2018_DQ University FUDS Proposed Plan.pdf

PROPOSED PLAN

for Groundwater Remedial Action

D-Q University FUDS, Yolo County, California

INTRODUCTION

The US Army Corps of Engineers (USACE), Sacramento District, presents this Proposed Plan to remediate impacted groundwater at the D-Q University Formerly Used Defense Site (FUDS) (No. J09CA1180) located in Yolo County, California (referred to as the Site). D-Q University is located on County Road 31 approximately 9 miles west of the City of Davis (Figure 1). This Proposed Plan summarizes the following information: regulatory framework for the remedial action; Site background and previous investigations; results of a groundwater remediation pilot test; results of a human health risk assessment (HHRA) and Feasibility Study (FS) of remedial alternatives; the preferred remedy; and how to provide comments. Italicized, bolded terms are defined in the Glossary of Terms located near the end of this document.

REGULATORY FRAMEWORK

The land on which D-Q University currently lies was owned and occupied by the U.S. Army from 1952 to 1969 and qualifies as a FUDS. In accordance with FUDS guidance, the overall project is being conducted consistent with the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) and the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA or Superfund). The Central Valley Regional Water Quality Control Board (RWQCB) is providing regulatory oversight. The USACE has completed the first three phases of the CERCLA process (Figure 2), and documents related to the Site Inspection (SI), Remedial Investigation (RI), and FS can be found in the Administrative Record for D-Q University FUDS located at the public library in Winters, California. The RWQCB has provided comments on the RI and FS and these comments have been addressed in those reports.

The USACE encourages the public to comment on this Proposed Plan. A comment form is included at the end of this document. A public meeting has been scheduled by USACE to facilitate public comments on DATE. The USACE will respond to public comments on this Proposed Plan and from the public meeting in the Decision Document which is the next phase of the CERCLA process.

~ NOTICE ~

Public Comment

Period ________ to ______, 2018

~ PUBLIC MEETING ~

__________, 2017 Winters Community

Library 708 Railroad Avenue Winters, CA 95694

(530) 795-4955

SITE BACKGROND

In 1952, the US Army purchased 651.55 acres of agricultural land for the West Coast Relay and Radio Transmitter Station to support the Signal Corps. Improvements to the Site during U.S. Army occupation included the construction of a transmitter building (Building 100), a power generation building (Building 101), a relay building (Building 102), barracks (Building 103), and other associated structures, like utilities, underground storage tanks (USTs), above ground storage tanks (ASTs), transformers, waste oxidation lagoons, and cooling water injection and water supply wells.

In 1969, 647.90 fee acres and 3.65 easement acres were reported as excess to the General Services Administration. In 1971, 4.85 fee acres were conveyed by quitclaim deed to the County of Yolo, State of California, and 643.05 fee acres and 3.65 easement acres were conveyed by quitclaim deed to D-Q University. Permanent ownership of the land was secured by D-Q University in 2001. The closest water supply well is located 0.4 mile north of the Site. This well is used for agricultural water supply and is located up-gradient of the campus property. Surrounding agricultural lands are currently leased to farmers that plant and harvest alfalfa.

SITE CHARACTERSTICS AND PREVIOUS INVESTIGATIONS

The Site and surrounding area are located on the geomorphic unit termed “low-alluvial plains and fans”, specifically the Putah Plain. Sediments that form these alluvial fan deposits consist primarily of silts and clays with coarse-grained sediments occurring locally. The Putah Creek Fan was formed by a creek that changed course many times throughout this area. Sands and gravels were deposited during high velocity flows at times of floods. Outside the ribbon-like strips of coarse channel deposits, lower velocity waters deposited silts and clays.

Based on the data collected at the Site, there appears to be four hydrostratigraphic zones:

• low permeable silts and clays (0 to 25 feet bgs to 32 feet bgs),

• a permeable relatively continuous sand/gravel unit (generally at 25 feet bgs to 40 feet bgs),

• low permeable silts and clays (generally 40 feet bgs to 130+ feet bgs), and,

• a discontinuous sand/gravel unit (generally 65 feet bgs to 80 feet bgs).

Through the FUDS program, USACE conducted investigations of five Areas of Concern (AOCs) to define potential source areas, evaluate the nature and extent of contamination, assess subsurface characteristics, transport mechanisms and contaminant fate, and develop a conceptual site model. The investigations eliminated from further consideration those AOCs that pose little or no threat to public health or the environment. Investigation results included recommendations for the need for remedial action, and helped to facilitate later evaluation of the release pursuant to the Hazard Ranking System conducted by the U.S. Environmental Protection Agency (USEPA). The investigations concluded that the chemicals of concern in groundwater are diesel fuel (TPH-DRO), and volatile organic compounds (VOCs), primarily trichloroethylene (TCE) with lesser amounts of dichloroethylene (DCE). Two AOCs were identified as requiring further investigation, and their impacts are described below.

