HomeMy WebLinkAboutAppendix_H_-_Hydrogeologic_Evaluation.pdfAn Equal Opportunity Employer
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(845) 534-5959 FAX: (845) 534-5999
Mountainville, NY (800) 829-6531
CORPORATE OFFICE
PO Box 37, 70 Pleasant Hill Road
Mountainville, NY 10953 www.tectonicengineering.com
Enfield Energy, LLC
863 Hayts Road
Ithaca, NY 14850
Attn: Ms. Marguerite Wells
April 6, 2012
RE: W.O. 6073.01
GROUNDWATER ANALYSIS
DRAFT ENVIRONMENTAL IMPACT STATEMENT
BLACK OAK WIND FARM
TOWN OF ENFIELD, NY
Dear Ms. Wells:
In accordance with our March 16, 2012 proposal for water resource engineering
services, Tectonic Engineering & Surveying Consultants P.C. (Tectonic) has prepared
the Groundwater component for the Water Resources Section (3.2) of the Draft
Environmental Impact Statement (DEIS) for the proposed Black Oak Wind Farm project.
This letter report presents our findings for that component, preceded by a brief summary
of the performed scope of work and a brief description of the proposed project. Figures
showing the proposed turbine locations, New York State Department of Environmental
Conservation (NYSDEC) registered residential drinking water wells, probable drinking
water wells (based on the presumed existence of residences), and area bedrock are
included as attachments to this letter report.
1.0 SCOPE OF SERVICES
The following water resource engineering services were performed for Enfield Energy,
LLC, herein referred to as Client:
1.1 Review and describe groundwater resources within the Project Area,
including general depth to groundwater within the Project Area, known
aquifers, and existing water supplies dependent upon wells and/or
springs.
Ms. Marguerite Wells April 6, 2012
2
1.2 Evaluate and describe the potential for impacts to groundwa ter resources
that may be caused by installation of subsurface facilities, including tower
foundations and buried electrical lines (e.g. blasting, sedimentation,
stormwater runoff, chemical spills, etc.).
1.3 Identify and characterize proposed means of avoid ing or mitigating the
potential impacts.
2.0 PROJECT AND GENERAL SITE DESCRIPTION
Based on review of the provided proposed site layout prepared by EDR Companies
dated March 2012, we understand that the proposed Black Oak Wind Farm project is to
consist of the construction of up to twelve wind turbines with associated buried
interconnects, a substation and access roads. The proposed area of development is
located in the Town of Enfield, Tompkins County, New York within an area roughly
bounded by Cayutaville Road on the South, the Schuyler County line on the west,
Weatherby Road on the north, and Connecticut Hill Road on the east (the “Proj ect
Area”). The Project Area, which measures approximately 1.5 square miles, straddles
an existing 15 kilovolt transmission line located north of Cayutaville Road. The Project
Area is mostly undeveloped land consisting of actively cultivated farm land, r elatively
recently cultivated farm land that has become overgrown with brush and small trees,
and in higher ridge areas, mature woods (Figure 1). Surface elevations range from
roughly 1,600 to 2,000 feet above mean sea level (Figure 2).
3.0 SOURCES SEARCHED
The sources searched in the preparation of this document consisted of the following:
“Black Oak Wind Project”, dated March 2012 by EDR Companies.
“Geologic Map of New York, Finger Lakes Sheet”, compiled by Lawrence V.
Rickard and Donald W. Fisher, March, 1970.
New York State Department of Environmental Conservation, Water Well
Database at http://www.dec.ny.gov/lands/33317.html.
“Unconsolidated Aquifers in Tompkins County, New York” by Todd S. Miller
2000.
United States Department of Agriculture, Natural Resources Conservation
Service, Web Soil Survey at
http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm.
Ms. Marguerite Wells April 6, 2012
3
4.0 EXISTING GROUNDWATER SETTING
The following section summarizes the existing geologic and hydrologic
conditions, sources of domestic water supply, and groundwater quality within the
Project Area.
4.1 Geology and Hydrogeology in the Project Area
Geology
The Project Area is located in the Town of Enfield, Tompkins County, New York.
Tomkins County resides within the Allegheny Plateau physiographic province.
Bedrock in the Project Area consists of the Beers Hill Shale which is an Upper
Devonian member of the West Falls Group (Figure 2). The Beers Hill Shale
consists primarily of thinly bedded fissile layers. The beds are approximately
horizontal with two primary vertical joint sets with one oriented roughly
north/south and the other oriented east/west. The estimated depth to bedrock in
the Project Area ranges from being exposed at the ground surface to being at
depths of more than twenty feet below existing ground surface.
The Beers Hill Shale is overlain by soils consisting of poorly sorted, densely
packed glacial till whose dominant clast size is characterized as silt and clay.
