letter transmitting the response to comments on the draft

• H G L ^ 7 HydroGeoLogic, Inc hiit.sfi.ynvOprniii

E x c e e d i n g E x p e c t a t i o n s

May 29, 2009

Mr. Jim Seller AES Project Officer U.S. Environmental Protection Agency, Region 7 901 North 5* Street Kansas City, KS 66101

RE: Final Remedial Investigation/Feasibility Study Work Plan for the Garvey Elevator Site, Hastings, Nebraska. U.S. EPA Region 7 AES Contract No. EP-S7-05-05; Task Order Nos. 0033 and 0034 EPA Task Order Project Officer: Brian Zurbuchen, Ph.D.

Dear Mr. Seller:

HydroGeoLogic, Inc. (HGL) is pleased to submit two hard copies of the final Remedial Investigation/Feasibility Study (RI/FS) Work Plan for the Garvey Elevator (OUl and 0U2) Site, Hastings, Nebraska. This document was prepared in accordance with Task Orders 0033 and 0034; our EPA-approved Task Order 0033 Proposal Revision 1 submitted to EPA on September 26, 2008; the Task Order 0034 Proposal Revision 2 submitted to EPA on October 15, 2008, comments to die draft RI/FS Work Plan received from the EPA oh April 3, 2009, the revised investigation approach submitted to EPA on Febmary 12, 2009, and several EPA communications from January 2009 to May 2009. A memorandum outlining the response to comments to the draft RI/FS Work Plan is also enclosed.

As requested by EPA, an additional hard copy of the final RI/FS Work Plan will be sent to Laurie Bmnner at the Nebraska Department of Environmental Quality. Should you have any questions or comments, please contact us at 913-317-8860.

Sincerely,

W. Alan Rittgers, HGL Task Order

^ -Ppjpf (_^yjcpyuAr'^ py>e^

Robert C. Overfelt, P.O., CHMM

AES Program Manager lllllIlffii™i?| IIIIIIII ||||

Enclosures Superfund

8245 Nieman Road, Suite 101, Lenexa, KS 66214 • Phone:(913)317-8860 Fax:(913)317-8868 "

www.hgl.com

http://www.hgl.com

• H G L ^ HydroGeoLogic, Inc kti/i.'«i.\ ( ih- Ojir/tilioii.s

E x c e e d i n g E x p e c t a t i o n s

RESPONSE TO EPA COMMENTS ON THE DRAFT RI/FS WORK PLAN

GARVEY ELEVATOR SITE - HASTINGS, NE

TO: FROM: THROUGH: CC: DATE: SUBJECT:

CONTRACT NO:

Jim Seller, EPA PO Alan Rittgers, HGL Task Order Manager Robert C. Overfelt, P.O., CHMM, HGL Program Manager Brian Zurbuchen, Ph.D., EPA Task Order Project Officer May 29, 2009 Response to Comments on Draft Work Plan, Remedial Investigation/Feasibility Study, Garvey Elevator Site, Hastings, Nebraska (submitted to EPA December 30, 2008) EP-S7-05-05

TASK ORDER NOs: 0033/0034

Reviewer Comments provided by the EPA Task Order Project Officer on April 3, 2009.

TECHNICAL ERRORS:

Comment 1 Text states that 20 fig/I converts to 131 ixg/m . The text further explains that the conversion factor is Ifig/l to 6.55 fxg/m . These statements are erroneous. Please revise accordingly.

Response The text has been revised to reflect that 20 /xg/L converts to 20,000 /xg/m^ and that 1 /ig/L is equal to 1000 /xg/m^

GENERAL COMMENTS

Comment 1 Numerous descriptions of previously performed environmental investigations and response actions identify a consultants (e.g. HWS, ENSR) as the party taking action (i.e. collecting, presenting, implementing, etc.). This creates confusion and is inaccurate. The consultants performed work on the behalf of the potentially responsible party (PRP). Modify the text throughout to indicate the PRP as performing the actions, with references to the appropriate reports.

Response The text has modified throughout the document to indicate either that the PRP or the PRP contractor performed the work, depending on the sentence stmcture. References to various contractors have remained where it is necessary to distinguish between different sets of data and/or results without making the text too cumbersome.

