| Action Date |
Action |
Description |
DEC Staff |
| 2/25/2013 |
Spill Transferred from Prevention Preparedness and Response Program |
Spill transferred by PERP staff John Ebel. Spill no. 09399916801; spill date = 6/17/09; substance = crude oil; quantity = unknown; PERP file no. 300.02.438. |
Mitzi Read |
| 2/28/2013 |
Site Added to Database |
A new site has been added to the database |
Mitzi Read |
| 3/1/2013 |
Exposure Tracking Model Ranking |
Initial ranking with ETM completed for source area id: 79412 name: BPX GC1 Skid 40 Snow Shelter |
Mitzi Read |
| 3/8/2013 |
Potentially Responsible Party/State Interest Letter |
|
Keather McLoone |
| 3/12/2013 |
Document, Report, or Work plan Review - other |
Reviewed GC-1, Skid 40 sampling report dated January 24, 2012. Hydrocarbon sheen was first observed in a tundra pond at the site in 2009. The source of the sheen is unknown, but is suspected to have migrated from Skid 40. The pond was dewatered and remedial excavation was conducted to a depth of 1-3 feet over the impacted area. Skid 40 was removed to facilitate cleanup. In January 2011, additional excavation was conducted based on 2009 sample results and field screening with a PID. Complete excavation was not feasible due to the presence of overhead flow lines. Confirmation samples contained DRO up to 4,370 mg/kg, GRO up to 681 mg/kg, and benzene up to 4.5 mg/kg. |
Bill O'Connell |
| 3/13/2013 |
Exposure Tracking Model Ranking |
A new updated ranking with ETM has been completed for source area 79412 BPX GC1 Skid 40 Snow Shelter. |
Bill O'Connell |
| 10/16/2015 |
Update or Other Action |
Letter sent on this date requesting the BP include this site in its 2016 field activities and submit a workplan. |
Keather McLoone |
| 8/9/2016 |
Document, Report, or Work plan Review - other |
Reviewed the 2016 Contaminated Sites Soil & Water Quality Monitoring Work Plan, dated August 2016. Proposed activities mainly consist of monitoring well sampling, surface water sampling, and surface soil sampling. |
Joshua Barsis |
| 2/9/2017 |
Document, Report, or Work plan Review - other |
Reviewed the 2016 Contaminated Sites Monitoring Report, dated February 2017 for the BPX GC1 Skid 40 Snow Shelter site. The described field effort was completed on August 17, 2016 and included a visual inspection of surface water, as well as analytical sampling completed at five co-located surface soil and surface water locations. All of the soil and water samples were submitted for laboratory analysis of gasoline range organics (GRO), diesel range organics (DRO), polycyclic aromatic hydrocarbons (PAHs), and benzene, toluene, ethylbenzene, and xylenes (BTEX). None of the results for soil or water exceeded applicable state cleanup levels or Alaska Water Quality Standards (AWQS) criteria. Please note that GRO was analyzed outside of holding times for all of the soil samples, and thus is considered biased low. |
Joshua Barsis |
| 1/3/2018 |
Exposure Tracking Model Ranking |
A new updated ranking with ETM has been completed for source area 79412 BPX GC1 Skid 40 Snow Shelter. |
Joshua Barsis |
| 1/4/2018 |
Update or Other Action |
Sent letter as follow up to ADECs February 9, 2017 letter, in which it was stated that this site would be evaluated for closure. ADEC has completed the closure evaluation and identified one remaining data gap that must be addressed (further delineation). Please see ADECs understanding of the site history below and data gap discussion. A work plan was requested by March 15, 2018.
SITE HISTORY:
Petroleum sheening was discovered on June 17, 2009 on a tundra pond southwest of the GC1 Skid 40 structure during flare pit dewatering activities. The source of sheening was unknown at the time, but was suspected to be from the contaminated soils beneath the skid 40 structure. Initial actions included placing shoreseal boom around the sheened area to prevent further migration, and daily dewatering until a cleanup action was performed.
