Summary
The heat exchange facility (HEF) and associated pipelines are to be constructed within the Cayuga Lake Valley, a glacially carved trough. A number of field investigations were performed to assess the environmental setting of geology and soils within the lake and along the chilled water pipeline route, including sub-bottom profiling and a bathymetric survey of the lake bottom, lake bottom sediment sampling, terrestrial soil borings, and analysis of soil samples.
The physical parameters of the subsurface soils have been investigated at both the proposed HEF site and along the terrestrial pipeline route through a series of soil borings (see Appendix C-15). A total of five borings were performed at the HEF site, and 16 borings were performed along the terrestrial pipeline route. These investigations were performed to develop the basis for selecting the most feasible and cost-effective HEF foundation and chilled water pipe alignment.
The intake and outfall pipelines will be installed at the lake bottom in dark organic silts and clays, which are approximately 50 to 125 ft thick. Sediment dredging will be required for intake and outfall pipeline installation where the depth of submergence will be less than 9 ft in the summer. The HEF, located at the southeastern edge of the lakeshore, will be situated atop sand and gravel deposits that are generally less than 10 ft thick. These deposits directly overlay shale and siltstone bedrock. Along the pipeline route, the depth to bedrock is generally less than 30 ft, and for much of its length, the pipelines will encounter previously disturbed soils and fill materials from prior human activities. Some bedrock removal will be required during installation of the pipeline and the HEF.
Based on the anticipated construction methods and knowledge of the environmental setting, we have drawn the following conclusions:
· Although dredging is expected to cause a temporary and local increase in turbidity (mitigation measures are discussed in Section 3.5 of this Draft Environmental Impact Statement [DEIS]), fish will not be affected by this occurrence since they tend to avoid turbid areas in the water column. Also, humans and other animals will not be affected by these temporary and local increases in turbidity. Dissolved oxygen levels are not expected to be affected significantly by the dredging.
· Water velocities at the intake and outfall locations will not cause an increase in turbidity levels.
· Construction activities relating to the HEF and the terrestrial pipelines are not expected to have a significant impact on soil or groundwater quality. The project is similar to previous area construction of buildings, roadways, and utilities, and so it will not alter the quality of the landscape or environment.
The pipelines can be constructed to minimize environmental impacts, and in some cases, may actually improve environmental conditions (e.g., where contaminated soils and lake sediments are removed from excavations and dredged trenches, respectively, and disposed of appropriately). With proper execution of the stormwater management and erosion control measures outlined in Appendix C-16, potential impacts can be controlled and minimized.
2.1.1 Lake Bottom Sediments.
2.1.1.1 Environmental Setting.
Cayuga Lake, one of New York's six major Finger Lakes, is situated in a glacially carved valley in Central New York. The Finger Lakes were surveyed by Cornell University Civil Engineering classes between 1874 and 1897, and physical data were summarized and published by Birge and Juday in 191 Cayuga is the second largest and deepest of the Finger Lakes, with a surface area of 171 square kilometers (66.4 square miles), a mean depth of 54.5 m (179 ft), and a maximum depth of 136 m (435 ft). The lake basin is long and narrow; Cayuga Lake is 61.4 kilometers long (38.4 miles) from Ithaca in the southern basin to the Seneca River outlet and has a mean width of 8 kilometers (1.75 miles). At its widest point, Cayuga Lake is 5.6 kilometers (3.5 miles) across. The lake volume is estimated at 9,380 million cubic meters (331,300 million cubic ft).Cayuga Lake sediment dredging is planned in order to install the Lake Source Cooling (LSC) intake and outfall pipes. Dredging will be required for approximately 275 m (900 ft) and 137 m (450 ft) from the shoreline for the intake and outfall pipelines, respectively (see Figure 1-1). The quantity of dredged material is anticipated to be approximately 5,000 cubic yards for the intake and outfall pipelines. In addition to these areas, dredging will be required (approximately 1,100 cubic yards) for the transfer barge loading and unloading activities to be conducted along the shoreline.
Sediment sampling and analysis was completed during both 1994 and 1996 to assess the chemical nature of the lake bottom sediments. In addition, a frozen sediment core was analyzed in 1996 to assess geotechnical properties of the lake bottom. Results of the sediment sampling and analyses are provided in Appendix C-12, Sediment Quality Investigations, and an in-depth discussion of sediment sampling and analysis results is provided in Section 3.5 of this Draft Environmental Impact Statement (DEIS).
The term "sediment" refers to the material that settles to the bottom of a water body. Cayuga Lake bottom sediments are a mixture of material that flows in through the tributaries and municipal outfalls, and material generated within the lake itself, such as decaying plants, animals and shells, and fragmentary material from parent rock. The United States Environmental Protection Agency (USEPA) defines sediment as soil, sand, and minerals washed from land into water usually after rain (USEPA, 1988c, as cited in USEPA 1993).
Sediment particles vary in chemical composition and physical characteristics, such as size and shape. Components of sediment include clay, silt, and sand-sized mineral particles, organic matter, hydrated iron, and manganese oxides. Associated characteristics of sediments include particle size, pH, and oxidation-reduction conditions (capacity to undergo chemical change). These components and associated characteristics of sediments can affect the interaction between sediment particles and contaminants.
2.1.1.1.1 Texture (Particle Size Distribution).
A sediment core taken from location P-4 (near the proposed intake location) was analyzed for texture, moisture content, organic content, specific gravity, and unconfined compressive strength. The sample was a 3-inch diameter frozen core cut into four sections totaling 81 inches long. The general soil classification included color, visual classification of soil type, and general layering. The index soils laboratory testing was performed in general accordance with American Society of Testing Materials (ASTM) testing methods. Geotechnical Appendix C-15 contains details of the approach, methods, and results of this investigation. The laboratory results for the frozen core are summarized in Table 1-1.The sediment soils are generally classified as grey-black organic silt and clay with observable organic particles (pieces of leaf, twigs, etc.) embedded in the sediment. The apparent layering was approximately 1/16 to 1/8 inch, with some layers as thick as 1/4 inch. There were obvious dark organic layers with thicknesses less than 1/16 inch within the layering sequence. Definite ice lenses were identified while the sample was still frozen. Pocket penetrometer results indicated values of unconfined compressive strength of 60 to 100 pounds per square ft (0.03 to 0.05 tons per square ft).
