Edmonds UNOCAL / Chevron Cleanup

LOWER YARD 2007-2008 CLEANUP (INTERIM ACTIONS): DATA GAPS INVESTIGATIONS

By Greg Glass 

Chevron completed Phase I of the Lower Yard Interim Action cleanup by April 2008.  A full report on those Phase I activities is being prepared and will be made available by the end of the year.  The work remaining for Phase II includes some minor areas of soil excavations and cleanup of contaminated sediments in a portion of Willow Creek along the western property boundary.  The planning and permitting for Phase II activities have been completed and as of the week of July 21^st mobilization to start Phase II cleanup activities has begun.

After the Phase II cleanup is completed in Fall 2008, additional ground water monitoring wells will be installed and periodic ground water sampling and analysis will be performed to establish whether ground water cleanup standards have been met and how any remaining ground water contamination is diminishing over time.

The Phase I soil excavations were more extensive than originally planned, based on field observations during the cleanup.  Even with such extensive excavations, the question was still posed whether there were any remaining data gaps that warranted additional investigation, with the goal of assuring the effectiveness of the Interim Actions at completion.  Doing additional investigations now allows any remaining areas of contamination to be included as part of Phase II cleanup actions.

On behalf of Chevron, ARCADIS prepared a report on potential data gaps, titled “Evaluation of Lower Yard Phase I Data and Work Plan for Additional Site Investigation, UNOCAL Edmonds Bulk Fuel Terminal, Lower Yard (May 30, 2008)”.  ARCADIS proposed a number of additional soil borings in three areas:  1) the far southwest corner of the Lower Yard, near the former railroad trestle; 2) adjacent to the Washington State Department of Transportation storm drain line in the central Lower Yard; and 3) near the southeast corner of Detention Basin 1, where a ground water monitoring well had historically shown evidence of floating petroleum product and no soil excavations were done.

I reviewed the ARCADIS report and also reviewed the cumulative data sets from site investigations to date as well as the history of site operations as presented in an earlier report by UNOCAL’s consultant EMCON Northwest, Inc. (Background History Report, February 15, 1994).  I agreed with ARCADIS’ proposed additional investigations, but identified three additional areas as potential data gaps where historic site operations suggested possible releases of contamination.  Those three areas were:  1) the “apron” off the eastern end of Detention Basin 1; 2) the footprint of the former asphalt warehouse south of Detention Basin 1; and 3) the former “slops pond” between the asphalt plant and Detention Basin 1, along the northwestern property boundary, on top of which lined Detention Basin 2 had been built.  On behalf of ECAC, I submitted my recommendations for additional investigations to Ecology (see memorandum of June 11, 2008:  ECAC Comments on May 30, 2008 Work Plan for Additional Site Investigation).

After receiving my review comments, Ecology met with ARCADIS to review the data gaps issues.  Additional borings were added to the original ARCADIS proposal to address my first two identified areas.  Locations near the former “slops pond” were already targeted for minor soil excavations during Phase II cleanup actions; depending on how extensive those excavations become, additional investigations were identified as a contingent part of Phase II field activities.

Except for the contingent “slops pond” borings, ARCADIS has completed the additional data gaps investigations prior to starting the Phase II cleanup.  Duane Uusitalo and I made site visits on two days to observe some of the additional borings and soil sampling.  A full report of results is not yet available.  Based on discussions with ARCADIS, the added borings at the location of the former asphalt warehouse showed Total Petroleum Hydrocarbon (TPH) contamination above the criterion for soil excavation.  The temporary water treatment plant was located on part of the former asphalt warehouse footprint where I identified potential data gaps; the just-completed borings showing soil contamination were placed just off the edge of the treatment plant pad.  ARCADIS will be relocating the water treatment plant at the start of Phase II so that additional investigations and soil excavations, as appropriate, can be completed in this area.

Phase II cleanup activities should start up within a few weeks.  Duane Uusitalo and I will be making periodic site visits to observe cleanup activities, and I will post updates as new information becomes available.

Feel free to contact me via e-mail ( HYPERLINK "mailto:gglassenviro@comcast.net" gglassenviro@comcast.net) if you have comments or questions.

