
be completed before the next begins. In addition, these activities could occur in a different order if
necessary to maintain adequate erosion and sediment control. If this is the case, the contractor shall
notify the Owner’s/Operator’s Engineer overseeing the implementation of the SWPPP.
The Contractor will be responsible for implementing the erosion and sediment control measures
identified on the plans. The Contractor may designate these tasks to certain subcontractors as they see
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fit, but the ultimate responsibility for implementing these controls and ensuring their proper function
remains with the Contractor.
In accordance with Part III.B.c.iv. a phasing plan for the project and sequencing plans for all phases have
been provided. The plans address clearing and grubbing, excavation and grading, utility and
infrastructure installation, final stabilization, and any other construction activity at the site that will result
in soil disturbance. Refer to the plans for further information on the project phasing and sequencing.
5.0 CONSTRUCTION-PHASE POLLUTION CONTROL
The SWPPP and accompanying plans identify the temporary and permanent erosion and sediment
control measures that have been incorporated into the design of this project. These measures will be
implemented during construction, to minimize soil erosion and control sediment transport off-site, and
after construction, to control the quality and quantity of stormwater runoff from the developed site.
Erosion control measures, designed to minimize soil loss, and sediment control measures, intended to
retain eroded soil and prevent it from reaching water bodies or adjoining properties, have been
developed in accordance with the following documents:
• NYSDEC SPDES General Permit for Stormwater Discharges From Construction Activity, Permit
No. GP-0-25-001 (effective January 29, 2025 through January 28, 2030)
• New York State Standards and Specifications for Erosion and Sediment Control, NYSDEC
(November 2016)
The SWPPP and accompanying plans outline the construction scheduling for implementing the erosion
and sediment control measures. These documents include limitations on the duration of soil exposure,
criteria and specifications for placement and installation of the erosion and sediment control measures,
a maintenance schedule, and specifications for the implementation of erosion and sediment control
practices and procedures.
Temporary and permanent erosion and sediment control measures that shall be applied during
construction generally include:
1. Minimizing soil erosion and sedimentation by stabilization of disturbed areas and by removing
sediment from construction site discharges.
2. Preservation of existing vegetation to the greatest extent practical. Following the completion of
construction activities in any portion of the site, permanent vegetation shall be established on
all exposed soils.
3. Site preparation activities to minimize the area and duration of soil disruption.
4. Establishment of permanent traffic corridors to ensure that “routes of convenience” are avoided.
5.1 Temporary Erosion and Sediment Control Measures
The temporary erosion and sediment control measures described in the following sections are included
as part of the construction documents.
5.1.1 Stabilized Construction Access
Prior to construction, stabilized construction access(es) will be installed, per accompanying plans, to
reduce the tracking of sediment onto public roadways.
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Construction traffic must enter and exit the site at the stabilized construction access(es). The intent is
to trap dust and mud that would otherwise be carried off-site by construction traffic.
The access(es) shall be maintained in a condition, which will control tracking of sediment onto public
rights-of-way or streets. When necessary, additional aggregate will be placed atop the filter fabric to
assure the minimum thickness is maintained. All sediment and/or soil spilled, dropped, or washed onto
public rights-of-way must be removed immediately. Periodic inspection and needed maintenance shall
be provided after each substantial rainfall event.
5.1.2 Silt Fencing
Prior to the initiation of and during construction activities, a geotextile filter fabric (or silt fence) will be
established downgradient of all disturbed areas. These barriers may extend into non-impact areas to
provide adequate protection of adjacent lands.
Clearing and grubbing will be performed only as necessary for the installation of the sediment control
barrier. To facilitate effectiveness of the silt fencing, daily inspections and inspections immediately after
significant storm events will be performed by the Contractor(s). Maintenance of the fence will be
performed as needed.
