Edmonds UNOCAL / Chevron Cleanup

LOWER YARD 2007-2008 CLEANUP (INTERIM ACTIONS): LONG-TERM GROUND WATER MONITORING PROGRAM UPDATE, December 2009

By Greg Glass

Ecology approved modifications to the ground water monitoring program on December 7^th.  The frequency of sampling will be reduced from six times per year to quarterly; the next sampling event will occur in January 2010, with results reported around mid-March.  The final round in October 2010 will include all of the analytical constituents that have been measured up to now, including geochemistry parameters for natural attenuation evaluations.  That will provide a complete “snapshot” of ground water conditions at the end of the planned two-year monitoring program.  The next three of four quarterly rounds will have a reduced set of analytical parameters, including TPH but dropping the natural attenuation parameters and PAHs.  With the extensive excavations that occurred during the 2007-2008 Lower Yard Interim Actions, the “source – plume” model assumed for monitored natural attenuation evaluations for ground water is no longer representative of site conditions, a conclusion shared by all parties involved with the site.

The reduced frequency for ground water sampling will provide a total of 11 rounds of data instead of the 13 originally planned.  Sampling will still cover a two-year period and provide a means to address seasonality effects, if any, on ground water contaminant concentrations.  Statistical evaluations of the complete data set – for example, tests of trends in ground water TPH concentrations at individual wells – will have to take into account the change in sampling frequency.

The results from Round 7 ground water sampling, conducted in October 2009, were submitted to Ecology by Chevron on December 9^th.  Time trend plots for total TPH concentrations at selected wells for Rounds 1 through 7 are provided below; see the monitoring well map to locate individual wells.  These time trend plots will be updated periodically to visually summarize some of the ground water data.

Well MW-510, located at the former slops pond, had measurable product (LNAPL) observed in the October 2009 sampling event.  No ground water sample was submitted for laboratory analysis because the presence of product indicated TPH concentrations would be significantly elevated; well MW-510 has had the highest TPH levels of any well sampled through Round 6.  The results to date indicate further remedial action will likely be needed for the former slops pond.

Consistent with previous results, the Round 7 data show generally higher TPH levels along perimeter (Point of Compliance) wells than in the interior of the site.  Ten of the 21 POC wells (not counting MW-510) exceeded [default] cleanup levels for TPH in Round 7.  [NOTE:  the default cleanup levels based on assumed TPH composition are 706 ug/L on the west side and 506 ug/L on the east side of the Lower Yard].  Several wells, including POC wells LM-2, MW-147, and MW-522 along the western margin of the Lower Yard, had their maximum TPH levels so far in Round 7.  Two wells marginally exceeded the [default] TPH cleanup level for the first time in Round 7, both located at the far southwestern corner of the Lower Yard (MW-149R and MW-150).

Several wells have shown markedly inconsistent or intermittent patterns for TPH contamination through the first 7 rounds of sampling.  Examples include MW-147, LM-2, MW-522, and MW-501 (all included in time trend plots below).  These patterns point to the need for caution in assuming that TPH concentrations will remain low after one or two successive low rounds, whether the reason(s) for the intermittent patterns are identified or not.  A similar intermittent pattern was noted from the long-term ground water monitoring record prior to extensive Lower Yard excavations at other wells, including MW-136.

In the southeast Lower Yard, 4 of 5 wells (MW-129R, MW-500, MW-135, MW-136) continue to show elevated TPH concentrations (approximately 1,500 to 2,600 ug/L).  The exception is MW-501, where TPH dropped from over 3,300 ug/L in Round 6 to less than 150 ug/L in Round 7.  That well also had an anomalously high ground water elevation, associated with the ground water mound in the southeast Lower Yard after excavations and backfilling.  The variability in TPH at southeast Lower Yard wells may be influenced by this ground water mounding.

 

In the northern part of the Lower Yard MW-510 remains highly contaminated (product observed in Round 7).  TPH at well LM-2 has varied over time but had its highest concentration yet (2,225 ug/L) in the most recent sampling round.  Well MW-507, located in the site interior just south of DB-1, has had an alternating pattern in TPH between about 500 and 1,100 ug/L.  (Note:  two versions of the time trend plot for northern wells are provided below.  The second one with a change in Y-axis scaling makes the trends at LM-2 and MW-507 easier to see, without the dominating effect of MW-510).

Southwest of the slops pond, along the western site perimeter, 5 POC wells exceed the [default] cleanup level for TPH.  Two wells in the far southeast corner had TPH between 700 and 800 ug/L, exceeding the [default] cleanup level for the first time (MW-149R and MW-150, not included in the time trend plot below).  The highest TPH occurred at MW-147, at over 2,700 ug/L – a new maximum level for that well and, except for MW-510, the highest to date along the western site boundary.  Wells MW-518 and MW-522 have been comparatively more consistent than MW-147 over time.

 

Most wells in the interior of the site have had TPH concentrations below cleanup levels.  At interior wells with higher TPH levels, the concentrations have been more consistent, even slowly declining, through Round 7 (for example, MW-512, MW-513, MW-514).  MW-502, located near the WSDOT storm drain line where remaining soil TPH contamination has been documented, has been somewhat more variable.

 

Chevron is expected to submit a Year 1 ground water monitoring program evaluation report early in 2010.  

Feel free to contact:   ( HYPERLINK "mailto:gglassenviro@comcast.net" gglassenviro@comcast.net)

  

LOWER YARD 2007-2008 CLEANUP (INTERIM ACTIONS): LONG-TERM GROUND WATER MONITORING PROGRAM UPDATE, October 2009

By Greg Glass 

Frances Murphy, Duane Uusitalo and Greg Glass, representing ECAC, met on October 13^th with Ecology, Chevron, WSDOT, and Chevron’s consultants ARCADIS to discuss reviewers’ comments on recent site reports and to review recent ground water sampling data.  [WSDOT, despite budget pressures, has found resources to support continued involvement on this site].

Review comments on the second of two As-Built Reports on the 2007-2008 Lower Yard Interim Actions, as well as the report on additional site investigations between Phases I and II of the Interim Actions, were discussed.  With relatively minor revisions, final versions of those two reports will be prepared by ARCADIS.

A review of site hydrogeology by ARCADIS, including water level data from recently installed piezometers in the southeast Lower Yard where ground water mounding has been observed post-Interim Actions, has resulted in some revisions to the interpretation of ground water flow directions.  The results were presented at the October 13^th meeting.  Under this new interpretation, Detention Basin Number 1 (DB-1) does not act as a sink for Lower Yard ground water, and Willow Creek does not prevent ground water from flowing out of the UNOCAL site to adjacent properties.  The interconnection between surface water in Willow Creek and the uppermost ground water at the UNOCAL site is minimal.  The mounding of ground water in the southeast Lower Yard appears to be a result of the contrast in soil characteristics between more permeable backfill materials at excavations and the less permeable non-excavated materials adjacent to those backfill materials.  Details of this revised model of site hydrogeology will be provided as part of the Year 1 Ground Water Monitoring Report, due to be submitted in early 2010.