• TCE Groundwater Plume (AOC-4): The TCE-impacted groundwater is primarily found within the shallow sand/gravel unit between 25 feet and 40 feet below ground surface (ft bgs) that underlies approximately 26 acres to County Road 31 (Figure 3). In 1998, the historical maximum TCE concentration of 1,700 micrograms per liter (µg/L) was detected in shallow groundwater in the source area just east of Building 100. The lack of TCE degradation products in Site groundwater samples indicated minimal biodegradation. However, subsequent sampling in the source area between 2006 and 2011 showed declining TCE concentrations: 1,100 µg/L in 2006, 390 µg/L in 2009, and 15 µg/L in 2011. Reductions from 2009 to 2011 were due to an active remediation (a pilot test) performed at the Site (see below for a detailed summary of pilot testing). Since termination of pilot testing in 2011, the groundwater has continued to be monitored. TCE concentrations were steadily declining until recent monitoring data in 2017 suggest that higher groundwater elevations due to heavy rains have flushed TCE from the overlying soil, or vadose zone, in to the groundwater.

The maximum concentration of TCE detected in 2017 was 120 µg/L. In addition, detections of TCE have historically been found in small discontinuous lenses of fine sand at depths between 80 ft bgs and 145 ft bgs. However, these detections appear isolated and are not part of the shallower water bearing zone.

• TPH-DRO Groundwater Plume (AOC-5): The extent of TPH-DRO in shallow groundwater is found in the same shallow sand/gravel unit as the TCE plume and originates at the four former fuel oil USTs, located near the northeast corner of Building 101 (Figure 3). TPH-DRO concentrations in this plume historically ranged from 120 µg/L to 480 µg/L and encompassed an area of approximately 0.5 acre.

Additional groundwater monitoring wells were installed in 2012 to more closely monitor the TPH- DRO plume and samples results indicated that TPH-DRO may no longer be present in the shallow water bearing zone. Historically, TPH-DRO was also found at depths between 80 feet bgs and 145 feet bgs. Like the TCE samples collected at these depths, the occurrence of TPH-DRO is isolated and part of the shallower water bearing zone. The historical TPH-DRO shallow groundwater plume is completely contained within the TCE shallow groundwater plume.

Groundwater Remediation Pilot Test

As part of the FS conducted by USACE, a pilot test was conducted to evaluate if enhanced biodegradation combined with groundwater recirculation could remediate the TCE source area. From August 2009 to November 2009, USACE conducted an aquifer test to determine hydrogeologic characteristics of the shallow water-bearing zone and installed monitoring wells, a mobile treatment system, and conveyance pipe network to support the pilot test. During the aquifer test, over 200,000 gallons of impacted groundwater were extracted, treated and disposed, and key aquifer parameters were evaluated for use in the pilot test. The treatment system was constructed/installed in October 2009 and operated from November to December 2009 to distribute nutrients throughout the TCE source area. The system was operated by extracting impacted groundwater from three wells, treating the water with activated carbon, amending the extracted water with nutrients, and returning the water to the subsurface through five wells. Two new performance monitoring wells were installed and sampled periodically to determine if natural microorganisms were biodegrading the TCE. From December 2009 to August 2010, the system was turned off and the plume was allowed to equilibrate or rebound. After this “rebound period”, the system was operated from August 2010 to February 2011. Monitoring indicated that conditions conducive to biodegradation had been established in groundwater and TCE concentrations in the source area were reduced from 390 µg/L to 15 µg/L. The introduction of nutrients resulted in some temporary increases of arsenic, manganese and iron concentrations in groundwater;

however, the overall success of the pilot test indicated that the combined technologies of groundwater recirculation and enhanced biodegradation are an effective remedial alternative. See the resulting graph below (Figure 4) that illustrates the reduction in TCE concentrations in the source area from 1998 to 2011.

SCOPE AND ROLE

The FS alternatives were developed to address the portion of the plume with TCE concentration above 5 μg/L. In addition, the detailed analysis of alternatives assumed that a single alternative would be implemented to address this portion of the plume. This approach allowed each alternative to be analyzed independent of each other and provided a consistent basis for relative comparison. In selecting a remedy, however, more than one alternative could be implemented concurrently for the entire plume or implemented for different areas of the plume.

