United States Environmental Protection Agency Office of Emergency and Remedial Response EPA/ROD/R07-90/03S September 1990 Superfund Record of Decision: Hastings Ground Water Contamination (FAR-MAR-CO), NE ------- ... 50272.101 REPORT DOCUMENTATION I,. REPORT NO. . PAGE EPA/ROD/R07-90/035 I ~ :I. AKIpIent'. AcC88810n No. 4. TlII8 Ind SubdII8 SUPERFUND RECORD OF DECISION Hastings Ground Water Contamination Second Remedial Action 7, Author(.) 50 Report 0- 09/28/90 (FAR-MAR-CO), NE I. .. Pertonnlng Organization Rapt. No. a. Perlormlng Orgelnlzetlon Name .nd Addr... 10. Pnlj8e1/T.8IIiWork Unit No. 11. Con1r8C1(C) or Grenl(G) No. (C) (G) 12. Sponeoring Org.nizatlon Name .nd Add..... U.S. Environmental Protection 401 M Street, S.W. Washington, D.C. 20460 1:1. Type of Aepor1 . Period Co-.cf Agency 800/000 '4. 15. Supplementary Nole. 16. Abetr.eI (Umll: 200 worda) The Hastings Ground Water Contamination site (FAR-MAR-CO) is a contaminated aquifer in and near the city of Hastings, Adams County, Nebraska. The site consists of seven source areas, or subsites, contaminated with volatile industrial chemicals. This Record of Decision (ROD) addresses the Zone 2 portion of the FAR-MAR-CO subsite, which has been divided into two general areas of contamination referred to as Zone 1 and Zone 2. Zone 1, which includes grain elevators and areas to the north of the elevators, contains soil, soil-gas, and ground water contaminated with ethylene dibromide and carbon tetrachloride originating from the disposal of liquid grain fumigants used in grain elevator operations. Zone 1 contamination was addressed in a 1988 ROD that documented the selection of a remedy to construct a soil vapor extraction system. Zone 2, which includes the area south of the grain elevators (between the elevators and manufacturing and production buildings owned and operated by the Hastings Irrigation Pipe Company (HIP CO)) contains soil contamination primarily due to 1,1,1-trichloroethane (TCA) resulting from the disposal of cleaning solvents used in the manufacturing operations. In December 1989, HIPCO performed a removal action excavating contaminated soil in Zone 2. Subsequent testing revealed that the concentration of TCA in Zone 2 had been reduced (See Attached Page) 17. Oocumenl An.lyel. L Oe.criplor, - Record of Decision - Hastings Second Remedial Action Contaminated Media: None Key Contaminants: None Ground Water Contamination (FAR-MAR-CO), NE b. ldentifler8l0pen-Ended T ann. Co COSA TI FIeIdIOroup 18. Av.lI.blllty SII18menl 18. Sec:wlty Ct... (Thi. Report) None 20. Security Ct... (Thia P.ge) None 21. No. of P.gee 11 I 22. Price See ANSI-Z3a.18 See Inetru<:tione on Re- (4-77) (Formerly NTlS-35) Department of Conwneree ------- \ ~ , EPA/ROD/R07-90/035 Hastings Ground Water Contamination (FAR-MAR-CO), NE Second Remedial Action Abstract (continued) to a protective level. Response actions for ground water contamination near the FAR MAR CO subsite, however, will be addressed in subsequent remedial activities. The selected remedial action for this site is that no further action be taken at this time with regard to the TCA soil contamination. Due to the small amount of residual contamination remaining in the soil and the significant depth to the water table, the possibility of transport of TCA from this source to ground water is minimal. Ground water monitoring will continue on a semi-annual basis for two years. HIPCO will conduct the ground water monitoring and has agreed to reimburse the EPA for all oversight costs. There are no additional costs associated with this remedial action. PERFORMANCE STANDARDS OR GOALS: Not applicable. ------- RECORD OF DECISION DECISION SUMMARY HASTINGS GROUND WATER CONTAMINATION FAR-MAR-CO SUBSITE HASTINGS IRRIGATION PIPE COMPANY TCA SOILS OPERABLE UNIT HASTINGS, NEBRASKA Prepared By: U.S. Environmental Protection Agency Region VII Kansas City, Kansas september, 1990 ------- STATE OF NEBRASKA DEPARDfE~ or ENVIROSMt~'T.u. CO!\"BOI. DBN SI! GRAMS DmscrOR ; September 21. 1990 Mr. Morris Kay Regione1 Administrator EPA R8g1cn VII 7Z5 Minnesota Avwnu8 «ansas City. I(~M5 88101 Dear t1r. Kay: Upon cons1derat1on 01 the Administrative Record and the draft Record of 08Cis1on (ROD). the Nebraska Oepart8ent 01 environmental Control (HOeC) concurs with the fnV1ronmenta, PrOteCtiOn Age~cy cePA) remedy selection for the Hastings Irrigation Pipe Company (HIPCO) TCA 50115 Operable Unit. WI understand that the removal aCtion ~as 11n181zea the pOtential for further degradation 0' the groundwater at tne site and no further actiOn w~l' be taken at this time. with regard to the 5011 Contamination. The two year groundWater 8onitor1ng plan w111 provide add1t1ona' assurance that groundwater at the site w~" not be adVersely affectld by the residua' contaminat1o" The selected re.edy W111 .eet ", st.te requirements. NDEC appreciates the opportunity for inVOlvement in tne remeay se,ectior. process and EPA's co~sld8ration of NDEC's 1n~ut throughout this investigation. S1ncere~y, ~\ .,~ J,..;.