The Sparks Solvent/Fuel Site (SSFS) is a rail yard and fuel-terminal tank farm located in Sparks, Nevada. Industrial activities at the site over the past century led to contamination of groundwater and soils by gasoline, solvents, diesel fuels, and other petroleum products. This webpage presents an overview of the site and provides information on the current status of the site investigation and cleanup.
History of the Sparks Solvent/Fuel Site — The rail yard was constructed in the late 1800's and has served as a major east-west thoroughfare for railroad traffic since its construction. The site has been used as a refueling and service area for Southern Pacific Railroad since about 1907 and has been a fuel storage and distribution facility since 1957. Before the 1950's, the rail yard was the largest industry in Sparks, with a roundhouse, powerhouse, machine and locomotive shops, crew lodging and commissary.
Operations at the terminal have included the storage, distribution, and loading of gasoline, heating oil, diesel fuels, military fuels, and fuel additives. Rail-yard operations have included maintenance, cleaning, refueling, and storage of railroad engines and other rolling stock. Currently, Union Pacific Railroad (UPRR) no longer performs fueling operations at the site.
In 1995, the terminal and rail-yard landowners and tenants began coordinated remediation and monitoring at the site through the Vista Canyon Group (VCG). The VCG includes the following entities:
- Berry-Hinkley Terminal, Inc.
- Chevron USA, Inc.
- Equilon Enterprises LLC, a joint venture between Shell Oil Company and Texaco Refining and Marketing, Inc.
- Kinder Morgan Energy Partners, L.P. through its operating partner SFPP, L.P. (formerly Santa Fe Pacific Pipelines, Inc.)
- Union Pacific Railroad Company (formerly Southern Pacific Transportation Company)
- Time Oil Co.
- Union Oil Company of California, d.b.a. UNOCAL
Site Geology and Hydrogeology —The SSFS lies within the Truckee Meadows, which contains layers of unconsolidated sediments deposited by fluvial, lacustrine and alluvial processes. At the SSFS, the geologic units consist of a coarse-grained, permeable upper unit, extending to depths ranging from 60 to 100 feet below ground surface (bgs). The upper unit includes layers and lenses of sand, gravel, cobbles and boulders. Interspersed thin clay layers may be floodplain deposits of the Truckee River. Below 60 to 100 feet, there are lower permeability layers that consist of clayey silt and silty clay with thin sand layers and interspersed gravel lenses.
Groundwater is unconfined in the upper unit, and semi-confined within the lower, less-permeable unit. The water level of the Sparks Marina Park Lake (SMP Lake) controls the local hydrology, including water levels and flow direction of groundwater underlying the SSFS. Most groundwater in the area flows toward the lake. The Truckee River runs approximately east and lies less than one mile south of the SSFS.
Sampling and Reporting — Monitoring wells across the site are sampled annually or semi-annually to provide the chemical data needed to evaluate and monitor the extent and behavior of contaminants in groundwater; water-level measurements are also collected from the monitoring wells. Samples of water from the SMP Lake are collected at depth (i.e., 45 feet below the water surface) and are analyzed for site-related chemicals of concern. The main site-related chemicals of concern include benzene, toluene, ethylbenzene and xylene (BTEX) compounds, methyl tert-butyl ether (MTBE), and the chlorinated solvents, trichloroethylene (TCE) and tetrachloroethylene (PCE).
Groundwater monitoring reports and remediation system reports are submitted semi-annually to the NDEP for review.
Remediation — Large-scale remediation of groundwater commenced in 1995, when an extraction and treatment system was installed for the cleanup of groundwater and a vapor extraction system operated for cleanup of soils. The vapor extraction system operated until mid-1997 in the eastern part of the SSFS and until the end of 1997 in the west. Monthly testing is conducted on the treated groundwater (that is, effluent from the remediation system) to ensure contaminants are not being discharged to the Truckee River.
In-situ chemical oxidation (ISCO) was employed in late 2010 and early 2011 to destroy contaminants in groundwater in two localized areas. The ISCO remedy consisted of ozone sparging in the vicinity of wells J1 and J2. The ozone sparging succeeded in decreasing the concentrations of TCE and MTBE in groundwater in the treatment wells and in surrounding wells.
Other remedies employed at the site include phytoremediation, using two stands of poplar trees, and a mobile soil vapor extraction (SVE) unit. Since remediation began in 1995, concentrations of contaminants in groundwater have decreased significantly, as shown below in Table 1.
Action levels for the main contaminants at the SSFS are 5 micrograms per liter (µg/L) for benzene, PCE and TCE; and 40 µg/L for MTBE.
Multi-Level Sampling (2007-2008) — In November 2007, NDEP concurred with a Multi-Level Sampling Work Plan. The purpose of the multi-level sampling was to evaluate whether site contaminants may have migrated into the deeper zones of the regional shallow aquifer. Water-supply wells for the Truckee Meadows Water Authority (TMWA) are screened at various depths, with the tops of screens ranging from 140 feet bgs (Sparks High Well) to 180 feet (Dilworth Well) and deeper, with the nearby Stanford Well first screened at 215 feet bgs.
