HomeMy WebLinkAbout24IWC7-339 Chesterfield Rd Development ReportJune 20, 2024 339 Chesterfield Rd 1
RCL THOMPSON LLC
Development Report
Prepared For
339 Chesterfield Rd
Oakdale, CT
June 20, 2024
Prepared By:
RCL Thompson LLC
19 Pepperbush Dr
Clinton, CT 06413
860-941-7721
_____________________________________
Ryan E. Thompson, PE No. 29817
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Table of Contents
Contents
1.0 Site Background ...................................................................................................................................... 3
2.0 Location Map .......................................................................................................................................... 4
3.0 Wetland Narrative ................................................................................................................................... 5
4.0 Stormwater Narrative .............................................................................................................................. 8
5.0 Cultec Calculations ............................................................................................................................... 11
6.0 Stone Diaphragm Calculations .............................................................................................................. 13
7.0 Soils Map .............................................................................................................................................. 14
Appendix A – Wetland Report
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1.0 Site Background
LOCATION: The project site consists of two lots that are to be merged into one. The total area of the two
lots combined is 55.01 acres. The site is located along Chesterfield Road in Oakdale. The two sites are
known as Map ID 021/001/000 (311 Chesterfield Rd) and Map ID 021/001/00A (339 Chesterfield Rd) on
the Montville Tax Maps.
ZONING: The site lies within the R80 Zone. The following data table depicts the existing and proposed
zoning data and requirements pertinent to this project.
EXISTING SITE CHARACTERISTICS:
The existing site consists of two parcels, shown as Parcel 1 and Parcel 2 on the Existing Conditions map
on Page 1 of the submitted plans. Parcel 1 is largely forested with wetlands in several locations
throughout the property. The southern end fronts along Chesterfield Road for 500’. There exists a
residential structure on the south end of the property between the road and part of the delineated wetlands
area. Additionally the wetlands connect to a pond to the east of the residential structure and northerly of
Chesterfield Road. The remainder of the parcel is vacant forested land with slopes ranging from 2-5% up
to 25%.
There are several wetland areas including a pond on the site. As the total area of the two properties equals
55.01 acres, this report only focuses on the wetlands that are applicable to consideration for feasible
development of the parcel. The wetlands in the project area were field delineated by Martin Brogie who
is a certified soil scientist in Connecticut. The flags were then surveyed and added to the map by Ryan
Thompson, PL, LS a licensed engineer and land surveyor in Connecticut. A separate report prepared by
the soil scientist is being submitted in addition to this report. A detailed wetlands narrative with
alternatives analysis is provided in later sections of this report.
There is an existing 50’ long paved driveway connecting to Chesterfield Road. Beyond the paved portion
of the driveway is a rutted driveway access that crosses over a 2’ diameter corrugated metal pipe culvert
and a concrete slab through the existing wetland area. The driveway then continues for approximately
200’ adjacent to the northern side of the wetlands and pond within the Upland Review Area (URA). After
leaving the URA, the rutted driveway terminates in a relatively flat clearing overlooking the pond. There
is an existing shed in the clearing.
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2.0 Location Map
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3.0 Wetland Narrative
The site consists of two parcels which are to be merged into one lot with an area of 55.01 acres. The site
hosts several wetland areas, but the only one pertinent to this project is the wetland system that exists at
the southern end of the site north of Chesterfield Road. The pertinent wetland system consists of a
wetland area on the western side of the lot that feeds into a pond on the eastern side of the lot. There are
other wetland areas on the totality of the 55.01 acre property. Those areas have not been delineated and
are not within the scope of this potential project. The closest that any of these wetland areas lie to the
north of the proposed project site approximately 350’ away.
IDENTIFIED WETLANDS:
The wetland / watercourse that falls within the scope of this project was field delineated on March 14,
2024 by certified soil scientist Martin Brogie. The flags and limits of these delineated wetlands are
depicted on the Existing Conditions map included in the plan set. Additionally, a wetland report was
produced by Mr. Brogie and is included in this submission.
AREA & SOILS:
The area of wetlands included in this project is 114,639 Square Feet (2.63 acres). The soils identified on
site include Ridgebury, Leicester, and Whitman; Timakwa and Natchaug; Caden and Freetown,
Woodbridge Fine Sandy Loam; and Charlton-Chatfield complex soils. The site falls within the Oxoboxo
Brook Sub-Regional Drainage Basin.
PROPOSED PROJECT DESCRIPTION:
The intent of this project is to merge the two lots together into one lot, demolish the existing residential
structure and septic system, construct a new residential structure, replace the 2’ CMP culvert with an
engineered water crossing increasing both the capacity of water flow through structure and the structural
capacity of the driveway to accommodate a 30’ long fire apparatus as required by the Town of Montville
Fire Marshall. Associated earthwork necessary to complete the project is summarized in the following
table. Due to the steep slopes to the rear of the proposed house location, a retaining wall not to exceed 5’
in height at its highest point is proposed. The earthwork associated with the house excavation and
retaining wall is included in the summary table below. All earthwork will be performed using typical
construction vehicles such as excavators, backhoes, loaders, and dozers. The emplacement of the culverts
for the proposed water crossing will be by hand and the emplacement of the stone will be with excavator.