We have previously noted that the ground water data from the three “plume” monitoring well systems in the interior of the Lower Yard are not consistent with typical contaminant plume geometry, and that Ecology’s multi-well data evaluation software for plumes would have limited applicability at this site.  Only within-well, not between-well, evaluations are likely to be supported.  ARCADIS has reached a similar conclusion, which was discussed at the October 13^th meeting.  ARCADIS provided notice that they will be submitting a request to Ecology to modify the Year 2 ground water monitoring program.  Anticipated changes include a reduced frequency of sampling, to quarterly (still providing data to address seasonality); collecting ground water samples for chemical analysis at fewer wells; and potentially dropping some geochemical analyses that were designed to support attenuation modeling.  No existing wells will be decommissioned, and all wells will still be observed for LNAPL product and water levels.  David South, Ecology’s site manager, suggested that all wells be sampled for the final round to provide a snapshot of total site conditions.  We will review the proposal once it is submitted and provide our comments to Ecology.  Wells will still be sampled in late October 2009.

The results from Round 6 ground water sampling, conducted in August 2009, were submitted to Ecology by Chevron on October 15^th.  Year 1 of the planned two-year post-Interim Action ground water monitoring program has thus been completed.

Two wells had reported minor (trace, at <0.01 foot apparent thickness) detections of LNAPL product in Round 6.  Those wells were MW-510 at the former slops pond location and MW-129R near the southeast corner of DB-1.  Those were also the two wells with the highest reported TPH concentrations in Round 6.  Well MW-510 had over 18,000 ug/L total TPH, a reduction of more than 25% from Round 5 and the first reversal from what had been a continuous upward trend over Rounds 1 through 5.  All 5 wells in the southeast Lower Yard remained relatively high for total TPH.  Well MW-129R at more than 4,400 ug/L was at a new maximum level for post-Interim Action sampling and was the highest of the 5 wells in the southeast Lower Yard; the other 4 ranged from about 2,200 to 3,400 ug/L.  The slops pond and the southeast Lower Yard remain the two areas of greatest interest for residual ground water contamination.

A few additional wells had total TPH levels marginally above ground water cleanup levels, with Round 6 results well below previous maximum TPH concentrations for those wells.  The highest observed TPH concentrations continue to be found at Point of Compliance wells along the outer property boundary and not in the Lower Yard interior where extensive excavations occurred.

The results from Round 7 sampling in October should be available by mid-December 2009.

Feel free to contact:  ( HYPERLINK "mailto:gglassenviro@comcast.net" gglassenviro@comcast.net)

LOWER YARD 2007-2008 CLEANUP (INTERIM ACTIONS): LONG-TERM GROUND WATER MONITORING PROGRAM UPDATE, September 2009

By Greg Glass 

ECAC awaits the formal issuance of a two-year continuation Public Participation Grant from Ecology to cover activities through June 2011.  It is typical for the formal grant agreement to take some months past the July 1 initiation date before completion.

A meeting has been scheduled among Ecology, Chevron and its consultant (ARCADIS), and ECAC for October to discuss review comments on two recent reports submitted to Ecology by Chevron:  1) the Phase II As-Built Report for the recent Interim Action cleanup of the Lower Yard (May 13, 2009), and 2) the Additional Site Investigations and Groundwater Monitoring Report (March 27, 2009).  The ground water monitoring results to date will also be discussed at that meeting.  WSDOT has been hit by budget reductions to address the current revenue problems in Washington and will have limited availability to continue its ongoing project reviews.

The Round 5 ground water monitoring results for June 2009 sampling of 40 monitoring wells at the site were reported to Ecology in mid-August.  When the results from Round 6 sampling in August are available, the first year of the planned two-year ground water monitoring program will be complete.  A Year 1 ground water evaluation report is scheduled to be submitted to Ecology by Chevron early in 2010.

Two wells installed in the southeast Lower Yard after Interim Action soil excavations were completed (MW-500 and MW-501) continue to show high (mounded) ground water elevations that are atypical for the rest of the site.  ARCADIS recently installed 8 piezometers to explore conditions near those wells and provide additional information to support interpretations of the cause of that ground water mounding.  The potential effects on ground water flowpaths in the central Lower Yard from the impermeable liner installed along the WSDOT storm drain line are still being discussed.

In the Round 5 sampling event, one well had a small amount (0.01 foot) of LNAPL product detected.  That well had a total TPH concentration somewhat above the ground water cleanup level (CUL); quite a few other wells had higher total TPH results but no product detected.

Ecology performed a recalculation of CULs for each well in each sampling round, based on the reported TPH composition at that well.  The number of wells among the 40 with analyzed samples that exceeded those sample-specific CULs has been fairly steady (lower in Round 2); for the 5 rounds so far, the number of exceedances are 17, 9, 17, 14, and 15, in sequence.  The two areas with notably higher total TPH concentrations – the slops pond (MW-510) and the southeast Lower Yard (MW-129R, MW-510, MW-500, MW-135, and MW-136) remained high in Round 5.  In fact, except for a high initial Round 1 measurement at MW-501 of more than 8,000 ug/L, all 6 of those wells had their highest TPH values in Round 5.  Well MW-510 at the slops pond exceeded 25,000 ug/L, a concentration approaching 50 times the calculated CUL.  The 5 southeast Lower Yard wells exceeded their CULs by factors of about 3.9 to 7.5 in Round 5; 4 of the 5 TPH concentrations were above 2,600 ug/L and the remaining one was almost 2,000 ug/L.  The potential source(s) for the continuing TPH observed in the southeast Lower Yard remains a matter of interest; trends at those wells over the continuing sampling rounds will be closely tracked.  The source of high TPH contamination at MW-510 is very likely associated with the unremediated former slops pond.

For the other 9 wells exceeding CULs in Round 5, three had their maximum exceedance factor in Round 5.  Wells exceeding their CUL in Round 5 included LM-2 at the northwest corner of DB-1; MW-507 and MW-508 at the downgradient extent of the eastern plume wells; MW-514 and MW-517 in the middle plume system; MW-143 at the upgradient end of the west plume system; and 3 wells along the western site boundary, MW-147, MW-104, and MW-518.  The CUL exceedance factors for those 9 wells in Round 5 were less than those for the two areas of highest TPH noted above; the range of exceedance factors was about 1.1 to 2.4.  The three wells with maximum exceedance factors in Round 5 were MW-507, MW-508, and MW-517.  Evaluations of the longer-term trends at all monitoring wells, and any seasonality effects (related to variations in ground water elevations and the infiltration of precipitation), will be supported by data from the total of 12 sampling rounds over two years.

