This article is related to April's 2009 ongoing action.

7558 Brooklyn Avenue NE

GREGORY L. GLASS Seattle, Washington  98115

Environmental Consultant tel:  (206) 523-1858

______________________________________________________________________________

MEMORANDUM

TO: David South, Ecology/NWRO

SUBJECT: UNOCAL Edmonds Site

2008 Additional Site Investigation and Groundwater Monitoring Report,

March 27, 2008

Review Comments

DATE: April 23, 2009

I have reviewed the March 27, 2009 report by ARCADIS on Additional Site Investigations during the recent Interim Actions.  On behalf of ECAC I am submitting the following review comments.  Please contact me if you have any questions or would like further discussion on any of these comments.

Technical Comments

Page 6, purposes of the additional site investigations.  I note that the area of the former slops pond was also identified as a data gap, particularly given the lack of any information that the slops pond area had ever been cleaned out during site operations or thereafter.  Information on the installation of one new monitoring well at that area (MW-510), and the results of soil samples collected during installation, will be included in the Phase II As-Built Report.  No additional soil borings were advanced in the area of the slops pond.  I recognize that detailed evaluations of ground water monitoring data will occur in the future.  However, given the ground water monitoring results for MW-510 to date, and the ground water flow direction maps that show flows into the Lower Yard near the slops pond, it seems likely to me that some residual contamination remains at the slops pond location.

Page 7, first full paragraph.  It is worth noting that the available locations for sampling in the vicinity of the former asphalt warehouse after Phase I was completed were constrained by the continued presence of the onsite WWTP for Interim Actions, which covered portions of the asphalt warehouse footprint.

Page 8, SB-80 results.  Soil boring location SB-80 appears to be far enough away from the WSDOT storm drain line that excavations there would not pose risks to the line.  The exceedance of RELs/CULs at SB-80 suggests there is another area of contaminated soils that could have been addressed as part of the Phase II Interim Actions.  An explanation of why it was not should be included, either in this report or the forthcoming Phase II As-Built Report.  (Note that SB-80 is close to MW-143 which had TPH above CULs in the February 2009 ground water sampling round).

Page 9, estimated volume of impacted soils.  There is a considerable interval (up to about 8 feet) between the last (deepest) sample that exceeded soil RELs/CULs and the next sample that did not in the soil borings near the WSDOT storm drain line (see Figure 8).  Was the depth of impacted soil, for the purposes of the volume calculation, assumed to be at the last interval exceeding, the assumed seasonal low ground water elevation, midway between the two adjacent samples bracketing exceedances, or something else?  The basis for the volume calculation should be stated.  (Note that the boring log for SB-66 has a notation of strong hydrocarbon like odor below the last sampled depth interval exceeding RELs/CULs).

Page 10, section 4.3:  asphalt warehouse area and section 4.4:  well MW-129 area.  It is worth noting that the boring logs for SB-76 and SB-78 both indicate that LNAPLs were observed.  Regarding the SB-78 boring log:  what is the “sample bag” referenced in the LNAPL notation?  Soil excavations apparently did not extend to include the SB-78 location near MW-129; the reported soil TPH concentration at the same depth interval where the LNAPL notation occurred was low.  Is there a reason to doubt that the LNAPL notation was accurate?  Given that one objective of the additional soil investigations was to evaluate possible sources of LNAPLs that had been reported historically at MW-129, some additional discussion on the boring log observation at SB-78 is warranted.

Page 11, soil excavations near MW-129 and the former asphalt warehouse.  The text states that the additional soil excavations during Phase II, based on the results of additional site investigations, were extended to include SB-76, SB-77, and SB-79.  (See also page 22).  The locations of the soil borings and the additional soil excavations as shown in the Figures (for example, Figures 4 and 5 versus Figures 11 through 15) do not appear to show excavations extending to SB-77 and SB-79.  Are locations shown accurately on the Figures?  Did soil excavations actually get as close to MW-129 as SB-77 and SB-79?  (I do not recall that they did, but perhaps I am mistaken).  Please review survey information for these locations and revise the text and figures as needed.

Page 12, identification of POC and MNA wells.  The three most downgradient wells in the west MNA system (MW-522, MW-523, MW-8R) are located very nearly on the property boundary.  I noted during our 2007 discussions on the Interim Action work plans that it would be difficult to conclude the site was in compliance with ground water CULs if any of those wells had concentrations above the CULs, given their location.  On that basis I proposed, and I recall we agreed, that all three most downgradient wells in that MNA system would also be evaluated as POC wells.  Only MW-8R is so designated in this report, while also being included as an MNA well.  Wells MW-522 and MW-523 should also be noted as being both POC and MNA wells.  This will increase the total number of POC wells to 21, and the discussions of the October and December 2008 ground water sampling rounds should be updated to reflect this change (e.g., 6 of 21 POC wells exceeded CULs in October 2008).

We also agreed that a single well, MW-509, that is not in any of the three MNA “plumes” would be evaluated for natural attenuation.  Prior to the start of 2007 excavations the maximum observed thickness of LNAPLs occurred in that area, and in lieu of a complete “fourth plume” system we agreed that a single well would be sampled and evaluated there.

The description of the 40 monitoring wells being sampled therefore should be as follows:  21 POC wells around the perimeter of the Lower Yard, 22 MNA wells including three “plume systems” of 7 wells each plus MW-509, and with 3 wells in both the POC and MNA systems (i.e., 40 = 21 + 22 – 3 “duplicates”).