8245 Nieman Road, Suite 101, Lenexa, KS 66214 • Phone:(913)317-8860 Fax:(913)317-8868 "

www.hgl.com

http://www.hgl.com

HGL~Response to EPA Comments, Draft RI/FS Work Plan, Garvey Elevator Site OUl and OUl—Hastings, NE

Comment 2 The text indicates formal reports, summarizing the investigations conducted by Garvey during the period they were under the Administrative Order on Consent, were not submitted to EPA. While the final report as described in the Soil Vapor and Groundwater Extraction and Treatment System Evaluation Work Plan (Revision I) (April 2006), was not submitted, the majority of work performed by ENSR on behalf of Garvey was documented in the series of monthly progress reports and other written communications. Revise document throughout to indicate this.

Response The text has been revised throughout the document to indicate the submittal to EPA of monthly activity reports.

Comment 3 Previous actions taken by the property owner/operator should be referred to as response actions, not remedial actions. Remedial action implies a phase of activity in the Superfiind cleanup process, whereas response actions are any actions taken to address a situation. At this site, actions were performed by the owner/operator prior to notifying the state and prior to the site being listed by EPA on the NPL. Therefore, it is more appropriate to refer to them in the general sense as response actions. Please modify text accordingly.

Response The text has been revised throughout the document to state that the PRP performed response actions.

Comment 4 Section 3 of the Work Plan summarizes previous investigations and response actions taken by Garvey, the NDEQ, and EPA. Instead of limiting the content of this section to the above, it should also include development of a conceptual site model (CSM) that presents sources, pathways, receptors, and routes of exposure (refer to Figure 2-2 of 1988 EPA RI/FS Guidance). The CSM along with the PRGs make it straightforward to identify the data gaps in the existing data and identify the areas of uncertainty. Revise accordingly. Note that some additional specific comments on Section 3 are provided below.

Response Section 4.0 CONCEPTUAL SITE MODEL has been added to the Work Plan. The format of this CSM section is consistent with the EPA guidance document referenced by the reviewer, and the conceptual site model section in the Final Site Characterization Work Plan for West Highway 6 and Highway 281 Site, Hastings, Nebraska that was approved by EPA Region 7.

SPECIFIC COMMENTS

Comment 1 Section 1.1.2, 7^ Paragraph - Include a bullet identifying the development of a conceptual site model as one of the data evaluation activities.

Response The text has been revised per reviewer comment.

Cirvey Elcvtior Site RTC

U.S. EPA Region 7 2 HydroGeoLogic, inc. Miy 2009

HGL—Response to EPA Comments, Draft RI/FS Work Plan, Garvey Elevator Site OUl and OUl—Hastings, NE

Comment 2 Section 1.2.1, 1" Paragraph -Paragraph is poorly worded and in some cases factually incorrect. Modify paragraph and figure appropriately according to the following: Site boundary defined on Figure 1.2 is not accurate in the northeast portion of the property. Refer to pages 2183 and 2184 of Garvey Elevator's November 18, 2003 response to NDEQ's request (Garvey 2003a) for the appropriate legal description of the Garvey Elevator property boundary as of 1958. At some point (not sure of exact date), Garvey sold a parcel (ID 010003206) of about 4 acres along the northern property boundary, to Alliance Electric Company and others. Revise language to indicate appropriate dates of ownership. Note that construction of the elevator began in 1959. Garvey operated the elevator until April 1, 1998, at which time a put-through agreement with AGP Grain Marketing, LLC (AGP) became effective. AGP purchased the property from Garvey in September 2005 pursuant to an Agreement (CERCLA Docket No. 072005-0268) between EPA, AGP, and Garvey Elevators. AGP currently owns and operates the grain elevator.

Response The paragraph has been reworded per the reviewers comments. However, the pages indicating the legal description of the site property land parcels referred to by the reviewer are not legible in the HGL copy of the Garvey response to the NDEQ request. Therefore, HGL added the legal description of the site property land parcels from the Adams County Assessor documents accessed online from an Adams County GIS database website. This website was added to the cited references.

Also, Figure 1.2 has been revised to reflect the boundary of the AGP-owned site property land parcels as indicated by the Adams County GIS database.

Comment 3 Section 1.2.1, 2^ Paragraph -This paragraph does not belong in this section that describes the site and current use. Move to Section 1.2.3.

Response The paragraph in question has been moved to Section 1.2.2 General Site History. HGL believes a brief description (including dates) regarding installation of monitoring wells and source controls is more applicable to discussion of site history than Section 1.2.3 Regulatory History. The response actions were not conducted at the direction of a regulatory agency.

Comment 4 Section 1.2.2, P' Paragraph - The first sentence begins, "The site began operation..." Please modify to the following: "Garvey Elevators began operation..."

Response The sentence has been revised per reviewer comment.