Previously reported high benzene concentrations at well MW-20R did not persist to Round 5, when benzene was not detected.  The highest Round 5 benzene result was at the slops pond area well, MW-510, at about one-third of the benzene CUL.

The Round 6 sampling results should be available by mid-October.  All questions and comments on these blog postings and the status of the UNOCAL Edmonds site are welcome.

On the left margin of the blog is the Monitoring Well site that can help in giving a visual orientation  of the wells discussed.

Feel free to contact:  ( HYPERLINK "mailto:gglassenviro@comcast.net" gglassenviro@comcast.net)

  

UNOCAL EDMONDS BULK FUEL TERMINAL SITE Public Participation Grant No. G0800139 (2007-2009) to Edmonds Citizens’ Awareness Committee, Brackett’s Landing Foundation PPG PROJECT EVALUATION REPORT

UNOCAL EDMONDS SITE

UNOCAL operated a Bulk Fuel Terminal in Edmonds, Washington from 1923 to 1991.  In addition to the large volumes of various fuels handled at this site for almost 70 years, an asphalt plant was also in operation at the site for about 20 years.  The site is located near Puget Sound, adjacent to Willow Creek and the Edmonds Marsh.  A fish hatchery is also located at the southeast corner of the property.

The UNOCAL Edmonds site includes an Upper Yard where storage tanks and distribution piping were located and a Lower Yard with offices, rail and truck loading facilities, the asphalt plant and associated warehouse, and storm water handling facilities (Detention Basins 1 and 2).  After extensive excavation of contaminated soils, the Upper Yard was sold and is now a residential condominium development.  The Lower Yard has been identified for use as a multimodal transportation hub, including relocation of the Edmonds ferry.  A purchase and sale agreement for the Lower Yard has been completed between UNOCAL (since purchased by Chevron) and the Washington State Department of Transportation (WSDOT).

Site characterization studies of the Lower Yard documented extensive contamination of soils and ground water with TPH and related contaminants.  Floating product (LNAPLs) was also detected at multiple wells over large portions of the Lower Yard.  After early attempts to recover LNAPLs, a series of Interim Actions began in 2001 and included excavation and removal of contaminated soils, removal and treatment of contaminated ground water, and product removal in localized areas of the Lower Yard.  The large Detention Basin 1 was also dewatered and cleaned out.  During 2007-2008 an extensive Interim Action covering most of the Lower Yard was undertaken, intended by Chevron to complete active site remediation.  A post-Interim Action two-year ground water monitoring program started in October 2008.  Ground water chemistry is being monitored at 40 wells to track compliance with ground water cleanup levels at the property boundary (the MTCA point of compliance), determine if remaining ground water contamination within the Lower Yard is naturally attenuating, detect any re-occurrence of LNAPLs, and determine if residual soil contamination will adversely affect ground water quality.

PUBLIC PARTICIPATION GRANT HISTORY

Reflecting community interest and concerns regarding cleanup of the UNOCAL Terminal Site, the Brackett's Landing Foundation established the Edmonds Citizens' Awareness Committee (ECAC) to support citizen involvement in the cleanup process.  Brackett's Landing Foundation has applied for and received a series of Public Participation Grants from Ecology, starting in 1995.  Those grants have allowed ECAC to hire its own technical consultants to review site information, provide technical review comments to Ecology, and help educate the community about site contamination issues.  The grants have also supported citizen participation in the extended MTCA cleanup process, so that Ecology can take community interests into account.

The formal cleanup process at the UNOCAL Edmonds site started in 1993 when Ecology and UNOCAL signed an Agreed Order for completion of a Remedial Investigation and Feasibility Study.  The time needed to complete site cleanup has far exceeded what was foreseen when ECAC received its first grant in 1995.  Ecology has provided ongoing community support through continuation grants as the cleanup process has been repeatedly extended.  Whether the 2007-2008 Interim Actions successfully completed active remediation, or whether even more remediation is needed, will be determined based on evaluations of the current two-year ground water monitoring program.  ECAC has applied for a continuation grant for 2009-2011 to continue oversight of this monitoring program and data evaluations and support community education and participation through final site cleanup.

CURRENT GRANT ACTIVITIES

Monitoring of Site Cleanup.  Mobilization for starting the Lower Yard Interim Actions took place in July 2007.  Given the relatively late seasonal start for cleanup activities, and in order to maximize work during favorable weather, a public comment period was held concurrently with the start of the Interim Actions.  Remedial actions were completed by September 2008 with installation of a large number of new ground water monitoring wells in preparation for a two-year monitoring program.  Throughout both Phase I and Phase II of the Interim Actions, ECAC made site visits approximately weekly to observe cleanup activities, identify issues needing resolution, and report to the community on progress through blog postings.  Our technical consultant provided a cumulative site visits log to ECAC throughout the cleanup process to reflect site status.  ECAC participated in several oversight visits by Ecology’s site manager.  After completion of Phase I, ECAC’s technical consultant met with ARCADIS’ staff at the Lower Yard to identify locations for collecting additional site characterization information to address data gaps.  As analytical results became available from sidewall and floor sampling at soil excavations, ECAC reviewed those results and discussed them with ARCADIS’ staff during frequent site visits.

Review of Site Reports.  Near the end of the previous grant period, in May/June 2007, a final Interim Action work plan was in preparation.  Ecology and UNOCAL/Chevron negotiated a new Agreed Order to cover additional Lower Yard cleanup activities.  At the start of the current 2007-2009 grant period, ECAC submitted written comments to Ecology during the public comment period on the Interim Action plans as well as the Remedial Investigation/Supplemental Remedial Investigation and new Agreed Order.  ECAC had been an invited participant in a series of meetings among Ecology, UNOCAL/Chevron, and stakeholders leading up to the public comment period.  Several recommendations by ECAC were adopted into the Interim Action work plans.

Lower Yard cleanup actions during the 2007-2008 Interim Actions were documented in two As-Built Reports by Chevron, corresponding to the two phases of remediation.  ECAC submitted written review comments to Ecology on the Phase I As-Built Report (January 8, 2009) on February 12, 2009.  Comments on the Phase II As-Built Report (May 13, 2009) will be submitted by August 2009, in the next grant period.