2.1.1.1.2 Chemical Composition.
Analyses of the bulk content of USEPA's target compound list of chemicals in the lake sediment were conducted in 1994 and 1996. In addition, sediment parameters affecting water quality (via dredging activities), such as ammonia, nitrogen, and total organic carbon, were analyzed during the 1996 investigations. The results of these investigations are provided in Appendix C-12, and a discussion of the results is provided in detail in Section 3.5 of this DEIS.2.1.1.1.3 Geotechnical Properties.
A sub-bottom survey was completed in April 1996 by Enviroscan, Inc., using an ORE Geo Pulse sub-bottom sonar system mounted on a boat provided by Cayuga Marine of Ithaca, NY. The survey included recording a sub-bottom profile along the centerline of the proposed intake pipe and along 10 parallel profiles spaced at 100-ft intervals on either side of the centerline. In addition, Enviroscan recorded a profile parallel to and offset 700 ft west of the centerline and crossing profiles near survey point K9 (approximately 700 ft from shore) and the proposed intake structure location (see Appendix C-15). Location control for the survey was provided by differential global positioning system (DGPS) navigation (with sub-meter accuracy) interfaced with HYPACK navigation software, which provided real-time positioning and position corrections to the boat pilot to facilitate maintenance of the correct ship track for each profile. It also provided profile distance tracking to the sonar operator to allow placement of event marks (fiducials) at 300-ft intervals. The sub-bottom profiling and a bathymetric survey have confirmed that there is a dropoff along the southern end of the lake (see Figure 1-2). Sub-bottom profiling indicates that the geotechnical nature of lake sediments is consistent to depths of 50 to 125 ft below the lake bottom. There were few reflections noted on the sub-bottom profile that would indicate changes in layer densities. In the vicinity of the base of the dropoff, the nature of the lake bottom suggests a history of slumping or sediment sloughing down the slope. In addition, subtle dipping sub-bottom reflectors beneath the hilly relief resemble potential original grade surfaces. This has resulted in an approximate 50 percent slope at the center of the survey swath (surrounding the pipeline route) with an approximate 25 percent slope at the western edge of the swath in the vicinity of the dropoff.2.1.1.1.4 Bathymetry Along Pipeline Route.
A bathymetric survey was completed in April of 1996 by Enviroscan, Inc., using an AlliedSignal ELAC bottom chart system. The ELAC provides coverage and resolution by scanning the bottom with a bidirectional, fan-shaped array of sonar transducers, which record swaths of bathymetric data rather than the profiles recorded by conventional echo-sounding fathometers. This technique makes continuous to overlapping coverage feasible. In addition, the ELAC was interfaced with:· DGPS to provide real time sub-meter positioning
· a motion detector to provide heave, pitch, and roll-compensation
· a Sperry gyrocompass to provide ship heading/transducer array orientation compensation
· a Digibar velocimeter sonde to provide the actual velocity profile of the water column (for correction of ray bending along non-vertical signal paths)
During the survey, location control was provided by an Omnistar DGPS. Vertical control was provided by a staff gauge set by Enviroscan at the dock of the Cayuga Boating Center, Ithaca, NY. The staff gauge was surveyed relative to the New York State Electric and Gas (NYSEG) benchmark T-921 with coordinates 42°28'03.34134 north latitude, 76°30'047863 west longitude, and elevation 400.130 ft above mean sea level (AMSL). The bathymetric data were referenced relative to a lake level of 383.05 ft AMSL (United States Geological Survey [USGS] datum) as recorded by the staff gauge during data collection.
Data were collected by scanning swaths with a width roughly three times the water depth beneath ship tracks roughly parallel to the centerline of the proposed LSC pipeline. In selected critical areas, crossing (or other variously oriented) tracks were also recorded to ensure complete sonar coverage and/or to ensure that critical bottom features (e.g., the face of the dropoff) were scanned with the transducer array in a favorable orientation. The distribution of the ship tracks provided overlapping sonar sounding coverage in the deep water north of the dropoff, along the face of the dropoff, and in the vicinity of a suspected shoal near survey point K9 (approximately 700 ft from the shoreline).
The results of the bathymetric survey are represented graphically in Figures 1-2 through 1-4. Figure 1-2 represents the most accurate contour depiction of the survey data. Figure 1-3 depicts color contours of the bathymetry of the full survey area referenced to a lake level of 383.05 ft AMSL (USGS datum). Note the steep northeast-trending dropoff and the deep ravine on the northwest corner of the survey area. This figure is provided as a compact visual reference only. Figure 1-4 is a three-dimensional (3-D) perspective view of the full survey bathymetry with superimposed color contours of the relative sonar signal return or backscatter amplitude. The nature of the lake bottom in the vicinity of the base dropoff suggests a history of slumping or sediment sloughing down the slope. In viewing the backscatter contours, note that the backscatter amplitude is principally related to two factors:
1. Reflector Orientation. With surfaces nearly perpendicular to the sonar beam path producing the strongest backscatter.
Density Contrast. With a higher density contrast at an interface producing higher amplitude backscatter.
Note that the first factor and the wavelength of the sonar signal typically produce a correlation between grain size and backscatter. Coarser-grained material provides many minute surfaces favorably oriented to produce strong reflections, while fine-grained material appears at the sonar wavelength to be much smoother and to produce less backscatter. In Figure 1-3, there appears to be a correlation between bathymetric deeps and zones of low backscatter. This indicates that deeper areas are subject to deposition of fine sediments, while shallower or steeper areas may be sloughed or washed clean of finer materials, and are supported by coarser and/or harder (i.e., higher density contrast with lake water) material.