Comment 5 Section 1.2.2 -This section appears to be regurgitated from previous reports and does not include information gleaned from the interviews with former employees

Girvey Ele /alor Site RTC

U.S. EPA Region 7 3 HydroGeoLogic, Inc. Miy 2009


conducted by EPA in October 2008. Revise as appropriate. Specifically address the use of EDB, slow leak at fittings, no mention of broken and/or repaired buried pipe section, etc.

Response Per the reviewer comment, Section 1.2.2 has been revised to include information obtained during the October 2008 interviews of former Garvey employees. Text was added to Section 1.2.2 that the former employees did not recall the pipe being dug up and fixed, but rather leaks at fittings were fixed periodically, which contradicts an ENSR letter to the Garvey attorney that indicates a break in the pipe was fixed. The use of MaxKill 10, and the presence of EDB in this fumigant mixture also was included in the text.

Comment 6 Section 1.2.2, 3"' Paragraph -This paragraph does not below [sic] here. Please move to the regulatory history.

Response The paragraph has been moved to Section 1.2.3 Regulatory History.

Comment 7 Section 1.3 -Move paragraphs 5 -7 forward in the section so they are the 2"'' through 4'' paragraphs. The Hastings city ordinance is a component of the selected remedy for the Area-Wide Operable Unit of the Hasting Ground Water Contamination Site, as described in the July 2001 Interim Action Record of Decision. EPA can provide a copy if HGL doesn 't have one already. The city is one of several PRPs that has entered into a Consent Decree with EPA to implement the remedy. First paragraph of the section should establish the importance of groundwater beneath area as a natural resource, the extensive nature of aquifer, the high transmissivity of the aquifer. Second paragraph should consist of material from your 5"' paragraph of the section. Move your 6"' and 7* paragraphs to be the 3"* and 4'' paragraphs, respectively. Introduce the area-wide operable unit (0UI9) of HGCWS in the last part of the new 4"' paragraph. Refer the reader to the administrative records for the West Hwy 6 & Hwy 281 site and HGWCSfor additional information. Move your 2"^ 3"' and 4" paragraphs to be the new J'*, 6"' and 7'' paragraphs.

Response The paragraph generally has been reorganized as indicated by the reviewer. HGL did retain as a second paragraph the following text:

"As early as 1983, the State of Nebraska had concerns regarding VOCs in groundwater, including commercial grain fumigants that were detected in the Hastings municipal water supply. Municipal supply wells #13 and #14 were taken out of service as a result of contamination, and other contaminated municipal wells have been placed on standby. Community Municipal Services, Inc., a private water supply system formerly servicing the areas east of Hastings, also took two of its three wells off-line due to contamination (USEPA, 2006)."

Garvey Elevator Siie RTC

U.S. EPA Region 7 4 HydroGeoLogic, Inc. May 2009


The above second paragraph then leads into a paragraph 3 beginning, "In addition to the Garvey Elevator Site, there are two...", which would have been the reviewer's second paragraph. HGL believes it critical that the above background information regarding impacted community water supply wells due to contaminated groundwater in the Hastings area is included in this section on area-wide groundwater contamination.

Comment 8 Figure 1.3 -Figure was compiled from different sources of information. There is no mention of this on the figure. For the West Hwy 6 & Hwy 281 site, display the gw plume as delineated during the RI/FS activities. Remove Three Points Tire designation for the CCU plume on the east side of the figure. Unless there is more than one sampling point for the plume, then remove it.

Response

Comment 9

Figure 1.3 has been revised per the comment. The older West Highway 6 & Highway 281 site PCE plume outline on Figure 1.3 has been replaced by the plume delineated during the RI/FS activities. The Draft RI Report for West Highway 6 & Highway 281 Site has been referenced on the figure. Also, the Three Points Tire plume has been removed from the figure. The remaining plumes on the figure were provided along with the base maps by Hasting Utilities (HU) from their GIS database. The HU GIS information was obtained by HGL for the West Highway 6 & Highway 281 Site, and has been adapted as a figure to illustrate generalized plumes in the Hastings area. HU is referenced on the figure.

Section 2.1, 4'' Paragraph -The text indicates that no wells can be installed without first being permitted by the Little Blue NRD. Confirm the accuracy of this statement. It is likely this only applies to industrial, municipal and irrigation wells and not to domestic wells of limited capacity.

Response HGL examined the Little Blue NRD rules and regulations posted on their website. They indicate that wells, or series of wells, that pump more than 50 gallons per minute (gpm) require permits. The text in question has been revised to reflect this information.