SUMMARY OF SITE RISKS

Although TCE concentrations within the source area were reduced to 15 µg/L, a maximum TCE concentration of 120 µg/L was recently detected slightly upgradient from the area treated by the pilot study (March 2017). The potential human health risks are evaluated based on the most recent Site maximum TCE concentration of 120 µg/L. USACE conducted a quantitative screening-level risk evaluation posed by two exposure scenarios: 1) VOC vapor intrusion into indoor air of existing buildings (e.g. Building 100) or potential future buildings at D-Q University; and 2) ingestion of VOC-impacted groundwater extracted from a potential future drinking water well.

• Soil Vapor Intrusion Pathway: Previous investigations indicated that VOCs in Site soil were near analytical detection limits and the tight, clayey Site soils did not allow for collection of active soil vapor samples; therefore, Site soil was subsequently deemed to require no further evaluation or remedial action. Consequently, groundwater data were used to evaluate this exposure pathway.

Results in Table 1 show that the current maximum TCE concentration in groundwater is below the California RWQCB Environmental Screening Levels for groundwater greater than 9 ft bgs in the residential use scenario for potential vapor intrusion concerns. In addition, the incremental lifetime cancer risk and hazard index for TCE are well below USEPA risk management ranges, indicating that further remedial action to address potential vapor intrusion from VOCs in groundwater is not required.

Table 1. Screening-Level Risk Evaluation of Soil Vapor Intrusion Pathway

Well Name Site Chemical Maximum Groundwater Concentration

CA Environmental Screening Level

USEPA Incremental Lifetime Cancer Risk

USEPA Hazard Quotient (non-cancer risk)

D-Q-GMW-6 TCE 120 µg/L 250 µg/L 1 x 10-7 - Action Limit <1 x 10-6 < 1.0

• Groundwater Ingestion Pathway: Groundwater data were compared to drinking water standards to evaluate the groundwater ingestion pathway. Results in Table 2 show that the maximum concentrations of Site chemicals in groundwater exceed California Maximum Contaminant Levels (MCLs), indicating that further remedial action is required (a human health risk assessment was not conducted for the drinking water exposure pathway; MCLs are promulgated standards that indicate remediation is required regardless of human health risk assessment results).

Table 2. Screening-Level Risk Evaluation of Groundwater Ingestion Pathway

Well Name Site Chemical Maximum Groundwater Concentration, Feb. 2011

CA Maximum Contaminant Level

USEPA Maximum Contaminant Level

D-Q-GMW-6 TCE 120 µg/L 5 µg/L 5 µg/L

REMEDIAL ACTION OBJECTIVES

Remedial Action Objectives (RAOs) are Site-specific, initial cleanup objectives that are established on the basis of the nature and extent of the contamination, Applicable or Relevant and Appropriate Requirements (ARARs), and the potential for human and environmental exposure. The RAOs generally address the contaminants of potential concern, exposure routes and receptors, acceptable contaminant level, and restoration time frame. USACE established the following RAOs on the basis of the nature and extent of contamination, potential human health risks, and ARARs.

1. Prevent ingestion of groundwater containing TCE and daughter degradation byproducts, and fuel-related compounds.

2. Restore TCE-impacted groundwater to MCL concentration levels of less than or equal to 5 µg/L.

3. Monitor the levels and extent of the groundwater plume.

EVALUATION OF ALTERNATIVES

In 1998, TCE concentrations were as high as 1,700 µg/L in the source area. Since then and due in part to the success of the pilot test, TCE concentrations have been reduced to less than 120 µg/L within the source area as of March 2017, which is equivalent to an estimated 6 pounds (less than 1 gallon) of TCE dissolved in groundwater. USACE will continue the success of remediating the source area and will expand their efforts. USACE has selected potential remedial alternatives that are primarily focused on the more concentrated portion of the plume (i.e., TCE greater than 50 µg/L) which represents half the TCE mass and covers about 2 acres located east of Buildings 100 and 102 (Figure 3). FUDS guidance requires that ARARs be complied with in the remedy selection process. USACE started the FS of remedial alternatives by identifying the following ARARs.

• Chemical-Specific ARARs: These are health- or risk-based numerical values for Site contaminants in groundwater. CERCLA 121(d) specifically identifies federal Safe Drinking Water Act MCLs as chemical-specific ARARs.

• Location-Specific ARARs: These are regulations intended to preserve or protect environmental, biological, or cultural resources on the Site that may be threatened by remedial actions. Since the portion of the Site requiring remediation is either covered by pavement and buildings or active agricultural land, there is unlikely suitable habitat for endangered species. No location-specific ARARs have been identified.

