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IF Golder Associates

June 22, 2010 073-81526

Fran Costanzi, Remedial Project Manager U.S. Environmental Protection Agency, Region VIII 1595 Wynkoop Street Denver, CO 80202-1129

RE: COMPLETION REPORT FOR GROUNDWATER REMEDIATION ACTIVITIES AT THE CASPER COMPRESSOR STATION

Dear Ms. Costanzi:

This letter presents a summary of the Superfund remediation activities related to groundwater at the Kinder Morgan, Inc. (KMI) Casper Compressor Station (Site), formerly owned by KN Energy. This summary was prepared on behalf of KMI by Golder Associates Inc. (Golder).

Since 1965, KN Energy (KN) and later KMI and its affiliates have operated a natural gas compression station at the Site located in Natrona County, northeast of Casper, Wyoming.

The site is divided into two Operable Units. Operable Unit 1 (OU1) includes the groundwater contaminant plumes and Operable Unit 2 (OU2) includes the sources for groundwater contamination. This letter presents information primarily related to OU1, groundwater contamination.

In 1987, groundwater under and immediately north of the Site was found to contain trace amounts of dissolved hydrocarbons that were suspected to have originated, in part, from the Site. Removal and remedial actions were conducted at the Site from 1989 through 1996 and consisted of groundwater pump-and treat, air sparging, soil-vapor extraction, and free product removal. Following removal and remedial actions, post-remedial action groundwater monitoring has been conducted in accordance with the Consent Decree, the Groundwater Monitoring Plan (Adrian Brown Consultants, Inc. (ABC) 1993), which was incorporated into the Consent Decree by reference, the 1997 U.S. Environmental Protection Agency (EPA) letter which moves OU1 into a post-remedial action status (EPA 1997), and a work plan approved by EPA on June 29, 2005 (EPA 2005). A detailed summary of activities is provided in Attachment 1.

REMOVAL ACTION In December 1987, KN entered into Administrative Order on Consent (AOC) to perform immediate removal actions to control suspected sources of groundwater contamination and prevent future migration of contaminated groundwater. In accordance with the AOC, KN prepared an Engineering Evaluation/Cost Assessment (EE/CA) that included an investigation for removal actions (Adrian Brown Consultants, Inc. 1989). In November 1989, removal actions designed to remove benzene, toluene, ethylbenzene, and total xylenes (BTEX) contaminants from groundwater and soil beneath the KN facility began. The remediation system included groundwater pump-and-treat with air stripping, air sparging, and soil vapor extraction.

REMEDIAL ACTION The Record of Decision (ROD) for OU1, issued in September 1990, specified continued operation of the groundwater extraction and treatment system under the removal actions to remediate contaminated groundwater. Remediation was to continue until performance standards for BTEX were achieved. In

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Lakewood, CO 80228 USA Tel: (303)980-0540 Fax: (303)985-2080 www.golder.com

Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America

Fran Costanzi U.S.EPA 2

June 22, 2010 073-81526

October 1991, the Consent Decree for remedial design and remedial action entered by the court required the following performance standards:

1. Remediate groundwater so that concentrations shall not exceed Maximum Contaminant Levels (MCLs) and proposed MCLs, as set forth in the ROD for BTEX

2. The area of attainment shall include the entire BTEX plume, including those areas of the plume inside and outside the KN facility.

The applicable MCLs for BTEX, established by the National Primary Drinking Water Regulations (40 CFR §141.61) are as follows:

MAXIMUM CONTAMINANT LEVELS FOR BTEX

Constituent MCL (mg/L)

Benzene 0.005 Ethylbenzene 0.7 Toluene 1 Xylenes 10

Concentrations of ethylbenzene, toluene, and xylenes have not been measured above the MCLs. Therefore, the groundwater remediation evaluation has focused on benzene as the indicator contaminant of concern.

The OU1 (groundwater) remediation system operated between November 1989 and August 1996 and included groundwater pump-and-treat (PAT) with air stripping and soil vapor extraction (SVE). The PAT system pumped groundwater to the surface where volatile hydrocarbons were removed by air stripping. The treated water was subsequently returned to the groundwater via injection or infiltration. The SVE system extracted vapor phase hydrocarbons from the unsaturated interval between the water table and the ground surface. Floating free product was removed from the groundwater extraction wells by the PAT system. The PAT system operated at approximately 55 to 75 gallons per minute. The OU1 remediation system (PAT and SVE) was turned off with consent of EPA in August 1996 (EPA 1996, Attachment 2 of this document).