Data Gaps in the UNOCAL/Chevron Cleanup

MEMORANDUM

TO: David South, Ecology/NWRO

SUBJECT: ECAC Comments on May 30, 2008 Work Plan for Additional Site Investigation

DATE: June 11, 2008

Thank you for the opportunity to review and provide comments on the recent ARCADIS report “Evaluation of Lower Yard Phase I Data and Work Plan for Additional Site Investigation”, May 30, 2008, submitted on behalf of the Chevron Environmental Management Company for the UNOCAL Edmonds Bulk Fuel Terminal site.  The primary focus of this report is to identify data gaps for site characterization, given the extensive remedial actions completed in the Lower Yard, and propose additional data collection to address identified data gaps.  I have reviewed the report and submit a few brief comments on behalf of ECAC.

Figures

In Figures 3, 4, and 5 Interim Action excavation area B3 in the southeast Lower Yard is annotated with “Planned Excavation Limit”.  Since excavations for Phase I have been completed, that annotation can be deleted.

The excavation depth in the small arsenic removal area of the far southwest Lower Yard was approximately 1 foot, but the pattern used for that area according to the legend on the Figures indicates an excavation depth of approximately 8 feet.  An alternate pattern, or annotation, for that one area of shallow excavation would be appropriate.

Figure 3 provides an “overlay” mapping of excavation areas and boring locations, which facilitated review.  Locations for which soils data are not available are not included in this overlay map.  A previous Lower Yard Exploration Map (see Drawing 1 in the June 25, 2007 Interim Action Report) does provide additional location mapping (e.g., additional monitoring well locations).  I found that earlier drawing to be a useful supplement to Figure 3 of the current report, even though it does not have the overlay of excavation areas.

Data Gaps and Proposed Additional Investigations

The three areas identified by ARCADIS for additional data collection are all reasonable and I support the proposals for additional data collection at those locations.  Based on my review, I have identified three additional data gap locations, all related to some aspect of past site operations, for which I recommend some additional data collection.

1.  Area adjacent to southeast end of DB1.  One soil boring was sampled in this area; SB-117 had 2,502 ppm TPH (see Figure 3).  I have confirmed with Scott Zorn that the DB-1 excavations did not extend far enough to include the SB-117 location.  Sidewall samples of the DB-1 excavation showed low to not-detected TPH concentrations.  The Background History Report (February 15, 1994) includes the following statement on page 6-2:  “An unknown quantity of off-specification emulsified asphalt was dumped in barrels along the southern edge of Detention Basin No. 1 and drained into the basin.  The product and some of the barrels were not removed (GeoEngineers, Inc., 1988b)”.  I recall that at least one drum/barrel was found near this area during excavation of DB1.  This area is located adjacent to Willow Creek.  No ground water monitoring data are available for this area; the closest monitoring wells are on the north side of DB1 (MW-109) and at the southernmost corner of DB1 (MW-122, MW-129).  During our discussions on the proposed Interim Actions last year, I suggested an additional monitoring well be installed in this area, and you deferred a decision on that recommendation.

I propose that 3 borings be spaced between SB-117 and MW-122 to investigate the presence of soil contamination in this area.  I recognize that there is considerable vegetation in this area, but without additional data the residual contamination from past practices there will remain uncertain. The data from SB-117 indicate that despite clean sidewall samples at the time of DB1 excavation soil TPH contamination approaching the remedial action level was detected beyond the excavation limits.

2.  Former asphalt warehouse.  Historic airphotos show the location of the large former asphalt warehouse south of DB1 (see Background History Report and ECAC’s website).  It extended to the southeastern limit of DB1.  The footprint of the warehouse therefore included areas southeast of Interim Action excavation areas A1 and B6 (see Figure 2).  ARCADIS has correctly identified MW-129 as being within this footprint area, although it is unknown whether the LNAPLs detected at that well were related to any warehouse operations or releases; other sources may have been the cause. I note that the maximum apparent product thickness measured in well MW-129 was 0.91 feet.  Information on the warehouse is limited.  The Background History Report includes the following statement on page 3-16:  “Asphalt was pumped from cooling tanks into a 6-inch-diameter header line, located in a trench in the warehouse floor, which ran the length of the building near the centerline”.  It is unclear whether this was a paved or unlined trench, or whether the floor of the warehouse had any cracks or gaps where releases to soils could have occurred.