• Action-Specific ARARs: These are regulations that apply to specific activities or technologies used to remediate the Site. No action-specific ARARs have been identified; once the remediation activity/technology has been established in the Decision Document, action-specific ARARs will be identified as appropriate.

USACE identified and developed five remedial alternatives to accomplish the RAOs. These alternatives are compared against the baseline alternative of No Action.

• Alternative 1 – No Action: This alternative involves no remedial actions of any kind and the status of the TCE groundwater plume is not monitored. CERCLA requires its inclusion for comparison purposes. It does not comply with ARARs since a significant portion of the groundwater plume is expected to still exceed the MCLs after the 30-year period considered for the FS.

• Alternative 2 – Monitored Natural Attenuation: This alternative consists of monitoring plume stability and the ability of natural groundwater processes to attenuate the TCE and TPH-DRO plumes. The plume appears to be stable due to several factors: aggressive remediation of the source area during the pilot test, relatively flat groundwater gradients, and natural attenuation of the diffuse portion of the plume. Natural attenuation is commonly associated with natural (or enhanced) biodegradation from naturally occurring organisms; however, it is also noted that abiotic degradation (i.e., degradation that is not related to biologic/organism) of TCE by reactive minerals has been recognized in the industry in the past 5 to 10 years. Prior to the pilot test, there was a significant decrease in TCE concentration most likely attributable to natural attenuation processes; however, recent monitoring indicates TCE biodegradation is minimal without enhancement (i.e., addition of nutrients and recirculating groundwater). Monitoring wells are within the plume itself, and cross-and down-gradient of the plume (Figure 3).

As discussed previously, the horizontal and vertical extent of TCE-impacted groundwater is defined and is primarily found within a sand/gravel unit at 25 feet to 40 feet bgs. TCE does not appear to be degrading via naturally occurring bioremediation. There are essentially no degradation (or breakdown) products found in soil or groundwater. Other natural attenuation mechanisms, such as dilution or dispersion, do not appear to be significantly affecting the plume. This fact is also supported by no decrease or increase in TCE concentration trends for the permanent groundwater monitoring wells. This option can be effective in reducing contamination, but can require an extended remedial timeframe. However, there is an extent of contamination still remaining that warrants treatment to expedite natural attenuation. Plateau conditions typically occur around 30-70 µg/L where it is not cost effective to perform active treatment. There are multiple wells representing a plume area with current TCE concentrations above 100 µg/L that justify active treatment.

Under this alternative, additional monitoring wells would be installed and groundwater samples routinely collected and analyzed for Site contaminants, degradation products, bioparameters, and general groundwater parameters. In addition, deed restrictions on groundwater use would be recorded to protect human health (deed restrictions are acceptable to the land owner). This alternative would eventually meet the RAOs, but a significant portion of the groundwater plume is expected to exceed MCLs after the 30-year period considered for the FS.

• Alternative 3 – Enhanced Biodegradation and Groundwater Recirculation: This alternative applies the two remediation technologies successfully demonstrated in the pilot test to the concentrated portion of the plume.

Treatment would occur in 13 treatment “cells” that would be operated sequentially (Figure 5).

Each treatment cell would require nine new groundwater wells to be installed: three extraction wells, four injection wells, and two performance monitoring wells. The existing mobile treatment system used in the pilot test would be connected to the new wells and treatment would be conducted for about six months before the system is moved to the next cell. Enhancing biodegradation is expected to reduce the timeframe required for remediation from over 30 years (in Alternative 2) to 15 years: about seven years for active treatment (i.e., 6-months per cell) in the concentrated portion of the plume, and eight years for natural attenuation processes to address the diffuse portion of the plume. Similar to Alternative 2, this alternative includes installing new groundwater wells relative to the plume, routine sampling and analysis, and groundwater use restrictions until the plume is remediated.

• Alternative 4 – Permeable Reactive Barriers:

This alternative uses a series of permeable trenches that would treat contaminated groundwater as it passes through a reactive material (e.g., zero valent iron) in the trench.

Two permeable reactive barrier (PRB) trenches would be installed across the width of the TCE plume: a 475-ft long trench located just downgradient of the TPH-DRO plume;

and a 345-ft long located just downgradient of the concentrated portion of the TCE plume (Figure 6). The trenches would each be 2 ft wide and extend to the bottom of the sand/gravel unit at about 40 ft bgs.

