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2. General Site Information

2.1 Former Radiation Disposal Site

2.1.1 Site History and Description

The Cornell University former RDS is a 290-foot by 300-foot disposal area surrounded by a fenced enclosure located on Snyder Road, north of the Ithaca Tompkins Regional Airport, in the Town of Lansing, Tompkins County, New York (Figures 1-1 and 2-1). This facility was utilized from 1956 to 1978 as a disposal area for low-level radioactive waste and associated materials generated by Cornell. Waste materials were disposed in trenches 6 to 12 feet deep.

During remedial investigations for the RDS, 34 groundwater monitoring wells and 42 surface water sampling locations were established to evaluate the nature and extent of contamination. Remedial investigations concluded that groundwater and surface water are the affected media in the RDS investigation area. Radionuclides (strontium-90, carbon-14, and tritium), paradioxane, dichloroethylene (DCE), and benzene are the contaminants of concern in the groundwater, and paradioxane is the contaminant of concern in the surface water. Identification of these contaminants of concern was based on contaminant mobility, potential health effects, frequency and distribution of detections, and comparison to background levels of radionuclides. Paradioxane is the most extensive contaminant in groundwater. The groundwater contamination is predominantly in the highly fractured shale zone, with paradioxane detected in groundwater in this zone approximately 2,500 feet downgradient from the disposal area. Paradioxane has been detected in surface water primarily north of Snyder Road and on airport property, although it also has been detected occasionally further downstream.

The RDS is being remediated under a 1996 Consent Order (NYS Hazardous Site Index #755001) with the New York State Department of Environmental Conservation (NYSDEC) (Index # A7-0333-95-08). A Record of Decision (ROD) selecting the final remedy was issued by the NYSDEC in March 2002.

Interim Remedial Measures (IRMs) to limit surface water infiltration into the waste at the RDS (Capping IRM) were performed in 1996-1997. A Groundwater IRM to capture paradioxane was constructed in 2001, and operated from 2002-2007 and from 2011-present. The final Source Area Remediation specified in the ROD was completed during 2004. These remedial measures are described in more detail below.

2.1.2 Remedial Measures

RDS Capping IRM

In 1996-97, capping IRMs were performed at the RDS that included: covering the disposal area with a high-density polyethylene cap system with gas vents; grading the area to provide surface water diversion and erosion protection systems; and installing a below-ground conveyance line to transport RDS site related water to the Groundwater Treatment Plant located near the CDS, approximately one-third mile to the southeast of the RDS. The Capping IRM eliminated volatilization, surface runoff, surface water infiltration, and direct contact as potential contaminant migration pathways.

Groundwater Recovery System

A Groundwater Recovery System to control the migration of the paradioxane plume emanating from the site was constructed as an IRM in 2001, and began operating on August 19, 2002. With the issuance of the ROD, this became part of the Final Remedy for the site. The Groundwater Recovery System consists of a series of 13 recovery wells on the north side of Snyder Road and monitoring wells to monitor its effectiveness upgradient, downgradient and between the recovery wells. The recovery wells pump contaminated groundwater to the Groundwater Treatment Plant, via the below ground conveyance line. Water from the site is treated using ultraviolet oxidation to remove paradioxane from the water.

Source Area Remediation

The ROD for the site specified a Final Remedy which included source area containment measures consisting of a grout curtain in the bedrock, a soil-bentonite wall in the soil layer, and a multi-layered capping system. Installation of these measures was completed during 2004. The grout curtain and soil-bentonite wall are intended to minimize transport of contaminants from the site via groundwater, while the cap is intended to prevent contact with the waste materials and to prevent infiltration of water into the waste.

2.2 Former Chemical Disposal Site

2.2.1 Site History and Description

Cornell University’s former CDS is also located north of the airport on Snyder Road, in the Town of Lansing, Tompkins County, New York (Figures 1-1 and 2-1). Waste chemicals were managed at the site in nine disposal cells by various techniques, including burial in trenches; open burning with burial of the residue; mounding; and evaporation (Figure 2-2). Cornell University operated the site from 1962 to 1978 in accordance with acceptable practices at the time.

During remedial investigations at the CDS, fifty-seven groundwater wells, twelve piezometers, and sixteen extraction wells were used to characterize, define, monitor, and control the chemical plume and the disposal site groundwater (Figure 2-1). Groundwater contamination, primarily from trichloroethylene (TCE) and other volatile organic compounds (VOCs), has been detected primarily in the two shallow zones (glacial till and fractured shale). The groundwater contamination is predominantly in the fractured shale zone, extending approximately 2,500 feet southwest of the disposal site.