5.1.3 Temporary Seeding
For areas undergoing clearing, grading, and disturbance as part of construction activities, where work
has temporarily ceased, temporary soil stabilization measures must be initiated by the end of the next
business day and completed within fourteen (14) days from the date the soil disturbance activity has
temporarily ceased.
5.1.4 Stone and Block Drop Inlet Protection
Concrete blocks surrounded by wire mesh and crushed stone will be placed around both existing catch
basins, and proposed catch basins once they have been installed, to prevent sediment from entering
the catch basins and storm sewer system. During construction, crushed stone shall be replaced as
necessary to ensure proper function.
depicted on the accompanying plans have been designed to provide 3,600 CF of storage per acre of
tributary watershed.
5.2 Permanent Erosion and Sediment Control Measures
The permanent erosion and sediment control measures described in the following sections are included
as part of the construction documents.
5.2.1 Establishment of Permanent Vegetation
Disturbed areas that will be vegetated must be seeded in accordance with the contract documents. The
type of seed, mulch, and maintenance measures as described in the contract documents shall also be
followed.
Permanent soil stabilization measures must be initiated by the end of the next business day and
completed within fourteen (14) days from the date the soil disturbance activity has permanently ceased.
Final site stabilization is achieved when all soil-disturbing activities at the site have been completed and
a uniform, perennial vegetative cover with a density of 80 percent has been established or equivalent
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stabilization measures (such as the use of mulches or geotextiles) have been employed on all unpaved
areas and areas not covered by permanent structures.
5.3 Other Pollutant Controls
Part I.C.1 of GP-0-25-001 prohibits discharges from construction material wastewater, pollutants used
in vehicle and equipment operation and maintenance, vehicle and equipment washing and toxic or
hazardous substances.
The following table identifies materials and/or chemicals commonly used and/or stored on
construction sites and should be addressed in the site-specific spill prevention and response plan:
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Table 11: Common Construction Pollutants
Material/Chemical Physical Description Stormwater Pollutants Location*
Pesticides
(insecticides,
fungicides,
herbicides,
rodenticides)
Various colored to
colorless liquid,
powder, pellets, or
grains
Chlorinated
hydrocarbons,
organophosphates,
carbamates, arsenic
Herbicides used for
noxious weed control
Fertilizer Liquid or solid grains Nitrogen, phosphorous Newly seeded areas
Cleaning solvents Colorless, blue, or
yellow-green liquid
Perchloroethylene,
methylene chloride,
trichloroethylene,
petroleum distillates
No equipment cleaning
allowed in project limits
Asphalt Black solid Oil, petroleum distillates Streets and roofing
Concrete White solid/grey liquid Limestone, sand, pH,
chromium
Curb and gutter, building
construction
Curing compounds Creamy white liquid Naphtha Curb and gutter
Hydraulic oil/fluids Brown oily petroleum
hydrocarbon
Mineral oil Leaks or broken hoses
from equipment
Gasoline Colorless, pale brown
or pink petroleum
hydrocarbon
Benzene, ethyl benzene,
toluene, xylene, MTBE
Secondary containment /
staging area
Diesel Fuel Clear, blue-green to
yellow liquid
Petroleum distillate, oil &
grease, naphthalene,
xylenes
Secondary containment /
staging area
Kerosene Pale yellow liquid
petroleum
hydrocarbon
Coal oil, petroleum
distillates
Secondary containment /
staging area
Antifreeze/coolant Clear green/yellow
liquid
Ethylene glycol, propylene
glycol, heavy metals
(copper, lead, zinc)
Leaks or broken hoses
from equipment
Sanitary toilets Various colored liquid Bacteria, parasites, and
viruses
Staging area
Construction
materials
Granular fill Various colored solids Sediment Stockpile / fill areas
Subbase course Gray/brown solid Sediment, dust Stockpile
Topsoil Brown solid Sediment Stockpile
Mulch Various colored solid Sediment, debris Staging area
Seed Brown/yellow solid Nutrients, debris Staging area
HDPE Storm Pipe Black solid Staging area
SDR-35, SDR-21
PVC Pipe
Various colored solid Staging area
Metals Frames and
Grates
Gray solid Staging area
Joint Sealant Light gray viscous
solid
Polyurethane Staging area
*(Area where material/chemical is used on-site)
July 17, 2026
Mr. Justin McNeal, Senior Civil Engineer
Town of Ithaca Engineering Department
114 Seven Mile Drive
Ithaca, New York 14850
RE: Bomber Heights Solar PV
Troy Road, Ithaca, New York
Project Number: 2240665
Dear Mr. McNeal:
Nexamp Solar, LLC and LaBella Associates, DPC (LaBella) received your copy of the Comment Letter
dated 04/29/2026. Please find the comment responses below.
