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Site Report: Alyeska Remote Gate Valve 35A

Site Name: Alyeska Remote Gate Valve 35A
Address: ~600 Feet SW of MP 218 Dalton Highway; ~40 Miles N of Coldfoot; Pipeline MP 193.96, Coldfoot, AK 99701
File Number: 330.38.125
Hazard ID: 26247
Status: Active
Staff: Laura Jacobs, 9074512911 laura.jacobs@alaska.gov
Latitude: 67.798093
Longitude: -149.819348
Horizontal Datum:WGS84

We make every effort to ensure the data presented here is accurate based on the best available information currently on file with DEC. It is therefore subject to change as new information becomes available. We recommend contacting the assigned project staff prior to making decisions based on this information.

Problems/Comments

On 6/12/13 crude oil was discovered in the galvanized steel sump at Alyeska pipeline remote gate valve (RGV) 35A. RGV 35A is located at Trans Alaska Pipeline milepost 193.96, near milepost 218 of the Dalton Highway. Initial response activities included recovery of 21 gallons of crude oil and removal of 2 cubic yards of contaminated soil. Additionally, 8 drums of water/oil saturated soils were removed. Analytical results indicated the presence of weathered hydrocarbons upgradient and downgradient of the vault. Diesel range organics and residual range organics were confirmed in groundwater above DEC cleanup levels, however soil samples collected were below. In 2018, soil contamination encountered and left in place was located 6 to 8 feet bgs. GW was clean, but was sampled at a depth of around 2 to 4 feet bgs. Contamination appears to be in subsurface below the GW table and appears limited in extent. It is assumed this is the same historic contamination investigated in 2013 from oil spray to the surface within the sump at RGV-35A. On 6/3/2022 a crude oil leaked from cracked threads on a pipe nipple connecting a 3/4" bleed valve to a welded fitting in a spool pipe between bypass valves at Remote Gate Valve-35A. The spill was released into vertical vault that is installed from above ground to approximately 8 feet below ground surface and backfilled with soil within the vault close to the outside ground surface. Oil accumulated within the vault and on top of 2" of meltwater. In addition, there was a light spray with an area of 20x20ft adjacent the pad. Immediate action was taken, and the valve was bypass by installing valves on either side. The leaking 3/4" valve threads have been closed and the leak is now isolated.