A Groundwater Monitoring Plan (GMP) was developed by ABC (1993) to evaluate the effectiveness of the Remedial Action (RA) and post-RA and determine compliance with the performance standards. Specifically, the GMP established that following shut down of the remediation system and after 12 months of groundwater sampling with results below the MCL, quarterly post-RA monitoring would begin. Compliance under post-RA monitoring was achieved after a minimum of eight quarterly sampling events were conducted in which, for each well, the 90% one-tailed upper confidence limit (UCL) concentrations for benzene, ethylbenzene, toluene and total xylenes were below the maximum contaminant levels (MCLs) for each compound.

The UCL for each compound and well is determined by taking the sample mean (x) and standard deviation (s) of concentrations from the previous eight quarterly monitoring events. Based on the number of samples (n=8) and a 90% confidence level, the UCL is calculated based on the following equation, where t is the Student t-statistic:

UCL = x + t(s/Vn)

POST-REMEDIAL ACTION Table 1 presents benzene concentrations measured in groundwater samples since October 1993. In August 1997, USEPA approved completion of the remedial action and moved the site into post-RA status

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_ Golder Associates

Fran Costanzi U.S.EPA 3

June 22, 2010 073-81526

(EPA 1997, Attachment 3 of this document) based on groundwater monitoring data submitted with the July 1997 progress report (ABC 1997). Near the end of the eight quarters of post-RA monitoring, benzene concentrations were detected above the remedial performance standards in two wells resulting in additional sampling. As part of the additional sampling, natural attenuation parameters were evaluated. Analysis of the parameters concluded natural attenuation was occurring.

Ultimately, a technical memorandum submitted to EPA in February 2010 summarized the previous eight quarters of sampling and concluded that the site has met the established compliance criteria (Golder 2010, Attachment 4 of this document). The technicalmemorandum and associated data are attached to this document. Quarterly post-RA sampling conducted since the February 2010 memorandum confirm that the Site continues to meet the standards for completion of the remedial action for OU1.

Sincerely,

GOLDER ASSOCIATES INC.

cc: D. White, KMI J. Toll, KMI J. Francis, WDEQ

REFERENCES 40 CFR §141.61, Maximum contaminant levels for organic contaminants

Adrian Brown Consultants, Inc., 1989, Revised Engineering Evaluation/Cost Analysis for a Removal Action at the KN Energy Casper Compressor Station Evansville, Wyoming, March 15,1989.

Adrian Brown Consultants, Inc., 1993, Remedial Action Groundwater Monitoring Plan for the KN Energy Gas Compressor Station, Casper, Wyoming, Report 1125A/930901, Sept. 1,1993.

Adrian Brown Consultants, Inc., 1997, Letter from Jeremy Kolenbrander (Project Manager, ABC) to Ms. Lisa Lloyd (Remedial Project Manager, USEPA) regarding: July Progress Report, KN Casper Compressor Station, July 29, 1997.

Golder Associates Inc., 2010, Technical memorandum from Walter Weinig and Sarah Doyle (Golder Associates Inc.) to Fran Costanzi (Remedial Project Manager, U.S. Environmental Protection Agency) regarding: Summary of the Previous Eight Quarters of Post Remedial Action Groundwater Monitoring at the Casper Compressor Station, February 12, 2010.

U.S. Environmental Protection Agency, 1996. Letter from Lisa S. Reed (Project Manager, U.S. Environmental Protection Agency) to Lawrence J. Corte, Esq. (KN Energy, Inc.), August 23,

U.S. Environmental Protection Agency, 1997. Letter from Lisa Reed Lloyd (Project Manager, U.S. Environmental Protection Agency) to Mr. Hayden Truscott (Environmental Manager, KN Energy, Inc.) regarding: Mystery Bridge Superfund Site - Remedial Action Completion, August 20,1997.