Comment Letter
General
1, It is noted that the final SWPPP will need to be stamped by a licensed NYS Professional
Engineer.
Response: Acknowledged
2. Section 1.1 of the SWPPP specifies that the site does not discharge to a 303(d) waterbody, but
Section 2.5 specifies that it does discharge to a 303(d). It appears that the on-site streams
discharge into the Sixmile Creek. Review and revise for consistency.
Response: Upon review of the project site location and the receiving waterbodies, it was
confirmed that the site will discharge into Sixmile Creek, which is not a 303(d) waterbody.
The SWPPP narrative was updated to reflect that on-site streams will not discharge to a
303(d) waterbody.
3. Please revise the SWPPP to include the negative Jurisdictional Determination in regards to
the on-site wetlands, and provide any correspondence with the USACE regarding the on-site
wetlands.
Response: A statement was added in the SWPPP section 2.7 Wetlands stating there is a
negative Jurisdictional Determination from the NYSDEC and the approach taken to obtain it.
A USACE submission is scheduled to be submitted in the near future, and all correspondence
will be updated when received.
4. Please provide correspondence with NYSDEC regarding the on-site Class A regulated
streams.
Response: As of this response letter there has been no correspondence with NYSDEC
regarding the on-site Class A regulated streams. Correspondence can be provided if and
when it is necessary and initiated.
2
5. It is noted that per NYSDEC’s Solar Development Webinar from July 28, 2025, the 2018
NYSDEC Solar Memorandum and the Maryland Department of the Environment’s Solar
Design Guidance are outdated design documents, and the aforementioned webinar is the
relevant guidance.
Response: The SWPPP narrative and appendices have been updated to reflect the removal
of outdated solar design guidance.
6. Section 3.4 of the SWPPP specifies that the entire WQv is provided in RRv. Table 7 indicates
that only 87.94% of the WQv is reduced, so Steps 4 and 5 should be completed. Review and
revise accordingly.
Response: The stormwater on-site was reevaluated and only 55% of the WQv is being
reduced
7. Based on the topography of the site and the mapped DEC streams on and adjacent to the
site, it is anticipated that there may be 1-2 additional locations where channelized water exits
the site. Review and revise to ensure the design points are representative of the discharge
points from the site.
Response: The design points were kept the same as all flow from the site meets at a common
point downstream. The analysis point that was chosen on-site is assumed to be the longest
path.
8. Question 5 of the eNOI specifies that the project is not subject to SEQR, review and revise
accordingly.
Response: Question 5 of the eNOI has been updated to state the project is subject to SEQR
and when the documentation that the project review has been satisfied is obtained, question
5.a. will be answered.
9. Please provide a phasing plan showing defined limits to be used during construction to
maintain a maximum disturbance of 5 acres at any given time.
Response: A phasing plan has been added to the project plan set as sheet C407.