Low concentrations of contaminants such as MTBE and PCE have been detected in other TMWA water-supply wells that are not near the SSFS. And although the sources of these contaminants are not well defined, their presence in the deeper portion of the potable water aquifer indicates that there is hydrologic communication between the shallow and deeper (water-supply) zones of the regional aquifer.
The multi-level sampling was used to evaluate the lithology and contaminant concentrations in the lower part of the aquifer, which contains more clay-rich zones than the upper portion (0 to 100 feet bgs) of the aquifer. Five borings were drilled to approximately 150 feet bgs at selected locations across the SSFS. Groundwater samples collected at multiple depths from within each boring were analyzed for site-related chemicals; results are summarized in Table 2 below.
Reconfiguration of the Groundwater Remediation System (August, 2011) —
In early 2010, the VCG proposed reconfiguration of the groundwater remediation system at the SSFS (CDM, March 17, 2010). In a December, 2010 letter, the NDEP concurred with the proposed changes, but required that VCG (1) implement the reconfiguration in phases and (2) provide a "work plan with details of monitoring and assessment (i.e., specific numeric and non-numeric criteria) prior to implementing Phase I modifications." The NDEP specified that"Cessation of pumping at the P-wells and wells M-3 and M-4 should be followed by at least a year of monitoring from these wells and the rest of the wells (as specified in the current monitoring plan) in the area east of McCarran, before transition from the remaining M-wells to the S-wells. Effects of the change in hydrological conditions (water levels and contaminant concentrations) can then be monitored for potentially unanticipated changes before the S-wells are turned on and the remaining M-wells are shut down" (NDEP, December 2, 2010)
Changes made to the remediation system during the third and fourth quarters of 2011 included the phased shutdown of certain extraction wells, while M-series wells M1, M2 and M5 continued pumping. The wells were shut down as described below:
- August 1, 2011 - Wells M3 and M4 shut down
- August 21, 2011 - Well P8 shutdown
- September 6, 2011 - Well P4 shutdown
- September 20, 2011 - Well P7 shutdown
- October 13, 2011 - Wells P9 and P10 shutdown
- October 27, 2011 - Well P5 shutdown
The Detection Monitoring Plan - June 23, 2011 —
The Detection Monitoring Plan (DMP) was prepared in response to the NDEP's request to provide a work plan that described response actions if concentrations of site-related contaminants exceeded action levels in sentinel wells, following changes to the remediation system. The DMP employed statistical methods to establish baseline conditions and develop standards for each sentinel well; these standards include Shewhart-CUSUM control limits and upper prediction limits (UPL), along with the chemical-specific action levels for the site.
Wells designated specifically as sentinel wells include MW-PLM-1, MW-203, MW-219, MW-226, MW-237, MW-238 and DWC-312. Offsite wells "Lincoln monitoring well" and "Victorian monitoring well" are also part of the sentinel-well network. Additional sentinel wells will be installed offsite at least one year prior to increased pumping of water-supply wells north of the SSFS; these will be "nested" wells, with a shallow and deep well at each location (see Figure below, from the June 23, 2011 DMP). Currently, only wells DWC-312, MW-226, MW-237 and MW-238 are actively analyzed as part of the DMP. The remaining sentinel wells pertain to conditions when TMWA's planned groundwater pumping north of the SSFS commences.
Current Conditions —
Some changes in contaminant concentrations in site monitoring wells may be expected as the extraction well network is reconfigured at the SSFS. The DMP outlines a process to be followed to ensure that changes in these concentrations do not adversely affect human health or water-supply wells. Three monitoring wells have shown an increase in PCE concentrations since selected extraction wells were shut down: DWC-305 south of the SSFS, DWC-310 near McCarran Boulevard and DWC-312 near SMP Lake; however, PCE concentrations decreased significantly in the most recent sample (4th quarter, 2012) from DWC-312.
TCE in well DWC-312 has also increased, with concentrations exceeding the action level in three quarterly samples collected since October, 2011. Similar increases were seen for MTBE in DWC-312. The most-recent samples (December 2012) collected from sentinel well DWC-312 reverse this trend of increasing concentrations, however (see graph below).
Some fluctuations in the concentrations of VOCs may be expected during the reconfiguration of the remediation system, so the data will continue to be closely watched and evaluated. Well MW-218 (PCE>5 µg/L), sentinel well DWC-312 (PCE and TCE>5 µg/L) and all the other monitoring wells will continue to be monitored regularly. In addition, as a health-protective measure, lake water will be sampled at an increased frequency of every other month during the reconfiguration of the remediation system.
Recent data (2011 through 2012) from all wells sampled for the SSFS were screened against site action levels. Results of this screening, showing all detected concentrations exceeding action levels for benzene, MTBE, PCE and TCE, are provided below in Table 3.
For additional "historic" information see the SSFS Archive Website
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