U.S. Environmental Protection Agency, 2005. Letter from Rebecca J. Thomas (Project Manager, U.S. Environmental Protection Agency) to Mr. Hayden Truscott (Kinder Morgan, Inc.) regarding:

Sr. Consultant

1996.

i:\07\81526\0100\ltr-ou-1-summafy_22june10\ltr ou-1-summary_22jun10.docx

Fran Costanzi U.S.EPA 4

June 22, 2010 073-81526

Mystery Bridge Superfund Site, Long-term Groundwater Monitoring and Well Abandonment Proposal, June 29, 2005.

Attachments:

Table 1: Analytical Results for Benzene (ug/L)

Attachment 1: Summary of Investigation and Remediation Activities, KMI Casper

Attachment 2: U.S. Environmental Protection Agency, 1996. Letter from Lisa S. Reed (Project Manager, U.S. Environmental Protection Agency) to Lawrence J. Corte, Esq. (KN Energy, Inc.), August 23,

Attachment 3: U.S. Environmental Protection Agency, 1997. Letter from Lisa Reed Lloyd (Project Manager, U.S. Environmental Protection Agency) to Mr. Hayden Truscott (Environmental Manager, KN Energy, Inc.) regarding: Mystery Bridge Superfund Site - Remedial Action Completion, August 20,1997.

Attachment 4: Technical Memorandum from Golder Associates Inc. to USEPA regarding: Summary of the Previous Eight Quarters of Post Remedial Action Groundwater Monitoring at the Casper Compressor Station, February 12, 2010

Attachment 5: Letter from USEPA regarding Mystery Bridge Superfund Site, Long-Term Groundwater Monitoring and Well Abandonment Proposal at the Casper Facility, June 29, 2005

Attachment 6: Letter from USEPA regarding Mystery Bridge Highway 20 Superfund Site Work, Approval of Requests for Changes, October 10,1997

1996

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June 2010 073-81526

TABLE 1

ANALYTICAL RESULTS FOR BENZENE (jiG/L)

T' DATE ABC-2 ABC-5 ABC-12 ABC-17 ABC-27 ABC-91 GW-2 MW-5 MW-6 MW-7 EPA-1-9 EPA-1-10 EPA-2-11 Q1 10-15-93 <0.8 <0.8 2 4 38 6 21 <0.8 130 2 <0.8 1 5 AS 12-2-93 15 30 Q2 1-12-94 <0.8 6 14 5 <0.8 6 13 <0.8 12 <0.8 <0.8 <0.8 <0.8 Q3 4-20-94 <0.8 <0.8 9 9 2 <0.8 15 <0.8 26 <0.8 <0.8 <0.8 <0.8 AS 6-28-94 7 24 Q4 7-21-94 TO

8-1-94 <0.8 2 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 0.9 <0.8 <0.8 <0.8 <0.8

M1 9/15/94TO 9/16/94

<0.8 30 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 1

M1 RES. 10-3-94 43 M2 10-14-94 <0.8 25 <0.8 1 2 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 2 M3 11-20-94

TO 11-21-94

<0.8 7 <0.8 1 4 0.9 <0.8 <0 8 <0.8 <0.8 <0.8 <0.8 <0.8

M4 12-17-94 <0.8 <0.8 2 1 1 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 M5 1-14-95 TO

1-15-95 <0.8 <0.8 <0.8 4 2 1 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8

M6 2-13-95 <0.8 <0.8 <0.8 2 1 1 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 M7 3-16-95 <0.8 <0.8 <0.8 2 3 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 M8 4-18-95 TO

4-19-95 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8

M9 5-15-95 TO 5-16-95

<0.8 <0.8 3 5 2 <0.8 <0.8 <0.8 <0.8 <0.8 1 <0.8 <0.8

M10 6-16-95 <0.8 <0.8 1 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 150 <0.8 <0.8 M11 7-14-95 <0.8 <0.8 7 <0.8 1 <0.8 <0.8 <0.8 <0.8 <0.8 110 <0.8 <0.8

M11 RES. 8-4-95 14 M12 8-13-95 <1 1.4J 17 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M13 9-15-95 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M14 10-17-95 <1 <1 3.7J <1 <1 1.2J <1 <1 1.8J <1 <1 <1 <1

M15 11-16-95 <1 <1 10 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M16 12-14-95 TO