Action Information

Action Date Action Description DEC Staff
6/23/2014 Site Characterization Workplan Approved The Alaska Department of Environmental Conservation (ADEC) Contaminated Sites Program (CSP) has received and reviewed the 2014 Work Plan RGV-35A submitted by SLR and dated May 2014. ADEC has no objections to the Work Plan and Alyeska may proceed with the following conditions: 1. The groundwater must be analyzed for GRO and BTEX; 2. This site appears to be below the 68o North latitude which is defined as the Arctic Zone in 18 AAC 75.990. Therefore it is assumed this site is in the Under 40 Inch Zone. However, if SLR believes this site is located within the arctic zone, ADEC will require additional site specific data for our records. Grant Lidren
6/27/2014 Spill Transferred from Prevention Preparedness and Response Program Spill transferred by PERP staff John Ebel. Spill no. 13399916302; spill date = 6/12/13; substance = crude oil; quantity = unknown; PERP file no. 330.02.053. Mitzi Read
7/7/2014 Site Added to Database A new site has been added to the database Mitzi Read
7/7/2014 Exposure Tracking Model Ranking Initial ranking with ETM completed for source area id: 79643 name: Crude Oil - Remote Gate Valve 35A Mitzi Read
7/10/2014 Potentially Responsible Party/State Interest Letter PRP letter sent to Alyeska on this date. Grant Lidren
1/9/2015 Site Characterization Report Approved On this date, ADEC received the 2014 Groundwater Monitoring Report Remote Gate Valve 35A submitted by SLR dated December 2014. MW-3 sampled on 7/25/14 for DRO and RRO contained detectable levels of DRO and RRO, but below ADEC Table C groundwater cleanup levels. MW-3 sampled again on 8/25/14, for GRO, DRO, RRO, and BTEX did not contain detectable levels of contaminants. Grant Lidren
3/3/2015 Cleanup Complete Determination Issued The Alaska Department of Environmental Conservation (ADEC), Contaminated Sites Program, has completed a review of the environmental records associated with this site. Based on the information provided to date and the administrative record, the ADEC has determined that the contaminant concentrations remaining on site do not pose an unacceptable risk to human health or the environment. No further remedial action will be required as long as the site is in compliance with established institutional controls. Grant Lidren
7/8/2015 Update or Other Action On this date; MW-1, MW-2, and MW-3 were decommissioned. SLR pulled the 1/4-inch outer diameter tubing connected to the stainless sampling points and filled the holes to the maximum extent possible with powdered bentonite. Grant Lidren
2/25/2019 Site Characterization Report Approved On this date, ADEC received the RGV-35A Sheen Investigation Report_Rev1 submitted by SLR and dated February 25, 2019. Heavy sheen was observed during a routine integrity investigation dig at RGV-35A in 2018 within the 10 foot in diameter historic CMP surrounding the valve. Historic trapped crude oil was observed around the valve housing and below the static water table. Crude oil saturated soils were encountered at 6 to 8 feet bgs in the SE quadrant of the newly installed 17 foot in diameter CMP. Contaminated soil was removed at this location as well as outside the newly installed 17 foot CMP to the best extent practicable to a depth of 8 feet bgs at the top of the pipe. No leaks or structural damage were identified on the valve body, bybass valve piping risers, and top of pipe, including all components on the southeast side of the valve where free crude was observed. Ten confirmation soil samples were collected from the sidewalls and floor of the excavation. Only one soil sample collected from the SE quadrant crude oil stained sidewall at 6 to 7 feet bgs contained contaminants above cleanup levels with DRO at 1,620 mg/kg, 1,2,4-trimethylbenzene at 1.62 mg/kg, 1,3,5-trimethylbenze at 0.825 mg/kg, benzene at 0.856 mg/kg, ethylbenzene at 1.59 mg/kg, naphthalene up to 1.55 mg/kg, and xylenes at 1.81mg/kg. Approximately 10 to 20 cys of contaminated soil was removed and transported to OIT for thermal remediation. A total of 11 MWs and wellpoints were installed to determine the extent of shallow groundwater contamination. None of the groundwater samples were above Table C cleanup levels. Groundwater was encountered from 1.62 to 4.44 feet bgs. Grant Lidren
7/16/2019 Site Characterization Workplan Approved On this date, ADEC received the RGV-35A Well Installation work plan submitted by SLR and dated July 15, 2019. Three borings will be advanced to a depth of 15 feet bgs and completed as monitoring wells. Two soil samples will be collected per boring, one at the groundwater interface and one from the highest pid reading/evidence of contamination. The groundwater will be sampled and groundwater direction will be evaluated. Grant Lidren
12/19/2019 Site Characterization Report Approved On this date, ADEC received the RGV-35A Well Installation report submitted by SLR dated November 22, 2019. Three soil borings were advanced 11.6 to 13.5 feet bgs and completed as monitoring wells (MWs). The MWs were installed 50 feet north, east, and west of the RGV-35A. Five soil samples collected 1.0 to 5.0 feet bgs did not contain contaminant concentrations above Method Two MTG cleanup levels. The monitoring wells were screened 6.63 to 13.45 feet bgs. Groundwater was encountered from the top of the casing during sampling from 2 to 4 feet bgs. Five groundwater samples collected did not contain contaminant concentrations above Table C cleanup levels. Groundwater flow was to the southwest towards the Dietrich River. Grant Lidren
6/10/2020 Site Characterization Workplan Approved On this date, ADEC received the RGV-35A Groundwater Sampling Work Plan submitted by SLR and dated June 10, 2020. Groundwater will be sampled from the three monitoring wells and groundwater direction will be evaluated. Grant Lidren