Construction would involve continuous trenching technology and a biopolymer slurry for trench support. In 25 years, the reactive material in the trenches would be spent and require replacement. This alternative would remediate groundwater faster than Alternative 2 since there is active treatment within the PRB itself, and a remedial timeframe of 25 years is estimated. Similar to Alternative 2, this alternative includes installing new groundwater wells relative to the plume, routine sampling and analysis, and groundwater use restrictions until the plume is remediated.

• Alternative 5 – In Situ Chemical Oxidation:

This alternative consists of injecting an oxidizing agent (e.g., RegenOx®) into groundwater to destroy contaminants in place.

Injection would occur at 330 points spaced 25 ft apart in the concentrated portion of the plume (Figure 7). About 500 gallons of oxidant would be injected at each location using a steel probe and direct-push drill rig.

Injection would occur throughout the thickness of the sand/gravel unit at about 25 to 40 ft bgs. In situ chemical oxidation (ISCO) can remediate contamination in a matter of weeks or months, but a second application is often necessary to treat residual contamination

– a total of 500 gallons would be injected at each of 100 points. This alternative is likely to remediate groundwater faster than any other alternative and a remedial timeframe of 10 years is estimated: about two years for active treatment in the concentrated portion of the plume, and eight years for natural attenuation processes to address the diffuse portion of the plume. Similar to

Alternative 2, this alternative includes installing new groundwater wells relative to the plume, routine sampling and analysis, and groundwater use restrictions until the plume is remediated.

After the remedial alternatives were developed, USACE evaluated them against the nine NCP criteria shown below. Threshold criteria must be satisfied in order for an alternative to be eligible for selection under the NCP. Primary balancing criteria are used to weigh major tradeoffs among alternatives.

Modifying criteria are taken into account after public comment is received on the Proposed Plan and reviewed with the various federal and state regulatory agencies to determine if the preferred alternative remains the most appropriate remedy.

• Overall Protection of Human Health and the Environment and Compliance with ARARs: Alternatives 2 through 5 meet these two threshold criteria and are eligible for selection. Alternative 2 would eventually comply with chemical-specific ARARs (i.e., TCE concentrations less than the MCL of 5 µg/L), but not within the 30-year period considered for the FS. Alternatives 3 through 5 would all comply with chemical-specific ARARs, and each would need to be constructed and implemented in compliance with various action-specific ARARs.

• Long-Term Effectiveness: This balancing criterion considers the adequacy of controls and the magnitude of residual risks. Alternatives 2 through 5 would all be adequately controlled through groundwater monitoring. Implementing Alternatives 3 through 5 may temporarily mobilize metals with known toxicity (e.g., arsenic or chromium); however, impacts are expected to attenuate in a relatively short timeframe following treatment.

• Reduction of Toxicity, Mobility or Volume through Treatment: This balancing criterion addresses the statutory preference for active treatment of contaminants and considers the amount of material treated, irreversibility of treatment, and treatment residuals. Alternatives 3 through 5 involve active treatment that would destroy, through biodegradation or oxidation, the highest contaminant concentrations remaining in groundwater. Alternatives 2 and 4 would have a lesser reduction in toxicity/volume than Alternatives 3 and 5.

• Short-Term Effectiveness: This balancing criterion addresses protection of the community and workers during construction and implementation of remedial actions, potential environmental impacts, and the time until RAOs are met. Alternative 5 would have the best short-term effectiveness since it has the shortest remedial timeframe (approximately 10 years) and construction activities would be considerably less involved than those in Alternatives 3 and 4.

Difference in the remediation timeframes for Alternatives 3 and 5 are based on the assumed methods of amendment delivery.

• Implementability: This balancing criterion addresses the technical/administrative feasibility of implementing remedial alternative including the availability of services and materials.

Alternative 2 is the most implementable because it does not involve any additional remedial actions and there would be adequate availability of services and materials for groundwater installation, abandonment, and monitoring. Alternatives 3 and 5 would be the next most implementable alternatives since they involve proven construction techniques, and reliable technology (e.g., the effectiveness of the enhanced biodegradation and groundwater recirculation pilot test). Alternative 2 is the most implementable since it involves only installation and periodic monitoring of groundwater wells. Alternative 4 would be the most difficult to implement since the installation of PRB trenches would be disruptive to D-Q University operations and the continuous trenching technology is relatively new.