12-18-95

<1 <1 13 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M17 1-21-96 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M18 2-14-96 <1 <1 4 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M19 3-14-96 <1 <1 <1 <1 1.5 <1 <1 <1 <1 <1 <1 <1 <1

M20 4-16-96 <1 <1 2.6 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M21 5-17-96 <1 <1 1.3 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M22 6-12-96 <1 <1 11 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M23 7-15-96 <1 <1 4.3 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M24 8-14-96 <1 <1 1.0 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

August 23, 1996 EPA Letter Remedial System Turned Off M25 9-11-96 1.7 M26 10-14-96 1.4 M27 11-14-96 <1 5.2 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M28 12-11-96 2.5 <1 M29 1-09-97 1.4 M30 2-03-97 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M31 3-17-97 <1 M32 4-14-97 <1 M33 5-5-97 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

M34 6-15-97 1.1 M35 7-15-97 1.8

Table 1 continued on next page

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Golder Vex Associates

June 2010 073-81526

T1 DATE ABC-2 ABC-5 ABC-12 ABC-17 ABC-27 ABC-91 GW-2 MW-5 MW-6 MW-7 EPA-1-9 EPA-1-10 EPA-2-11 August 20, 1997 RAC Letter Remedial Action Completed (RAC)

PRA1 8-22-97 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 PRA2 11-16-97 <1 4.5 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 PRA3 2-9-98 <1 <1 <1 <1 1.3 <1 2.1 <1 <1 <1 <1 2.3 <1 PRA4 5-26-98 <1 <1 <1 <1 <1 7.1 1.2 <1 <1 <1 <1 <1 1 PRA5 8-18-98 <1 <1 <1 <1 1.4 21 2.3 <1 <1 1.3 <1 1.8 <1 PRA6 11-9-98 <1 1.7 <1 <1 <1 <1 <1 <1 3.7 <1 <1 1.9 <1 PRA7 2/13/99 <1 2.6 <1 <1 1.3 7.0 2.3 <1 1.2 9.4 <1 3.5 <1 PRA8 5/13/99 <1 8.6 <1 <1 <1 3.7 <1 <1 <1 16 <1 <1 <1 PRA9 12/14/99 <1 470 <1 110 1.7 35 1.6 <1 <1 460 <1 11 <1 PRA9 1/11/00 270 25 33 270 4.6

