FOLLOW UPREVIEW COMMENTSDATE: 6/25/04Item LocationNo.IIPROJECT: Gambell DOCUMENT: Draft Proposed PlansLOCATION: St. Lawrence Island, AlaskaPHONE: 269-3053REVIEWER: Jeff Brownlee (ADEC)COMMENTSReviewConference1.Page 5Please expand the discussion that the area around Gambell is notsuitable for drinking water. Please briefly discuss the extent ofpermafrost and the location of the village water supply aquifer.It may be helpful if the footprint of the aquifer can be overlayedon figure 2 or reference Figure 4. Jim Munter's hydrology reporton the aquifer may have an inferred boundary map.2.Page 9Site 2Please add "(See Figure 3)" at the end of the first sentence.Please expand the discussion about the UXO investigation andnote that the area was included in an investigation targetedspecifically for unexploded ordinance using geophysics andanomaly verification.IIAlaska District ResponseFigure 4 was revised to more clearly indicate the estimated aquiferboundary, and a reference to this figure was added on Page 5. The textwas also expanded as follows:Groundwater from the central gravel spit is not suitable as a source ofdrinking water. Groundwater in the gravels is often saline, difficult torecover in useable quantities, and located in an active lens overpermafrost. Drinking water wells installed in the gravel have beenabandoned in the past. Groundwater encountered at the site has beenlimited in quantity, and only intermittently detected. Permafrost inGambell is conunonly encountered at depths ranging from 3 to 15 feetbelow the ground surface. The village water supply is located at thebase of Sevuokuk. Mountain, on the far eastern edge of the gravel spit(see Figure 4). According to a State of Alaska hydrogeologicalinvestigation report (Ireland, 1994), the Gambell aquifer is canoeshaped, originating along the front of the steep bluff of Sevuokuk.Mountain, and continuing down the hydrological gradient across ahighly permeable gravel bar to the ocean. The aquifer appears to be athaw bulb in the permafrost, and as the permafrost expands or recedes,the aquifer dimensions vary. The influence of warm recharge waterfrom Sevuokuk. Mountain has produced the thaw bulb effect on thearea permafrost. The majority of the water recharging the aquiferoriginates from two springs that flow from the steep bluffs of themountain into the gravel. Shallow groundwater across the gravel spitdoes not appear to be continuous because of the presence of shallowpermafrost (Munter and Williams, 1992).Reference to Figure 3 was added.Discussion of ordnance was expanded as follows:Earth Tech, Inc. conducted two geophysical surveys at Site 2 duringJuly and September 2000, to determine the presence or absence ofburied ordnance. First, the field team visually surveyed the area andremoved metallic scrap and debris from the surface. Next, metaldetectors were used map the location of subsurface anomalies overthree site grids. Each target location was then further investigated,excavated and searched for the source of the metallic anomaly. Noevidence of any ordnance was found during the investigation.200-1fF10AK069603_08.12_0004_8FOLLOW UPREVIEW COMMENTSDATE: 6/25/04Item I LocationNo.IPROJECT: Gambell DOCUMENT: Draft Proposed PlansLOCATION: St. Lawrence Island, AlaskaPHONE: 269-3053REVIEWER: Jeff Brownlee (ADEC)COMMENTSReviewIConferenceIAlaska District Response3.General,Site 2, 9,13These sites have been proposed for closure using the ingestionpathway; however there does not seem to be any contaminantconcentration exceeding migration to groundwater levels. Pleaseuse the more conservative migration to groundwater pathway forthose sites that meet the cleanup levels. Exceedences of arsenicand chrome in the majority of locations would be consideredbackground and would not exclude the site from meeting themigration to groundwater pathway (see next comment).The Cleanup objective subsections will remain ADEC Method 2 soilcleanup levels based on the Ingestion pathway, following the rationalepresented on pages 4-5. However, a statement was added to thePreferred Alternative subsections for Sites lA, lB, 1C, 8, 9, 13, 16, 17,24, 25A, 25B, 26, 27, and 28 which states:Site X also meets the more stringent ADEC cleanup levels based on theMigration to Groundwater pathway.Site 2 does not meet the soil cleanup levels based on the Migration toGroundwater pathway if you consider the disposal characterizationsamples collected from the excavated soils by aSCI to be equivalent tothe potential concentration of DRO remaining in the gravels (which isunknown). Site. 2 does meet the Ingestion cleanup levels, and thepotential remaining DRO-contaminated soil may be attributable to nonDOD sources.4.Table3,Arsenic,chromiumlevelsthroughoutPlease change the table to 26 mg/kg for chromium and changethe cleanup level mentioned in the text to 18 AAC 75.341 ratherthan the EPA Region 3 RBCs. Plotting the average of the resultsfor chromium and arsenic and attributing the levels tobackground would be a reasonable approach. There was the oneoutlier at Site 2 and the detections at site 7 which are planned forremoval. The one at site two can just be considered an outlierthat couldn't be reproduced. This approach eliminates the needto try and qualitatively explain exceedences.Table 3 was revised to show Screening Levels based on ADEC18AAC75, Migration to Groundwater levels. Text was revised to state:Only one sample from 1994 exceeded the screening levels forchromium and lead. The 12 other soil samples contained low levels ofchromium (ND to 21 mg/kg) and lead (1 to 70 mglkg). Chromiumwas not considered a contaminant of concern following the 1994investigation. During 