2.1.1.2 Impacts of Proposed Action.
Installation of the LSC pipelines will have some impacts on the physical characteristics of the lake bottom sediments within the immediate pipeline vicinity. These impacts are discussed in Sections 1.1.1 through 1.1.4 below.2.1.1.2.1 Installation of Intake and Outfall Pipelines Along the Lake Bottom.
Installation of the intake and outfall pipelines along the lake bottom will require dredging in areas where the mean summer water level is less than approximately 14 ft. Dredging activities will cause a temporary increase in turbidity as sediment materials are released to the water column. Backfilled and settled sediment materials will be arranged differently than the original configuration. Heavier particles will settle first as they descend from the water column most rapidly. The finest sediments (smallest, lightest particles) from the dredged material, will settle out last, blanketing the lake bottom surface. As the finest sediments generally contain the greatest proportion of organic content, biochemical oxygen demand may increase within the silt curtained area as a result of dredging as the biota respond to the temporarily increased food availability in the water column. Dissolved oxygen levels may drop temporarily, until the particles settle. However, the shallow lake waters are well-oxygenated and dissolved oxygen depression is not likely to occur. Fish will not be affected by this confined temporary occurrence, as they tend to avoid areas of high turbidity within the water column. Lake bathymetry in the immediate area of the pipelines may exhibit microcontours that differ from the original bathymetric configuration by several inches.In-lake drinking water supplies should not experience any impacts due to construction and operation of the LSC system. Turbidity increases during construction will be limited to within the silt curtained area.
2.1.1.2.2 Disposal of Dredge Spoils.
Dredge spoils will be placed in lined roll-off containers and transported to an NYSDEC-approved upland disposal site. Based on the solids content of the dredged material, solidification methods could be employed to increase the solids content to a level suitable for practicable transport and disposal, if necessary. If required, any water removed from the roll-off containers following dredging will be pumped to a temporary sediment dewatering basin constructed of hay bales and filter fabric (see Appendix C-16). Temporary increases in the water column turbidity in the immediate area of the pipeline excavation activities will be the most significant sediment-related unavoidable environmental impact.2.1.1.2.3 Turbidity Induced by LSC Intake.
The movement of water caused by the LSC intake was examined to determine the shape and extent of the flow field approaching the intake and the bottom velocities near the intake. Bottom velocities were examined relative to the potential for bottom scour.The LSC system will draw water at a maximum rate of 2 cubic meters per second (m3/s), or 32,000 gallons per minute (gpm). The velocity at the face of the intake is determined by the surface area of the pipe, and is approximately 1.2 meters per second (m/s), or 3.9 ft per second (ft/sec). Based on an analytical calculation of the velocity fields in the region of the LSC intake, water velocities are reduced to 1 to 2 centimeters per second (cm/s) (0.04 to 0.07 ft/s) within 5 to 10 m of the intake. These velocities are within the range of naturally occurring bottom velocities in this portion of the lake as predicted by the lakewide model CE-QUAL W Results of the analysis indicate that bottom velocities induced by the LSC system will not exceed naturally occurring water velocities, and will not cause any bottom scouring. A more technical description of the modeling effort is provided in Appendix C-8, Hydrothermal Modeling.
2.1.1.2.4 Turbidity Induced by LSC Outfall.
The LSC outfall system is designed to minimize turbidity impacts associated with steady-state operations through the installation of a 75-ft outfall diffuser. Turbidity impacts are estimated based on velocities in excess of the maximum ambient lake water velocity at the lake bottom in the vicinity of the outfall. The continuous outfall water velocity will not cause an increase in turbidity associated with operation of the LSC system. Turbidity will rise in the outfall area when the LSC system starts up, however, as the boundary velocities of the outfall plume overcome the weight and cohesion of the top layer of fine sediments. Turbidity impacts caused by the outfall should be considered in three phases:Phase 1: Temporary, moderate turbidity accompanies the outfall plume immediately following system startup (disturbance lasting less than one day).
Phase 2: Phase 1 sediment turbidity has settled. Continuous operation at Phase 2 scours small quantities of sediments from the lake bottom as boundary velocities approach a breaking point where water velocity can no longer overcome sediment weight and cohesion.
Phase 3: Phase 2 mild sediment turbidity has settled. Outfall plume boundary velocities no longer overcome sediment weight and cohesion. No increased turbidity will occur from this point on throughout continuous system operation.
2.1.1.3 Mitigating Measures.
Mitigating measures will be implemented during all phases of construction and continuous operation of the LSC system to minimize and/or eliminate impacts to the lake bottom sediments. Most of these mitigating measures are incorporated into the system design. Construction management techniques will help to minimize the temporary impacts associated with lake bottom dredging and pipeline construction.2.1.1.3.1 Burial of Intake and Outfall Pipelines in Shallow Water.
The LSC intake and outfall pipelines will be installed within the sediments in water that is less than approximately 14 ft deep at mean summer water level (384 ft AMSL [USGS]). This design will eliminate potential boating hazards below the water surface.2.1.1.3.2 Plan for Construction in Lake.
The LSC pipeline in-lake construction plans include the use of silt curtains as a measure to mitigate temporary turbidity plumes associated with dredging activities. In order to minimize the disturbance of sediments, and thus minimize turbidity increase, we propose to utilize environmental dredging equipment (mechanical type). This will include the use of an environmental trenching bucket, which incorporates modifications from the traditional bucket that enable it to achieve a high solids-to-liquid ratio and secure closure of the mouth through electronic sensors and compressible seals. The environmental trenching bucket has been demonstrated to reduce construction turbidity levels up to 90 percent, as compared to conventional trenching methods (Hempel 1993). The dredging will raise small volumes of fine sediment material into the lake's water column. These fine sediments will be confined within a silt curtain that surrounds the work area. Silt curtains will remain in place until sediments have been allowed sufficient time to settle. They will then be moved to the next segment of the pipeline construction area. Careful operation of dredging equipment will also be used as a mitigating measure to further reduce the temporary impacts associated with sediment dredging. As a further mitigation measure, clean fill will be placed in dredge areas that are within 30 m (100 ft) from the shoreline. This measure will soften any potential visual impacts associated with the placement of pipeline in the lake.2.1.1.3.3 Dredge Spoils Disposal Plan.
