REGULATED STORAGE TANK DIVISION CORRECTIVE ACTION PLAN FACILITY:

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1 REGULATED STORAGE TANK DIVISION CORRECTIVE ACTION PLAN FACILITY: Kerr-McGee Service Station #6400 Highway 270 & Old Military Road Malvern, Arkansas ID # LUST # AUTHORIZATION Name: Title: James R. Shell Chief, Regulated Storage Tank Division Signature: Date: Name: Title: Ed Dunn Petroleum Storage Tank Trust Fund Administrator Signature: Date: Name: Title: Mikel R. Shinn, PG Technical Branch, Regulated Storage Tank Division Signature: Date:

2 INTRODUCTION After completing an investigation for soil and groundwater cleanup, the Technical Branch staff has concluded that a corrective action plan is necessary for responding to the release from the referenced site. This document describes how the case developed, where ADEQ s regulatory interests lie, and what goals are proposed for the solution. CASE DEVELOPMENT Leaking Underground Storage Tank case # was initiated on 4/8/88, when the Arkansas Department of Pollution Control & Ecology received a telephone report from Kerr-McGee Corporation. Soil and groundwater contamination by petroleum hydrocarbons had been discovered during removal of underground storage tanks at the former Kerr-McGee service station #6400 site in Malvern. The Arkansas State legislature had not yet passed an underground storage tank law in 1988 and ADPC&E apparently did not formally respond to the LUST report by requesting corrective action. Kerr-McGee performed a site investigation in May, 1988 which confirmed significant petroleum contamination across the site. The results of this investigation were not forwarded to the State environmental agency until No further corrective action was taken at the #6400 site until August, 1999 when a Preliminary Site Investigation was conducted for Kerr-McGee by Burns & McDonnell Waste Consultants. The report of this investigation (dated 10/27/99) was forwarded to ADEQ RST Division on 11/1/99. After review, RST Division requested (1/11/00) that Kerr-McGee provide all additional file material relating to the LUST case and also requested a work plan for comprehensive site assessment. After RST plan approval (3/15/00), a soil and ground water investigation was conducted in April, 2000 and reported on 5/19/00. Data from the 5/00 report indicated that contaminated backfill material from the 1988 tank closure had been returned to the UST excavation and that the product piping was probably still in the ground at the #6400 site. On 10/12/00, RST Division requested that Kerr-McGee prepare a plan for interim corrective action which would ensure removal and proper disposal of the UST backfill material and adjacent contaminated native soils and all remaining fuel system elements. An Interim Corrective Action Work Plan was approved by RST on 1/12/01, implemented in April-May, 2001 and reported out on 7/2/01. The interim corrective action resulted in complete fuel system removal (including all piping and a waste oil tank) and the excavation and disposal of 1,102 cubic yards of contaminated soils and backfill material. After reviewing the results of the interim corrective action, RST requested (7/16/01) initiation of a groundwater assessment monitoring program. Immediate installation of an adequate monitoring well network to completely delineate the level and extent of groundwater impact was specifically requested. The first quarterly report of the GAM program was received by RST Division on 11/26/01. Because of technical problems and access delays, complete determination of the limits of groundwater contamination was not achieved until receipt of the third GAM report by RST Division on 6/6/02. Groundwater assessment monitoring has been conducted quarterly through January, The eighth of eight quarterly reports which have included all the wells within the contaminated area was received by RST Division on 2/20/04. Adequate data are now available to conduct an appropriate risk assessment.

