HomeMy WebLinkAbout13 - Full Expanded EAF - 2024-12-03 - Attachment O - Subsurface Soil and Groundwater Investigation ReportATTACHMENT O
LETTER REPORT ON SUBSURFACE
SOIL AND GROUNDWATER INVESTIGATION,
PREPARED BY CARLIN – SIMPSON &
ASSOCIATES, LLC., DATED DECEMBER 20, 2023
CARLIN SIMPSON & ASSOCIATES, LLC
Consulting Geotechnical and Environmental Engineers
61 Main Street, Sayreville, New Jersey 08872
Tel. (732) 432-5757
Fax. (732) 432-5717
20 December 2023
Principal:
Robert B. Simpson, P.E.
Associates:
Meredith R. Anke, P.E.
Stephen Rossi, P.E.
Catherine K. Andersen, P.E.
Michal Wroblewski, P.E.
Kurt W. Anke
Eric J. Shaw
Toll Brothers
42 Old Ridgebury Rd.
Danbury, CT 06810
Attn: Mr. Kevney Moses
Land Entitlement Manager, NY Metro
Re: Letter Report on Subsurface Soil and Groundwater Investigation
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY (CSA Job #23-148)
Dear : Mr. Moses:
In accordance with our proposal dated 9 November 2023 and your subsequent
authorization, we have completed a Subsurface Soil and Groundwater Investigation for the
referenced site. The purpose of this study was to determine the nature and engineering properties
of the subsurface soil and the groundwater conditions for the new development. We understand
that the planned construction will consist of town home development, clubhouse, pool, tennis
courts, roadways and parking areas, and a stormwater management system. This letter report is to
provide information for the design of the proposed stormwater management system.
Our scope of work for this project included the following:
1.Reviewed the proposed layout, the existing site conditions, the expected soil
conditions, and planned this study.
2.Retained Traficante Contracting, Inc. to excavate twenty-four (24) test pits
throughout the site.
3.Performed ten (10) infiltration tests for the planned stormwater
management areas.
4. Laid out the test pit locations in the field, visually identified the soil layers
encountered, obtained soil samples, and prepared detailed test pit logs and
a Test Pit Location Plan.
5. Tested selected samples in our laboratory. Analyzed the field data and lab
data, and prepared this report containing the results of this study.
1.0 STORMWATER MANAGEMENT SYSTEM
We understand that the planned construction will include a new stormwater management
system that will include several stormwater infiltration basins. To determine the subsurface soil
and groundwater conditions for the proposed stormwater management system, twenty-four (24)
test pits were completed in November and December 2023. All test pits were performed under the
full-time inspection of Carlin-Simpson & Associates. Detailed test pit logs have been prepared and
are included in this report. Our field engineer visually identified all of the soil layers and obtained
soil samples during the test pit operations. The summary of the test pit observations during this
study are located in Table 1 below.
Table 1 – Summary of Test Pit Observations
Test Pit
No.
Approximate
Ground
Surface
Elevation
Depth to Groundwater
(Elevation)
Depth to
Bottom of
Existing Fill
(Elevation)
Depth to Probable
Bedrock (Elevation)
TP-1 +424.0 1’3” (+422.8) NE NE to 5’6”
TP-2 +421.0 2’8” (+418.3) NE NE to 6’0”
TP-3 +442.0 2’4” (439.6) NE NE to 6’6”
TP-4 +443.0 5’8” (+437.3) NE BR @ 6’8” (+436.3)
TP-5 +437.0 2’8” (+434.3) NE NE to 6’6”
TP-6 +446.0 5’0” (+441.0) NE NE to 7’0”
TP-7 +450.0 4’4” (+445.7) NE BR @ 6’3” (+443.8)
TP-8 +431.0 NE to 8’0” NE NE to 8’0”
TP-9 +456.0 NE to 7’0” NE NE to 7’0”
TP-10 +486.0 6’3” (+479.8) 1’2” (+484.8) NE to 8’0”
TP-11 +488.0 7’6” (+480.5) NE NE to 9’0”
TP-12 +464.0 5’2” (+458.8)* NE NE to 8’0”
TP-13 +438.0 NE to 7’0” NE NE to 7’0”
TP-13A +432.0 1’8” (+430.3)*
SHGW @ 0’9” (+431.3) NE NE to 8’0”
TP-13B +436.0 NE to 6’6” NE NE to 6’6”
TP-14 +500.0 NE to 8’6” NE NE to 8’6”
TP-15 +472.0 4’10” (+467.2)* NE NE to 9’0”
TP-16 +454.0 NE to 7’0” NE BR @ 7’0” (+438.0)
TP-17 +517.0 NE to 8’0” NE NE to 8’0”
TP-18 +506.0 NE to 7’0” NE BR @ 7’0” (+499.0)
TP-19 +509.0 NE to 7’3” NE BR @ 7’3” (+501.8)
TP-20 +519.0 NE to 8’6” NE NE to 8’6”
Test Pit
No.