Page 12, CULs.  I understand that detailed evaluation of ground water monitoring data will not occur until later.  I note, however, that the different TPH CULs for the east versus west portions of the Lower Yard were derived based on typical TPH compositions as determined from historic ground water monitoring results.  Final compliance will be based on the actual TPH compositions as measured during the current monitoring program (a matter of some interest given changes in the reported composition for some wells in the February 2009 sampling round).  I recommend that a footnote be added to the two bullets with TPH CULs that says the following:  “Ground water TPH CULs presented here were derived based on historic TPH composition data; final CULs for each POC well will reflect the actual composition of TPH as measured at that well.  All data presentations in this report are based on the default TPH CULs shown here”.

Page 12, statistical analysis of compliance with ground water CULs.  There are likely to be considerations besides a statistical calculation of the mean concentration involved in compliance decisions.  For example, even if the mean (UCL) over all 12 sampling rounds, or the last 6 rounds, meets the CULs, it would be difficult to conclude that ground water is in compliance if there was an increasing trend at a POC well – especially if the last one or two sampling rounds showed exceedance of a CUL.  The CUL to which a statistically calculated mean should be compared should also take into account the variability in TPH composition documented for a well.  Finally, the spatial characteristics of ground water contamination in the interior of the Lower Yard may not be in accordance with the assumption of “plumes” with spatial continuity.  This may affect the applicability of standard approaches to evaluate “plume stability”.  All of these detailed issues related to compliance will be ripe for evaluation as long-term ground water monitoring data are compiled.

Page 13, monitoring well installations.  Please clarify the status of MW-122.  The text identifies a total of 29 wells installed in October 2008, including 25 new “500” series wells and 4 replacement wells:  MW-149R, MW-8R, MW-139R, and MW-129R.  On Figure 11, MW-122 has footnote 1 which states “monitoring well was abandoned during interim action and replaced in October 2008”.  The text in section 4.4 (pages 10-11) which discusses additional investigations in the MW-129 area states that MW-129 was decommissioned and replaced, but does not mention MW-122.  If MW-122 was in fact replaced (perhaps it was so close to MW-129 it had to be abandoned and replaced because MW-129 was being replaced?) the text on page 13 should be updated to reflect 30 well installations.  If not the footnote on Figure 11 should be removed.

Page 15, water levels and ground water flow direction contour mapping.  See also Table 2.  The large, anomalous rise in ground water elevations at MW-500 and MW-501 between October and December 2008, as shown in Table 2, should be noted in the text.  For these wells, the December 2008 measurements are not “consistent with past measurements”.  MW-135, located next to MW-500 and MW-501 in the southeast Lower Yard, showed a significant decrease over these two months and is also not consistent with the general pattern over the entire Lower Yard.   It is questionable whether the December  MW-135 elevation should be used for contouring (see Figure 13).  The general pattern of ground water flow directions would not be markedly affected by the omission of the MW-135 value.  The October 2008 water level at MW-524 also appears anomalous and should be considered for omission for contouring.

Table 5.  The pH at well LM-2 at the northwest corner of DB1 was anomalously low (<4) both in October and December 2008.  Is there any prior pH data for that well that is consistent with such low readings?

Appendix C, ISI Low-Flow Logs.  This appendix presents data as recorded, which is sufficient for this report.  Detailed evaluations are not presented here, but when they are provided (Year 1 and Year 2 annual ground water monitoring reports) a number of items merit discussion and a screening process to delete unacceptable data should be completed.  There are some indications of meter malfunctioning.  The last readings for MW-500 in October, for example, include a temperature of 87.65 degrees F (very unlikely) and a dramatic change within minutes for other parameters.  There are repeated notations that ORP did not stabilize before samples were collected, and cases where only one set of readings was obtained before sampling (see LM-2 in October).  A few wells show high and variable turbidity values (see multiple well records in December), which may indicate a meter problem or a well screen or well development issue (although these wells had much lower turbidity in October).  If these ISI data indicate some potential questions about the field monitoring equipment or the condition of monitoring wells it would be very desirable to address those questions now and take appropriate actions as required, so that high quality data can continue to be collected for later evaluation.

Minor Edits

Page 5, first paragraph.  The statement that the WSDOT storm drain line crosses the Lower Yard at a depth of 9 to 12 feet bgs, given that the line is described as a 72-inch line, is unclear.  Compare to Figure 8, showing the line extending from about 8 to 14 feet bgs.  Is this sentence on page 5 intended to describe the top of drain line elevation as it varies across the site?  Consider rewording the text for clarity, and consistency with Figure 8.

Page 6, third paragraph below bullets.  Change “…in the most southeastern portion of the Lower Yard…” to “…in the most southwestern portion of the Lower Yard…”.

Page 8, first bullet.  Add TPH-O as a listed analyte.  Compare to the third bullet at the top of page 14.

Page 9, bottom paragraph.  Since none of the soil samples collected as part of the additional site investigations near the former railroad trestle area exceeded RELs or CULs, the areas of impacted soils are better characterized as having been “confirmed” by the additional site investigations rather than “identified” by those investigations.

Page 19, fourth bullet.  Change “surrogate percent recovery were…” to “surrogate percent recoveries were…”.