During development of the Interim Action work plans, ECAC reviewed all site information to identify possible data gaps and made a presentation on that issue to the working group.  Decisions on data gaps requiring additional investigation were deferred at that time pending completion of Interim Action soil excavations, which were deemed likely to expand somewhat beyond planned excavation areas based on field observations and sidewall sampling.  After completion of Phase I of the Interim Actions, Chevron prepared a report titled “Evaluation of Lower Yard Phase I Data and Work Plan for Additional Site Investigation” (May 30, 2008).  ECAC submitted comments on that work plan to Ecology on June 11, 2008 and recommended three additional data gap areas where further site characterization was warranted.  Additional information was collected in two of those three areas; at one, the former asphalt warehouse, additional soil excavations were performed.  At the third recommended area, the former slops pond, no additional information was collected.  A new ground water monitoring well (MW-510) was installed and has shown the highest TPH contamination of any of the 40 monitoring wells currently being sampled.

Chevron submitted a report titled “2008 Additional Site Investigation and Groundwater Monitoring Report” (March 27, 2009) that documented the findings of the additional site characterization investigations after completing Phase I of the Interim Actions, and also summarized the data from the first 2 of 12 planned rounds of post-Interim Action ground water monitoring.  This report included an evaluation of the residual contamination near the WSDOT storm drain line in the Lower Yard which was not removed during the Interim Actions.  ECAC submitted comments on this report to Ecology on April 23, 2009.

Meetings.  ECAC met periodically with its technical consultant to discuss the status of site cleanup activities, evaluations of recent sampling results, and plans for community updates via the weblog.  Ecology, Chevron and its consultant ARCADIS, and ECAC, along with WSDOT, continued the cooperative approach established earlier through the Technical Work Group to identify and discuss issues as they arose.  ECAC participated in a stakeholders meeting in Edmonds on March 12, 2008 at which ARCADIS presented an overview of Phase I of the Interim Actions.  After review comments on the Phase I As-Built Report were compiled, ECAC participated in a meeting at ARCADIS’ offices on March 17, 2009 to discuss the review comments and agree upon report revisions.

Long-Term Ground Water Monitoring Program Data Reviews.  The post-Interim Action two-year ground water monitoring program started with round 1 sampling in October 2008.  A total of 40 wells are being sampled and analyzed each round, with additional wells observed for ground water elevations and product occurrence.  During the current grant period results from the first 4 of 12 planned rounds of sampling were reported by Chevron (as attachments to monthly progress reports to Ecology).  Chevron is to submit detailed ground water data evaluation reports to Ecology at the end of Year 1 and Year 2.  ECAC reviewed the results from each round as they were reported, and started looking at within-well trends as of round 4.  Multiple wells continue to show TPH concentrations above the ground water cleanup levels, many within the perimeter point-of-compliance well system.  The analytical lab performing ground water analyses was changed after round 2 to achieve lower detection limits.  ECAC has called attention to the fact that the TPH type designation changed at several wells after this change in analytical laboratory.  Ground water cleanup levels are affected by the type(s) of TPH detected; this issue will need to be addressed as part of future ground water data evaluations.  In addition to the perimeter compliance monitoring wells, additional wells in the interior of the Lower Yard are being sampled to track changes at several historically-defined “plumes” of TPH contamination.  The data through round 4 are generally not consistent with the spatial continuity assumed for ground water contaminant plumes for two of the three sets of interior wells.  Future evaluations of natural attenuation processes may have to take that pattern into account and focus on within-well evaluations.

Weblog.  During the current grant period ECAC established a website ( HYPERLINK "http://www.ecac-unocal.org" www.ecac-unocal.org) as a primary means of keeping the community informed about the status of site cleanup, issues needing resolution, and opportunities to participate and comment on the overall cleanup process.  As of the end of the current grant period there have been several thousand hits on this blog site.  Biographies of key ECAC officers and consultants and a series of historic site photos are posted on the blog.  Periodic postings kept the community up to date on the Interim Action site remediation activities and the results for each round of post-Interim Action ground water monitoring.  Time trend charts of TPH concentrations at selected wells were included in the posting after round 4 sampling as a means of allowing citizens to easily visualize current conditions at the Lower Yard.  Copies of ECAC written comments submitted to Ecology on reports submitted by Chevron are also being posted on the blog.

SITE STATUS AS OF JUNE 30, 2009

Attempts at floating product (LNAPLs) recovery in the Lower Yard date back to 1987.  After a series of more limited and localized cleanup actions, the 2007-2008 Interim Actions completed an extensive excavation program to remove contaminated soils, while also removing free product and removing and treating a large quantity of contaminated ground water during excavation dewatering.  The excavation areas and volumes of soils removed were considerably larger than identified during planning of the Interim Actions, based on site characterization information.  Buried drums with product and assorted debris were found buried in the southeast Lower Yard, an area without significant historic operations associated with Bulk Fuel Terminal operations. 

 

Some TPH-contaminated soils remain in the Lower Yard, including soils with TPH below the selected remediation level of 2,975 ppm, a few locations with TPH levels marginally above that remediation level, and more substantially contaminated soils near the WSDOT storm drain line.  It is also possible that one or more areas with elevated TPH concentrations have not yet been detected (as substantial portions of the southeast Lower Yard were not identified before excavations began).

No continuing pump-and-treat ground water remediation system has been included as part of the planned Lower Yard cleanup program.  A system of 40 ground water monitoring wells, including both perimeter compliance wells and interior natural attenuation monitoring wells, has been established for ongoing sampling and analysis of ground water quality.  A two-year ground water monitoring program is about one-third completed as of June 30, 2009.  Through the first four rounds of sampling, a substantial fraction of the wells have shown TPH concentrations above the preliminary ground water cleanup levels (based on assumed TPH component types).  Except for one well at the former slops pond location (MW-510), with very high and increasing TPH levels, the TPH concentrations are well below historic levels from mid-1990s sampling during the Remedial Investigation.

Data from the ground water monitoring program will be evaluated after Year 1 and Year 2 sampling are completed to determine if remaining TPH contamination will naturally attenuate and if cleanup levels are attained at the point of compliance wells (property boundary).  If further cleanup actions are deemed necessary based on those evaluations, or if product is detected in the monitoring wells, a Feasibility Study will be prepared to evaluate alternative actions (e.g., further excavations or ground water treatment).  If no further cleanup actions are needed, a Cleanup Action Plan documenting the Interim Actions as final cleanup actions will be prepared.

With further PPG support from Ecology, ECAC intends to continue to review all ground water monitoring data and evaluations and continue to inform the community and encourage citizen participation in the cleanup process.

LOWER YARD 2007-2008 CLEANUP (INTERIM ACTIONS): LONG-TERM GROUND WATER MONITORING PROGRAM UPDATE, June 2009

By Greg Glass (gglassenviro@comcast.net)

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Preliminary Notes. The second of two reports describing the Interim Action cleanup

activities in the Lower Yard during 2007-2008 was submitted by Chevron to Ecology on

May 13, 2009. That Phase II As-Built Report covers the final soil excavation activities,

Willow Creek sediment remediation and restoration, and the installation of new ground

water monitoring wells. ECAC review comments on the Phase II Report will be

submitted later this summer. The Phase I As-Built Report has been revised in response to

review comments from Ecology, ECAC, and the Washington State Department of

Transportation (WSDOT) and is now Final.