PRA10 5/18/00 1.1 470 <1 5.0 16 14 <1 <1 <1 4.4 1.6 22 <1 PRA11 9/25/00 <1 153 <1 120 6.5 12 <1 <1 <1 4.4 <1 1.1 <1 PRA12 11/15/00 <1 48 <1 64 31 70 <1 <1 <1 5.3 <1 <1 <1 PRA13 2/13/01 <1 81 <1 38 12 3.7 <1 <1 7.9 <1 <1 PRA14 5/17/01 <1 110 <1 46 9.2 2.3 1.8 <1 <1 <1 <1 1.0 1.5 PRA15 8/14/01 <1 74 <1 14 5.4 1.5 <1 <1 <1 2.9 <1 1.7 <1 PRA16 11/8/01 <1 10.5 <1 25 7.4 3.9 1.4 <1 1.5 <1 <1 14 <1 PRA17 2/11/02 <1 11 <1 3.4 14 <1 <1 <1 <1 <1 <1 <1 <1 PRA18 5/22/02 <1 12 <1 18 11 <1 <1 2.3 <1 6.3 <1 <1 <1 PRA19 8/14/02 <1 3.8 <1 <1 <1 <1 18* <1 <1 <1 <1 <1 <1 PRA20 11/18/02 <0,5 1.4 <2 <1 <2 <1 <1 <0.5 <0.5 <0.5 <0.5 <0.5 <1 PRA21 2/11/03 <0.5 2.2 <0.5 <0.5 4.2 <0.5 1.4 <0.5 1.2 2.2 <0.5 <0.5 <0.5 PRA22 5/29/03 <0.5 0.73 <0.5 <0.5 2.6 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 PRA23 8/13/03 <0.5 110 1.5 1.0 10 0.71 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 PRA24 11/20/03 <0.5 <0.5 3.6 6.1 6.4 20 2.8 <0.5 <0.5 29 <0.5 15.5 1.2 PRA25 2/17/04 <0.5 <0.5 0.58 1.7 3.9 <0.5 25 <0.5 13 1.4 1.3 <0.5 0.71 PRA26 6/11/04 <0.5 54 <0.5 4.6 9.0 6.6 2.5 <0.5 1.5 1.2 12.5 <0.5 <0.5 PRA26 6/30/04 <0.5 PRA27 8/9/04 <0.5 14.5 <0.5 1.5 8.4 60 1.4 <0.5 0.72 0.72 <0.5 1.2 <0.5 PRA28 11/9/04 <0.5 5.1 1.6 0.84 0.98 18.5 1.2 <0.5 <0.5 51 <0.5 <0.5 0.58 PRA29 2/8/05 <0.5 1.2 6.8 0.98 0.84 4.5 0.69 <0.5 <0.5 0.72 <0.5 <0.5 <0.5 PRA30 5/19/05 <0.5 <0.5 0.72 2.1 0.89 <0.5 0.75 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 PRA31 8/18/05 <0.50 1.3 <0.50 <0.50 <0.50 33 0.86 <0.50 <0.50 2.4 <0.50 <0.50 0.59 PRA32 11/29/05 <0.5 9.6 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.50 <0.50 0.59 PRA33 2/21/06 <0.5 11.5 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.50 <0.50 0.59 PRA34 5/22/06 <0.50 <0.50 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.50 <0.50 <0.50 PRA35 8/22/06 <0.50 2.7 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.50 2.6 <0.50 PRA36 11/22/06 <0.5 9.1 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.50 4.8 <0.50 PRA37 2/22/07 <0.5 24 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.50 <0.50 <0.50 PRA38 5/22/07 <0.5 0.71 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.50 <0.50 <0.50 PRA39 8/22/07 <0.5 <0.50 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.50 <0.50 <0.50 PRA40 11/15/07 <0.5 <0.50 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.50 <0.50 1.8 PRA41 2/19/08 <0.5 0.77 NS NS Abndn Abndn Abndn Abndn NS Abndn 1.3 <0.50 4.7 PRA42 5/30/08 <0.5 <0.5 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.5 1.7 <0.5 PRA43 8/22/08 <0.5 <0.5 NS NS Abndn Abndn Abndn Abndn NS Abndn <0.5 4.4 3.3 PRA44 11/17/08 <1.0 <1.0 NS NS Abndn Abndn Abndn Abndn NS Abndn <1.0 <1.0 0.6J PRA45 2/23/09 <1.0 <1.0 NS NS Abndn Abndn Abndn Abndn NS Abndn <1.0 <1.0 2.1 PRA46 5/30/09 <1.0 <1.0 NS NS Abndn Abndn Abndn Abndn NS Abndn <1.0 9.7 3.8 PRA47 8/26/09 <1.0 <10 NS NS Abndn Abndn Abndn Abndn NS Abndn <1.0 <10 <10 PRA48 11/12/09 <1.0 <1.0 NS NS Abndn Abndn Abndn Abndn NS Abndn <1.0 <1.0 <1.0 PRA49 2/22/10 <1.0 <1.0 NS NS Abndn Abndn Abndn Abndn NS Abndn <1.0 <1.0 <1.0 PRA50 5/27/10 <1.0 <1.0 NS NS Abndn Abndn Abndn Abndn NS Abndn <1.0 <1.0 <1.0

Type: Q# denotes the quarter of GMP monitoring; AS denotes sampling associated w/ air sparging program; M# denotes the sampling month of the 12 month sampling period as set forth in the RA GMP PRA# denotes the post-remedial quarterly sampling period.

Note: pg/L = micrograms per liter Shaded values are in excess of the MCL for benzene of 5 pg/L.

"J": Indicates that the analyte concentration was found between the quantitation limit and the detection limit or otherwise outside of calibration limits. The value is therefore an estimate.

• = Method 8260 revealed 4.5 ppb, and 8020 revealed 8.1 ppb. The evaluation is included with the fall 1997 quarterly report. = Analysis for August 14, 2002 sample from GW-2 was outside quality control limits due to high surrogate recovery. This result is likely

inaccurate and higher than the true concentration. NS = Not Sampled., per June 29, 2005 EPA approval of work plan Abndn = Well abandoned October 2005 per June 29, 2005 EPA approval letter

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Golder Associates

ATTACHMENT 1

SUMMARY OF INVESTIGATION AND REMEDIATION ACTIVITIES, KMI CASPER

SUMMARY OF INVESTIGATION AND REMEDIATION ACTIVITIES, KMI CASPER

Date Activity Date USEPA and Wyoming Department of Environmental Quality (WDEQ) begin investigation o the area in and around the Brookhurst subdivision. Three monitoring wells installed on the property by KN.