--- ... Dennis Grams. P.E. p. O. 80X 91912. UNCOLN. NDiRASKA 68509-8911. PHONE (401)m.2186 ~ EQUA.L OPPOR1l1Nm' I A1F1ItM.An\'E A.CTIO". DtPLm'ER ------- RECORD OF DECISION DECLARATION SITE NAME AND LOCATION Hastings Ground Water Contamination, FAR-MAR-CO Subsite HIPCO TCA Soils Operable Unit Hastings, Nebraska STATEMENT OF BASIS AND PURPOSE This decision document presents the selected remedial alter- native for that part of the FAR-MAR-CO subsite of the Hastings Ground Water contamination Site, where TCA soil contamination has been found. This document is developed in accordance with the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as amended by the Superfund Amendments Reauthorization Act of 1986 (SARA), 42 USC ~9601 et. ~ and consistent with the National oil and Hazardous Substances Pollution Contingency Plan (NCP) to the extent practicable. This decision is based upon the contents of the administra- tive record for the Hastings Irrigation Pipe Company (HIPCO) TCA soils operable unit. In accordance with CERCLA section 121(f) (1) (E) and (G), the state of Nebraska has reviewed and commented on the Remedial Investigation/Feasibility Study (RI/FS), the Baseline Risk As- sessment and the Proposed Plan. The state concurs with the selected alternative for this operable unit and has determined, through a detailed evaluation, that the selected action is con- sistent with its laws and regulations. DESCRIPTION OF THE SELECTED REMEDY: NO FURTHER ACTION This operable unit refers to that portion of the FAR-MAR-CO subsite where trichloroethane (TCA) was found in the soils. HIPCO, under an administrative agreement with the Environmental Protection Agency (EPA), conducted a removal action in December 1989. Further testing done after the removal action revealed that the concentration of TCA had been reduced to a protective level. Due to the small amount of residual contamination remain- ing in the soils and the significant depth to the water table at this site, the possibility of transport of TCA from this source to the ground water is minimal. The Nebraska Department of Environmental Control (NDEC) has concurred with EPA's selected alternative for the TCA operable unit at the FAR-MAR-CO subsite. That alternative is to take no further action at this time, with regard to the TCA soil contami- nation. Response actions for ground water contamination at the FAR-MAR-CO subsite will be addressed in subsequent decision docu- ments. .. 'l..J;1.~i""'r ~Plt..'j.o,''-.''';'.,~... ~ .'~. . ------- DECLARATION The results obtained subsequent to the removal action indi- cate that the level of TCA in the site soils has been reduced to a protective level. Because any hazardous substances within site soils above health based levels have been removed, a five year review will not be required at this operable unit. However, ground water monitoring in connection with the HIPCO TCA Soils Operable Unit will continue on a semi-annual basis for two years following implementation of this Record of Decision (ROD). In addition, EPA will continue to monitor ground water at the FAR- MAR-CO subsite as part of its ongoing response actions at the Hastings Ground Water Contamination site. ~'-J1~ q - 7-- '6 - erO . /Y1,,-j < /r Morris Kay Regional Administrator Date Attachments: Index to Administrative Record Decision Summary Responsiveness Summary ------- . , . Record of Decision Decision Summary Contents section I. site Description II. site History III. Enforcement History IV. Community Relations V. site Characteristics VI. Scope of Operable Unit VII. Summary of site Risks VIII. Description of the "No Further Action" Alternative IX. State Role Paqe 1 2 3 3 4 9 10 12 13 WtPr..3"."''' "~'.: '. J 'a' t.:.,N~ ";'1. ------- HASTINGS DECISION SUMMARY FAR-MAR-CO SUBSITE IRRIGATION PIPE CO. (HIPCO) TCA SOILS OPERABLE UNIT HASTINGS GROUND WATER CONTAMINATION ~ DESCRIPTION The city of Hastings (pop. 23,000), is located in Adams county, in south-central Nebraska. The EPA has been investigating sources of ground water contamination in Hastings since 1984. Through these investigations several sources of contamination have been identified. Each