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ECAC submitted comments to Ecology on the recent Chevron report titled “2008

Additional Site Investigation and Groundwater Monitoring Report” (March 27, 2009).

Our comments, submitted on April 23, 2009, are provided in a separate posting.

Chevron’s report summarized the results of “data gaps” soils investigations as well as the

results from the first two rounds of the planned two-year ground water monitoring

program. I note that while we identified a potential data gap for soils characterization at

the former slops pond location, no additional soil samples were collected there. One new

ground water monitoring well was installed in that area (MW-510). One portion of this

recent Chevron report addressed the remaining soil contamination that was not removed

during Lower Yard excavations because of concerns over damaging the large WSDOT

storm drain line that traverses the Lower Yard. Soil TPH concentrations near that line

ranged up to almost 17,000 ppm.

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ECAC’s current Public Participation Grant from Ecology ends on June 30, 2009.

Ecology has notified ECAC that it will be receiving an additional grant for the two-year

period through June 30, 2011. That continuation grant will support continued review and

evaluation of the long-term ground water monitoring results as well as any additional

cleanup actions that may be required. We plan to continue periodic postings to this blog

as a primary means of keeping the community informed of the status of site cleanup

activities and remaining issues.

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Ground Water Monitoring Results. Round 4 sampling of 40 ground water monitoring

wells occurred in April 2009; results have now been submitted to Ecology. Since the

long-term ground water monitoring program started in October 2008 15 wells have had

total TPH concentrations above 1,000 ug/L at some point. In Round 4 there were 9 wells

above that level, with 7 of the 9 around the perimeter of the Lower Yard rather than in the

interior. One well – MW-510, at the location of the former slops pond and along the

western site boundary between Willow Creek and Detention Basin 2 (DB-2) – has shown

steeply increasing TPH concentrations over time. In Round 4 it had a TPH value of

22,930 ug/L, more than 10 times the second highest result and by far the highest single

result in any sampling round.

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After a change in analytical laboratory before the third round of sampling (see the April

2009 posting), the reported dominant type of TPH (gasoline versus diesel) changed at

several west-side perimeter wells. Those changes persisted through Round 4. The mix of

TPH types will affect cleanup levels, so this apparent change in type will need to be

carefully reviewed. So far the earlier “default” cleanup levels for the east and west sides

of the Lower Yard (506 and 706 ug/L, respectively) are just being carried forward in all

reporting and data summaries. I expect this issue will be addressed in the Year 1 ground

water evaluation report early in 2010.

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In general, the TPH concentrations in perimeter wells have been more variable (up and

down at a single well over the repeated rounds of sampling) than the interior wells. The

layout of the interior wells was meant to provide information to track changes in ground

water contaminant “plumes” and residual contamination that could move with ground

water to and beyond the property boundary. For each of three “plumes” the set of

monitoring wells included one upgradient well and six additional wells covering both

downgradient and cross-gradient areas. Conceptually this would support tracking

changes in both space and time as any remaining ground water TPH attenuated naturally.

The cumulative results through Round 4 are not very consistent with the assumption of

spatial “plumes”. For two of the three sets of plume wells TPH has been detected at the

upgradient and far-downgradient wells, but not at any wells in between. Single well

(within-well) data evaluations will always be possible, but it remains to be seen whether

multi-well analyses for spatially-extensive “plumes” (as anticipated in an Ecology

software package for natural attenuation evaluations) will be meaningful.

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One well (MW-20R along the western property boundary) remains a high outlier for

benzene concentration. The level in Round 4 declined somewhat to just below the

benzene cleanup level for ground water. The second highest benzene level was at MW-

510 (slops pond), at less than one-third the MW-20R value.

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The ground water conditions in the Lower Yard can be illustrated using some simple data

visualization plots. These plots are intended for data descriptions and not formal data

evaluations (which are initially scheduled to be provided in Chevron’s Year 1 ground

water monitoring report). The X-axis in these plots is time, reflecting ground water

sampling dates; the Y-axis is total TPH concentrations in ug/L. [Any not-detected results

for component TPHs (e.g., TPH-D or TPH-G) are included in total TPH at one-half the

detection limit. Note that those detection limits changed when the analytical lab changed.

The fractional contribution of not-detected results, and instances of all TPH types being

not-detected, are not identified in these simple plots].

g

A few of the wells currently being sampled were installed many years earlier for initial

site investigations. The long term data sets for such wells provide a historic context for

the recent monitoring results. Figure 1 shows time trend plots from 1995 on for three

wells: LM-2, at the northwestern corner of DB-1, MW-104 on the western boundary near

Willow Creek, and MW-136 in the far southeastern corner. All three wells had much

higher TPH concentrations when first sampled in the mid-1990s. Recent results appear

somewhat elevated compared to pre-2007/2008 Interim Actions.

g

Short-term trends over the first four rounds of the current two-year monitoring program

can be illustrated using various groupings of wells. [Look for changes in the Y-axis

scales for TPH concentrations].

g

Figure 2 shows recent trends for 5 wells along the western property boundary. From

southwest to northeast they are: MW-147, MW-522, MW-20R, MW-104, and MW-518.

Figure 3 shows recent trends for 3 wells in the northern Lower Yard near DB-1 and DB-

2: MW-510 (slops pond well, which has shown the most dramatic upward trend in TPH),

LM-2, and MW-507.

Figure 4 shows recent trends for 5 wells along the southeastern boundary of the Lower

Yard. From northwest to southeast they are: MW-129R, MW-501, MW-500, MW-135,

and MW-136. The Round 1 TPH value of more than 8,000 ug/L at MW-501 is the

highest TPH at any well apart from MW-510 so far.

Figure 5 shows recent trends for selected interior (“plume” monitoring) wells: MW-502,

MW-512, MW-513, and MW-514.

The Round 5 sampling results should be available by mid-August. 

All questions and comments on these blog postings and the status of the UNOCAL Edmonds site are

welcome.

LOWER YARD 2007-2008 CLEANUP (INTERIM ACTIONS): LONG-TERM GROUND WATER MONITORING PROGRAM UPDATE, April 2009

By Greg Glass

The Round 3 sampling of ground water monitoring wells took place in February 2009.  The results for Round 3 have just been submitted to Ecology by Chevron.  Detailed evaluation and interpretation of ground water conditions at the site will not occur until after the first year of monitoring has been completed, when ARCADIS (Chevron’s consultant) will prepare a Year 1 Ground Water Report.  Based on my initial review of the most recent data, I provide some brief observations in this note.