The remaining soil constituents are variable and include sand, gravel, cobbles
and boulders.
As the soils in the area consist dominantly of silt and clay sized soil grains , low
lying areas may have wetland areas due to the poor drainage in these soil types.
According to the USDA web soil survey, the partially hydric soils in the wetland
areas throughout the Project Area are comprised of Volusia Channery silt loam
and Erie Channery silt loam.
Hydrogeology
Groundwater for potable use in the Project Area is obtained primarily from the
Beers Hill Shale. The horizontal bedding layers in the shale have little primary
porosity therefore most of the water in the aquifer is derived from secondary
porosity which includes the vertical joint fractures and horizontal bedding plane
openings. As these joints and bedding planes are usually tight, the shale
typically has low yield wells.
Ms. Marguerite Wells April 6, 2012
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Groundwater flow typically follows local topographic gradients, flowing from
higher elevations towards lower elevations and discharging into wetlands,
springs and local streams. Recharge in the shale aquifer is not localized and is
therefore dependent on regional recharge zones across the formation.
Considering that the gradients in the Project Area range up to 25 percent,
groundwater recharge likely occurs outside of the Project Area to the west.
Within the Project Area, localized recharge likely occurs by infiltration of
precipitation along bedrock fractures that typically trend along stream valleys.
A seasonal perched water table may exist in the spring and fall which does not
represent the depth of water used for potable purposes. Rather, this perched
water is the result of poorly drained soils.
4.2 Sources of Groundwater Supply
The Town of Enfield does not have a municipal water system. Therefore, the
main domestic water supply source for residences in the Project Area is
groundwater from private wells. The potable groundwater supply in the region is
obtained from a bedrock aquifer, which as previously stated, consists of the
Beers Hill Shale in the Project Area. Though depth to groundwater has been
reported by the USDA soil survey as being less than eight inches from the
ground surface in some locations within the Project Area, this is the result of
water perched in poorly drained areas and is typically not suitable for potable
use.
4.3 Groundwater Quality
Private well locations and groundwater quality data for the Project Area and
immediate surroundings are not maintained by the Town of Enfield. Additionally,
no information pertaining to regional groundwater quality is available from
Tompkins or Schuyler Counties.
The NYSDEC water well information database was consulted in order to infer the
depth to potable drinking water supplies. Note that the NYSDEC started its well
database in 2001 and, therefore, data for wells installed prior to 2001 are not
included in the database. Based on the results of this search, two wells were
reported to be in the vicinity of the proposed Black Oak Wind Farm. Only one of
these two NYSDEC database entries had information pertaining to groundwater
depth recorded for it. This well is located along Connecticut Hill Road. The
NYSDEC database reports bedrock at twenty-seven feet below ground surface
Ms. Marguerite Wells April 6, 2012
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and groundwater at a depth of thirty feet below ground surface. Though the
NYSDEC database only has two wells registered in its database that are located
within the Project Area, there were multiple wells listed in the areas around the
project. Based on a review of data from the wells in the immediate surrounding
areas, the depth to potable water in a well is reported to be as shallow as twelve
feet below existing ground surface. Additionally, based on a review of aerial
photographs and the location of residential dwellings, there are likely numerous
potable drinking water wells within a half mile radius of the Project Area (Figure 1
and Figure 2) associated with each residence that were likely installed prior to
the 2001 NYSDEC required reporting date.
Due to the nature of the bedrock, shale typically does not yield sufficient
quantities of water except to supply individual residences and farms. The USGS
notes that the region usually has a surplus in groundwater budget. However,
bedrock aquifers comprised of shale generally transmit small amounts of water
and typically have yields that range from 1 gallon per minute to 10 gallons per
minute. The NYSDEC well database indicates that the existing well along
Connecticut Hill Road yields 7.5 gallons per minute.
The Beers Hill Shale has been classified as“black shale” by the USGS. Due to
their chemical composition, groundwater obtained from black shales is generally
very hard and contains some dissolved heavy metals. Therefore, groundwater
drawn from potable water wells within the Beers Hill Shale aquifer is expected to
have similar water quality as that of adjacent municipalities which obtain their
potable water from similar shale aquifers. It is expected that potable
groundwater in the project area contains high mineral concentrations consisting
of iron, calcium, magnesium, sodium, bicarbonate, sulfate and chloride.
5.0 Potential Impacts
The following section describes potential impacts to the groundwater in the
Project Area as the result of groundwater withdrawal, excavation and
construction dewatering activities, the installation of the foundations, the creation
of impervious surfaces, blasting operations, and chemical spills.
5.1 Impacts from Groundwater Withdrawal
The proposed Black Oak Wind Farm does not contain any habitable spaces. As
such, there is no anticipated need for a new potable water supply for the Project.