of these sources represents a subsite where specific contaminants can be traced back to a distinct source area. The EPA has thus far identified seven subsites (Figure 1) in and around the city. Ground water associated with each of these subsites (except South Landfill) has been sampled and found to contain levels of contamination which exceed allowa- ble standards for safe drinking water. Due to this contamination the city of Hastings decommissioned several of its wells, and the CMS public supply system, operating east of the city has decom- missioned two wells. HASTINGS 1 7. I" ,. Subslte t WELL NUMBER 3 2. COLORADO NENUE S. SECOND STREET 4. SOUTH LANDFILL Locations 5. NORTH LANDFILL e. FAR-MAR-CO 7. FORMER NAVAL AMMUNITtON DEPOT ~ Figure 1. - Location of subsites for the Hastin;s Groln:1 Water a:a,taminatioo site '~.' ~..' ";-':," '~'. 1 ------- .. . ~ HISTORY The Hastings Irrigation Pipe Company (HIPCO) property lies within the FAR-MAR-CO subsite and is part of an industrial enter- prise zone located between U.S. Highway 6 and a Burlington North- ern Railroad right-of-way. Several areas within the FAR-MAR-CO subsite have been identified in which varying concentrations of volatile organic compounds (VOCs) have been detected in the soil and in the underlying aquifer. Numerous VOCs have been identi- fied in monitoring wells located both upqradient and downgradient to the FAR-MAR-CO aubsite. These compounds include 1,1,1 tri- chloroethane (TCA), tetrachloroethene (PCE), vinyl chloride, 1,2 dichloroethene (DeE), and trichloroethene (TCE). The direction of ground water flow is generally from west to east. Through previous studies, the EPA has defined the nature and extent of soil contamination at the FAR-MAR-CO subsite. These studies identified two general areas of contamination within this subsite (Figure 2); "Zone 1", which includes the grain elevators and areas immediately to their north, and "Zone 2", the area between the grain elevators and the HIPCO production buildings. Ethylene dibromide (EDB) and carbon tetrachloride (CC14) have been found in soils, soil-gas, and ground water associated with Zone 1. EPA selected a response to address the EDB and CC14 contamination in its September 30, 1988 Record of Decision (ROD). Zone 1 contamination has resulted primarily from disposal of liquid grain fumigants used in operations at the grain elevators, while Zone 2 TCA soil contamination is due to the disposal of cleaning solvents used in the manufacturing operations at the HIPCO facility. o ! ~ . IIW-7 c DO HIPCO SCALI IN fr&T I I o tOo aoo 100 IIW-I -$[? c I: , .Y. u.s. . Fiqure 2. - f,a)es 'of CD1tmninatian identified within the FAR-M1VHD 8Ub&i te 1 ~ , , ------- ENFORCEMENT HISTORY On September 30, 1988, EPA issued a Record of Decision (ROD) documenting the remedy EPA selected for remediating Zone 1 soils. The selected alternative entails the construction of a soil vapor extraction system within Zone 1. Negotiations are on-going with the responsible parties for Zone 1 to implement the selected alternative. EPA documented the detection of the Zone 2 TCA soil contami- nation at HIPCO in a February 1987 Remedial Investigation report for the FAR-MAR-CO subsite. Subsequent to the completion of EPA's field investigation in 1988, HIPCO was notified of its liability at the site and entered into negotiations with EPA to remediate the contaminated soils within Zone 2. In October 1989 EPA and HIPCOentered into an Administrative Order on Consent. Under this Consent Order, HIPCO agreed to remove the TCA contami- nated soil and transport it to an EPA permitted disposal facili- ty. In addition to conducting the removal action, HIPCO agreed to submit a Baseline Risk Assessment and a Feasibility Study. COMMUNITY RELATIONS Community relations activities for the Hastings Ground Water Contamination site were initiated by the EPA in 1984. Since that time, EPA has conducted periodic meetings with Hastings city officials to inform them of site progress. The EPA Publt~ Af- fairs Division has provided fact sheets to parties who have expressed an interest in the Hastings Ground Water Contamination site. The Public Affairs office has also routinely responded to inquiries regarding this site from news media and the general public. In February 1987, the Remedial Investigation report for the FAR-MAR-CO subsite was placed in a public repository. This docu- ment as well as other relevant FAR-MAR-CO documents were incorpo- rated by reference in the administrative record compiled for the TCA Operable Unit. This administrative record was made