From sampling round to sampling round there have been some notable changes in reported TPH concentrations in the monitoring wells.  Overall, Round 3 showed an increase in reported levels of contamination.  This was more pronounced in the perimeter wells than the interior wells.  A total of 12 of the 40 wells where samples were analyzed had total TPH greater than 1,000 ug/L, versus only 5 in the previous round.

Round 3 analyses were performed by a new analytical laboratory, which achieved lower detection limits and therefore more precise measurement of low-level TPH.  Since total TPH is calculated using one-half the detection limit for not-detected TPH results (gasoline, diesel, or heavy oil), the lower detection limits should provide better estimates for total TPH.  (For an example of total TPH calculations involving not-detected results, see the February 2009 posting).

All TPH represents a mixture of a large number of different but related hydrocarbon compounds.  The analytical chemist at the laboratory designates the type of TPH based on a review of the output from the analytical instrument and a comparison to standard profiles; analyst judgment is therefore involved.

It is noteworthy that Round 3 results for a number of wells reflect a change in the dominant type of TPH (from TPH-G to TPH-D) versus earlier rounds and previous site characterization studies.  This is important because the cleanup level for ground water depends on the mixture of types of TPH present.  The separate numerical cleanup levels being used so far for the east and west sides of the Lower Yard reflect assumed TPH compositions that were developed from earlier ground water analyses.  Final compliance will be evaluated based on the actual composition found, so changes in the TPH composition (types) can affect cleanup levels and the status of the site.

The highest concentration of TPH continues to be found at MW-510 at the location of the former slops pond along the western site boundary.  The Round 3 result of more than 16,000 ug/L is more than 3 times higher than the Round 2 value.  Based on water levels measured in each sampling round, the ground water flow direction at that location is from the perimeter into the Lower Yard.  The upgradient side of this flow direction is within Willow Creek, which was substantially remediated during the recent Interim Actions.  I found no information indicating that the former slops pond was ever cleaned out.  It seems very likely to me that the MW-510 contamination is a localized response to residual contamination at the slops pond.

The southeast Lower Yard showed significant changes from Round 2.  TPH was detected at all 5 monitoring wells, from MW-129R at the corner of DB1 to MW-136 in the far southeast corner.  Three of these 5 wells had total TPH exceeding 1,000 ug/L, with the highest value of over 3,000 ug/L at MW-136 and the second highest of over 2,600 ug/L at MW-129R.  Over the long period of ground water monitoring at the site well MW-136 has shown quite an up-and-down pattern in TPH concentrations, with markedly elevated TPH levels following multiple sampling rounds with not-detected TPH.  The Interim Action soil excavations in the southeast Lower Yard covered virtually all of the areas nearby and upgradient from the current set of perimeter monitoring wells.  Unlike the central portions of the Lower Yard, there are no interior (Monitored Natural Attenuation:  MNA) wells in the southeast Lower Yard.

Several wells showed their first detected results for TPH in Round 3.  Monitoring well LM-2 at the northernmost corner of DB1 had over 1,800 ug/L total TPH.  Extensive sampling of DB1 soils after it was cleaned out showed almost no remaining TPH contamination.  Well MW-143, the most upgradient well in the western MNA system of wells, had over 2,000 ug/L total TPH.  With the exception of MW-143, the MNA plume wells had TPH results that were pretty consistent with earlier rounds.

A ground water cleanup level has also been established for benzene.  Well MW-20R along the western property boundary near the tidal basin marginally exceeded that cleanup level in Round 3, the first exceedance of the benzene cleanup level in the post-Interim Action monitoring program.  Benzene concentrations have increased at MW-20R over the first three rounds to levels much higher than at any other monitoring well.

The results for Round 4 sampling, occurring in April, should be available by mid-June.

The Final Phase I As-Built and Draft Phase II As-Built Reports are due to be submitted to Ecology on May 17^th.  Chevron submitted another report on March 27^th:  “2008 Additional Site Investigation and Groundwater Monitoring Report”.  The results from Rounds 1 and 2 of the post-Interim Action ground water monitoring program are presented in that report without any attempt to evaluate trends or status.  The results of the soil investigations that addressed “data gaps”, between Phases I and II of the Lower Yard Interim Actions, are provided and discussed.  Residual contamination near the WSDOT storm drain line is one of the main topics covered.  We will be submitting review comments on this report shortly.

More information related to this article can be found under "Additional Info" on the left margin.

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LOWER YARD 2007-2008 CLEANUP (INTERIM ACTIONS): UPDATE, FEBRUARY 2009

By Greg Glass

 

We completed our review of the first of two “As-Built” reports describing the Interim Action cleanup activities at the site.  That report covers cleanup actions through the Spring of 2008.  It provides an effective summary of those actions.  Our technical review comments were mostly editorial in nature and were submitted to Ecology and Chevron’s consultant, ARCADIS, on February 12, 2008.  The second As-Built report should be available within a few months.

The results of Round 2 ground water sampling, which occurred in December 2008, were submitted to Ecology by Chevron on February 13^th.  A total of 49 wells were inspected; no LNAPL product was observed in any of the wells.  [The correct number of wells being observed is 49, not 50 as previously cited].  Water samples from 40 wells were chemically analyzed for Total Petroleum Hydrocarbons (TPH) and related constituents.  More than half of those analyzed samples (21 of 40) had no detected TPH concentrations.  Included among the wells with no detected TPH in Round 2 were the two recently installed wells in the southeast Lower Yard that had elevated TPH in Round 1 – MW-500 and MW-501.  This reinforces the notion that conditions are better evaluated only after several rounds of sampling are completed.  It is noteworthy that the ground water levels in those two wells showed large changes between the October and December sampling rounds, unlike almost all other monitoring wells.  How that relates to the variation in TPH, if at all, is still unclear.

TPH is typically measured as one or more of three types based on composition:  gasoline, diesel, or heavy oil.  Total TPH is the sum of these three analytical measurements.  When all three types are reported as not detected (ND), the total TPH is also reported as ND.  When some but not all of the three types are ND, the total TPH value includes one-half of the detection limit for ND types.  For example, a sample with TPH-G, TPH-D, and TPH-O results of 100, <250, and <500 ug/L, respectively, would have total TPH reported as 100 + 125 + 250 = 475 ug/L, even though the only TPH actually measured and quantified was 100 ug/L TPH-G.  In some cases where the ground water cleanup level for the UNOCAL Edmonds site is exceeded this is largely because of the inclusion of one-half the detection limit for ND TPH results.  In an attempt to achieve lower detection limits and better characterization of site conditions, samples being collected in February 2009 will be sent to a different analytical laboratory.