Dredge spoils will be placed in lined roll-off containers and transported to an NYSDEC-approved upland disposal site. Silt curtains will be utilized to limit (to the greatest extent possible) the turbidity increases to the construction corridor. To mitigate unnecessary increases in turbidity, sediments will be removed from the lake utilizing an environmental trenching bucket. Any excess water handled during the dredging operation will be pumped to a temporary sediment dewatering basin constructed of hay bales and filter fabric (see Appendix C-16).2.1.1.3.4 Intake Orientation and Velocity to Prevent Sediment Entrainment.
The LSC intake structure is designed to reduce velocity-induced sediment scouring in the intake vicinity, and subsequent sediment transport through the LSC system. The raised elevation of the intake pipeline off of the lake bottom and the use of a base pad will help to minimize sediment entrainment. This mitigating measure will reduce the possibility of turbidity increases in the intake region, and will also serve to reduce internal wear of the LSC system.2.1.1.3.5 Outfall Design to Prevent Bottom Scouring.
The LSC outfall design includes the installation of a diffuser, which will direct the outfall waters upward and away from the lake floor. This mitigating measure will reduce the possibility of localized turbidity associated with bottom scouring from continuous LSC system operation. However, some temporary increase in turbidity at the outfall will occur during system startup. See Section 1.1.2.4 above for a description of the startup turbidity (scouring) phases.2.1.1.4 Unavoidable Impacts.
The LSC intake and outfall system construction will result in temporary increases in turbidity in the southeastern Cayuga Lake basin. Construction and installation activities will also result in slight alterations to lake bathymetry within the dredging work area. The microbathymetric landscape could not possibly be restored to its original dimensions following pipeline installation activities. Lake bottom sediments raised during the construction activities should settle quickly following heavy disturbances. The heavier, larger particles will tend to settle out first, leaving the finest sediments on the very topmost layer.LSC system startup will result in temporary bottom scouring and turbidity. Lake bottom bathymetry may exhibit a slight depression (several inches) in the outfall diffuser area following Phase 2 of the LSC system startup.
2.1.2 Facility Site.
The facility site includes the northern area, where the HEF building will be located, and the area along the lake shore, where the pipelines will extract water (pipeline intake) and discharge water (pipeline outfall) to Cayuga Lake. The LSC construction will have no significant impact on the geology of the area. The construction will not entail any deep drilling. Pile driving will follow standard construction procedures, and will have no significant impact on subsurface conditions. There are no anticipated significant changes to internal earth stresses caused by any surface or subsurface loadings (e.g., blasting, heavy machinery operation, and installation of footings and foundations).
The project area is not prone to earthslides (characterized by unstable slopes or land surfaces), and there will be no significant exposure of soil or rock to wetting, drying, heating or cooling processes. Further, no extremely steep slope gradients will be cut, and any grading operations will attempt to return contours to their approximate original configuration. The only area where contours may be significantly altered are at the HEF and in the soil disposal area south of Renwick Brook.
2.1.2.1 Environmental Setting.
2.1.2.1.1 Physical Properties.
The facility site is located within the Appalachian Uplands physiographic province of New York State. This area is the northern extreme of the broader Appalachian Plateau. The hilly landscape formed from the erosion of a thick sequence of sediments that was originally deposited as a delta. The original flat, yet elevated landscape was carved into hills and valleys over millions of years, and was later modified by glaciers, resulting in the high relief topography we see today. With the exception of Cattaraugus Creek, the Genesee River, the Finger Lakes, and minor streams, the province drains to the southwest into the Allegheny, Susquehanna, and Delaware River systems.The northern edge of the province is cut by the Finger Lake troughs, which drain to the north. The Finger Lakes formed in glacially modified valleys of preglacial rivers, and at least two are known to have bedrock floors below sea level (Cayuga and Seneca). A generally thin veneer of glacial sediments overlays the bedrock across the area, although thicker sequences of sediments can occur in north-south valleys.
The City of Ithaca is located at the southern edge of Cayuga Lake. Soil thickness is variable across the city area. Within the southern extension of the Cayuga Lake trough, there may be up to several tens of meters of sediments overlying bedrock. Soil thickness decreases to the east and west of this trough, and bedrock is exposed or very close to surface in many places along the valley walls and outlying areas. Area bedrock is Devonian age and consists primarily of shales and sandstones, with limestone confined to two formations, the Tully and the Onondaga.The facility site is located on the southeastern shore of Cayuga Lake at the base of the lake valley wall. Although regional topography is characterized by high relief, the local topography across the project site is relatively flat because the site is located within the floodplain of the lake (Figure 1-5).
2.1.2.1.2 Soil Types.
Geologically, soil types are classified according to two general properties: composition and texture. Composition refers to the mineral make-up of the soil, whereas texture refers to the size of the individual soil grains. These two soil properties are determined by the chemical composition of the sediments that were originally deposited, and the erosional forces that modified those sediments after deposition. Other soil classification schemes consider the soil's suitability for various land usages, such as soil descriptions offered by the Natural Resource Conservation Service. Both geologic characteristics and soil conservation classifications are discussed below.Soils across the region are derived from sediments deposited by glaciers and glacial meltwater. After the glaciers left the area approximately 12,000 years ago, the sediments that were left behind were later modified by chemical and physical processes that result in the distribution of soils we see today.
Regionally, the primary soil type is glacial till, which is an unsorted mixture of clay-, silt-, sand-, and gravel-sized grains (Figure 1-6). Tills are deposited directly by glacial ice, and since glaciers do not substantially sort the materials they carry, tills tend to be variable in both texture and composition. Because tills contain many different grain sizes, the empty spaces between coarser grains tend to become filled with finer-grained materials, resulting in a very low porosity. It is for this reason that tills tend to have a low capacity to transmit water.