Approximate
Ground
Surface
Elevation
Depth to Groundwater
(Elevation)
Depth to
Bottom of
Existing Fill
(Elevation)
Depth to Probable
Bedrock (Elevation)
TP-22 +459.0 1’7” (+457.4) NE NE to 8’0”
TP-23 +413.0 1’4” (+411.7)* NE NE to 4’0”
NE – Not Encountered
(*) – Possible Perched or Trapped Water
SHGW – Evidence of Seasonal High Groundwater
BR – Bucket Refusal on Probable Bedrock
During this study, ten (10) infiltration tests were performed for the proposed stormwater
management areas. The infiltration tests were performed in accordance with NYSDEC procedures.
The results of infiltration tests that were performed are summarized in Table 2 below. The vertical
permeability rate (Km) was also calculated using the equation below.
Should stormwater management areas be planned in other portions of the property, they
should be evaluated on a case-by-case basis. The stormwater management systems must be
designed in accordance with the applicable New York State Department of Environmental
Conservation (NYSDEC) regulations and the most recent New York State Stormwater
Management Design Manual. The testing requirements are outlined in Appendix D of the manual.
Table 2 – Stormwater Infiltration Test Results
Test Pit
No.
Approximate
Ground Surface
Elevation
Test Depth Infiltration Rate
(in/hr)
Calculated Vertical
Permeability Km (in/hr)
TP-4 +443.0 3’0” (+440.0) 10.5 1.34
TP-6 +446.0 4’0” (+442.0) 6.0 0.67
TP-8 +431.0 4’0” (+427.0) 5.5 0.61
TP-13 +438.0 2’0” (+436.0) 24.0 23.55
TP-13B +436.0 4’0” (+432.0) 8.5 1.02
TP-14 +500.0 1’5” (+498.6) 2.0 0.20
TP-16 +454.0 4’0” (+450.0) 12.0 1.62
TP-17 +517.0 1’9” (+515.3) 20.0 4.18
TP-19 +509.0 1’9” (+507.3) 0.0* 0.0
TP-20 +519.0 1’11” (+517.1) 24.0 23.55
(*) - Presoak dropped 12.5 inches in approximately 20 hours. The test did not move the
remainder of the day, 0.0 in/hr issued.
2.0 GENERAL
The findings, conclusions and recommendations presented in this report represent our
professional opinions concerning subsurface conditions at the site. The opinions presented are
relative to the dates of our sitework and should not be relied on to represent conditions at later
dates or at locations not explored. The opinions included herein are based on information provided
to us, the data obtained at specific locations during the study and our past experience. If additional
information becomes available that might impact our geotechnical opinions, it will be necessary
for Carlin-Simpson & Associates to review the information, reassess the potential concerns, and
re-evaluate our conclusions and recommendations.
This report is provided for the exclusive use of Toll Brothers and the project specific design
team and may not be used or relied upon in connection with other projects or by other third parties.
Carlin-Simpson & Associates disclaims liability for any such third party use or reliance without
express written permission. Use of this report or the findings, conclusions or recommendations by
others will be at the sole risk of the user. Carlin-Simpson & Associates is not responsible or liable
for the interpretation by others of the data in this report, nor their conclusions, recommendations
or opinions.