Therefore, as no need for potable water is anticipated as a result of th e
Ms. Marguerite Wells April 6, 2012
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completion of the Project, no impacts to the aquifer water levels from
groundwater withdrawals is expected to occur.
5.2 Impacts to Groundwater from Excavation and Construction
Dewatering
It is expected that the wind turbines proposed for the Black Oak Wind Farm will
be constructed using mat foundations. As such, excavation for the foundation is
not expected to be deeper than 20 feet below ground surface. In order to
maintain a dry excavation, the groundwater level will likely be lowered up to five
(5) feet below the depth of the excavation. Dewatering activities will temporarily
lower groundwater levels within the immediate vicinity of the excavation during
pumping. As none of the proposed turbines are within 1/8 mile of any existing
structure, dewatering activities for foundation placement will not impact water
levels in individual residential water wells. Further, the water from the dewatering
activities will likely be discharged back into the project area allowing for infiltration
of the water back into the aquifer. Therefore, it is not anticipated that potable
groundwater supplies will be affected by excavation or dewatering activities.
Additionally, as the Project Area is larger than one acre, the NYSDEC will likely
require a State Pollution Discharge Elimination System (SPDES) permit for the
project. As a result, a Stormwater Pollution Prevention Plan (SWPPP) will be
submitted as part of the construction documents. Discharge and treatment of the
pumped water from the excavations will be performed as stipulated in the project
SWPPP and is not expected to impact residential potable water supplies.
5.3 Impacts to Groundwater from Foundations
Groundwater data obtained from the NYSDEC database indicates that potable
groundwater in the region can range from twelve to more than thirty feet below
existing ground surface. Excavation for the foundations of the wind turbines and
substation is not anticipated to exceed twenty feet below ground surface. It has
been conservatively estimated that each turbine foundation will occupy an area
of approximately 0.02 acres. Due to the small area of disturbance and shallow
depths of excavation, the excavations for the foundations is not expected to
significantly change the characteristics of the bedrock aquifer as a result of the
project construction.
The foundations will be constructed of concrete which once cured will not impact
groundwater quality. Additionally, as the closest existing building structure likely
to have a foundation is over 1/8 mile from the nearest proposed wind turbine, no
Ms. Marguerite Wells April 6, 2012
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significant adverse impact to groundwater supply, quantity or quality from the
foundation materials will occur.
Excavations for the buried interconnect utility lines are not expected to exceed
ten feet below existing ground surface. As potable groundwater is found at
depths of greater than ten feet below existing ground surface, no significant
impact will result from these excavations or the utility lines.
The substation and service roads are essentially surface features and will not
have an impact on the aquifer from which potable water is drawn. Neither the
substation nor the service roads for the Project will extend to depths that would
impact the aquifer or groundwater. The service roads are surface features which
are not expected to disturb bedrock. The substation will likely require shallow
foundations and slab on grade construction less than five feet below grade and
therefore also will not have an impact on groundwater aquifer. .
5.4 Impacts to Groundwater from the Creation of Impervious Surfaces
As most of the turbines in the proposed Black Oak Wind Farm are located along
ridgelines and on the sides of hillsides where surface water is likely to run off into
nearby streams before it percolates into the aquifer, there will be insignificant
impact to the local aquifer recharge area as a result of the construction of the
proposed Black Oak Wind Farm.
The Project Area covers an area of approximately 960 acres of land. It is
conservatively estimated that each wind turbine will have an approximate
footprint area of 0.02 acres which will be impervious. Considering that the
Project consists of a maximum of twelve turbines and that there will be additional
impervious surfaces associated with the construction of the substation, a total
long term impervious surface area of 0.3 acres has been estimated to be
generated in the Project Area. This conservative estimate results in a total area
of less than 0.04 % of the Project Area to be converted to impervious surfaces,
which will not significantly alter the recharge area of the aquifer.
Additionally, as stormwater at each area of the Project will be shed to the sides of
the tower and substation and will be allowed to drain into the vegetated soils
around the improvements, the total quantity of water recharging the aquifer in the
project area will not be significantly reduced as a result of the construction.
Ms. Marguerite Wells April 6, 2012
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5.5 Impacts to Groundwater from Blasting
Bedrock in the Project Area ranges from being exposed at the surface to depths
of over twenty feet below existing grade and consists of Beers Hill Shale.
Therefore, rock removal may be required for construction of the turbine
foundations. Due to the fissile nature of the Beers Hill Shale and poor water
carrying capacity, blasting near existing wells could result in temporary increases
in turbidity levels in the water. In order to protect groundwater quality of existing
residences, excavation of rock using explosives is not recommended to be
performed within 1/10 of a mile from any existing residence. In these areas close
to residences, where encountered, bedrock should be removed by using large
excavator mounted hydraulic hammers. Dozer mounted rippers may also be
effective for minor quantities of rock excavation. Construction specifications
should be prepared to address the need to disallow blasting.