• Cost: This balancing criterion is based on estimated direct and indirect capital costs, and the estimated present value of recurring costs (e.g., groundwater monitoring). From a cost perspective, remedial timeframe has considerable effect on the present value of recurring costs and thus the total estimated cost of the alternative. However, the estimation of a remedial timeframe is often subjective. For example, matrix diffusion rebound could increase the actual timeframe for all of the FS alternatives, as well as the inability of timeframe estimating techniques to account for the various complex subsurface conditions that can increase the timeframe. Any increases in timeframe would also increase the remedy costs. Alternative 2 has the lowest total estimated cost followed by Alternative 5.

• State and Regulatory Acceptance: these criteria will be evaluated after receiving comments on this Proposed Plan.

Comparative analysis of the remedial timeframes and costs mentioned above is provided in Table 3.

Table 3. Comparative Analysis of Remedial Timeframe and Costs

Category Alt. 1 No Action

Alt. 2 Monitored Natural

Attenuation

Alt. 3 Enhanced Bio-

Degradation

Alt. 4 Permeable

Reactive Barriers

Alt. 5 In Situ Chemical

Oxidation Remedial Timeframe 30+ years 30+ years 15 years 25 years 10 years Capital Cost N/A $ 142,000 $ 2,069,000 $ 3,160,000 $ 1,329,000 Recurring Cost (present value) N/A $ 430,000 $ 311,000 $ 409,000 $ 216,000 Total Estimated Cost N/A $ 572,000 $ 2,380,000 $ 3,569,000 $ 1,545,000 Cost per Pound Treated* N/A $ 95,000 / lb $ 397,000 / lb $ 595,000 / lb $ 258,000 / lb

* Estimated 6 lbs TCE remaining in shallow groundwater N/A = not applicable

PREFERRED REMEDY

The results of the FS are summarized in Table 4 by ranking the relative performance of the alternative in each NCP criterion. Alternative 5 is ranked the highest, but has a cost of nearly $258,000 per pound of TCE treated and is an unproven treatment technology at the Site. Only 6 pounds (or less than 1 gallon) of TCE is estimated to be remaining dissolved in groundwater. Alternative 3 has been proven to be an effective treatment based on the pilot test. Alternative 2 is the most cost effective, but has the longest remedial timeframe. Natural processes most likely were responsible for the initial decrease of TCE concentration from the historical maximum of 1,700 µg/L in 1998 to 390 µg/L in 2009.

Based on the RI, HHRA, and FS, USACE recommends the following remedy for impacted groundwater at the D-Q University FUDS:

• Alternative 3 - Enhanced Biodegradation and Groundwater Recirculation in the source area of the TCE plume; and

• Alternative 2 - Monitored Natural Attenuation for the remaining portion of the TCE plume.

From August 2009 to February 2011, USACE implemented Alternative 3 in the source area as part of the pilot test, and enhanced biodegradation and groundwater recirculation was effective in reducing TCE concentration from 390 µg/L to 15 µg/L. The remaining maximum TCE concentration in groundwater is 120 µg/L (as of March 2017) and deed restrictions on groundwater use will be recorded to protect human health. Groundwater samples will be routinely collected and analyzed for Site contaminants, degradation products, bioparameters, and general groundwater parameters. Specific details regarding implementation of the remedy will be developed during the remedial design phase.

Transition criteria will be developed during the remedial design phase for the termination of active treatment and implementation of the natural attenuation remedy component in the source area.

Groundwater treatment history has shown that there may be technical practicability limitations to attaining MCLs throughout an entire plume in what may be considered a reasonable timeframe. This can be attributable to matrix diffusion rebound and other site-specific conditions (e.g., heterogeneous geology). Modifications to the remedy components, RAOs, and/or methodology used to determine attainment, may be necessary in the future in the event findings from future five-year reviews determine that these types of technical practicability limitations are impacting the ability to meet the RAOs in what may be considered a reasonable timeframe.

COMMUNITY PARTICIPATION

Public input is important to the decision-making process. Nearby residents and other interested parties are encouraged to use the comment period for questions and concerns about the preferred alternative for the Site. The public comments will be summarized and responded to in a responsiveness summary, which will become part of the official Decision Document. More information, including reports referenced in this report, can be found in the administrative record which is located at:

Winters Community Library 708 Railroad Avenue Winters, CA 95694

(530) 795-4955

References:

Brown and Caldwell, 2008. Remedial Investigation Report. May 9.

Brown and Caldwell, 2010. Final Data Gap Remedial Investigation and Treatability Study Report. September 7.

Brown and Caldwell, 2011. Final Enhanced Biodegradation and Groundwater Recirculation Pilot Test Results Report. August 29.