10. As a portion of the proposed solar array is located on slopes greater than 8%, the array falls
under CGP 0-25-001 Appendix B’s Table 2. The NYSDEC has provided accommodations in
their July 28, 2025 Solar Development Webinar for ground mounted solar arrays based on the
following two scenarios:
a. In areas of slopes greater than 8% slope, if it is determined by the engineer that sheet
flow can be maintained (using gravel diaphragms spaced in accordance with the below table)
or the relevant or equivalent Blue Book practices, then this meets the WQv and RRv
requirements (i.e., gravel diaphragms do not need to be sized to hold WQv), and the panels
may be considered “pervious” in modeling for the 1-year, 10-year, and 100-year storm events.
b. If it is determined by the engineer that sheet flow cannot be maintained on slopes
greater than 8%, gravel diaphragms or equivalent Blue Book practices may still be used to
meet the WQv and RRv requirements, but they must be sized to hold the entire WQv. In this
3
case, the panels would be considered “impervious” in modeling for the 1-year, 10-year, and
100-year storm events.
The SWPPP appears to show the gravel diaphragms being sized to store the WQv
(scenario 2), but the panels are currently modeled as pervious in the HydroCAD model
(scenario 1), so it is unclear if the engineer has determined that sheet flow can be maintained
on site. The SWPPP should be revised to clearly specify the approach and specify that sheet
flow can/cannot be maintained at the site.
Response: It is determined by engineer that sheet flow will be maintained across the site but
the level spreaders were still sized to hold the WQv and the panels were modeled as
pervious. The level spreaders have been reduced to 1’ x 1’, spaced per table 1 above and
have been modeled as pervious in the HydroCAD modeling.
11. In reference to comment 12 above, it appears that the gravel diaphragms are sized to store
the WQv to meet the WQv/RRv requirements for panels on slopes greater than 8%. If this is
the case, this is considered a deviation from the 2024 Stormwater Design Manual. Question 37
of the eNOI should be revised accordingly to account for this.
Response: See response number 10. Question 37 of the eNOI was not updated.
12. Per the 2024 Stormwater Manual, local rainfall distribution curves should be utilized rather
than the generalized “Type II” rainfall distribution curves. Review and revise as necessary.
Response: The SWPPP narrative and HydroCAD models were updated to reflect the relevant
local IDF rainfall data for the project site.
13. The proposed dry swales should be modeled in HydroCAD to confirm the required design
standards such as flow depth and velocity.
Response: The proposed dry swales were modeled in HydroCAD to confirm the required
design standards such as flow depth and velocity are adequate to handle the flows on-site.
14. If no infiltration is anticipated within the dry detention basin, it is recommended that the
lowest orifice be at the bottom of the basin to completely drain the basin between rain
events.
Response: The lowest orifice was lowered to be at the bottom of the basin to completely
drain the basin between rain events.
4
15. BIO-1 has a peak elevations above the storage in the 100-year event. It is recommended to
add additional storage to accommodate this peak elevation or revise the outlet structure to
pass additional flow.
Response: The stormwater was reevaluated and Bio-1 has been removed from the design
and replaced with dry swales.
16. Please provide calculations for pre-treatment requirements for the practices where pre-
treatment volume is not included in HydroCAD.
Response: The pretreatment for the bioretention basin is accounted for in the HydroCAD
model. According to the NYS Stormwater Design Manual, the bioretention basin must have
25% of the WQv as pretreatment. The HydroCAD model takes this into account by adding the
forebay into the storage section and showing that 25% of the required WQv is being met.
According to the NYS Stormwater Design Manual Section 6.5.3, a 2’ x 1’ pea gravel
diaphragm at the downgradient edge of the impervious surface with a maximum
contributing slope of 5% is sufficient as pretreatment for a Dry Swale. The pea gravel
diaphragm is shown in detail 3 on sheet C501.
17. Please provide calculations for the proposed culverts beneath the access road.
Response: Calculations for the proposed culverts beneath the access road have been
included in the HydroCAD modeling. Appendix C of SWPPP.
18. Revise the construction sequence on sheet C001 of the plans to include the installation of
stormwater management practices (dry swales and bioretention basins) after grading is
complete and the site is stabilized.