Thank you for allowing us to assist you with this project. Should you have any questions
or comments, please contact this office.
Very truly yours,
CARLIN-SIMPSON & ASSOCIATES, LLC
CATHERINE K. ANDERSEN, P.E.
Project Engineer
ROBERT B. SIMPSON, P.E.
Principal
File No. 23-148
C A R L I N S I M P S O N & A S S O C I A T E S , L L C
Consulting Engineers • Geotechnical & Environmental
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
Test Pit Logs
TP-1 (Elev. +424.0)
0’0”-0’8” Dark brown topsoil
0’8”-2’2” Yellow brown Clayey SILT and, coarse to fine Sand,
trace coarse to fine Gravel soft, wet
2’2”-5’6” Gray, brown coarse to fine SAND, some (+) Silt,
some coarse to fine Gravel, with cobbles dense, wet
Groundwater encountered @ 1’3”
TP-2 (Elev. + 421.0)
0’0”-0’6” Dark brown topsoil
0’6”-2’2” Light brown coarse to fine SAND, some Silt,
trace coarse to fine Gravel medium dense, moist
2’2”-6’0” Brown coarse to fine SAND, some (+) Silt,
some (-) coarse to fine Gravel, with cobbles and boulders dense, wet
Groundwater encountered @ 2’8” (slow inflow)
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-3 (Elev. +442.0)
0’0”-0’6” Dark brown topsoil
0’6”-1’10” Yellow brown Clayey SILT some, coarse to fine Sand,
trace coarse to fine Gravel medium stiff, moist
1’10”-2’6” Brown coarse to fine SAND, some (+) Silt,
some (+) coarse to fine Gravel, with cobbles and boulders dense, moist
2’6”-3’6” Mottled gray, orange brown coarse to fine SAND,
and (+) Silt, some (-) coarse to fine Gravel with cobbles medium dense, moist
3’6”-6’6” Brown coarse to fine SAND, and Silt, some (-)
coarse to fine Gravel, with cobbles medium dense, moist
Groundwater encountered @ 2’4” (slow inflow)
TP-4 (Elev. +443.0)
0’0”-0’6” Dark brown topsoil
0’6”-2’6” Yellow brown Clayey SILT some (+), coarse to
fine Sand, little coarse to fine Gravel, with cobbles soft, moist
2’6”-4’4” Gray, brown coarse to fine SAND, and Silt,
some coarse to fine Gravel, with cobbles and boulders dense, moist
4’4”-6’8” Gray, brown coarse to fine SAND, some (+) Silt,
some coarse to fine Gravel, with cobbles and boulders
(glacial fill) very dense, moist
6’8” Possible Bedrock Unrippable
Groundwater encountered @ 5’8” (slow inflow)
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-5 (Elev. +437.0)
0’0”-0’6” Dark brown topsoil
0’6”-1’8” Light brown coarse to fine SAND, and Silt,
trace coarse to fine Gravel medium dense, moist
1’8”-6’6” Brown coarse to fine SAND, some Silt, some (-) coarse
to fine Gravel, with cobbles and boulders dense, moist
Groundwater encountered @ 2’8” (slow inflow)
TP-6 (Elev. +446.0)
0’0”-0’7” Dark brown topsoil
0’7”-1’10” Light brown coarse to fine SAND, some (+) Silt,
trace coarse to fine Gravel medium dense, moist
1’10”-7’0” Brown coarse to fine SAND, some (-) Silt,
little (+) coarse to fine Gravel, with occasional cobbles dense, moist
7’0” Refusal on backhoe, possible boulders
Groundwater encountered @ 5’0” (slow inflow)
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-7 (Elev. +450.0)
0’0”-0’7” Dark brown topsoil
0’7”-2’0” Light brown coarse to fine SAND, and (-) Silt,
Trace medium to fine Gravel medium dense, moist
2’0”-6’3” Brown coarse to fine SAND, some (+) Silt,
Some coarse to fine Gravel, with cobbles and boulders dense, moist
6’3” Refusal on backhoe, possible bedrock