ALTERNATIVES ANALYSIS:
Three alternatives were considered for the development of this property. They include the proposed
project described in the previous paragraph, a modified version of the proposed project that realigns the
driveway, and an option to remodel and update the existing structure.
The details of the preferred proposed option have already been discussed in previous paragraphs.
However, for summary, this option requires improving the existing wetland crossing and driveway
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leading to the clearing north of the pond. The proposed residential structure and septic systems are all
greater than 50’ from the wetland and are outside of the upland review area.
The modified version of the proposed project includes realignment of the driveway further uphill and
upland of the wetland. This realignment would seek to push the driveway approximately 15 feet north of
the existing alignment. This would require substantial earthwork in the upland review area due to the
steep slopes upland of the current alignment. The ground slopes at approximately a 2h:1v rate which
would require significantly more earthwork within the upland review area than the preferred option.
The remodel option would result in less earthwork in the wetland area; however, it presents other less
optimal situations. Specifically, the existing house sewage is serviced by an antiquated septic system
which is currently located approximately 5’ from the edge of the delineated wetland. Additionally, there
is a well located within the delineated wetland limits. As the existing septic system is approximately 40’
from the well, in order to be code compliant, a new septic system will need to be installed 75’ from the
existing well. There is no location south of the wetlands between the wetlands and the road to place a new
code compliant septic system that is further away than 5’ from the edge of the delineated wetlands and 75’
away from the well.
Additionally, any septic system placed in this area would surely be challenged by a high ground water
table, requiring that the system be designed to stringent MLSS spread lengths (ensuring a much large
septic system than will be required in the location proposed). Based on similar sites, in the absence of
soil testing done in this location, the length of the leach field is estimated to be approximately 75’ with an
excavation depth of 18”. This will result in a total excavation of approximately 20 CY. However, it must
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be noted that is simply the excavation volume and there would be approximately 40-50 CY of septic fill
material placed 5’ from the wetland edge.
Finally, it should be noted that more than half of the existing residential structure is constructed within the
upland review area. Therefore, any activity that is related to remodeling of the structure or rebuilding of a
structure in that location is all within the regulated area. The location of the proposed structure is outside
of the regulated area. It also should be noted that the existing structure is not compliant with current
zoning regulations. In order to rebuild a new structure in the vicinity of the existing structure, it would
not be possible to stay within the required setback limits while also not impacting the wetlands.
The following summary table highlights the key points of consideration between each option.
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EROSION & SEDIMENT CONTROL:
All open cuts / earthwork locations will be protected via the installation of silt fencing as shown on the
Site Development Plan. The existing asphalt driveway will serve as a construction entrance. Stockpile
locations will be protected with silt fencing around the base of the pile. All final grading shall be seeded
or stabilized within 7 days after grading.
4.0 Stormwater Narrative
The project site is in the southern quarter of two lots which shall be merged into one 55.01 acre parcel.
The project includes the demolition of an existing residential structure and shed, the construction of a
water crossing sufficient to support emergency vehicles, and the construction of a new residential
structure further away from Chesterfield Road and overlooking a pond on the southern end of the
property.
DRAINAGE AREA:
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This project proposes to utilize a Cultec infiltration system and a stone diaphragm along the downgradient
side of the proposed driveway to mitigate the slight increase in runoff due to the project. The runoff
increase is the result of additional impervious area as shown in the table below:
PRE-DEVLOPMENT RUNOFF CALCULATIONS:
Pre-development runoff was calculated for the 10-yr and 25-yr storm events and are shown in the
following figure. The 10-yr storm runoff is 0.28 cfs and the 25-year storm runoff is 0.34 cfs.
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POST-DEVLOPMENT RUNOFF CALCULATIONS:
Post-development runoff was calculated for the 10-yr and 25-yr storm events and are shown in the
following figure. The 10-yr storm runoff is 0.30 cfs and the 25-year storm runoff is 0.36 cfs.
The Cultec HD-180 system is chosen to mitigate the runoff on this property by collecting runoff from the
roof of the proposed residence and infiltrating it into the soils. The use of the Cultec system reduces the
runoff in the 10-year and 25-year storms by 0.01 cfs.
The use of the stone diaphragm for 120’ linear feet along the driveway immediately north of the wetland
limits allows for some infiltration to occur and allows for the settlement of any pollutants coming off of
the driveway. The reduction in runoff from the stone diaphragm in the 10-year and 25-year storms is 0.01
cfs.
The combined reduction between both mitigation measures is 0.02 cfs which brings the post-development
runoff to the same level as the pre-development runoff. See detailed calculations on the following pages.
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5.0 Cultec Calculations
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6.0 Stone Diaphragm Calculations
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7.0 Soils Map