available at three public repositories in and around the city of Hastings on August 9, 1990. A 30 day public comment period began on August 9, 1990 and continued to September 7, 1990. EPA held a public meeting on August 15, 1990 to present the preferred alternative, accept comments, and answer questions regarding the proposed plan. Public comments submitted at the meeting and received by EPA during the 30 day comment period are addressed in the responsive- ness summary attached to this ROD. 3 ------- .J ... . SITE CHARACTERISTICS The Remedial Investigation conducted for the FAR-MAR-CO subsite utilized soil-gas sampling as a method to locate source areas of contaminants. The instrumentation used was capable of detecting and quantifying four contaminants: trich1oroethene (TCE), carbon tetrachloride (CC1~), tetrach1oroethene (PCE), and 1,1,1 trichloroethane (TCA) whicti had previously been detected in ground water samples taken at the FAR-MAR-CO subsite (Refer to Figure 3 for soil-gas sampling locations). Results from this sampling (Table 1) indicated that discriminant samples within the FAR-MAR-CO subsite contained concentrations of TCA, PCE, and CC14 at levels above the detection limit of 1 ug/1 (micrograms per liter). TABLE .1 Soil-Gas Samp1 ing Results - April 1986 Sample! TCA (ua/l) ~ (ua/l) CCl4 (ua/l) 056 140 140 56 083 ND 6 780 ... 086 ND 41 1900 130 13 0.1 ND 131 49 0.7 ND 133 27 3 . 0.1 136 10 ND 6 142 ND ND 1500 144 ND ND 200 149 ND ND 440 151 ND ND 420 157 ND ND 220 188 120 2 ND ND - Compound Not Detected All Other Locations Were Below 1 ug/1 4 ------- v ~ , L I ] [ J ICALf IN nn I I o '00 200 300 \? ~ [? c 8 8 HWY. u.&. . 15 16 Figure 3. - Soil~as sampl~ locations at the FAP.-l~ subsite, Analyses of these results revealed two distinct zones of contamination. Zone 1 was defined by the presence of CCl., which was consistently observed in the highest concentrations 1n an area located north of the grain elevators and south of the Burl- ington Northern railroad tracks. Significant levels of the con- taminants TCA anq PCE were detected at sampling location 056. This area, located south of the grain elevators was defined as Zone 2. Sample 056 did indicate the presence of CC14 which may have been due to off-site migration from Zone 1. The other loca- tions around HIPCO's buildings were sampled and found to be relatively free of contaminants. Based upon the results of the soil gas contaminant analyses, a soil sampling plan was developed by EPA for the FAR-MAR-CO subsite. A number of soil borings were conducted within the area defined as Zone 2 (Figure 4). Five samples were collected from borings SB-11 and SB-1J at two foot intervals to a depth of ten feet. This sampling method was used to define the vertical dis- tribution of the contaminants. Results from soil boring '13 (Table 2) located near the rear entrance of HIPCO production building '1 indicated the location of the highest concentration of contaminants. ------- AM . 0\ AJ8. w- II . II -Nt 0 ....- -."" ..... - .AJ8 r AR- MAR-CO ROAD ",. . .. "" . . .. .' ":'..' ~,' , .-ss CIt'DIn ,; '-..',',< ~'- . .. " . .tPnOOM1t 1M:( 01 UtIII--. 8- ......, ~ .... . ~t;~::.:~.:<:.. HIPCO BUILDING No.1 lEC£NO -- 'OCAI'I. 8f . 1 1 II J .... ~ 1/11'. .. - l..... tit -... MK. OIl --..... .'" ...- fIT -- 8U . .' . ',' .. . ~ .'.. . :0'. ,.:'.'. '.- '... HIPeO BU1lDINC No.2 8 . ,.. .. fin Figure 4. - Incatioo of soil borings used to define Zone 2. Area of soil excavation is denoted by hachures. to ~11M C...,... ......... IMA ------- TABLE ~ Sample Results From Soil Boring #13 -,June, 1986 Depth 1. 1. 1 TCA (ua/1) PCE (ua/l) .L..1 DCA (ug/l) 0-2 ft. 60,000 1200 M ND 2-4 ft. 12,000 ND 410 M 4-6 ft. 180 11 M 110 6-8 ft. 200 180 21 8-10 ft. ND 9.8 ND ND = compound Not Detected M = Estimated Concentration Below the Quantification Limit Analyses of the soil sampling results suggested that a spill or surface discharge of TCA had occurred in the immediate area of soil boring #13. TCA was found to be concentr~ted at levels up to 60,000 (ug/1) at the surface and decreased with depth to a non-detectable amount below 8 feet. The highest concentration of PCE was also detected at this soil boring location (1200 ug/l). As with TCA, the PCE showed a marked decrease in concentration with depth. other contaminants of concern which were detected in samples from this event include 1,1 dichloroethane (DCA), and 1,1 dichlo- roethene (DCE). The highest level of DCA (410 ug/l) was observed from a depth of 2-4 feet at this location. Although not shown above, the highest level of DCE (430 ug/l) was detected