Characterization of the site was initially performed on July 10, 2009. A total of 64 surface soil samples were collected from depths of three and six inches below ground surface (bgs). Sample results varied and revealed some sporadic contamination; however the mass of contamination was consolidated near Samples GC1-13 and GC1-14, both of which had levels of GRO, DRO, RRO, and BTEX above Method Two human health soil cleanup levels at 3 and 6 inches bgs.
Following the characterization effort, an area of roughly 2,900 square feet was excavated to between one and three feet bgs, however excavation was limited by the Skid 40 Snow Shelter. The shelter was removed during the summer of 2010, and additional excavation and sampling was completed in 2010 and 2011. A 225 square feet (15 feet by 15 feet) grid was established over the excavation to allow for confirmation soil sampling. Sampling along the flow lines near the southern grid area could not be accomplished during the winter because of drifted snow. For this reason, two additional analytical samples and two surface water samples were collected during summer 2011 to evaluate the area near the flowlines. Confirmation soil samples were submitted for GRO, DRO, RRO, BTEX and polycyclic aromatic hydrocarbons (PAHs). Water samples were submitted for BTEX and PAHs for comparison to the Alaska Water Quality Standards (AWQS) total aromatic hydrocarbons (TAH) and total aqueous hydrocarbons (TAqH).
Results of the investigation concluded that most of the contamination was successfully removed, except for beneath the flow lines where excavation could not be feasibly accomplished without jeopardizing the structural integrity of the vertical support members (VSMs). Because of this limitation, an estimated 10 cubic yards (cy) of DRO contaminated soil and 50 cy of benzene contaminated soil is estimated left in place. Petroleum contamination remain in the subsurface soils at this site above Method One Table A2 soil cleanup levels, but below the less stringent Method Two Tables B1 and B2 cleanup levels: GRO up to 113 mg/kg, DRO up to 4,370 mg/kg, RRO up to 7,110 mg/kg, and benzene up to 4.5 mg/kg. Water samples results exceeded the TAqH criteria, but not TAH. This is likely because of elevated method detection limits (MDLs) for the PAH analysis and not necessarily because of contaminants.
Additional characterization was completed on August 17, 2016 and included a visual inspection of surface water, as well as analytical sampling completed at five co-located surface soil and surface water locations. Sheens were not evident during the inspection. All soil and water samples were submitted for laboratory analysis of GRO, DRO, PAHs, and BTEX. None of the results for soil or water exceeded applicable cleanup levels or AWQS criteria.
The remaining contamination is primarily covered by a tundra pond that contains few feet of water. The tundra pond is bordered by a gravel pad to the east and north. Water level in the pond varies seasonally, but is mainly driven by snowmelt in the spring. Vegetation is poorly developed in the area and the section of the site off the gravel pad is continuously under water unless artificially dewatered.
DATA GAP DISCUSSION:
As noted above it was not possible to remove contamination beneath the flow lines. Surface soil sampling completed in 2011 revealed levels of DRO and RRO remaining below the flow lines up to 4,370 mg/kg and 7,110 mg/kg, respectively, which exceeds the Table A2 cleanup levels. Surface soil sampling was completed again in 2016 in the same area and contamination was not present above cleanup levels. However, surface soil sampling is not necessarily representative of contamination at the gravel-water interface, which is the most likely zone of contaminant transport. Further delineation should be completed to Table A2 levels in the vicinity of DD-14, EE-14, and EE-13 from the gravel-water interface.
|
Joshua Barsis |
| 3/4/2020 |
Document, Report, or Work plan Review - other |
Reviewed the Sheen Testing Report and Site Closure Request, dated March 3, 2020. Additional sheen investigation was completed in September 2019. No apparent sheens identified. Site should be evaluated for closure. |
Joshua Barsis |
| 3/26/2020 |
Cleanup Complete Determination Issued |
Cleanup complete issued 3-26-2020 |
Joshua Barsis |
| 3/26/2020 |
Exposure Tracking Model Ranking |
A new updated ranking with ETM has been completed for source area 79412 BPX GC1 Skid 40 Snow Shelter. |
Joshua Barsis |