1996, further soil sampling was conducted todetermine the extent of lead contamination. Eight surface soil sampleswere collected and analyzed for lead only. Sampling results areshown in Table 3. The 1996 results were significantly lower,indicating the 1994 sample was an isolated occurrence. The averagelead concentration at the site does not exceed the ADEC cleanuplevels. The maximum chromium concentration is considered anoutlier. See Table 3 for a summary of the Phase II results. Althoughthe detected arsenic concentrations exceed the ADEC cleanup level,the levels are consistent across many sites in Gambell, and do notappear associated with past military activity.5.Site 3Please add "See Fig. 3" in the site description.See Figure 3 added to site description.In 1994 added to Investigation summary.Sentence added to paragraph which states: Both monitoring wells arePlease add "in 1994" after "Phase I investigation" in theInvestigation summary.FOLLOW UPREVIEW COMMENTSDATE: 6/25/04Item LocationNo.IIPROJECT: Gambell DOCUMENT: Draft Proposed PlansLOCATION: St. Lawrence Island, AlaskaREVIEWER: Jeff Brownlee (ADEC)PHONE: 269-3053COMMENTSReviewConferenceIIAlaska District ResponseInvestigative Sununary - please mention in the paragraph aboutthe lead exceedences in groundwater that the site is downgradientof the drinking water supply well.located downgradient of the village drinking water supply well.6.Site4AIn the "Preferred alternative" section - there were contaminantconcentrations that exceeded cleanup levels. Please change thetext from "there were no contaminants above..." to "cleanup upto the extent feasible, as there is minimal soil above bedrock.Paragraph revised to state:No Further Action. All hazardous debris and contaminated soil wereremoved during the 1997 and 1999 field seasons. Site 4A has beencleaned up to the extent feasible, as there is minimal soil above bedrock.7.Site4EPreferred alternative - are there plans to remove the debris underNALEMP?Yes. Sentence added to Preferred Alternative subsection which states:The debris is not eligible for further action under FUDS. However,NALEMP plans to address the remaining debris at this site.8.Site 5Preferred alternative - are there plans to sample these monitoringwells two more times? After the detection of 1.9 mg/kg DRO in1998 an investigation of the water supply well and thesurrounding monitoring wells was done. Please mention thisstudy here.No further studies have been performed since the 1998 investigation.,which recommended one additional season of groundwater monitoring.Text of Preferred Alternative subsection revised to state:No further action. However, one additional round of groundwatersampling will be conducted to confmn groundwater does not exceedADEC Table C cleanup levels. Existing monitoring wells at Site 5 willbe sampled at upgradient and downgradient locations to verify thatdiesel range organics are not impacting the Village water supply well.9.Figure 4If this blue line is the inferred aquifer boundary, please note onthe figure.Figure 4 revised to more clearly indicate the inferred aquifer boundary.10.Site 6Cleanup Action - Please delete the word "gross" in the lastsentence and say that about 2 Y2 tons of impacted soil wereremoved. Please reference the NALEMP report.Text of Cleanup Actions to Date subsection revised to state:According to the fmal report (MWH, 2004), approximately 1,000 drumsand other debris, and 2.5 tons of fuel-contaminated soils wereexcavated. There was no notable evidence of fuel contaminationassociated with the buried debris.11.Site 9Site description - are there more drums remaining? Maybe wecan just say all the drums were removed.There are no drums remaining. Text of Site Description revised to state:This site is located on the east side of the local airport runway. Drumsleaking tar were observed in two areas. A debris inventory preparedby Montgomery Watson in 1997 indicated drums containing asphalt(6,200 estimated pounds) and empty drums (900 pounds) were locatedwithin Site 8, which includes the area referred to as Site 9. Theasphalt drums were initially attributed to non-military activities duringthe Phase I investigation and not investigated further.12.Site 15Please expand the description on the UXO investigation andText ofInvestigation Summary subsection revised to state:FOLLOW UPREVIEW COMMENTSDATE: 6/25/04ItemNo.l Location IPROJECT: Gambell DOCUMENT: Draft Proposed PlansLOCATION: St. Lawrence Island, AlaskaREVIEWER: Jeff Brownlee (ADEC)PHONE: 269-3053COMMENTSReviewConferenceIreference the EE/CA document.IAlaska District ResponseDuring 2000 and 2001, Troutman Lake was investigated usinggeophysical surveying techniques. The entire lake bottom wasmapped along a series of transect lines, to detect underwateranomalies representative of piles of steel ammunition boxes. Metallicanomalies detected by the equipment were then further investigatedusing ice augers, depth sounding equipment, poles, and an underwatervideo camera to determine the source of the metal signal. An openwater investigation was also conducted to verify the anomaly sourceusing dredging anchors, depth-sounding leads, and an underwatercamera. Anomaly locations within 20 feet of the lakeshore wereverified by visual inspection. The source of the magnetic anomaliesranged from runway matting and 55-gallon drums, to geologic featuressuch as iron or other mineral deposits. No evidence of ordnance orlarge piles of ammunition boxes was discovered in Troutman Lake.Additional details regarding the ordnance investigation can be foundin the report Final Engineering Evaluation/Cost Analysis (Earth TechInc., 2002).