In contrast to tills, sediments that are deposited by moving water tend to be better sorted in terms of both grain size and mineral composition. This is because a moving stream of water is able to move finer-grained materials for further distances than coarser-grained materials. For example, sand- and gravel-sized grains are larger and heavier than silt- and clay-sized grains. Silt and clay are transported farther by moving water than sand and gravel, and are therefore deposited separately from sand and gravel. As a result, the sediments deposited by glacial meltwater are more uniform in grain size and composition than are the unsorted tills.
As the glaciers melted, the meltwater was channeled into specific low-lying areas, and so the sediments found in these areas are distinct from the surrounding tills. It is for this reason that the distribution of different soils types across the area is influenced by the topography of the landscape.
For sand and gravel deposited by meltwater, the lack of significant amounts of silt and clay between the individual grains results in a relatively high porosity compared to tills, and thus water is more easily transmitted through these well-sorted deposits. The different soil types and the depositional processes that formed them are therefore related to the occurrence of area aquifers, as will be discussed later.
Two distinct soil types are present in the area of the proposed HEF site and pipeline route (Figure 1-6). Running along the southeastern shoreline of Cayuga Lake is an area where soil cover is quite thin. Bedrock occurs within a few feet of ground surface in this area, and in many areas bedrock outcrops are observed. The thin soil cover in this area is a mixture of gravel, sand, silt, and clay. Extending south of the lake and to the west of this area of thin soil cover are fine to coarse sand and gravel deposits that comprise the second soil type. These deposits extend to greater depths than the thin soil cover to the east. The distinction between these two soil areas results from physical differences in the landscape, which influenced the way in which the sediments were originally deposited. Sediments deposited within the Cayuga Lake valley are well-sorted sand and gravel, because they were deposited by meltwater that swept away finer-grained sediments. These sediments are thicker than those along the valley walls because the erosion of steep slopes strips away the valley wall sediments.
The proposed HEF site is located over sand and gravel deposits of the lake valley that grade into finer-grained soils up the valley wall. The depth to bedrock is roughly 20 ft near the lake at the proposed intake/outfall area, and becomes shallower to the east at the facility building location. Area bedrock consists of siltstone and shale of the Genesee Group (Rickard and Fisher 1970).
A total of nine soil borings were advanced at the proposed facility site as part of a geotechnical investigation of the area. Four borings were located near the on-shore area of the intake and outfall pipelines (BH-1, -1A, -2, and -3), and five were located further east of the lake, in the area of the proposed HEF (BH-4, -5, -6, -7, and -8). The soil borings indicate that depth to bedrock varies from greater than 20 ft near the lakeshore, to less than 10 ft further up the valley wall (see Appendix C-15). The soil type close to the lakeshore is a fine to coarse sand and gravel with variable amounts of silt. Further away from the lake, there is a gradual increase in the proportion of silt and clay, and in isolated areas there are cobbles present near the bedrock surface. The bedrock identified at the facilitylocation is weathered gray shale and siltstone, consistent with the geologic survey maps (Figure 1-7).
Sieve analyses were performed on a number of soil samples from across the facility site to determine the relative amounts of various grain sizes in area soils. A sample collected at the HEF site from Soil Boring BH-8 had a grain size distribution that indicates approximately 68 percent silt and clay (by weight), with lesser amounts of sand and gravel (27.5 percent and 4.5 percent, respectively). A second soil sample, collected from Boring BH-2 near the proposed on-shore outfall pipeline route had an almost equal mix of gravel, sand, silt, and clay. The sieve results show that there is a greater relative abundance of finer-grained soils in the building area than near the lakeshore.
According to soil conservation classification schemes, soils on the HEF site are predominantly Channery silt loam soils with a fragipan at 30 to 80 centimeters. Based on field investigations, the facility site contains mostly shallow and very shallow Lordstown, Tuller, and Ovid soils (less than 20 inches deep over bedrock). These soils are further classified based on the ground slopes. Shallow and very shallow (0 to 15 percent slope) Lordstown, Tuller, and Ovid soils are designated as LtB. Moderately steep to steep (15 to 35 percent slope) Lordstown, Tuller, and Ovid soils are designated as LtC. Lordstown soils with 35 to 70 percent slopes are designated as LoF. Slopes are moderately steep (15 percent) to steep (35 percent) (LtC), and generally are convex, with some slopes of 0 to 15 percent (LtB) particularly in the southern portion (see Figure 1-8). The undifferentiated unit contains soils similar to the Lordstown, Tuller, and Ovid soils, except that they lie less than 20 inches deep over bedrock. In the lower, western section of the site, which contains Lordstown soils (LoF), the depth to bedrock ranges from 2 ft to 13 ft, as shown in Figure 1-9. Bedrock is exposed in the southern portion of the site, where Renwick Brook has eroded a channel. The soil in this area has two distinct layers, the upper layer consisting of a dark, grayish-brown Channery silt loam, and the lower subsoil layer that is a yellowish-brown, unmottled Channery silt loam.
Moving eastward across the HEF site (and uphill) the depth to bedrock decreases, developing the Lordstown, Tuller, and Ovid soil complex. Tuller soils typically lie at higher elevations than the Lordstown soil, and also form in channery loamy material. The material appears to be crushed or broken rock that has been moved short distances. The depth of bedrock is typically less than 24 inches. Ovid soils tend to exhibit moderately fine texture, as well as somewhat poor to moderate drainage qualities.
2.1.2.1.3 Chemical Properties of Surficial Soils.
The minerals present in soils reflect the rock material from which the soils were originally derived, and the erosion that later modified them. The chemical content of area soils is thought to be diverse, owing to the mixed array of sediments that was eroded by past glaciers and later deposited across the area. Mineral diversity is particularly common for glacial till, because very little sorting of sediments takes place prior to deposition.Underlying the facility site are shales and siltstones, so it is likely that local soils will share chemical attributes with this type of rock. However, it is also likely that the mineralogy of areas to the north is also present in local soils, since the glaciers were capable of transporting materials from source areas far away and depositing them as sediments.