Early-mid 1987 Ecology and Environment performs Expanded Site Investigation of Brookhurst subdivision and surrounding facilities.

Summer 1987 KN, Dow, Dowell, and LARCO notified of status as Potentially Responsible Parties (PRPs)

December 1987 KN enters into Administrative Order on Consent to perform EE/CA of its property. DowfDowell and KN enter into Administrative Order on Consent to perform an RI/FS of the Brookhurst Subdivision site (sites later known as Mystery 8ridge Superfund Site). LARCO facility work performed under RCRA 3008(h) order.

January 1988 Removal activities begin at Dow/DSI site, including excavation of 440 cubic yards of contaminated soil from chlorinated sump area and removal of other inactive facilities. SVE systems installed and operated.

March 1988-June 1990

O'Brien & Gere performs RI/FS activities for Brookhurst subdivision.

Early-mid 1988 ERT performs Phase I and Phase II studies under contract to KN, focusing on area around flare pit. 2 feet of floating product found in piezometer KNP-2.

Mid-late 1988 ABC performs Phase III study to identify extent of free product at KN facility. Study expanded to include information necessary for EE/CA

January 1989 Brookhurst subdivision connected to Evansville public water suodv system March 1989 EE/CA report completed and submitted to USEPA

November 1989-August1996

OU-1 (groundwater) remediation system constructed and begins operation 11/21/89. System includes groundwater pump-and-treat with air stripping and soil vapor extraction Pump-and-treat system operates at about 55-75 gpm. Treated water re-injected to aquifer.

December 1989 - April 1991

Groundwater elevations relatively low. Total of about 10,600 gallons (approximately 65,00 pounds) of free product, identified as absorption oil, extracted horn on-site wells. Approximately 30 pounds of benzene estimated to be contained in the free product, for averaae benzene content of 0.05%.

July 1990 Continuing OU-1 remediation and free-product removal. Free-product thicknesses noted to vary inversely with groundwater elevation.

September 24, 1990 ROD entered for OU-1 (groundwater). August 14, 1991 Consent Decree for Mystery Bridge Superfund Site

September 14, 1993 EPA issues Certification of Functional Remedy. Groundwater pump-and-treat and SVE continue.

December 1993 New infiltration aallerv constructed for re-introduction of treated groundwater to aauifer May 1995 6.31 inches of precipitation recorded. Groundwater elevations rise about 10 feet in spring

and summer 1995. June-July 1995 150mg/Land 110 mg/L benzene measured at well EPA 1-9, possibly related to high water

levels. Prior and subsequent concentrations near or below detection limits. August 23, 1996 OU-1 remediation system (groundwater pump-and-treat and SVE) turned off with consent

of USEPA Quarterly monitoring at all performance wells except ABC-12, which continues monthly monitoring.

August 20, 1997 EPA Issues certification of remedial action (RA) completion. 8 quarters of post-RA monitorina beain

October 10,1997 EPA approves change to February, May, August, and November quarterly monitoring schedule to coincide with first round occurring in August 1997. EPA also approves change to 8020/8021 analytical method from 6260.

November 1998 5-year review conducted, May 1999 6 quarters of post-RA monitoring completed. Statistical test fails at two wells, post-RA

monitoring continues. Quarterly sampling augmented for this round to include evaluation o natural attenuation parameters. Quarterly report includes discussion of natural attenuation and risk evaluation due to residual groundwater contamination. Natural attenuation demonstrated to be occurring in groundwater at site, and residual risk concluded to be minimal or non-existent

December 1999 Benzene concentrations 470 mg/L at ABC-5, 460 mg/L at MW-7. These were among highest ever recorded at site.

April 23, 2000 Approximately 6,000 gallons of lean oil spilled in process area. 3,500 gallons recovered immediately. Remainder remediated throuah enhanced bioremediation of affected soils.