at a depth of 0-2 feet, also at soil boring #13. These high levels of DCA and DCE coincide with the high levels of TCA and PCE. This coincidence supports a conclusion that DCA and DCE may be the result of biological degradation, or may have been primary co- contaminants. Ground water sampling has been conducted on a quarterly basis at the FAR-MAR-CO subsite since 1986. The primary contami- nants at Zone 2, TCA and PCE, have been detected in ground water located both up-gradient and down-gradient to the FAR-MAR-CO subsite. Water samples were collected by HIPCO in June 1990 from three monitoring wells at Zone 2 (Table 3). Split samples were collected by EPA from wells MW-25 and IT-HI. Two wells, MW-25, and IT-H2 are located directly up-gradient of Zone 2 (Figure 5), while the third well, IT-HI is located immediately down-gradient of the highest amount of TCA soil contamination within Zone 2. Additional EPA monitoring wells are located to the west at the North Landfill sUbsite, which is not shown on Figure 5. 7 ------- ~ . , I I~ t ! : ~ : : I , : ] : : I I I I I ! I : I I : : i ; . 1 I I 1 : : : : 1 I I I , I . I , . I : . I ; ; , I I I I I ' , I . . . I . e I t.4W-1' 1111: Ii' 1111111111 ! 111: ! j : 111111! 111111111: 11111111: 111111::: I; :: : Irl . MW-18e e I [p t.4W-8 I I I . I o e I ! ~w-,~ I ' I D I J ! @ I I "'W-16 " D t I I ~ o o ISO .......... ...-.... t--c 100 I 'EET Figure s. - lobU wring wells at the FAR-M1\R~ subsi te. 8 ------- TABLE 1 Ground Water Sampling Results - June, 1990 Compound IT-HI IT-H2 MW-25 1,1,1 Trichloroethane (TCA) 6.0 J ND (65) ND (5) Tetrachloroethene (PCE) ND (5) ND (5) ND (5) 1,1 Dichloroethane (DCA) ND (5) ND (5) ND (5) 1,1 Dichloroethene (DCE) ND (5) ND (5) ND (5) 1,2 Dichloroethene (Total) 11 J NA 22 J Vinyl Chloride ND (10) ND (10) ND (10) NA - Compound Not Analyzed J - Qualitative Estimate Analyses of the results from the June 1990 sampling event were consistent with previous analyses of ground water samples at the subsite. The data collected indicates that TCA has not mi- grated from surface soils to the underlying aquifer in signifi- cant quantities. TCA was found present in the ground water at levels ranging from non-detect to 48 ppb. The maximum contami- nant level established by EPA under the Safe Drinking Water Act for TCA in drinking water is 200 ppb. The contaminant 1,2 DCE (total) was found to be present in the ground water sample taken from IT-HI at 11 ppb and from an up-gradient well (MW-25) at 22 ppb. The higher level of total 1,2 DCE found in the up-gradient well suggests that the source of 1,2 DCE may be up-gradient. SCOPE OF THE OPERABLE UNIT As set forth in the National Contingency Plan (NCP) an operable unit is a discrete action that comprises an incremental step towards a final remedy. The cleanup of TCA soils contamina- tion at this subsite where other soil and ground water contamina- tion are present is a part of a comprehensive plan for cleanup at the FAR-MAR-CO subsit~. This operable unit is fully consistent with all ~uture site work, including on-going ground water inves- tigatio~s: - ~, 9 ------- . . \, The TCA and lesser PCE concentrations discovered in the soils near the rear exit of HIPCO production building #1 prompted EPA to consider a removal action at Zone 2. While the contami- nants were found in significant concentrations in the surface soils at Zone 2, significant migration of contaminants to the ground water table had not yet occurred. Subsequently, a deci- sion was made to remove the soils at the localized source to prevent the migration of contaminants from the soils to the aquifer. The excavation of surface soils within Zone 2 was identified as the most effective and expedient option to address remediation at the HIPCO TCA soils operable unit. An Administrative Order on Consent (AOC) was entered into between EPA and HIPCO on October 26, 1989. Under this AOC, HIPCO agreed to conduct the removal action for Zone 2 and to reimburse EPA for oversight costs in- curred during response activities. Under EPA oversight, HIPCO began excavating soil on December 18, 1989. Excavation occurred within Zone 2 where the highest concentration of TCA soil contamination was discovered (Figure 4). A pit was excavated using backhoe equipment, to a depth of approximately five feet. The excavation was deepened to approxi- mately 6.5 feet in the area of highest known TCA concentration. The corresponding volume of soil removed from the pit was approx- imately 43 cubic yards. The soil was then loaded into transport trailers and hauled by licensed waste transporters