Comment 10 Section 3.0 -Include a subsection that describes the Contaminants of Concem (as based on past investigations and response actions) and the Contaminants of Potential Concern (based on known usage of pesticides, herbicides, etc.). As an example, PCBs would be COPCs since the site had its own large liquid filled transformer over the period of known PCB use. Include reference to the current Table 3.1 in this section. Discuss the pesticide formulations used, storage, methods of application, and periods of use. Summarize general storage and application procedures (include information from recent interviews).

Garvey Eli valur Site RTC

U.S. EPA Region 7 5 HydroGeoLogic, Inc. May 2009

HGL—Response to EPA Comments, Draft RI/FS Work Plan. Garvey Elevator Site OUl and OUl—Hastings, NE

Response Secdon 4.0 CONCEPTUAL SITE MODEL has been added to the Work Plan. This section includes a Subsection 4.1 HISTORICAL SOURCES OF CONTAMINATION that examines chemicals of concern and chemicals of potential concern related to both known and potential sources. These discussions include pesticide formulations, application procedures, and chemical storage practices. Information sources include the Garvey response to the 104E request and the EPA interviews in October 2008. Also, Section 5.1 has been renamed CHEMICALS OF KNOWN AND POTENTIAL CONCERN and now addresses in separate paragraphs the known and potential chemicals of concern that remain to be evaluated based on the discussion in Section 4.0 CONCEPTUAL SITE MODEL.

Comment 11 Section 3.1 - This section should be titled something like "Known and Potential Source Areas." Discuss areas of application of the various fumigants and handling. Discuss that there are discrepancies between information presented in previous reports regarding how the Maxkill 10 was released to the environment. Historic reports mention a leaking buried pipe that was replaced, but interviews suggest main source to have been a consistently leaky valve on the tank. Discuss other potential sources of these or other COCs or COPCs. Note that the text in the second paragraph states that the leak occurred at a fitting. My recollection was that the leak occurred at the valve and that periodically, the valve was replaced. Note that the memorandum summarizing the interviews refers to leaks at fittings. Fittings is a more general term for a small standardized part, whereas valve is a mechanism to opens, shuts, or partially obstructs a passageway. Review notes from the interviews and revise as appropriate.

Response The Section 3.1 header has been changed to "KNOWN AND POTENTIAL SOURCE AREAS". A sentence also has been added at the end of Section 3.1, as follows: "A detailed discussion of known and potential source areas and their associated contaminants of concern and potential contaminants of concern is provided in Section 4.0 below." Section 4.0 CONCEPTUAL SITE MODEL has been added to the Work Plan. This section includes a discussion of known and potential source areas and the contaminants or potential contaminants related to them. Conflicting information from the various information sources also is discussed. Also, see the response to Comment #10 above.

Regarding use of the terms "valve" or "fitting", HGL notes taken during the interviews show that interviewees used the term "fitting". Therefore, the term "fitting" has been retained in the work plan document. As the reviewer stated, "fitting" is a more general term, which includes the more specific term "valve" and other specific parts of a liquid delivery system. Because interviewee historical recollections can be vague; usage of the term "fitting" may be more appropriate to describe the point of leakage from the liquid fiimigant delivery system at the Garvey site.

U.S. EPA Region 7 Garvey Elevator Site RTC 6 HydroGeoLogic, Inc. May 2009


Comment 12 Section 3.2 -The first sentence should also include NDEQ as having previously conducted investigations at the site. Revise accordingly.

Response The first sentence of Section 3.2 has been revised per reviewer comment.

Comment 13 Section 3.2 -The first paragraph includes only four of the six COCs for the site, as defined in the AOC (Refer to Section III.d for the definition of COCs). Revise accordingly.

Response The first paragraph has been revised to include all six COCs as indicated in Section Ill.d of the Administrative Order on Consent.

Comment 14 Table 3.2 -Revise last reference to include monthly activities reports submitted by ENSR.

Response The last reference on Table 3.2 has been revised to include a reference to ENSR Monthly Activity Reports from 2006 and 2007.

Comment 15 Section 3.2.1 -This section describing past surface soil sampling should not include language eliminating surface soil as a primaty or secondary source based on an incomplete consideration of COPCs. This type of analysis belongs in another section and must be more complete if this argument is to be made.

Response Per reviewer comment, the conclusions regarding whether surface soils are a source or threat to human health and the enviromrient have been removed from Section 3.2.1.

Comment 16 Section 3.2.2 -It is not clear from the figure in Attachment 1, where the samples lifted in the table came from. Please clarify in the Attachment or within the text.