Brown and Caldwell, 2011. Draft Final Feasibility Study Results Report. September 8.RWQCB, 2008. Environmental Screening Levels for potential vapor intrusion concerns from groundwater. ESL Table E-1. http://www.swrcb.ca.gov/rwqcb2/water_issues/available_documents/ESL_May_2008.pdf.

May.

State Water Resources Control Board (SWRCB), 1988. Resolution 88-63: Sources if Drinking Water. May 19. (Amended on February 1, 2006).

SWRCB, 2011. A Compilation of Water Quality Goals. http://www.waterboards.ca.gov/water_issues/programs/water_quality_goals/index.shtml.

September 9.

USACE, 2004. Formerly Used Defense Sites Program Policy, Engineer Regulation 200-3-1. USACE Headquarters, Washington, DC. May 10.

USEPA, 2011. EPA 820-R-11-002. Drinking Water Standards and Health Advisory Tables.

http://water.epa.gov/action/advisories/drinking/drinking_index.cfm. January.

List of Acronyms:

1,2-DCE 1,2-dichloroethylene

AOC Area of Concern

ARARs applicable, relevant, and appropriate requirements

AST above ground storage tank bgs below ground surface

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act cis-1,2-DCE cis-1,2-dichoroethylene

DCE dichloroethylene

DRO diesel range organics

ESL Environmental Screening Level

FS Feasibility Study

FUDS Formerly Used Defense Site

ISCO in situ chemical oxidation

MCL maximum contaminant level

MNA monitored natural attenuation

NCP National Contingency Plan

PRB permeable reactive barrier

RAO remedial action objective

RI Remedial Investigation

RWQCB California Regional Water Quality Control Board

SI Site Inspection

SWRCB State Water Resources Control Board

TCE trichloroethylene

TPH-DRO total petroleum hydrocarbons - diesel range organics trans-1,2-DCE trans-1,2-dichloroethylene µg/L micrograms per liter

USACE U.S. Army Corps of Engineers

USEPA U.S. Environmental Protection Agency

UST underground storage tank

VOCs volatile organic compounds

Glossary of Terms:

Administrative Record (AR) File is a body of documents that “forms the basis” for the selection of a particular response at a site. Documents that are included are relevant documents that were relied upon in selecting the response action as well as relevant documents that were considered but were ultimately rejected. Until the Administrative Record is certified, it shall be referred to as the “Administrative Record file”.

Applicable or Relevant and Appropriate Requirements (ARARs) are cleanup standards, standards of control, and other substantive environmental protection requirements promulgated under Federal or state environmental law that specifically address a hazardous substance, pollutant, contaminant, remedial action, location or other circumstance found at a CERCLA site. Relevant and appropriate requirements are cleanup standards that, while not “applicable”, address situations sufficiently similar to those encountered at a CERCLA site that their use is well suited to the particular site.

Area of Concern (AOC) is a location that has experienced environmental degradation.

Environmental Screening Levels (ESLs) are contained within a document provided by the California Regional Water Quality Board, San Francisco Bay Region. This document is not intended to establish policy or regulation. The document presents lookup tables of conservative ESLs for over 100 http://www.waterboards.ca.gov/water_issues/programs/water_quality_goals/index.shtml http://water.epa.gov/action/advisories/drinking/drinking_index.cfm chemicals commonly found in soil and groundwater. The ESLs are intended to help expedite the identification of potential environmental concerns at sites where contamination has been identified, and expedite the evaluation regarding the need for possible cleanup of these properties.

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund, is a federal law that regulates environmental investigation and cleanup of sites identified as potentially posing a risk to human health and/or the environment.

Chemical of Concern (COC) is a chemical identified in a site-specific human health risk assessment as a potential risk driver or a chemical that exceeds its Federal or State drinking water maximum contaminant level (MCL).

Feasibility Study (FS) is a study that identifies and evaluates cleanup technologies and alternatives for a site based on effectiveness, availability, cost, and other criteria.

Formerly Used Defense Site (FUDS) property is defined as a facility or site (property) that was under the jurisdiction of the Secretary of Defense and owned by, leased to, or otherwise possessed by the United States at the time of actions leading to contamination by hazardous substances. By the Department of Defense Environmental Restoration Program (DERP) policy, the FUDS program is limited to those real properties that were transferred from Department of Defense (DoD) control prior to 17 October 1986. FUDS properties can be located within the 50 States, District of Columbia, Territories, Commonwealths, and possessions of the United States. The purpose of the FUDS program is to reduce, in a timely and cost effective manner, the risk to human health, safety, and the environment from contamination resulting from past DoD activities.