6/10/2021 Document, Report, or Work plan Review - other The 2020 groundwater monitoring report described the groundwater from the wells installed in 2019 results included estimated concentrations of diesel range organics (DRO) and residual range organics (RRO) between the lab's method detection limit (MDL) and the limit of detection (LOD). Groundwater gradients indicated south-southeasterly flow direction, a change from the southwesterly gradient measured in 2019. Some of the wells have begun to frost-jack. The 2021 work plan describes the intention to sample wells MW-191, MW-192, and MW-193 after trimming the wells casings and re-surveying the top-of-casing elevations. Laura Jacobs
4/7/2022 Document, Report, or Work plan Review - other A review of the RFG-35A Groundwater Monitoring Report summarized three years of groundwater monitoring that continued to result in contaminants of concern being either non-detect or well below the groundwater cleanup level. It is assumed that remaining contaminants from historical leaks are limited to the immediate vicinity of the valve as was documented in 2018. Approval was given to decommission monitoring wells. Laura Jacobs
6/6/2022 Update or Other Action A release of crude oil has been reported at the RGV-35A site after it was observed that a 1/2" valve had a cracked threaded fitting that caused a leak. The observed 6" of product in the 25 foot corrugated metal pipe has been removed by vacuum truck. Coordination has begun to determine the extent of remaining crude oil. Laura Jacobs
6/6/2022 Site Reopened Evonne Reese
6/22/2022 Spill Transferred from Prevention Preparedness and Response Program Alyeska Mile Post 193.962 Crude Oil Gal55; Spill #: 22399915401; File #: 165.02.02; PPR Staff: Nate Collin Mandy Salminen
7/15/2022 Site Characterization Workplan Approved A work plan was submitted by the RP on July 14, 2022 for a groundwater sampling work plan that follows remedial efforts to pick up released crude oil from the remote gate valve at this location. Three groundwater monitoring wells remain from the earlier investigations related to other historic releases. Groundwater samples will be collected from the three monitoring wells to evaluate the potential migration of hydrocarbons associated with the June 3, 2022 release. An approval for the work plan was sent on this date. Laura Jacobs
6/12/2023 Document, Report, or Work plan Review - other DEC staff reviewed and approved the 2022 Groundwater Monitoring Report and the 2023 Groundwater Sampling Work Plan with the request that the sampled well screen interval be measured and reported. Results from the 2022 monitoring report indicate that petroleum hydrocarbon impacts are present in soils within the corrugated metal pipe (CMP). Soil samples were not collected because of the presence of standing water within the CMP surrounding the gate valve. Groundwater monitoring results all analytes below DEC groundwater cleanup levels or were non-detect. The approved work plan proposes soil excavation and confirmation sampling to address petroleum-impacted soils within the CMP, and another round of groundwater samples from the existing well network. Laura Jacobs
7/5/2023 Document, Report, or Work plan Review - other A work plan was approved to screen and sample the remaining contaminated soils within the corrugated metal pipe (CMP) surrounding the gate valve where in 2021 a leak was found. Over ten soil samples from the floor of the pipe will be screened and the locations where screening reveals a photo-ionization detector (PID) reading above 20 ppm, an analytical sample will be collected and analyzed for gasoline range organics (GRO), diesel range organics (DRO), residual range organics (RRO), polycyclic aromatic hydrocarbons (PAHs), and petroleum volatile organic compounds (PVOCs). Soils removed from the CMP will be screened as well to determine whether to remediate the soils prior to spreading, or spread them across the pad. Laura Jacobs
4/12/2024 Document, Report, or Work plan Review - other DEC reviewed the 2023 RGV-35A Groundwater Monitoring Report received by our office December 19, 2023 and has issued an approval. Despite there being some QA/QC issues with sample results for several polyaromatic hydrocarbons, and as a result the data being rejected, all other aspects of the sample results indicated data usability was not affected. Sample results continue to indicate that historical and recent impacts from crude oil leaks at the RGV-35A have not impacted groundwater beyond the immediate vicinity of the valve within and just downgradient of the corrugated metal pipe containment(CMP). DEC agrees with continued sample collection at the existing groundwater monitoring wells, removal of contaminated soils remaining in the CMP, and determining groundwater flow direction by a level-loop survey in 2024. Laura Jacobs
5/31/2024 Document, Report, or Work plan Review - other DEC approved the 2024 RGV-35A Groundwater Monitoring Work Plan and contaminated soil removal as approved in the 2023 Contaminated Soil Removal and Sampling Work Plan (July 5, 2023). Groundwater samples will be collected from the site's three wells and analyzed for gasoline range organics (GRO), diesel range organics (DRO), residual range organics (RRO), petroleum-related volatile organic compounds (PVOCs), and polynuclear aromatic hydrocarbons (PAHs). Contaminated soil removal within the corrugated metal pipe (CMP) surrounding the gate valve will be removed if pad water levels are favorable. Laura Jacobs

Contaminant Information

Name Level Description Media Comments
DRO < Table C Groundwater
RRO < Table C Groundwater

Control Type

Type Details
No ICs Required

Requirements

Description Details
Advance approval required to transport soil or groundwater off-site.
Movement or use of contaminated material (including on site) in a manner that results in a violation of the water quality standards is prohibited (18 AAC 70)

No associated sites were found.

Missing Location Data

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