Response The text of Section 3.2.2 has been clarified to indicate the figure(s) on which the various sample locations in the data table are shown.

Comment 17 Section 3.2.2 -The conclusion at the end of the section that "... a soil source area has not been discovered at the site..." is incorrect. Carbon tetrachloride was detected in soil samples in the vicinity of the former AST. This is a source area since CCU is anthropogenic and not naturally occurring. Revise accordingly.

Response The text has been revised per the comment. The final paragraph of Section 3.2.2 now reads, "Based on the combined soil sample data from the PRP-lead investigations, a soil source area does exist in the area of the former fiimigant AST. However, the low levels carbon tetrachloride observed in soils in this

U.S. EPA Region 7 Garvey Elevator Site RTC ' HydroGeoLogic. Inc. Mav 2009


source area do not indicate the presence of a significant residual contaminant source."

Comment 18 Section 3.2.2 -The reader is referred to Attachment 2 for the soil sampling results. It is impossible for the reader to decipher the depth interval or location from which these samples came. Please provide description of how to decode sample identifications, or better, add two header rows, the first identifying sample location and the second identifying sample depth.

Response The text has been revised to clarify how the results on the table in Attachment 2 relate to the red triangle boring locations on Figure 1 in Attachment 2. HGL briefly explained the PRP contractor ENSR sample labeling convention. Also, two rows have been added within the ENSR data table to indicate the sample location and depth of each sample.

Comment 19 Section 3.2.3, Final Paragraph -Discuss influence of lithology beneath the site on the results. Upper 50 feet or so is Peoria Loess and Loveland Loess and this strongly inhibits movement of the soil gas. The only area of identified by the shallow soil gas sampling as a source area was the vicinity of the CCU AST. There may be other source areas that could be revealed if the density of sample points was higher. The deeper sampling revealed the very high concentrations near the scale house, so it may be implied that additional soil gas or soil sampling should be performed in that vicinity. Revise as appropriate.

Response The last two paragraphs of Section 3.2.3 has been revised as follows: "Based on the soil gas sampling discussed above, it generally appears that the upper 50 feet beneath the facility has minimal carbon tetrachloride in soil gas. At 50 feet, the data indicates that an area of low concentrations is present beneath the west end of the silos in the general area of known carbon tetrachloride contamination. Below 50 feet to 80 feet, the area of relatively higher carbon tetrachloride concentrations increases in size to include the flat storage building the area to the east towards the rail lines. Below 80 feet there are more isolated carbon tetrachloride hot spots in the soil vapor. It should be noted that the upper approximately 65 feet of subsurface material is consists of finer-grained silts and clays with fine sands. These deposits will inhibit lateral movement of contamination.

The only area identified by shallow soil gas sampling as a carbon tetrachloride source is in the vicinity of the former fumigant AST. The other two areas of higher carbon tetrachloride concentrations in soil gas are north of the buildings in the vicinity of the scale house, and south of the buildings on the southeastern portion of the property. The source of these hot spots is unknown. When samples are collected near the water table, it is likely that the soil gas data shows greater influence from volatilization of contaminated groundwater. Also,

U.S. EPA Region 7 Garvey Elevator Site RTC 8 HydroGeoUgic. Inc. May 2009

HGL—Response to EPA Comments, Draft RI/FS Work Plan, Garvey Elevator Site OUl and OUl—Hastings. NE

the sediments from approximately 65 feet bgs to tlie water table at approximately 115 feet bgs, consist of sands with varying amounts of fines. These sediments will allow greater dispersal contaminants in soil gas laterally then the loess units comprising the shallow sediments. The upper approximately 65 feet of the subsurface consists of the Peoria and Loveland loess, which will inhibit movement of soil gas. It is possible that a higher soil gas sampling density in shallow soils, or placement of sample borings immediately at potential source areas, may reveal other carbon tetrachloride source areas. If other source areas were identified, their inclusion in the CSM might better explain the elevated carbon tetrachloride concentrations observed more widespread in the deeper unsaturated sediments."

Comment 20 Section 3.2.3, Last Sentence of Final Paragraph - Replace "...vaporization..." with "... volitization... ".

Response The text has been revised per reviewer comment.

Comment 21 Section 3.3, V Paragraph - The first sentence misleads the reader into assuming the site was in the Superfund Remedial Action phase at the time. However, it wasn't even on the NPL then. PRP was under State oversight during that period. Revise for clarity.

Response The sentence has been revised so that the terms remedial and remediation are not used, and it now indicates that the site was under state oversight.