Response: The construction sequence reflected on C001 has been updated to reflect the
installation of stormwater management practices after finalization of grading and approval
of stabilization by the qualified inspector.
19. Portions of the proposed solar panels overhang the dry swales and conveyance swales.
Please confirm that the panels in these locations will not impede access and maintenance of
the stormwater management practices.
Response: The layout has been revised and solar panels are not proposed to overhang the
dry swales and conveyance swales.
20. Please provide a slopes analysis plan for the areas where solar panels are proposed showing
slopes greater than 8%, 20%, and 35%.
Response: Additional sheets labeled C405 and C406 were added to the project plan set to
depict the site slope heat map. The ranges shown on the plan sheet demonstrate slopes 8-
10%, 10-20%, 20-35%, and slopes >35%, which correlate with the gravel diaphragm design
requirements.
21. Please provide a detail showing the spacing between rows of solar panels.
5
Response: Detail 5 on sheet C502 has been amplified, detailing the row spacing for the
proposed solar panel installation.
22. The eNOI indicates 34.0 acres of disturbance but the SWPPP narrative indicates 31.8 acres of
disturbance. This discrepancy should be corrected.
Response: The eNOI, SWPPP narrative and plan set were updated to display the accurate
limit of disturbance for the project.
23. Please include a landscaping plan that details all proposed plantings.
Response: A landscaping plan has been included in the plan set starting with sheets L100.
24. Provide soil borings in accordance with the NYSDEC Stormwater Design Manual. Water table
elevation should be confirmed for bioretention areas and dry swale area to determine if an
impermeable liner will be required.
Response: Soils borings were performed in the areas of the bioretention and dry swales. Due
to the shallow bedrock, impermeable liners have been proposed in the design. Please see
detail 5 sheet C503 and detail 3 sheet C501 respectively.
25. For bioretention areas, filter media layer thickness should be 30-inches minimum.
Response: Detail 5 on sheet C503 has been updated to reflect the 30-inch minimum for
bioretention filter media layer thickness.
26. The model for BIO-2 shows 24-inches of storage during the 100-year event whereas the
maximum allowable in 18-inches.
Response: BIO-2 was adjusted so only 18-inches of storage is being utilized in the 100-year
event.
27. Provide a check dam detail in accordance with NYSDEC Blue Book standards.
Response: A stone check dam detail was added to the project plan set on sheet C501 as
Detail 8. Sizing was done in compliance with this detail shown in detail 8 on sheet C501.
28. The dry swale underdrain shall be a minimum of 6-inch diameter.
Response: Detail 3 on sheet C501 has been updated to reflect the 6-inch minimum diameter
for the dry swale underdrain.
29. It is recommended that stone outlet protection be provided at the bioretention and detention
pond outfalls to prevent the potential for erosion.
Response: Stone outlet protection was added to the downstream end sections for the
bioretention and detention ponds. A detail has been added to sheet C503 as Detail 10 in
accordance with the NYSDEC stone outlet protection requirements.
30. Prior to issuance of a building permit, a Stormwater Operation and Maintenance Agreement
will be required in accordance with Chapter 228 of the Town of Ithaca Town Law.
6
Response: Acknowledged.
31. Please include in the SWPPP that weekly inspections shall be submitted to the Town of
Ithaca Engineering Department.
Response: Submission of weekly inspection reports has been added to the SWPPP in sections
6.2.1 and 7.4 of the narrative.
32. Once the SWPPP has been deemed acceptable by the Town Engineer, the Applicant will
need to apply for a SWPPP Permit through OpenGov. Final approval will not be issued until
the application has been submitted and the Fee has been paid.
Response: Acknowledged.
If you have any questions or require any additional information, please do not hesitate to contact me
via email at agraham@labellapc.com.
Respectfully submitted,
LaBella Associates
Andrew Graham, PE
Civil Engineer