3 CONCEPTUAL SITE MODEL The following profiles summarize what is currently known about the facility and the regulated substance release which is the concern of this document. A fairly extensive investigation has been conducted for this site, and more-detailed information can be found in the case file for the release. Facility Profile Attachment #1 shows the location of the Kerr-McGee #6400 site on the outskirts of Malvern, Arkansas, approximately one half mile south of the US Highway 270 intersection with Interstate 30. The station site is actually within the corporate limits of the city of Rockport, at the southeast corner of the intersection of Highway 270 and Old Military Road. Kerr-McGee Corporation constructed the #6400 retail automotive service station in approximately The original Notification for Underground Storage Tanks by Kerr-McGee (filed 3/3/86) registered three gasoline UST s (two 8000-gallon tanks and one 3000-gallon tank) and a 300-gallon used oil tank. The fuel system was indicated to be permanently out of use at the time of registration. (Note: although there is no record of diesel fuel storage at the site, both soil and groundwater samples have indicated impact by Diesel-Range Organics (TPH-DRO). As noted above, Kerr-McGee removed the fuel UST s from the site in April, 1988 and reported the presence of soil and groundwater contaminants. All surface structures were removed from the property before August, The waste oil tank, product piping and 1,102 cubic yards of contaminated soils were removed during interim corrective action in April-May, The site is currently a vacant lot. Physical/Geological Profile The Kerr-McGee #6400 LUST site is situated near the crest of an east-west ridge which plunges toward the Ouachita River, approximately 0.6 miles to the west. The ridge is bounded to the north and south by intermittent streams which flow toward the Ouachita. Surface elevations at the service station site itself are from above sea level, approximately 70 feet higher than the river. Ground slope immediately south of the former station is toward the southsouthwest at a gradient of about 4 /100. Attachment #2 is a large-scale map of the release site and surrounding neighborhood, with generalized surface topography estimated from monitoring well TOC elevations and field observations. Soils encountered at the Kerr-McGee site and in off-site borings are actually Lower Tertiary bedrock. The shallowest materials are composed primarily of alluvial gravels and sands of the Lower Eocene Wilcox Group. These deposits were derived from the erosion of uplifted lower Paleozoic rocks in the Ouachita highland area immediately to the north and west. The Wilcox sediments unconformably overlie marine clays of the Paleocene Midway Group at significantly variable depths (2-17 ). The depth to Paleozoic rocks is not known, but is probably less than fifty feet, based upon nearby outcrops of Arkansas Novaculite along the Ouachita River. The local uppermost groundwater aquifer is contained within the Wilcox sands and gravels, with the underlying Midway clay acting as an effective perching horizon. Attachment #3 is a potentiometric map for the unconfined aquifer from the most recent monitoring event (1/04).

4 The groundwater surface has consistently reflected ground surface topography. Groundwater flows to the southwest from the release site at a gradient of approximately 5 /100. Measured depths to groundwater at most wells have typically varied seasonally within a range of around four feet. Several wells which are apparently screened in relatively low-permeability materials have exhibited more pronounced depth ranges. Release Profile No data are available regarding the nature and estimated quantity of the release(s) at the former Kerr-McGee #6400 station during its (maximum) fifteen years of operation. Data from the excavation work performed in 2001 indicate that the most serious releases probably occurred at the fuel UST tankhold rather than in the product lines or at the dispensers. Simple spills or overfills at the tanks during product delivery (in the period before mandatory spill/overfill protection) may account for all observed soil and groundwater impact.

5 EXPOSURE ASSESSMENT Land Use The former Kerr-McGee #6400 site is in a predominantly commercial neighborhood. The site itself is likely to remain in commercial land use. The closest private residence borders the site to the northeast in (fortunately) the up-gradient direction. There is no evidence that this property has been impacted by the fuel release(s). Commercial properties to the south of the site (as well as the Arkansas Highway & Transportation Department right-of-way) have been impacted by contaminants released from the #6400 site. The only underground utility in the neighborhood of the release site which might possibly be impacted by fuel contaminants is a buried telephone cable located beneath the highway ROW on the west side of the #6400 site. Only very minor levels of groundwater contamination (if any) are likely to be present along this line and the potential for either physical damage or harmful worker exposure during maintenance operations is remote. Human Exposure Profile All local residents and businesses are served by the Malvern municipal water supply and drinking water ingestion is therefore not a likely pathway for human exposure to contaminants. No residual contaminants are present in surface soils and human exposure to residual contaminants in subsurface soils is unlikely. Indoor Air Vapor Impact Assessment - Attachment #4 is the dissolved Benzene groundwater plume map for the January, 2004 sampling event. The down-gradient portions of dissolvedphase plumes which originate at the #6400 site extend beneath the St. Joseph Mercy Medical Clinic at 1424 Tanner Street. Therefore, a potentially complete pathway for human exposure to contaminants exists through volatilization of vapors from the dissolved state, with subsequent possible intrusion into the indoor air of the clinic. The clinic is floored by a concrete slab constructed directly on the ground surface. Depth to contaminated groundwater during the January event was estimated at about five feet, based upon measurements in nearby monitoring wells. Dissolved Benzene levels in wells on three sides of the clinic (MW-9A, -11 and -12) during the 1/04 event were all below the Risk-Based Screening Level of 74 micrograms per liter used for commercial vapor intrusion scenarios in the ASTM E Standard Guide for Risk-Based Corrective Action at Petroleum Release Sites (Table X2.1, p.22). Benzene groundwater levels have not exceeded 74 :g/l during any of seven previous quarterly monitoring events in any of the three wells nearest the clinic. None of the other BTEX constituents -Toluene, Ethylbenzene and Xylenes - have ever been reported at dissolved levels above their respective risk-based screening levels in any of the wells near the clinic building. Based upon these data, we conclude that there is no risk to human health associated with the presence of dissolved petroleum contaminants in groundwater beneath the clinic.