Most wells with detected TPH were in the western half of the Lower Yard.  A few wells showed increases in total TPH from Round 1 to Round 2; more showed a decrease.  However, it is premature to evaluate any true trends in ground water contamination.  All but one of the monitoring wells where TPH was detected were mostly TPH-G.  The exception is MW-510, located at the former slops pond along the site boundary near Detention Basin 1 (DB-1).  TPH at that well is mostly TPH-D.  MW-510 had the highest reported total TPH concentration in Round 2 at over 5,000 ug/L, as well as the largest increase in total TPH.  Four other wells exceeded 1,000 ug/L:  two perimeter (compliance) wells, MW-104 and MW-518, and two interior wells (monitored for natural attenuation of ground water contamination), MW-502 and MW-514.

Benzene is another constituent being analyzed.  One well, MW-20R along the western site boundary near the tidal basin, had a large increase in benzene concentration to 22.2 ug/L, more than 7 times the result from Round 1.  This concentration is still well below the ground water cleanup level for benzene.

The results for Round 3 ground water sampling should be available by mid-April.

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LOWER YARD 2007-2008 CLEANUP (INTERIM ACTIONS): UPDATE, January 2009

By Greg Glass 

The first of two reports documenting all of the 2007-2008 Interim Action cleanup activities has been submitted to Ecology by Chevron’s consultants, ARCADIS (Phase I Remedial Investigation As-Built Report, UNOCAL Edmonds Bulk Fuel Terminal Lower Yard, January 8, 2009).  That first report provides information on the major soil excavation, product removal, and ground water treatment activities through the Spring of 2008.  ECAC received a copy of the report and will be submitting review comments to Ecology.

A second report (the Phase II As-Built Report) will be submitted within the next few months to document the results of additional site investigations (data gaps sampling), small additional soil excavation activities, and sediment remediation in Willow Creek that occurred later in 2008.

Ecology, the Washington State Department of Transportation, and Chevron have also been discussing the remaining soil contamination adjacent to the WASHDOT storm drain line at the site.  A separate report on alternatives to address that remaining contamination will also be prepared and submitted to Ecology by Chevron within the next few months.

Another major flooding event hit western Washington early in January.  Areas near Seattle and Edmonds were spared the worst effects this time by virtue of being largely in the rain shadow of the Olympic Mountains; areas to the north and south were hit much harder.  I visited the site just after the peak rainfall to observe conditions; water levels in the marsh, in Detention Basin 1, and in Willow Creek were all pretty high, but there was no significant flooding of the Lower Yard.

The planned two-year ground water monitoring program has started.  Results from the first round of sampling in late October 2008 are available.  Additional rounds of sampling will occur every two months.  A map of monitoring well locations and designation numbers has been added to the blog (see below).  A total of 40 wells are being sampled each round, with observations but no sampling in 10 additional wells.  There are two systems of monitoring wells being sampled:  a “perimeter” set of wells for compliance with cleanup levels, and an “interior” set of wells for natural attenuation of any remaining ground water contamination (see the text accompanying the well location map for details).  Refer to the map to pinpoint the locations of monitoring wells discussed in this and subsequent postings on the ground water monitoring results.

While the results of each monitoring round are being submitted to Ecology as they are validated, the first data evaluation report will not be prepared until after the first year of monitoring (6 rounds of sampling) is completed.  Only significant, and unexpected, observations – for example, the reoccurrence of a significant amount of product in wells - are likely to lead to any earlier decisions for actions beyond the planned ground water monitoring program.

After the soil and sediment excavations were finished, 25 new monitoring wells (numbered 500 through 524) were installed at the site to prepare for the ground water monitoring program.  A few replacement wells were also installed where existing wells retained as part of the long-term monitoring program had to be removed during excavations.  Those wells were all properly developed before any samples for chemistry analyses were collected.  Even so, it has been my experience that the initial round or two of sampling at newly installed wells sometimes produce results not typical of longer duration monitoring, which may reflect a degree of “new well effects”.  (Call this a personal bias).  Thus, I would suggest caution when reviewing the initial results.  Cumulative results over the first 4 to 6 rounds are likely to be more representative.

Results from round 1 sampling from October 2008 were reported to Ecology by ARCADIS in mid-December 2008.  No product (LNAPL) was observed in any of the wells.  The levels of Total Petroleum Hydrocarbons (TPH) at many of the wells were below detection limits, and overall ground water conditions throughout much of the soil excavation/product removal areas appear much improved.  Among the interior wells, the highest remaining concentrations approached 1,500 ug/L TPH, with slightly above 1,000 ug/L TPH-gasoline and lesser amounts of TPH-diesel (wells MW-502 and MW-514).

The highest TPH levels were reported at several of the perimeter monitoring wells.  One of the two new wells adjacent to the southeast Lower Yard, MW-501, had over 8,000 ug/L TPH (1,040 ug/L gasoline, 6,690 ug/L diesel, and 597 ug/L oil).  Excavations in the southeast Lower Yard were extensive and had indications of previously undocumented disposal activities.  The second new well in this area, MW-500, also had relatively elevated contamination with 1,180 ug/L TPH-diesel and 280 ug/L TPH-gasoline.  These two new wells provide the first ground water data for parts of the southeast Lower Yard, where the lack of significant historic operations had suggested lower impacts.  The high levels at MW-501 were not anticipated.  It will be interesting to see what the next several rounds of sampling show in this area.

The second highest TPH results from round 1 were reported for well MW-510, located near the southwest corner of Detention Basin 1 along the western property boundary.  The TPH at that well was over 3,700 ug/L, with 3,400 ug/L as TPH-diesel and a lesser amount as TPH-gasoline.  This well is at the location of the former “slops pond” associated with operations of the historic asphalt plant.  No significant soil TPH contamination was seen during the boring for this well.  We identified characterization of this slops pond area as a potential data gap in our comments to Ecology after completion of Phase I of the Interim Actions.

Several additional perimeter wells near the tidal basin and along Willow Creek had TPH concentrations marginally above the required ground water cleanup level of 706 ug/L for the western part of the Lower Yard.  The cleanup level for the eastern part of the Lower Yard is 506 ug/L.  The difference in cleanup levels reflects the historically different composition of TPH by location.  Final compliance decisions will be based on the actual measured composition of TPH at each well.

Results for round 2 sampling should be available within about a month.  We will provide an update once they are received.

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A Map of Ground Water Monitoring Well Locations: January 2009

Map of Ground Water Monitoring Well Locations:  2009

This map of the locations and designation numbers for ground water monitoring wells at the UNOCAL Edmonds site was prepared by ARCADIS and is shown here with their permission.  It provides a handy reference for identifying the locations of monitoring wells mentioned in blog postings.  To enlarge the map so that details, including well numbers, can be easily seen, use the magnification tool and scroll around on the map.