Comment 22 Section 3.3.1, 2' Paragraph - Second sentence should state that SVE-9 through SVE-11 are the deep wells, not SVE9 through SVEIO.

Response The text has been corrected per reviewer comment.

Comment 23 E.stablish the following naming convention for SVE wells. SVE- _. For example SVE well should be named SVE-OL SVE well 10 should be name [sic] SVE-10, etc. Revise document throughout text and figures. Use a similar convention for the extraction wells and revise throughout text and figures.

Response The naming convention used in text, tables, and figures produced by HGL has been revised per reviewer comment. Also, the injection wells have been consistently presented as IW-1 and IW-2.

Comment 24 Section 3.3.2, 1" Paragraph - Revise second sentence to indicate past tense.

Response The text has been revised to past tense per reviewer comment.

Comment 25 Section 3.3.2, T'' Paragraph -Text describes pumps as "capable of..." such and

U.S. EPA Region 7 Gar\Ty Ele«IorSlleRTC 9 HjdroOeoLogic, Inc May 2009


such flow rate. Please use more accurate description such as pumps were rated at a "capacity of..." such and such flow rate for the conditions at the site (i.e. head lifi and pipe losses).

Response The text has been revised to state the pump flow rates as capacity rated at a total footage of head.

Comment 26 Section 3.3.2, 2" Paragraph - Please describe water as being injected into the lower aquifer instead of being "discharged back into the hydrogeologic system. "

Response The last sentence of the second paragraph has been moved up to follow the sentence in question, and "hydrogeologic" was replaced with "groundwater". The last portion of the second paragraph now reads, "The extracted water from the wells is piped through a 500 gpm capacity packed tower carbon air stripper and discharged back into the groundwater system through two injection wells (I-1 and 1-2) (Figure 3.5). The 10-inch diameter injection wells are screened in the lower aquifer (D and E zones) from 175 feet to 230 feet bgs (ENSR/AECOM, 2006). The injection wells are located west and upgradient of the contaminant source areas in the agricultural field on the western portion of the site property."

Comment 27 Table 3.1 - // was established through interviews that the Liquid 80-20 formulation contained EDB. Revise accordingly. Incorporate information from 104E responses and interviews into this table.

Response The table has been revised to indicate that the fiimigant mixture specifically noted as having been used at the site, MaxKill 10 liquid 80/20 fiimigant, includes EDB. This was the only new information noted from the employee interviews. The remainder of the information came from the response to the 104E request. Also, both these information sources have been added to the table.

It should be noted that HGL had already referenced the 104 E response in the third paragraph of Section 3.1, which reads, "...The 2003 PA/SI conducted by NDEQ included the following table of previous and current pesticide use at the site, and the locations where these chemicals were stored (Table 3.1). This information is based on the response to the CERCLA 104E request letter submitted to Garvey Elevator as part of the PA/SI activities. (TetraTech, 2003; Garvey, 2003)."

Comment 28 Section 4.1.1 -There is insufficient information to limit the list of COPCs to the set described within this paragraph. The COPCs evaluation should include other chemical compounds known to have been used at the site and their degradation compounds. Review Garvey's 104E responses (Garvey, 2003a, 2003b) and

U.S. EPA Region 7 Garvey Elevator Site RTC 1 0 HydroGeoLogic. Inc. .May 2009


revise as appropriate.

Response Section 4.0 CONCEPTUAL SITE MODEL has been added to the Work Plan, which discusses additional COPCs based on the background documents. Degradation compounds of carbon tetrachloride have been included in the discussion.

Comment 29 Section 4.1.5.1, 1" Paragraph -The second sentence states that the removal action was "...transferred to EPA Region 7..." This was not a transfer. It was a work takeover because it was clear that after filing for bankruptcy, Garvey would not be performing the work required under the AOC. Garvey filed for bankruptcy March 27, 2008. The EPA initiated federal lead Removal Actions on May 19, 2008 in order to address the immediate threat to human health posed by the contaminated private wells and to prevent further impacts to the ground water at the former Garvey Elevator facility. Revise as appropriate.

Res|)onse The text has been revised and now reads, "After Garvey Elevators, Inc. filed for bankruptcy on March 27, 2008, and did not continue work at the site, EPA Region 7 took control of the removal actions. EPA initiated federal lead removal actions on May 19, 2008." It should be noted, that the last part of the subject paragraph already addresses the intended mitigation of the immediate threats posed by the contaminants at the site, and the prevention of further off-site migration of contaminants.