to an EPA permitted disposal facility in Waynoka, Oklahoma. The excavated pit was then backfilled with clean soil and mounded to promote surface water runoff. Soil samples were collected from all four walls and the floor of the excavation. Results of the soil sampling indicated that TCA had been reduced from over 60 parts per million (ppm) before the removal action, to less that 3 ppm. In addition, residual PCE in the soil had been reduced to an average of less than 0.2 ppm. The reduced level of contamination due to the source removal combined with the significant depth (120 feet) to ground water, and the low potential for meteoric water to filtrate through site soils, suggest that the possibility of migration of TCA or PCE from this source to the water table is minimal. Due to the removal action undertaken by HIPCO, the threat of TCA soil con- tamination to human health and the environment has been reduced to a protective level. SUMMARY OF SITE RISKS During the Remedial Investigation/Feasibility Study (RI/FS) which was undertaken in part by EPA, and in part by HIPCO, an analysis was conducted to estimate the health or environmental 10 ------- problems that could result from exposure to Zone 2 soils. This analysis is commonly known as the baseline risk assessment. The purpose of the baseline risk assessment is to provide a public health evaluation with respect to contamination remaining after the removal action. The assessment was performed using TCA as the key indicator species. DCA and PCE, which were found in small quantities in the surface soils at Zone 2, were included as indicators due to their association with TCA. The focus of this assessment was on the potential health effects which could be expected to result from direct exposure to any contaminants remaining at Zone 2. The baseline risk assessment examined both the nature of contamina- tion and the potential pathways for human exposure. Three mechanisms for migration exist at the HIPCO site: vapor phase transport through the soil, volatilization to the atmosphere, and aqueous phase transport in ground water. The exposure pathway to the public to contaminants by means of direct soil contact, or ingestion, has been eliminated by the removal action. Thus, the primary potential for human health impacts from Zone 2 is the exposure of residents living east (down-gradi- ent) of the subsite who utilize the underlying aquifer as a source of drinking water. Of the three indicator species evaluated in the risk assess- ment, TCA and DCA are considered to be non-carcinogens, while PCE is considered a potential human carcinogen. Consequently, PCE which was found in small quantities in the soils at Zone 2, .1nd has been detected in ground water both up-gradient and down- gradient of Zone 2, was used to evaluate risk. A worst case carcinogenic risk (CR) from the PCE contamiga- tion was determined. The worst case CR estimate is 1.89 X 10- . This translates to approximately two excess cancers per 100,000 population exposed to the PCE in the ground water. This worst case scenario assumes that the PCE found at low levels (an aver- age of less than 0.2 ppm) in the soils at Zone 2 will migrate approximately 120 feet to ground water and thereupon be trans- ported to a water supply well. To date, ground water monitoring at Zone 2 has indicated that TCA, the primary contaminant at Zone 2 representing approximately 93% by volume of the disposed sol- vents, has not migrated in significant quantities to the underly- ing aquifer. The removal of the most contaminated soils in Zone 2 provided additional assurance that further ground water degra- dation due to the TCA soil contamination would be greatly re- duced, if not eliminated. Furthermore, since PCE is present in the ground water west of the HIPCO property, it is unlikely that further remediation of HIPCO soils would significantly improve the ground water quality of the underlying aquifer. under current site conditions, a reasonable maximum exposure scenario indicates that unacceptable exposures to TCA and PCE in the soils at Zone 2 will not occur. The ground water contamina- 11 ------- tion which is due to off-site sources will be addressed in future response actions. DESCRIPTION Ql IH£ "NO FURTHER ACTION" ALTERNATIVE The EPA and the NDEC have concurred that the removal action was successful. Consequently, this action should prevent any further ground water degradation which could be attributed to Zone 2 soils. The data available indicates that no significant health threat is presently derived from the small amount of