Of the 49 monitoring wells shown on the map, 9 are no longer being sampled for ground water chemistry analyses.  Those 9 wells are: 203 and 134-X in the eastern portion of the site; 13U, 122, E, and 131 in the central portion of the site; 126 and 151 in the western portion of the site; and 301 to the west of the site, across the railroad tracks.

The remaining 40 wells are being sampled every other month and include two sets of wells.  A “perimeter” set of 21 wells is being sampled for compliance with cleanup levels (from southwest to southeast along the site perimeter, those wells are:  150, 149R, 524, 147, 523, 8R, 522, 20R, 104, 101, 518, 139R, 510, LM2, 108, 109, 129R, 501, 500, 135, and 136).  An “interior” set of 22 wells is being sampled to evaluate the improvement in ground water quality (i.e., natural attenuation) after the Interim Action cleanup activities.  These Monitored Natural Attenuation (MNA) wells include three sets of 7 wells each along three ground water flowpaths (shown as elongated enclosed areas on the map), plus one additional well at a location where product (LNAPL) was present at the start of the recent Interim Actions.  The flowpath wells are:  East – 502, 503, 504, 505, 506, 507, and 508; Middle – 511, 512, 513, 514, 515, 516, and 517; and West – 143, 519, 520, 521, 522, 8R, and 523.  The additional well, in the north central portion of the site near Detention Basin 1, is 509.  Note that the three most downgradient wells in the West MNA system are near the property boundary and are therefore included in both the Compliance and MNA well systems.

The complicated numbering system for current monitoring wells results from the completion of wells at various times over the long history of site investigations and the retention of wells from earlier investigations within the post-Interim Action ground water monitoring program.  Many early wells have been removed in the course of various cleanup activities at the site.  This map will help readers follow events as the two-year ground water monitoring program unfolds through 2010.

Enlarge this figure by double-clicking.

LOWER YARD 2007-2008 CLEANUP (INTERIM ACTIONS): UPDATE, October 2008

By Greg Glass 

By the first week of October Phase II cleanup activities of the Lower Yard were clearly headed toward completion.  The major remaining task is the installation of a large number of new or replacement ground water monitoring wells.  An extended ground water monitoring program will start this Fall, and will provide information on the status of site ground water contamination after the large-scale remediation efforts.  I have visited the site to observe cleanup activities 12 times from early August through early October.

The cleanup of a segment of Willow Creek along the western margin of the Lower Yard was finished in late September.  Sediment removal was done to a planned depth below original grade with no additional confirmational sampling. After sediment removal and re-establishment of the original elevations with clean backfill materials, erosion control mats were placed and both banks were re-vegetated using native plant species.  Periods of higher rainfall during the sediment remediation program, while the coffer dams were in place, resulted in some ponding of water in the marsh upstream of the work area.  On September 26^th (a Friday) when the upstream coffer dam was removed water levels in the marsh were probably between 6 and 12 inches higher than below the dam.  I observed the removal of this upstream dam, which was done in a controlled manner to minimize erosion and siltation as water levels equalized.  A temporary silt plume still occurred but was contained by the fact that the downstream coffer dam was still in place.  It was removed the following Monday, September 29^th, after which Willow Creek was again free-flowing.  

Soil removal at the few remaining excavation areas was also completed during September.  The largest of these Phase II excavations was in the southeast Lower Yard (area B1), a location not used for normal bulk fuel plant (or asphalt plant) operations but apparently a location of some disposal activities.  A number of crushed drums, as well as assorted concrete debris, were uncovered during the excavation of that area.  A few seeps of product were also observed on hot days along the excavation sidewall, prompting additional soil removal.  Sampling of the sidewalls and floor of the excavation at the end of excavation activities showed no contaminant levels above removal criteria.

Small additional excavations were also completed at three locations next to Willow Creek (areas B7, B8, and B9).  Excavations at those three areas were suspended at the end of Phase I and the final work next to the creek was done in Phase II at the end of the period when sediment removals were occurring.  Based on the results of “data gaps” soil sampling, one new excavation area was added to Phase II near the southeast end of Detention Basin 1.  This was the location of the former asphalt plant warehouse.  The additional excavation area was relatively small compared to other Lower Yard excavations.  As with all of the previous soil excavation areas, confirmational sampling was done at these final Phase II excavation areas and showed no exceedances of soil removal criteria.

The Lower Yard Interim Actions clearly removed a very large fraction of the contamination that was present at the site as late as 2006, some 15 years after the end of bulk fuel plant operations.  (Earlier cleanup actions in the Lower Yard, and the Upper Yard, had also removed a substantial mass of contaminants).  Cleanup actions included the removal of free product, extensive excavation of contaminated soil, and pumping and treatment of a large quantity of contaminated ground water.  While almost all of the residual contamination has been addressed, the Lower Yard is still not pristine.  Soils below the removal criterion of almost 3,000 parts per million (ppm) total petroleum hydrocarbons (TPH) did not have to be removed, and confirmational sampling at the excavations has documented some residual soil TPH contamination up to that limit.  A small area near the Washington Department of Transportation storm drain line in the middle of the Lower Yard has substantially higher levels of contamination.  Those soils have not been removed so far because of the risks of damaging the storm drain line.  There is also a possibility (probably slight) that some relatively small areas of significant contamination have not been identified despite the extensive site investigations.

The purpose of monitoring ground water for a period of two years after planned physical cleanup activities have been completed (as they now are) is to document whether the remaining levels of contamination at the site will cause ongoing ground water quality problems.  That is, the ground water data will be used to determine whether or not the completed cleanup actions are sufficient.  Ground water monitoring will also determine how quickly any remaining ground water contamination, still present because of historic rather than current site contamination, diminishes.  The ground water monitoring program includes wells along the perimeter of the Lower Yard (compliance wells) and wells in the interior of the Lower Yard (natural attenuation wells).  More than 40 wells will be sampled and evaluated over the two-year monitoring period.  Existing wells will be used where they are available, but approximately 28 new wells will also be installed to prepare for the ground water monitoring program.  New well installations are scheduled to start on October 8^th and should be completed within about 10 days.  Ground water monitoring should therefore start by early November.

With completion of Phase II except for well installations, the removal of all of the equipment onsite has started.  For example, the automated vehicle wash station has been disassembled and removed, as well as all of the piping and pumps associated with the sediment remediation work and rerouting of Willow Creek flows.  Demobilization should remove all of the equipment and materials stored onsite during cleanup efforts, preparing the site for transfer to the Department of Transportation.

A full report documenting all of the Lower Yard Interim Action work will be prepared and submitted to Ecology in a few months.  We will be reviewing all of the ground water monitoring results as they are submitted and intend to provide updates here through the blog.

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