Comment 30 Section 4.1.5.1 -This section is the only one that addresses additional data needs, and it is limited to a discussion of additional data needs to evaluate alternatives. If additional data needs are to be broken down in the report according to use (e.g. risk assessment, alternatives evaluation, etc.), then there need to be similar sections elsewhere in the report that address the other uses.

Response Section 6.1 IDENTIFICATION OF DATA GAPS has been added to Section 6.0 REMEDIAL INVESTIGATION APPROACH AND ACTIVITIES. This section addresses additional data needs by type of media or migration pathway.

Please note: the addition of Section 4.0 CONCEPTUAL SITE MODEL, and the splitting of the "project goals and approach information into a separate Section 5.0, resulted in draft Work Plan Section 4.0 being Final Work Plan Section 6.0.

Conmient 31 Section 4.2.1.1, 3" Paragraph - Remove text describing collection of two samples from each of the two fined grained units during drilling of the hydraulic test well. Numerous lithologic samples have already been collected from MW-33 and elsewhere and additional samples are not necessary.

Response Based on HGL's review of the available site background information, no

U.S. EPA Region 7 Gan-ey l-levator Sue RTC 1 1 HydroGeoLogic. Inc May 2009

HGL—Response to EPA Comments, Draft RI/FS Work Plan, Garvey Elevator Site OUl and OUl—Hastings. NE

geotechnical samples were collected and submitted for analysis during the PRP activities at the site. Although the available boring logs will provide estimates of soil and aquifer parameters based on published values, they will not be site-specific measurements.

HGL does possess three Shelby tube samples collected by the PRP that were not submitted for analysis, which HGL will submit for select analyses. However, only one of these samples may have been collected from the fine-grained units that HGL is targeting.

HGL recommends that EPA consider collecting at least two geotechnical samples from the fine-grained units on site. If one or more additional monitoring wells are installed on site, the most appropriate location for these samples would be as close to the source area and/or recovery wells area as possible.

Comment 32 Section 4.2.1.1, Last Paragraph -Borehole flow meter testing and dipole flow testing are two unique and separate hydraulic test techniques. Revise paragraph to indicate dipole flow testing will be performed.

Response The paragraph in question has been revised to indicate dipole flow testing, not borehole flowmeter testing, will be conducted at the hydraulic test well.

Comment 33 Section 4.2.1.1, 4'' Paragraph - Soil samples submitted for geotechnical analysis of grain size distribution, etc., should also be analyzed for maximum index density and unit weight using a vibratory table according to ASTM D 4253-00.

Response HGL has contacted several geotechnical labs in the region for information regarding the method. ASTM D4253 is a specialized analysis conducted by only select laboratories, and requires a sample volume equivalent to a 5-gallon bucket. Also, according to literature reviewed by HGL, ASTM D4253 is applicable only to cohesionless, free-draining soils. HGL has proposed collection of one geotechnical soil sample from a saturated sand unit, if the chosen drilling method is capable of collecting a large volume of cohesionless soil. The remaining samples will be collected only from the fine-grained unit(s).

Comment 34 Section 4.2.2, 1" Paragraph - The last sentence of this paragraph describes what the data will be used for. Absent from this description is use in the risk assessment. Migration to groundwater from the subsurface soil is part of the pathway through which exposure can occur. Please revise. Review statements in other sections regarding use of the data and ensure use in the risk assessment is included where appropriate.

U.S. EPA Region 7 Garvey Elevator Site RTC 1 2 HydroGeoLogic. Inc. May 2009

HGL—Response to EPA Comments. Draft RI/FS Work Plan. Garvey Elevator Site OUl and OUl—Hastings. NE

Res ionse The text has been reviewed, and statements indicating use of certain data in the risk assessment has been inserted as appropriate.

Comment 35 Section 4.7.1 - The presented preliminary site conceptual model is [sic] does not adequately utilize existing site information. Nor does it summarize and present in an organized manner, the sources, release mechanisms, potential secondary sources and their release mechanisms, pathways, and receptors. Revise as appropriate in accordance with project planning activities outlined in the Risk Assessment Guidance for Superfund, Volume 1, Human Health Evaluation Manual, Part A, Interim Final (EPA540/1-89/002) and subsequent revisions and updates.

Respionse A Section 4.0 CONCEPTUAL SITE MODEL has been added to the Work Plan. The format of this CSM section is consistent with the EPA guidance document referenced by the reviewer, and the conceptual site model section in the Final Site Characterization Work Plan for West Highway 6 & Highway 281 Site, Hastings, Nebraska that was approved by EPA Region 7. The insertion has necessitated shifting sections in the draft Work Plan as illustrated in the table below.