Soil samples from selected boring locations at the facility site were analyzed for metals, and the results indicate a variety of naturally occurring trace metals, including antimony, beryllium, cadmium, chromium, copper, lead, nickel, selenium, silver, and zinc. The reported concentrations in the soil samples were very similar from one location to another, suggesting that they are present naturally. The concentrations were also similar to those typically found in shale (Drever 1988) indicating that the underlying shale bedrock has influenced local soil chemistry by providing a source of the detected metals. The detected concentrations of trace metals are presented in Table 1-2.
A portion of the project site near the lakeshore at the marina (Boring BH-1A) was found to have relatively high levels of cadmium and lead compared to the soil samples from other locations, suggesting that those two metals are not natural at those levels for that area. Further laboratory analysis on soils from that boring has indicated the presence of a number of organic compounds that are produced as a byproduct of coal burning. Cadmium and lead are known to occur as byproducts of coal burning as well (Hem 1992), so it is concluded that the cadmium and lead at Boring BH-1A, as well as the detected organic compounds, are derived from wastes of coal burning processes. A previous Phase I investigation of the facilities area conducted in 1995 revealed that a coal burning steam plant was once operated at the facility site location. It is likely that the former operation of that plant is the source of the elevated metals and detected organics. The extent of such wastes is evidently limited to the area near the marina, since similar chemical conditions were not identified elsewhere.
2.1.2.1.4 Earthquake Potential.
The majority of New York State is subject to a moderate level of earthquake risk. The highest level of seismic activity in the state is in the northern Adirondacks, the New York City area, and western New York near Buffalo and Attica. On the average, a damaging earthquake occurs in New York State about once every 20 years.The entire state is divided into four seismic zones that correspond with varying levels of earthquake risk, as shown in Figure 1-10. The cluster of Steuben, Yates, Schuyler, Chemung, Tioga, and Tompkins Counties comprise Zone A, which is an area of very little earthquake activity. Surrounding Zone A across Central New York State is Zone B, which includes 14 counties that have historically experienced slightly higher earthquake activity than Zone A, but are generally characterized by very low earthquake activity. Western, southern, and northern New York State are within Zones C and D, where there has historically been higher earthquake activity.
There are reportedly only two known earthquakes that have occurred in Zone A (Ebel 1987), and both of these earthquakes were less than a magnitude of 3 on the Richter scale. There have been no measurable quakes in Zone A since routine seismic monitoring began in 1970, and no earthquakes have ever been reported to occur in Tompkins County. Figure 1-11 shows the locations of earthquakes occurring between 1970 and 1979 across the northeastern United States. The absence of quake activity near the project site is evident. Based on the historical occurrence of earthquakes across New York State, the potential risk of earthquake activity within Tompkins County is considered to be low.
Despite the low risk of earthquake activity in the area around the facility site, it is possible that an earthquake in another area might potentially affect the site. Although the western United States has much more earthquake activity than the northeast, northeastern earthquakes tend to release greater amounts of energy when they occur than their western counterparts. Furthermore, given the same level of earthquake energy, the tremors of an eastern quake are felt over a larger area than a western quake. This occurs for two reasons. First, bedrock in the eastern U.S. is generally more continuous. (In other words, there are fewer faults and breaks, so the energy is conveyed a greater distance from the source.) Second, eastern geology generally consists of layers of soft sediments that overlay hard bedrock. This contrast of soft over hard tends to amplify the seismic waves. The potential for a distant earthquake to affect the pipeline corridor was therefore evaluated.
The largest earthquake ever recorded in New York State occurred in September 1944 in the Cornwall-Massena area along the New York/Canada border. That quake had an intensity of 5.9 on the Richter scale. According to the Modified Mercalli scale, which assigns 12 levels of intensity from barely noticeable (I), to total destruction of buildings (XII), the Cornwall-Massena earthquake had a considerable intensity level of eight (VIII). During that earthquake, the Ithaca area experienced a disturbance comparable to the passing of heavy trucks, but not enough for any structural damage (Hays 1984). Interpreted as a realistic worst-case scenario, the risk of earthquake damage relating to northeastern quakes is evidently minimal.
2.1.2.2 Impacts of Proposed Action.
2.1.2.1 Site Topography.
The facility is located near the base of the lake valley wall, and at present the ground surface slopes down to the lake. Portions of the project site will need to be regraded to accommodate the building structure and parking area (see Figure 1-12).2.1.2.2 Chemical Content of Surface Soils.
Construction-related activities are not expected to result in significant chemical impact to local natural soils. The proposed construction plan is quite similar in scope to much of the previous development of the area which, aside from the above-referenced coal burning plant, is not known to have noticeably impacted area soil chemistry.In order for soil chemistry to be significantly altered by construction of the facility, construction materials would either need to: (1) directly introduce chemical constituents into the surrounding soils; or (2) produce chemical changes that indirectly cause constituents already in the soils to dissolve and migrate away. The materials that are to be used in the facilities construction, including concrete, mortar, wood, steel, glass and sheet rock, are not expected to provide a source of chemical constituents that could significantly alter soil quality.
Possible chemical changes that could indirectly cause soil materials to dissolve are those that change the controls over mineral solubility. The primary controls over solubility of most soil materials are pH and oxygen availability (expressed as Eh). Most metals become more soluble in a low pH, low oxygen (anoxic) environment, but facilities construction is not likely to produce these chemical conditions. Therefore, a significant chemical change is not expected.