September 2000 Normal August quarterly sampling delayed 1 month to include 9 additional wells. Extent of

October 23. 2000 USEPA approves abandonment of groundwater extraction wells and dismantling of groundwater pump-and-treat system. Air sparging system components remain in place.

November - December 2000

Groundwater pump-and-treat system abandoned and dismantled.

February 28. 2001 Free product observed by Western Water Consultants at well EPA 2-11 during routine monitoring for Dow/DSI remediation system. Groundwater elevations near low levels seen in 1989-1991.

March - April 2001 ABC and Cordilleran Compliance Services investigate occurrence of free product at KMI facility. Free product on site identified 3S highly weathered lean oil. Product at well EPA 2 11 identified as most likely highly weathered lean oil with a heavier oil component as well. Monthly monitoring of groundwater elevations and free-product thickness initiated.

Early 2001 - April 2003 Groundwater elevations remain near lows for period of record. Sporadic detections of free product in several monitoring wells. Benzene concentrations decline from historic high

April 2003 Last detections of measurable free-product thickness. Summer 2003 - present Groundwater elevations recover to near-average conditions.

June - October 2004 Second 5-year review by USEPA Report indicates remedy continues to be protective of human health and the environment. Next 5-year review scheduled for 2009.

August 2004 Monthly monitoring of groundwater elevations and free-product thickness discontinued witf USEPA approval, regular quarterly monitoring and sampling continues.

September 2004 SVE/air-sparging system and groundwater infiltration gallery decommissioned and removed from site per approved work plan.

June 2005 Work plan for removal of redundant monitoring wells approved by USEPA Work pten calls lor reduction from 13 to 5 wells for ongoing quarterly sampling.

September 2005 Initial draft Notice of Deed Restrictions submitted to USEPA for review and comment.

October 2005 29 groundwater monitoring wells abandoned per June 2005 work plan. Quarterly sampling continued with 5 wells sampled from original 13.

July 2006 Revised Notice of Deed Restrictions and Environmental Covenant incorporating USEPA comments submitted for review and approval.

December 2006 Additional comments on Notice of Deed Restrictions received from USEPA

December 18, 2007 Revised draft Notice of Deed Restrictions sent to USEPA Revised draft includes WDEQ as party to the Notice.

August 19, 2008 USEPA indicated that revised draft Notice of Deed Restrictions was sent to WDEQ for review.

August 21,2009 Site visit for 2009 5-year review. Site visit included Fran Costanzi from USEPA and Jane Francis from WDEQ.

September 30. 2009 Five-year review report for Mystery Bridge issued by USEPA Review concluded that the remedy as implemented is protective of human health and the environment.

ATTACHMENT 2 U.S. ENVIRONMENTAL PROTECTION AGENCY, 1996

LETTER FROM LISA S. REED (PROJECT MANAGER, U.S. ENVIRONMENTAL PROTECTION AGENCY) TO LAWRENCE J. CORTE, ESQ. (KN ENERGY, INC.),

AUGUST 23,1996

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION VIII

999 18th STREET - SUITE GOO DENVER. COLORADO 80202-2466

AUG 2 3 i396

August 23, 1996

Lawrence J. Corte, Esq. KN Energy, Inc. 12055 W. 2nd Place P.O. Box 15265 Lakewood, CO 80215

Dear Mr. Corte:

In the Revised Remedial Action Interim Progress Report dated June 13, 1996, KN Energy (KN) requested to shut off the groundwater pump and treatment system and reduce the monitoring frequency. Based on this request, EPA is approving some modifications to the Groundwater Monitoring Plan. The approved changes and conditions are described below.

Per the request, KN may shut off the groundwater pump and treatment system. Quarterly sampling may also be initiated at all monitoring wells except ABC-12. Monthly sampling and analysis of ABC-12 must continue until it meets the clean up criteria specified in the Groundwater Monitoring Plan section 7.1. This section states that compliance with MCLs is achieved when the 90% one-tailed confidence concentrations for benzene, ethelybenzene, toluene and xylene for a 12- month period are below the MCLs. Should ABC-12 not meet the clean up criteria within the next twelve months, FN should provide EPA a proposal on how the situation will be addressed. This proposal should consider additional remediation work but may also consider a technical infeasibility waiver.