Draft Work Plan Not applicable Section 4 - Remedial Investigation Approach... Section 5 - Communication, Data Management... Section 6 - Schedule Section 7 - References

Final Work Plan Section 4 - Conceptual Site Model Section 5 - Remedial Investigation Approach... Section 6 - Communication. Data Management... Section 7 - Schedule Section 8 - References

Comment 36 Section 4.7.1, 3"' Paragraph - Unless there is a strong basis for carrying forward in the risk assessment the unlike scenario of contaminating irrigated soil via irrigation water, then remove it from consideration. Research has shown sprinkler irrigation to be highly efficient (>957o removal) in volatilizing carbon tetrachloride (Spalding et al., 1995; US EPA, 1998). This same comment applies to the scenario of the inhalation pathway fiom volatilization of irrigation water to the atmosphere.

Resfionse The HGL risk assessors advise that the scenario of irrigation wells spreading contamination should be evaluated in the risk assessment. The reasoning is that carbon tetrachloride in exceedence of 100 /xg/L is present in groundwater, which at 95 percent removal from sprinkler irrigadon, only lowers the concentration to the MCL (5 /xg/L). Therefore, the potential exists that concentrations above the MCL are being applied to the fields and available in the air for inhalation.

Garvey Elevator Site RTC

U.S. EPA Region 7 13 HydroGeoLogic. Inc. May 2U09


Comment 37 Appendix B, Section 3.5.2 - Borehole fiowmeter testing is not part of the investigation activities planned for the site. Dipole Flow Testing is on [sic] of the planned activities. Please revise section title and text accordingly.

Response The text of the FSP in Appendix B has been revised to indicate that dipole flow testing, and not borehole flow meter testing, will be conducted at the hydraulic testing well.

Comment 38 Appendix C - Please include signatures on signattire page of QAPP.

Response A signed QAPP signature page provided as requested.

Reviewer Comments provided by the EPA Task Order Project Officer on April 3, 2009. (Comments provided by EPA TOM in email dated April 2, 2009)

Comment 1 Replace heading "Source Area" in the Table Summary of Field Sampling Rationale - OUl to Potential Source Area.

Response The column header in the table has been revised per the comment.

Comment 2 Rename "Possible Disposal Pit" to "Construction Debris Disposal Pit"

Response The change has been made to the table per the comment.

Comment 3 The Construction Debris Disposal Pit is not identified on the figure.

Response The Construction Debris Disposal Pit has been added to Figure 3.1 Source Area Map.

Comment 4 Include geoprobe groundwater sampling location slightly upgradient of the former Garvey Supply Well in order to evaluate if there is an upgradient source from the contamination detected in the Garvey Supply Well.

Response A geoprobe groundwater sampling location has been added upgradient to the west-northwest of the Garvey Supply well. It also has been illustrated on all appropriate figures.

Comment 5 Unless there is expected to be a naturally occurring source having an impact on outdoor air then it is not necessary to determine background levels of VOCs in air. Please remove the 2 locations, identified in the last row of the spreadsheet, from the sampling regime.

Response HGL has discussed this comment with the project risk assessors. The risk assessors have indicated that it is necessary to collect outdoor air samples to

U.S. EPA Region 7 Garvey Elevator Site RTC 1 4 HydroCeoI.ogic. Inc. .May 2009

HGL -Response to EPA Comments. Draft RI/FS Work Plan, Garvey Elevator Site OUl and OUl—Hastings, NE

provide background data to evaluate against the indoor air samples because the indoor air can be affected by outdoor air concentrations. Otherwise, it cannot conclusively be determined if detections in indoor air samples are the result of volatilization of contaminants through the building foundation and floor, or are the result ambient air contamination at the facility.

Comment 6 (Comment provided verbally as an addition to emailed comments on April 2, 2009.) Remove the sediment and surface water sample from the pond. Add a second background location upgradient of the site in the drainage ditch situated between the rail spur and railroad tracks.

Response The second background sediment sample has been added upgradient of the site in the drainage ditch situated between the rail spur and railroad tracks.

Regarding the pond sediment and surface water sample, HGL has discussed this comment with the project risk assessors. The risk assessors have indicated that it is necessary to collect the pond samples for the ecological risk assessment. The risk assessors also advised that another sediment sample be collected immediately downgradient from the pond to evaluate potential contaminant concentrations just beyond the outfall of this surface water body.

Cariey Elevator Sue RTC

U.S. EPA Region 7 15 HydruGeoLugic. Inc. Miiy 2009

letter transmitting the response to comments on the draft

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