6 Ecological Profile There is no evidence that surface waters of the State of Arkansas have been impacted by releases at the #6400 site. All contaminants within the dissolved-phase groundwater plumes are completely attenuated within the subsurface environment. No ecological risks have therefore been identified. Source Characterization The source control action performed in 2001 resulted in the removal of over 1000 cubic yards of contaminated soils which had remained at the site since the facility closed in the 1980 s. Samples on the excavation margins indicated that total removal of impacted soils had not been achieved. However, residual dissolved contaminant levels of TPH-GRO and TPH-DRO in both on-site and off-site monitoring wells have never approached values typically associated with groundwater in contact with mobile non-aqueous phase liquid. Therefore, additional remediation in order to achieve source control will not be required. CORRECTIVE ACTION GOALS The program goals for RST Division corrective action shall be: To eliminate impacts to human health and the environment from regulated substance contamination. (40 CFR ) To control the source of regulated substance contamination to the maximum extent practicable in order to prevent further spread of contaminants. (40 CFR ) Contaminant concentrations which might impact human health and the environment are below risk-based screening levels. The source materials generated by the release have been satisfactorily addressed, and the success of this action has been verified by an adequate monitoring program. No further assessment or remediation is planned. Any investigation-derived wastes which remain at the site must be managed to proper disposal, and the monitoring well network should be abandoned according to the regulatory requirements of the State Waterwell Construction Commission.

7 CORRECTIVE ACTION PLAN TASKS The RST Division s Corrective Action process is diagrammed below:

8 PUBLIC PARTICIPATION Public participation in the authorization of corrective action by ADEQ is required by 40 CFR Review/comment on Corrective Action Plans and Remedial Action Plans will be solicited in two ways: A copy of the draft Plan will be sent under a cover letter to the stakeholders directly impacted. The mailing addresses for these stakeholders are found in Attachment #5. A general notification of the availability of the draft Plan for review will be made by a legal notice advertisement in a newspaper of general circulation in the area of the facility. This action will be taken by the O/O at Department request, using the format and sample language below. The comment period will be thirty days, measured from the date upon which each stakeholder is notified. Comments should go to: Technical Branch Manager Regulated Storage Tank Division Arkansas Dept. of Environmental Quality P.O. Box 8913 Little Rock, AR (501) Comments may be received by ADEQ staff in any form, but only those attributable to specific persons and in writing will enter the casefile to be formally considered. At the end of the comment period, the comments will be evaluated by the technical staff of the RST Division, and if significant changes are advised, a new draft Plan will be advertised. Otherwise, implementation of the Plan will be requested in writing.

9 Example Legal Notice ADEQ will cause to be placed by the responsible party a legal notice in a newspaper of general circulation in the area adjacent to and directly affected by the release. In the absence of a local newspaper, the state-wide newspaper may be selected. The notice only has to run one day, and the day of the week is not critical. The legal notice must be substantially in the form below: STATE OF ARKANSAS DEPARTMENT OF ENVIRONMENTAL QUALITY Notice is given that a Corrective Action Plan has been drafted for the former Kerr-McGee #6400 facility, located at Highway 270 and Old Military Road in Malvern, Arkansas. Under the provisions of 40 CFR (b), the draft Plan is available for public inspection under the provisions of the state s Freedom of Information Act at: Arkansas Department of Environmental Quality Regulated Storage Tank Division 8001 National Drive Little Rock, AR (501) Public comment on authorization, according to the procedures in the Draft Plan, will be received by the Department for 30 days from the date of this advertisement. ADEQ may authorize implementation of the Plan, or a portion of the Plan, before the public comment period is completed, if such action is necessary to protect public health and welfare.

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13 Attachment #4

14 Attachment #5 The stakeholders proposed for direct mail notification are listed below: Mr. Satya Sinha Staff Environmental Specialist Kerr-McGee Share Services Company, LLC Suite MT-2004 P.O. Box Oklahoma City, Oklahoma Mr. Dale Horn Horn's Used Cars 1749 Martin Luther King Blvd Malvern AR Mr. Brian Cotten Director of Plant Operations St. Joseph s Mercy Health Center P.O Box Hot Springs, Arkansas Mr. David Lambert District 6 Engineer Arkansas Highway & Transportation Department P. O. Box Little Rock, AR