During this period of Remedial Action (RA), EPA 1-9 should be sampled after a period of higher than normal precipitation or run off, or when the water level in KN-MW-6 exceeds 5090 feet AMSL. If two consecutive quarters of sampling of any well (except ABC-12 which is addressed above) exceed the MCL, monthly sampling should be reinitiated at that well. If the additional monthly monitoring results also show the groundwater exceeds the MCL, KN should notify EPA and propose additional work, such as restarting the groundwater pump and treatment system. This notification should occur within one week of obtaining the sampling results which show higher than MCL values. Additionally, if the groundwater no longer exceeds MCLs after one to three months of monthly sampling, KN may request to go back to quarterly sampling. Until this is approved by EPA monthly sampling and any other remedial measures previously approved by EPA should continue.

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Per the Consent Decree, post-RA monitoring cannot begin until all the RA monitoring wells are in compliance with the clean up standards. Thus, this period where most wells will be sampled quarterly will still be RA. Once ABC-12 meets the specified criteria, KN should submit a request to move to post remedial action monitoring. The two-year post-RA monitoring for all wells will begin upon EPA approval of that request.

If you have any questions about the conditions and modifications to the Groundwater Monitoring Plan described in this letter, please contact me at 293-6537.

Sincerely,

Lisa S. Reed

cc: Don Fischer, WDEQ-WQD Joe Pollara, ABC

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ATTACHMENT 3 U.S. ENVIRONMENTAL PROTECTION AGENCY, 1997

LETTER FROM LISA REED LLOYD (PROJECT MANAGER, U.S. ENVIRONMENTAL PROTECTION AGENCY) TO MR. HAYDEN TRUSCOTT (ENVIRONMENTAL MANAGER,

KN ENERGY, INC.) REGARDING MYSTERY BRIDGE SUPERFUND SITE -REMEDIAL ACTION COMPLETION, AUGUST 20,1997

UNITED S .TES ENVIRONMENTAL PROTECT. JK AGENCY REGION VIII

§ 999 18th STREET - SUITE 500 (C If. U\-' l£J. 6^- DENVER, COLORADO 80202-2466 111 ]\t ~~

P*$ef: 8EPR-SR |u 1 SEP ~ 3 199T • August 20, 1997 lltUj \l

r 7/M2I— Hayden Truscott \ -—•-—T~ Environmental Manager <2<2 • j KN Energy, Inc. _• • 370 Van Gordon St. u

P.O. Box 281304 Lakewood, CO 80228-8304

RE: Mystery Bridge Superfund Site - Remedial Action Completion

Dear Mr. Tuscott:

I have received the remedial action completion certification for the KN portion of the work at the Mystery Bridge Superfund Site. This letter approves the completion of the remedial action.

I have reviewed the July 29, 1997, progress report that summarizes the remedial action groundwater monitoring data. The report shows that KN has met the groundwater performance standards as described in the September 1, 1993 Remedial Action Groundwater Monitoring Plan (amended by EPA's August 26, 1996 letter). On July 16, 1997, Don Fischer, of Wyoming DEQ, and I completed the pre-certification inspection that is required by the October 1991 Consent Decree. Pursuant to Section XV, Subsection 46, of the Consent Decree, the above two items and the certification fulfil the requirements for remedial action completion.

The requirements of the post remedial action groundwater monitoring are outlined in the Groundwater Monitoring Plan. A minimum of eight quarters of post remedial action groundwater monitoring is required. The sampling conducted this month will serve as the first quarter of the post remedial action sampling.

If you have any questions about the post remedial action requirements, please do not hesitate to contact me.

Sincerely,

Lisa Reed Lloyd Project Manager

cc: "Jeremy Kolenbrander, ABC Don Fischer, WYDEQ Dale Vodehnal, EPR-SR Mr. John Miller, Dowell C.W. Brannan, Radian International Tom Mueller, WWC

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ATTACHMENT 4 TECHNICAL MEMORANDUM FROM GOLDER ASSOCIATES INC. TO USEPA

REGARDING SUMMARY OF THE PREVIOUS EIGHT QUARTERS OF POST REMEDIAL ACTION GROUNDWATER MONITORING AT THE CASPER COMPRESSOR STATION,

FEBRUARY 12, 2010