Soil TPH concentrations in borings SB-148 and SB-164, near the warehouse centerline, were only moderately elevated (see Figure 3).  Monitoring well MW-E, located just east of the limit of Interim Action excavation area A1 and west of SB-164, had elevated TPH as recently as the ground water sampling round of February 2006 (at 1,391 ug/L TPH).  Ground water flow directions have been mapped as northerly near MW-E (see Figure 2, Groundwater Sampling Report – February 2006 Sampling Event, May 24, 2006).

To provide additional information for the warehouse footprint area, and to increase confidence that there are no remaining areas of soil contamination exceeding the remedial action levels, I propose 3 additional borings.  Two borings should be placed between SB-164 and SB-148, equally spaced, approximately along the centerline of the former warehouse footprint.  The third boring should be located 20 feet south of MW-E (and moved slightly east if necessary to be at least 20 feet from the limit of excavation area A1).  I recognize that the temporary water treatment system and soil stockpile are located in this area, which could affect the timing for additional data collection, or may indicate some modifications of proposed sampling locations to still address the identified data gap.

3.  Former slops pond near DB2.  The Background History Report states that the asphalt plant was constructed in about 1953 (page 3-14).  It also notes that the shorter leg of the original L-shaped DB1 was segmented to provide a slops pond:  “In the late 1960s, the basin was modified by cutting off the southern leg to create an impoundment to contain refinery and asphalt plant sludges and runoff” (page 3-12).  The history report further states that DB2 was constructed on top of this slops pond:  “The modifications included backfilling the sludge impoundment portion of the southern leg and constructing a PVC-lined outfall basin (Detention Basin No. 2) along the southern perimeter of Detention Basin No. 1” (page 3-12).  Thus, it appears reasonable to assume that the slops pond sediments would have been contaminated and that they were not removed when DB2 was built on top of the slops pond area.  The former slops pond area is located next to Willow Creek.

The presence of (lined) DB2 during the period of prior site investigations, from the 1980s to the present, meant that no samples were taken from portions of the former slops pond area (see Figure 3).

Phase II of the Lower Yard Interim Actions will include soil excavations at area B7 between DB1 and DB2 and sediment excavations within Willow Creek along the northwest side of the former slops pond.  Scott Zorn has also told me that a “shoulder” area will be created by pulling back the head end of DB2 (closest to Willow Creek) when sediment remediation takes place.  It is possible that excavations from area B7 and Willow Creek will continue and end up covering the full extent of the former slops pond area.  If that does not occur, I propose that two to four additional borings (the number depending on the remaining unexcavated slops pond area) be located here to confirm the presence or absence of significant remaining contamination associated with slops pond operation.  The depths of those borings should be deep enough to encounter the bottom of the original slops pond.  The creation of the “shoulder” area along Willow Creek should make sampling easier.

I have assumed that additional sampling here would best be approached as contingent sampling at the time of Phase II remedial activities.  I would have no objection, however, to this sampling occurring earlier.

Ground Water Monitoring Plans

The Interim Action Report (June 25, 2007) included plans for interior ground water monitoring systems for monitored natural attenuation (see, for example, Drawing 14).  Those flow path MNA monitoring systems were based on the interpreted locations of LNAPL and ground water contamination “plumes” from ground water monitoring events.  The MNA ground water monitoring systems are not the subject of the report currently being reviewed.  However, I want to suggest that we discuss whether the information compiled during the extensive Lower Yard Interim Actions just concluded indicate that any modifications to those MNA wells should be considered.  Some combination of the most recent perimeter well sampling results from 2006, ground water flow directions, and the actual encountered (as opposed to interpreted) extent of LNAPLs in the Lower Yard may, for example, suggest that a realignment of some of the MNA wells would be appropriate.  It may be timely to have these discussions in July or August; new well installations are scheduled for around October, after Phase II excavations are completed.

Thank you for considering these technical review comments on behalf of ECAC.  Please contact me if you have any questions or conclude that further discussion would be helpful.

Sincerely,

Gregory L. Glass

ECAC technical Consultant