Groundwater encountered @ 4’4” (slow inflow)
TP-8 (Elev. +431.0)
0’0”-0’8” Topsoil
0’8”-2’10” Brown coarse to fine SAND, some (+) Silt medium dense, moist
2’10”-8’0” Gray, brown coarse to fine SAND, some Silt, dense, moist
little coarse to fine Gravel, with cobble
No groundwater encountered
TP-9 (Elev. +456.0)
0’0”-0’7” Dark brown topsoil with many roots
0’7”-7’0” Gray, brown coarse to fine SAND, and (-) Silt,
little coarse to fine Gravel, with occasional cobbles medium dense, moist
No groundwater encountered
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-10 (Elev. +486.0)
0’0”-1’2” FILL (Gray coarse to fine Sand, trace silt, some
coarse to fine Gravel) medium dense, moist
1’2”-1’8” Light brown coarse to fine SAND, and Silt medium dense, moist
1’8”-8’0” Brown coarse to fine SAND, some Silt,
some coarse to fine Gravel, with cobbles and boulders dense, moist
Groundwater encountered @ 6’3”
TP-11 (Elev. +488.0)
0’0”-0’7” Dark brown topsoil with many roots
0’7”-2’4” Light brown coarse to fine SAND, and Silt,
little coarse to fine Gravel, with occasional cobbles medium dense, moist
2’4”-9’0” Gray, brown coarse to fine SAND, some Silt,
some (-) coarse to fine Gravel, with cobbles and boulders dense, moist
Groundwater encountered @ 7’6” (moderate inflow)
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-12 (Elev. +464.0)
0’0”-0’6” Dark brown topsoil with many roots
0’6”-2’3” Light brown coarse to fine SAND, and Clayey Silt,
little coarse to fine Gravel medium dense, moist
2’3”-8’0” Gray, brown coarse to fine SAND, some (+) Silt,
some (+) coarse to fine Gravel, with many cobbles
and boulders dense, moist
Groundwater encountered @ 5’2” (slow inflow, trapped)
only visible in one corner of the test pit, bottom of excavation dry
TP-13 (Elev. +438.0)
0’0”-0’8” Dark brown topsoil with many roots
0’8”-2’3” Light brown coarse to fine SAND, some (+) Silt,
little coarse to fine Gravel medium dense, moist
2’3”-7’0” Gray, brown coarse to fine SAND, little Silt, some (+)
coarse to fine Gravel, with cobbles and boulders dense, moist
No groundwater encountered
TP-13A (Elev. +432.0)
0’0”-0’9” Brown topsoil
0’9”-8’0” Mottled gray, orange brown, brown coarse to fine SAND,
and Silt, some coarse to fine Gravel dense, moist
Evidence of Seasonal High Groundwater (i.e. Mottling) @ 0’9”
Groundwater encountered @ 1’8” (slow inflow)(perched)
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-13B (Elev. +436.0)
0’0”-0’10” Dark brown topsoil with many roots
0’10”-1’6” Gray, brown coarse to fine SAND, some (+) Silt medium dense, moist
1’6”-2’10” Light brown coarse to fine SAND, and (-) Silt,
trace coarse to fine Gravel medium dense, moist
2’10”-6’6” Brown coarse to fine SAND, some (+) Silt,
some (-) coarse to fine Gravel medium dense, moist
6’6” Refusal on boulders
No groundwater encountered
TP-14 (Elev. +500.0)
0'0"-0’10" Dark brown topsoil with many roots
0’10"-2’2" Brown coarse to fine Sand, some Silt,
little coarse to fine Gravel, with cobbles and boulders medium dense, moist
2’2"-5’0” Gray, brown coarse to fine Sand, little (+) Silt,
some coarse to fine Gravel dense, moist
5’0”-8’6” Gray, brown coarse to fine Sand, little (+) Silt,
and coarse to fine Gravel, with many cobbles and
boulders very dense, moist
No groundwater encountered
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-15 (Elev. +472.0)