residual TCA and PCE contamination remaining in the soil at Zone 2. The EPA and the NDEC are in agreement that no further remedi- al action need be taken at this time with regard to the soil contamination within Zone 2. continued ground water monitoring will be conducted by HIPCO for a period of two years following issuance of the Record of Decision (ROD). Under EPA and NDEC oversight, HIPCO will sample wells MW-25, IT-H1, and IT-H2. These sampling events will be conducted on or about December 1990, June and December 1991, and June 1992. This monitoring program will provide additional assurance that the underlying aquifer will not be adversely affected by residual contamination from the soils at Zone 2. Analysis of the results of each sampling round will center on the contaminants of concern for the soils within Zone 2 at the FAR-MAR-CO subsite. Specifically, concentrations of TCA, PCE, and their degradation products DCA, DCE and vinyl chloride will be compared to Maximum Contaminant Levels (MCLs) established by EPA for safe drinking water (Table 4). Where final MCLs have not been promulgated, the proposed MCLs for those compounds will be applied. TABLE i EPA Regulatory Status For Chemicals in Drinking Water 1,2 Dichloroethane (DCA) 1,1 Dichloroethene (DCE) Proposed Final MCL ug/l MCL ug/l 200 5 7 5 100 2 Compound 1,1,1 Trichloroethane(TCA) Tetrachloroethene (PCE) Trans-1,2 Dichloroethene (DCE) Vinyl Chloride 12 ------- Should an MCL exceedence be confirmed for any compound listed in Table 4, which could be attributed to the soils within Zone 2, EPA and NDEC will consider taking further action at the site. If further response actions are deemed necessary, the potential remedial alternatives that were developed in the feasi- bility study will be evaluated for implementability. STATE ROLE The state of Nebraska's Department of Environmental Control (NDEC) has reviewed all technical site documents upon which EPA has based this decision, and has concurred with the selected action. Additionally, the NDEC has agreed to conduct oversight activities at HIPCO through the duration of the ground water monitoring program. 13 ------- ... '1 ATTACHMENT 1 RESPONSIVENESS SUMMARY HIPCO TCA SOILS OPERABLE UNIT HASTINGS, NEBRASKA SEPTEMBER 1990 ------- HIPCO TCA SOILS OPERABLE UNIT RESPONSIVENESS SUMMARY A. OVERVIEW The Hastings Irrigation Pipe Company (HIPCO) TCA Soils operable unit consists of that portion of the FAR-MAR-CO subsite where 1,1,1 trichloroethane (TCA) was found in the soils. HIPCO, under an administrative agreement with the Environmental Protec- tion Agency (EPA), conducted a removal action in December, 1989 to excavate the most contaminated soils. Approximately 43 cubic yards of TCA contaminated soil was removed and transported to an EPA permitted disposal facility. Further testing conducted after the removal action indicated that the concentration of TCA had been reduced to a protective level. Due to the small amount of residual contamination remaining in the soils and the significant depth to the water table at this site, the possibility of trans- port of TCA from this source to the ground water is minimal. In the Proposed Plan released to the public, the EPA pre- sented a preferred alternative for the TCA soils operable unit at the FAR-MAR-CO subsite. That alternative is to take no further action at this time, with regard to any residual TCA soils con- tamination at HIPCO. Ground water monitoring in connection with the HIPCO TCA soils operable unit will continue on a semi-annual basis for two years following implementation of the Record of Decision (ROD). In addition, EPA will continue to monitor ground water at the FAR-MAR-CO subsite as part of its ongoing response actions at the Hastings Ground Water Contamination Site. B. BACKGROUND ON COMMUNITY INVOLVEMENT Community relations activities for the Hastings Ground Water Contamination Site were initiated by EPA in 1984. Since that time, EPA has conducted periodic meetings with Hastings city officials to inform them of site progress. Public meetings have been held on three occasions to present Proposed Plans for other Hastings subsites. In addition, the EPA Public Affairs office has routinely responded to inquiries regarding this site from new~ media and the general public. A thirty day public comment period began on August 9, 1990 and continued to September 7, 1990. EPA held a public meeting on August 15, 1990 to present the preferred alternative, accept comments, and answer questions regarding the Proposed Plan. The Responsiveness Summary addresses comments received