It is possible that during the course of pipeline construction, contaminated soils may be encountered in some areas. The most probable classes of contaminants are organic compounds related to fossil fuels (gasoline, fuel oil, coal), and perhaps trace metals associated with them (lead, cadmium). These types of contaminants are common in many developed areas because the use of fossil fuels is so pervasive in industrialized society. Standard procedures for handling, staging, and disposing of contaminated soils will be followed during construction of the pipeline. Based on the analyses performed on soil samples, the only identified constituents that might require special handling considerations are the organic compounds detected at a single boring location (BH-1A) at the marina site, and the metals cadmium and lead. These constituents are all known byproducts of the burning of coal, and are therefore presumed to be derived from that single source. If these constituents are confirmed in the excavated soils during construction, they will be disposed of as a nonhazardous solid waste. In this sense, construction would actually improve the overall quality of subsurface soils by removing encountered contamination and replacing those soils with clean fill.
2.1.2.3 Erosion Potential.
The erosion potential at the HEF site ranges from slight to moderate, and is directly related to the degree of slope on the project site. Steps will be taken to minimize the risk of erosion on the site both during and after construction. Several alternatives for handling overburden (soil and other cut and fill material) are presented in Appendix C-16, all of which offer good potential for success in preventing erosion during construction. After construction, the area around the heat exchange facility will be returned to a stable slope and restored, and the cut and fill slopes will be stabilized through grading and revegetation.2.1.2.3.1 Stormwater Management and Erosion Control.
Lake Source Cooling engineers and scientists have been working with the Town of Ithaca officials to ensure that final construction plans will comply with all town and site planning requirements. The stormwater management and erosion control measures (Appendix C-16) have been designed to control erosion during construction and minimize the release of any nutrient or sediment runoff into draining tributaries and receiving waters. The mitigating measures will include both structural and vegetative measures, such as the seeding of temporary berms, levees, and topsoil piles, which will be inspected and maintained by Cornell personnel on a regular basis.2.1.2.3.2 Soil Contingency Plan.
Because the pipeline construction project does not transect any known waste disposal areas or areas classified as active spill sites, a continuous soil screening and monitoring program is neither required nor necessary during construction activities. However, reasonable care by field personnel will adequately determine whether excavated soils may potentially be contaminated. Soils removed from excavated areas will be examined for visual and olfactory evidence of contamination. Strong or foul odors or discoloration will require that the soils be surrounded by plastic when work in any particular area is completed each day. Samples of the staged soils will then undergo laboratory analysis for organic and semivolatile organic compounds, as well as trace metals, to verify that they are not hazardous. Once analytical results are received, the soils will be disposed of in an appropriate manner.2.1.2.3.3 Site Restoration.
The soils on the facility site will be restored according to the landscape and grading plan for the HEF. Any areas subject to clearing as a result of the construction of the HEF, such as utility rights-of-way, roadway grades, and access rights-of-way, stormwater and sediment control facilities, and other setbacks, will be returned to a stable grade after construction and revegetated according to the stormwater management and erosion control measures outlined in Appendix C-16.2.1.2.4 Unavoidable Impacts.
In isolated areas where soil contamination is encountered, those soils will need to be staged and possibly disposed. From the environmental screening that took place at the facilities site, there was only one identified location, at Boring BH-1A at the marina site, where these special soil handling procedures might be warranted. Although the detected metals and organic compounds do not make the soil hazardous, the soils that contain them should not be immediately used as fill material for the project. Instead, confirmatory sampling should take place. When construction takes place in this area, the soils will need to be staged and sampled to confirm the presence of the previously detected compounds. If they are not found to be present, the soils can be used as a general construction or fill material as needed. If the analysis verifies the previously detected compounds, these soils will have to be handled as non-hazardous solid waste and disposed of appropriately. The removal and disposal of soils that are evidently impacted by various contaminants, and their replacement with clean fill, will result in an overall improvement of environmental conditions.There is a small chance that erosion could occur as a result of an accidental washout during construction. Such a washout could be caused by a heavy rain event, or by water accidentally expelled from the pipeline. The volume of soil affected would depend on the volume of water involved. However, the implementation of mitigative measures as outlined in Appendix C-16 would minimize any potential impacts from accidental washouts.
2.1.3 Chilled Water Pipeline Route.
2.1.3.1 Environmental Setting.
2.1.3.1.1 Composition and Thickness of Underlying Materials.
The pipeline route traverses an area with varying thickness of soils, and runs very close to the contact between this thin soil cover and the thicker sand and gravel deposits. Overall, the depth to bedrock is less than 30 ft for most of the route. Along portions of the route where previous construction activity is likely to have disturbed bedrock, it is expected that perhaps 10 to 20 ft of disturbed soils and gravelly fill might overlay the bedrock. In other areas along the route, particularly the eastward-reaching segment that approaches Cornell University at the end of the route, bedrock occurs between 5 and 10 ft below ground. The northern portion of the pipelines near the HEF site is also likely to encounter bedrock within a few feet of ground surface. The area closest to the lake at the building site has approximately 30 ft of sand and gravel soils overlying bedrock. Refer to Appendix C-15 for a summary of the rock profiling work conducted at the proposed HEF site and along the pipeline route.South of the Fall Creek crossing, the pipeline turns to the east, and the depth to bedrock decreases over a short distance. This section of pipeline is completely within the area of thin soils mapped by Muller and Cadwell (1986), and soil borings verified bedrock at 6 ft below ground. The apparent decrease in soil thickness corresponds to the rise in elevation as the pipeline route leaves the valley area south of Cayuga Lake and approaches the university area.
Natural soils across the pipeline route are primarily sand and gravel, with intermixed silt and occasional cobbles just above bedrock. Portions of the pipelines near existing roadways and utilities are likely to encounter a variety of fill materials as well. Sieve analyses from soil samples from along the pipeline route reflect the variability of soil texture across the area. Variable amounts of gravel, sand, silt, and clay were reported. Results of the sieve analyses are included with the soil boring logs as Appendix C-15.