0’0”-0’7” Brown topsoil with many roots
0’7”-2’6” Light brown coarse to fine SAND, some Silt,
some coarse to fine Gravel, with cobbles medium dense, moist
2’6”-7’0” Gray, brown coarse to fine SAND, some (-) Silt,
some coarse to fine Gravel, with cobbles dense, moist
7’0”-9’0” Gray brown coarse to fine SAND, little Silt,
some (-) coarse to fine Gravel dense, moist
Groundwater encountered @ 4’10” (trapped)
Bottom of excavation dry
TP-16 (Elev. +454.0)
0’0”-0’10” Dark brown topsoil with many roots
0’10”-5’6” Brown coarse to fine SAND, some (+) Silt,
little (-) coarse to fine Gravel, with occasional cobbles
and boulders medium dense, moist
5’6”-7’0” Gray, brown Schist; completely weathered dense, moist
7’0” Probable Bedrock unrippable
No groundwater encountered
Probable Bedrock @ 7’0”
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-17 (Elev. +517.0)
0’0”-1’0” Dark brown topsoil with many roots
1’0”-2’6” Brown coarse to fine Sand, some (-) Silt,
some coarse to fine Gravel, with cobbles and boulders medium dense, moist
2’6”-8’0” Gray, brown coarse to fine Sand, little (+) Silt,
some coarse to fine Gravel, with cobbles and boulders dense, moist
No groundwater encountered
TP-18 (Elev. +506.0)
0’0”-0’10” Dark brown topsoil with many roots
0’10”-1’8” Brown coarse to fine Sand, some Silt,
little coarse to fine Gravel, with cobbles and boulders medium dense, moist
1’8”-2’8” Light brown coarse to fine Sand, some (+) Silt,
some coarse to fine Gravel medium dense, moist
2’8”-7’0” Gray brown, brown coarse to fine Sand, little (+) Silt,
some coarse to fine Gravel, Schist; completely weathered very dense, moist
7’0” Refusal on backhoe, probable bedrock unrippable
No groundwater encountered
Probable Bedrock @ 7’0”
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-19 (Elev. +509.0)
0’0”-1’5” Dark brown topsoil with many roots
1’5”-4’0” Gray brown, brown coarse to fine SAND, little (+) Silt,
little coarse to fine Gravel medium dense, moist
4’0”-7’3” Gray brown, brown coarse to fine Sand, little (+) Silt,
some coarse to fine Gravel, with cobbles and boulders very dense, moist
7’3” Refusal on backhoe, possible bedrock unrippable
No groundwater encountered
Probable Bedrock @ 7’3”
TP-20 (Elev. +519.0)
0’0”-1’2” Dark brown topsoil with many roots
1’2”-2’6” Light brown coarse to fine SAND, little Silt,
little coarse to fine Gravel, with cobbles medium dense, moist
2’6”-8’6” Gray brown, brown coarse to fine SAND, little Silt,
some coarse to fine Gravel, with cobbles and boulders very dense, moist
No groundwater encountered
Proposed Residential Development
Stormwater Management System Study
2300 Catherine St.
Cortlandt, NY
23-148
21 November 2023
TP-22 (Elev. +459.0)
0’0”-0’8” Dark brown topsoil with roots
0’8”-7’0” Brown coarse to fine SAND, and Silt, little coarse to
fine Gravel medium dense, moist to wet
7’0”-8’0” Gray, brown Clayey SILT some, coarse to fine Sand medium stiff, moist
Groundwater encountered @ 1’7” (slow inflow)
TP-23 (+413.0)
0’0”-0’10” Dark brown topsoil with roots
0’10”-1’4” Gray coarse to fine SAND, some Silt loose, wet
1’4”-4’0” Mottled gray, orange brown SILT some, coarse to fine Sand,
trace coarse to fine Gravel, with occasional cobbles very dense, moist
Groundwater encountered @ 1’4” (slow inflow)(perched)
Bottom of excavation dry