during this period. ------- 4 . ~ C. SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD Comments received during the public comment period on the Feasibility Study and the Proposed Plan for the HIPCO TCA Soils operable unit are summarized below. The basis for EPA's position on these matters can be found in the following published docu- ments: PRC Environmental Management, Inc., 1990. Ground Water Report, Hastings Ground Water contamination Site, April 1990. Woodward-Clyde, 1985. Work Plan for Remedial Investigation/Feasi- bility Study, Hastings Ground Water contamination Site, Vol. 1, October 9, 1985. Woodward-Clyde, 1987a. Report of Investigations, Hastings Ground Water contamination Site, FAR-MAR-CO SUbsite, February 24, 1987. Woodward-Clyde, 1987b. Ground Water Evaluation, Hastings Ground Water contamination Site, May 7, 1987. 1. A commenter asked whether EPA considered the Naval Ammunition Depot (NAD) a subsite of the Hastings Ground Water contamination Site, as listed on the National Priorities List (NPL). EPA Response: The Hazardous Ranking System (HRS) scoring package submitted for. the Hastings Ground Water Contamination Site con- sidered the use of the Community Municipal Services (CMS) water supply wells as potential routes of exposure to the ground water contamination. These CMS wells are located on property which was once the site of a portion of the former Hastings Naval Ammuni- tion Depot. Further discussions are planned between the EPA and the Army Corps of Engineers to define the status of the remaining portions of the former NAD not considered in the original HRS scoring package for the Hastings Ground Water Contamination site. 2. A commenter asked EPA to speculate on the source of contami- nation for CMS water supply well 24. EPA Response: Two CMS supply wells (CMS-20 and CMS-24) have been removed from service since 1985 due to the presence of volatile organic compounds. The EPA, through field investigations con- ducted as part of an overall Remedial Investigation (RI) has characterized the contamination found in these wells. The RI submitted for the FAR-MAR-CO subsite suggested that CMS-24 con- tained concentrations of carbon tetrachloride (CC14), ethylene dibromide (EDB) , and trichloroethene (TCE) above health based levels. Sampling analyses indicate that ground water located up- gradient of the FAR-MAR-CO subsite is free of CC14 contamination. Concentrations of CC14 ranging from 1 ppb to 22 ppb were detected ------- at CMS-24 for the sampling period April 1985 through June 1986. Based upon decreasing concentrations observed down-gradient, it appears that a source of CCl4 exists in the vicinity of the FAR- MAR-CO subsite. EDB was not detected in wells located up-gradient of the FAR-MAR-CO subsite. It has been detected in wells down-gradient of the FAR-MAR-CO subsite at concentrations which decrease with distance. This evidence combined with the high concentrations of EDB observed in soils at the FAR-MAR-CO subsite suggests that the EDB source of contamination is in the immediate area of soil Boring SB-16 (Zone 1, FAR-MAR-CO subsite). TCE has been detected at several locations with a range concentration from trace levels to moderately high amounts. has identified four potential source areas of TCE based upon disposal practices: (1) the central industrial area, (2) the North Landfill, (3) the South Landfill, and (4) surface impound- ments, drainage ditches, and other disposal areas on the former NAD (Hastings East Industrial Park sUbsite). The types of com- pounds (i.e., chlorinated volatile organics) detected at each of these source areas are the same with the exception of EDB found in CMS-24. in EPA past 3. A commenter inquired about the availability of sampling data for wells IN-2 and IN-9 located within the FAR-MAR-CO subsite. EPA Response: These wells have been monitored by EPA and the state of Nebraska on an intermittent basis since 1983. EPA has sampled IN-9 on four occasions: December 1985, March 1986, Sep- tember 1989, and December 1989. Results from these events can be found in the PRC Report entitled: Ground Water Report, Appendix A, and in data transmittal letters referenced in the Administra- tive Record for the Hastings site. The state of Nebraska sampled well IN-2 (also known as the Western Plastics well) in August 1983. Results from this event can be found in EPA's Remedial Investigation/Feasibility Study Work Plan prepared by Woodward- Clyde Consultants for the Hastings Ground Water Contamination Site. EPA has no record of any further sampling events for well IN-2. ------- |