5.6 Impacts to Groundwater from Chemical Spills
It is anticipated that concrete will be used for the footings of the wind turbines
and substation. Additionally, diesel powered equipment, miscellaneous gasoline
powered equipment, and vehicles will also be used for construction of the
Project. Normal turbine operation requires the use of hydraulic fluid. No
significant quantities of other chemicals are generally used in the construction or
maintenance of wind farms.
Cement truck wash out will be performed as stipula ted by the Project SPDES
permit. Therefore, no impact to groundwater will be created by the use of
concrete within the Project Area.
Should gasoline, diesel fuel or hydraulic fluid be spilled as a result of turbine
construction or their maintenance, the NYSDEC spill hotline will be notified by the
responsible party within two hours of the spill. Spill clean-up will be performed in
accordance with NYSDEC Final Commissioner Policy, CP-51 by an experienced
remediation contractor. Further, as no turbine is within 1/8 mile of an existing
structure and the quantities of petroleum products to be used will be minor, it is
unlikely that any existing groundwater well will be impacted if such a spill should
occur.
Ms. Marguerite Wells April 6, 2012
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6.0 FINDINGS AND CONCLUSIONS
The following findings and conclusions can be drawn with regard to the groundwater
quality at the proposed Black Oak Wind Farm Project:
The proposed Black Oak Wind Farm is located in Tompkins County, New
York and consists of an approximately 1.5 square mile Project Area in an
area of agricultural development, residential dwellings and undeveloped
woodlands.
Potable water within the Project Area is obtained from the Beers Hill Shale
bedrock aquifer.
Depth to top of bedrock can be found at depths ranging from the surface to
over twenty feet below existing ground surface.
As excavation for the wind turbine foundations is not expected to exceed
twenty feet below ground surface, the bedrock aquifer will not be significantly
impacted by their construction.
It has been conservatively estimated that a maximum of 0.04% of the Project
Area will be permanently converted to impervious surfaces. Stormwater will
be shed to the sides of the impervious surfaces created by the construction of
the Black Oak Wind Farm. Therefore, no significant reduction of groundwater
recharge will be created.
Due to the fissile nature of the bedrock, there is the potential for limited
impacts to groundwater if blasting is used to reach required foundation depths
near residences.
There is the limited potential for impacts to groundwater from accidental
spills, during the construction and maintenance of the wind turbines.
7.0 Mitigation Recommendations
As the Project Area is over 1 acre in size, a NYSDEC SPDES permit will be
required during construction of the proposed Black Oak Wind Farm. Any
water pumped from the ground as a result of dewatering excavations will be
treated and discharged as stipulated in the SPDES permit. Temporary
impacts to the local shallow groundwater due to pumping will not be
significant; therefore, no mitigation is required.
The Project will not require a potable water source and therefore will not
withdraw any water from the aquifer. As no potable water is anticipated for
Ms. Marguerite Wells April 6, 2012
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Attachments: Figure 1 – Aerial Map
Figure 2 – Topographic Map
G:Mountainville/Environmental/6073 Black Oak Wind Farm/Report/Draft DEIS Report Letterhead.docx
FIGURE 1
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¯Figure 1: Aerial Mapof Project Area
ProposedBlack Oak Wind Farm
March 2012
W.O. 6073.01COPYRIGHT TECTONIC 2012
This map is computer generated using dataacquired by Tectonic from various sources andis intended only for reference, conceptualplanning and presentation purposes. This mapis not intended for and should not be used toestablish boundaries, property lines, location ofobjects or to provide any other informationtypically needed for construction or any otherpurpose when engineered plans or land surveysare required.
Legend
!(Proposed Turbine Locations
&(NYDEC Registered Residential Drinking Water Wells
&(Probable Domestic Well Locations
Buried Interconnect
FIGURE 2
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¯Figure 2: Topographic MapShowingTurbines &Well Locations
ProposedBlack Oak Wind Farm
March 2012
W.O. 6073.01COPYRIGHT TECTONIC 2012
This map is computer generated using dataacquired by Tectonic from various sources andis intended only for reference, conceptualplanning and presentation purposes. This mapis not intended for and should not be used toestablish boundaries, property lines, location ofobjects or to provide any other informationtypically needed for construction or any otherpurpose when engineered plans or land surveysare required.
Legend
!(Proposed Turbine Locations
&(NYDEC Registered Residential Drinking Water Wells
&(Probable Domestic Well Locations
Buried Interconnect