Hazard Quotient (HQ) is a measure of the potential non-cancer health effect and is the ratio of a chemical’s exposure concentration to the chemical’s toxicity reference value.

Hazard Index (HI) is the summation of HQs for multiple chemicals. An HI value of less than 1 is considered to be protective of human health.

Human Health Risk Assessment (HHRA) is an analysis of the potentially adverse human health effects caused by potential exposure to hazardous substances released at a site. The HHRA characterizes the nature and magnitude of health risks to humans (e.g., residents, workers, recreational visitors) from chemical contaminants and other stressors that may be present in the environment.

Incremental Lifetime Cancer Risk is estimated as the incremental probability of an individual developing cancer over a lifetime as a result of exposure to the potential carcinogen (i.e., incremental or excess individual lifetime cancer risk).

In Situ Chemical Oxidation (ISCO) is involves the introduction of a chemical oxidant into the subsurface for the purpose of transforming groundwater or soil contaminants into less harmful chemical species. There are several different forms of oxidants that have been used for ISCO;

however, the most commonly used oxidants include: permanganate (MnO4-), Fenton’s (hydrogen peroxide [H2O2] and ferrous iron [Fe+2]) or catalyzed hydrogen peroxide, Ozone (O3), and persulfate (S2O82-).

Maximum Contaminant Level (MCL) is the highest level of a contaminant that is allowed in drinking water. The MCLs are set by the United States Environmental Protection Agency and/or the State of California.

Natural Attenuation are naturally occurring processes that reduce contaminant concentrations through dilution and dispersion or through destructive processes associated with the activity of natural microbes and reactions with natural minerals in the aquifer.

National Oil and Hazardous Substances Pollution Contingency Plan (NCP) describes organizational structure and procedures to be followed by the Federal government to prepare for and respond to discharges of oil and releases of hazardous substances, pollutants, and contaminants.

Permeable Reactive Barrier (PRB) is a zone of reactive material that extends below the water table to intercept and treat contaminated groundwater. The goal of the PRB is to passively capture a plume of contaminants, remove or break down the contaminants, and release uncontaminated water. For Alternative 4 in the FS at D-Q University, the reactive material proposed is zero valent iron.

Preferred Alternative is the remedial alternative identified by USACE in conjunction with the regulatory agencies that best satisfies the remedial action objectives, based on an evaluation of alternatives presented in the FS Report.

Proposed Plan is a document that reviews cleanup alternatives, summarizes recommended cleanup actions, explains the reasons for recommending them, and solicits comments from the community.

Remedial Action is a general term used to describe technologies used to contain, remove, or treat hazardous contaminants to protect human health and/or the environment.

Remedial Action Objectives (RAOs) are goals established for the protection of human health and the environment.

Remedial Investigation (RI) identifies the nature and extent of potential contaminants at a site and evaluates human health and environmental risks.

Site Inspection (SI) are activities undertaken to determine whether there is a release or potential release and the nature of associated threats. The purpose is to augment the data collected in the Preliminary Assessment and to generate, if necessary, sampling and other field data to determine the presence, type, distribution, density, and location of hazardous substances or military munitions.

Trichloroethylene or TCE is a VOC and includes commonly used as a solvent and degreaser. TCE degradation products include cis- and trans-1,2-dichloroethylene (DCE) and vinyl chloride.

Total Petroleum Hydrocarbons (TPH) are a group of chemicals derived from crude oil. The chemicals are subdivided into ranges based on their boiling points. Diesel Range Organics or DRO is a range of TPH associated with Diesel fuel.

Volatile Organic Compounds (VOCs) make up a general category of organic (carbon-containing) compounds that evaporate easily at room temperature. Some VOCs are known cancer causing compounds.

COMMENT FORM

Proposed Plan for Groundwater Remedial Action D-Q University FUDS, Yolo County, California

Optional Information Name/Organization: ________________________________________________________________ Address: _________________________________________________________________________ Telephone: (____) _____________ e-mail: ____________________________________________

Comments (use additional pages if needed) Date: ________________

Send Comments to:

Mail: Mr. Tim Crummett, Project Manager e-mail: tim.r.crummett@usace.army.mil U.S. Army Corps of Engineers, Sacramento District fax: (916) 557-7865 1325 J Street, Sacramento, CA 95814-2922 Or

Mail: Mr. Walter Floyd e-mail: walter.floyd@ waterboards.ca.gov Central Valley Regional Water Quality Control Board fax: (916) 464-4645 11020 Sun Center Drive, Suite 200, Rancho Cordova, CA 95670-6114