The pipeline route covers an area where glacial sediments were originally deposited and later modified by glacial meltwater. As a result, the degree of sorting and chemical alteration is expected to be greater than that for till soils. Soils around the pipeline route should have a more limited chemical mix and grain size distribution than the more variable tills from outlying areas. For some portions of the route, the original natural soils have been disturbed by construction of roadways, bridges, and buildings. For these areas, the chemistry of the fill materials will be the decisive factor that determines soil chemistry. A number of soil samples were analyzed for pH, as was done for soil from the facility area soils. The reported pH values were generally between 7.5 and 8.5. Fill materials along the route that have a significant component of limestone-type materials in the form of cement, concrete, and gravel would tend to have a near neutral pH, like those reported for the soils analyses.
2.1.3.1.2 Earthquake Potential.
Along the pipeline corridor, there are no known faults or areas of seismic activity. Like the facility site, the entire corridor is located within Zone A, which is characterized by minimal earthquake activity in New York State. Historically, there are no recorded earthquakes originating within Tompkins County. The risk of earthquake-related damage to the pipelines is low.2.1.3.1.3 Map of Soil Types.
The majority of the soils along the route fall into the category known as Made Land (Mc). This miscellaneous soil type occurs in areas that have been previously filled with a variety of materials. Some of these areas have been filled with soil material that was hauled onto the site, or was disturbed and supplemented with other fill material. In some cases, these areas have been filled with trash or rubble and have then been leveled and covered with soil. This has occurred mostly near buildings or adjacent to villages, chiefly in the vicinity of Ithaca and Cayuga Heights. Some areas have been leveled and used for commercial establishments, like those along Route 13. Most of the pipeline route that is within or directly adjacent to roads (i.e., East Shore Drive, Lake Street, University Avenue) and on the Cornell Campus will fall within this soil type.Just south of the HEF, some shallow and very shallow (0 to 15 percent slope) (LtB) Lordstown, Tuller, and Ovid soils will be traversed, as well as a short length of Lordstown soils (35 to 75 percent slope) (LoF), and some Chenango gravelly loam (5 to 15 percent slope) (CdC).
Across much of the pipeline route, the natural soils have been obscured or removed as a result of urbanization. The United States Soil Conservation Service survey for Tompkins County indicates that in the Greater Ithaca area, natural soils are unmapped. Geologic mapping recognizes a number of general surficial geologic deposits across the area, including unsorted till, silt/clay deposits, and sand/gravel deposits (Figure 1-5). Specific areas where soil cover is very thin and bedrock outcrops are common have likewise been identified.
The pipeline corridor runs along a mapped contact between relatively thick sand and gravel deposits, and an adjacent area of very thin deposits containing gravel, sand, silt, and clay. For portions of the pipeline route where urbanization is more extensive, these natural deposits have been disturbed, and in some cases replaced with a variety of construction fill materials.
2.1.3.1.4 Physical Properties.
For most of its length, the pipelines will run along the base of the eastern wall of the Cayuga Lake valley. The pipelines will traverse primarily an urban landscape for most of the route, and will follow existing corridors used for roadways and utilities. The pipelines will encounter fairly flat grades over the majority of the route. At the point to the south of Fall Creek where the pipelines turn to the east toward Cornell University, however, the grade will steepen substantially as the pipelines ascend Gun Hill.Bedrock may be encountered along the Gun Hill segment of the pipeline route. In this area, bedrock is generally very near or at the ground surface. The results of these borings are detailed further in Appendix C-15.
2.1.3.2 Impacts of the Proposed Action.
2.1.3.2.1 Pipeline Route Topography.
The proposed pipeline route follows existing roadways and utility rights-of-way for most of its length, and is therefore in an area that has already experienced construction-related soil removal and modification. For much of the proposed route, only fill materials are expected to be encountered. The addition of the proposed pipeline to the area is not expected to result in a significant change to the character of the landscape.2.1.3.2.2 Chemical Content of Surface Soils.
The pipelines are to be constructed of inert materials that will not degrade or otherwise introduce chemicals into the subsurface. It is anticipated that fill materials will be primarily sand, which does not contain appreciable amounts of soluble materials that would significantly alter local soil chemistry.2.1.3.2.3 Erosion Potential.
The erosion potential for the pipeline route is highly variable, ranging from slight to severe in a few specific very steep slope areas. Table 1-3 summarizes the soil types that will be disturbed during construction. Only a small portion of the soil has a severe erosion rating. Many of the soils encountered, such as the Lordstown, Tuller, and Ovid soils, the rock outcrops, and the Made Land, consist of miscellaneous land types and undifferentiated units in which the soil properties are so variable that evaluation of erosion hazards cannot be made without critical on-site inspection at the time of construction. However, the soil restoration and impact mitigation strategy presented in Appendix C-16 has good potential for success at preventing erosion during construction. Following construction, the excavated pipeline ditch will be primarily backfilled with select fill, the pipeline route and adjacent cut and fill area will be returned to a stable slope and restored, and the cut and fill slopes will be stabilized through grading and revegetation (as discussed in Appendix C-16).2.1.3.3.1 Construction and Reclamation Techniques to Minimize Subsurface Impacts.
Lake Source Cooling engineers have been working with the Town and City of Ithaca officials to ensure that final construction plans will comply with all town and city requirements. The stormwater management and erosion control measures summarized in Appendix C-16 have been designed to control erosion during construction and minimize the release of any nutrient or sediment runoff into draining tributaries and receiving waters. The mitigating measures will include seeding of temporary berms, levees, and topsoil piles, which will be inspected and maintained by Cornell personnel on a regular basis.2.1.3.3.2 Site Restoration Plan.
Any areas subject to clearing as a result of the construction of the pipeline, such as access roads and rights-of-way, will be returned to stable grade after construction and revegetated according to the restoration details outlined in Appendix C-16.2.1.3.4 Unavoidable Impacts.
There is a small chance that erosion could occur as a result of an accidental washout during construction. Such a washout could be caused by a heavy rain event, or by water accidentally expelled from the pipelines. The volume of soil affected would depend on the volume of water involved. However, the implementation of mitigative measures would minimize any potential impacts from accidental washouts.