Between 1990 and 1992, interim remedial measures (IRMs) were designed and constructed in accordance with NYSDEC Consent Order #T042887, as amended on March 25, 1992. The IRMs included a Source Control System (SCS) for the disposal area and a Plume Collection System (PCS) for contaminated groundwater downgradient of the site. These IRMs are further described in section 2.2.2.

In December 1998, the PCS was upgraded to prevent the migration of contamination beneath and past the initial groundwater collection trench. This project was referred to as the CDS Trench Upgrade, and is further described in Section 2.2.2. This work was performed in accordance with a new NYSDEC Consent Order (Index # A7-0289-92-10), dated August 19, 1998, that incorporates the requirements of the earlier Consent Order by reference and formalizes the previously issued ROD for the site.

During 2004, Cornell completed installation of the remedial measures required under the Order on Consent (Index #A7-0289-92-10) and the subsequent ROD by installing a concrete capping system for the cylinder burial area and an engineered cap covering the landfill.

Cornell University is currently operating and maintaining these remedial measures, which are designed to control and remove VOC contamination from groundwater in and around the site, as well as to prevent further releases from the former disposal area. The groundwater treatment plant, which treats contaminated groundwater pumped by the IRMs, operates in accordance with NYSDEC Effluent Limitations and Monitoring Requirements #755002.

2.2.2 Remedial Measures

CDS Source Control System

The SCS was designed to minimize the release of contaminants from the former chemical burial site. It consists of a groundwater barrier wall, a groundwater extraction system, and a capping system. The soil-bentonite groundwater barrier wall surrounding the one-acre site extends into the upper fractured shale bedrock. Pumping from four groundwater extraction wells, located inside the four corners of the enclosure, controls migration of contaminants by maintaining an inward hydraulic gradient across the groundwater barrier wall. A concrete containment structure covers an area containing buried gas cylinders. The entire source area is covered with a multi-layer impervious capping system with soil and vegetation at the surface.

CDS Plume Collection System

The PCS was designed to prevent further migration of, and reduce contaminant concentrations in, the CDS groundwater plume. It consists of a groundwater collection trench and extraction wells, which control the plume by pumping contaminated groundwater for treatment at the groundwater treatment plant, located adjacent to the former one-acre disposal area. Two scavenger wells (SW-1 and SW-2) are located at what once were the more highly contaminated locations within the plume. The collection trench, which is approximately 900 feet long and 8 to 14 feet deep, is located near the downgradient boundary of the plume. Three extraction points (EP-1 to EP-3) are located inside the trench. This portion of the Plume Collection System is known as the PCS Shallow recovery system (PCS-Shallow).

To recover the deeper portion of the plume in groundwater from the upper portion of the bedrock (10 to 40 feet below land surface), seven extraction wells (EW-1 to EW-7) were installed in December 1998 immediately downgradient of the collection trench. Known previously as the PCS Trench Upgrade, this system is now referred to as the PCS-Deep recovery system (PCS-Deep). Contaminated groundwater from the three extraction sumps in the trench and the two scavenger wells is combined and pumped to the treatment plant. Water from the seven extraction wells is combined in a second pipeline and conveyed to the treatment plant where it joins with the PCS-Shallow system water upon reaching settling tank T-3. Figure 2-1 shows the location of the PCS scavenger wells, extraction points and extraction wells.

CDS Groundwater Treatment System

The 1992 groundwater treatment system was designed to meet effluent requirements by removing a variety of VOCs and suspended metals and sediment. It was modified in December 1998 to treat flows from the new extraction wells added to the PCS and again in 2001 to treat flows from the RDS Groundwater IRM recovery system (Figure 2-3). SCS groundwater is filtered, pumped through granular activated carbon (GAC) to remove VOCs, and then passed through the UV/Oxidation system and bag filters to remove paradioxane and suspended solids. The PCS groundwater is pumped to settling tank T-3, filtered, and finally processed by adsorption by GAC. The CDS groundwater treatment system as currently designed can process up to approximately 178 gallons per minute. Effluent from the treatment system meets New York State Class GA groundwater guidelines and is discharged to an intermittent stream in accordance with NYSDEC effluent discharge requirements. The stream discharges to a one-acre pond (CDS Outfall Pond), which discharges to Cayuga Lake over a three-mile course of culverts and open channel flow.