UNITED STATES ARMY CORPS OF ENGINEERS

IIIIIIIIIIIIIIIIIII2.2.1Naval Ammunition Depot Operations and DecommissioningThe NAD was built in the early 1940s following government purchase of approximately48,800 acres of land in Adams and Clay Counties. The NAD was an active "load, assemble, andpack" ammunition facility during World War II and the Korean Contlict. During peak periods,the NAD was responsible for producing nearly one-half of the ordnance used by the UnitedStates Navy during World War II and the Korean Contlict.The principal production areas of the NAD included a rocket motor loading acility, a bag chargefilling plant, a 40MM loading and filling' area, medium and major caliber projectile loadingplants, a case overhaul and tank repair facility, a 20MM loading and filling area, and the Bomband Mine Complex Most of these production areas were located in the western portion of theNAD. A large array of storage bunkers and:acomplex network ofroads and railroad spurs wereconstructed at'the NAD to support theptoduction areas. Other infrastructure included twosewage treatmentplaitts, water supply wells, and an extensive network of utilities.Environmental contamination at the NAD resulted from the waste management practices duringthe facility operational period and subsequent decommissioning processes. Additionally,post-NAD operations have contributed to the contamination at the site.Decommissioning of the NAD facilities began in 1958 and was completed in 1967.2.2.2Post-Naval Ammunition Depot History and UsesBeginning in the mid-1960s, large tracts of the NAD were' sold to various individuals,businesses, and municipalities or transferred to other governmental agencies. The primaryrecipient of NAD property was the u.s; Government. e U.S. Department of Agriculturereceived over 35,000 acres of the NAD property that were developed as the Roman L. HruskaU.S. Meat Animal Research Center. The Army received over},OOOacres that were leased to theNebraska Army National Guard and developed as a training facility. The western 6,000 acres ofthe NAD were used to establish Central Community College and a privately developed industrialpark referred to as the Hastings East Industrial Park (HElP).Currently, over 60 different owners hold property in Various areas of the former NAD (Figure 2,"PropertyOwnership . at the Former NAD"). Land at the former NAD is largely oWned by the.federal government (Army and U.S. Department of Agriculture). Land use on the HElP islimited to industrial development by existing Adams County zoning ordinances.RJchDP-OUI5 RODJdoc8,21102-3

LegendC-u.IIa fII P : NavalAmIllUlltoln Depot- - . C4U1t 8oun1111YProperty OYIIIW hIp Boundart. c. c &ntWc.u U.l.A"Y .un,. East Indultrlal ParkNT -4' AmITIlJ] Pltva.".,. o us. D. . . . . . of A,rtCUltln1.252.5MilesFigure 2Property Ownership at the Former NAD2.3Previous Investigations and Response ActionsAs a result of finding groundwater contamination at the former NAD in the mid-1980s, the EPAincluded the western portion of the former NAD as part of the Hastings GroundwaterContamination Site (HGCS), a regional area of groundwater contamination in south-centralNebraska. The HGCS was added to the National Priorities List in 1986. As investigations at theformer NAD continued in the late 1980s and 1990s, the entire NAD was made part ofthe HGCS.RichDP-OU15 ROD f.doc8.23.102-4IIIIIIIIIIIIIIIIIII

IIIIIIIIIIIIIIIIIIIThe u.s. Army Corps of Engineers began initial environmental investigations of the formerNAD in 1987. Initial investigations focused on the primary production facilities of the formerNAD located within the HElP sirice this area comprises most of the production facilities of theformer NAD. Subsequent investigations of the former NAD targeted other production facilitiesand waste disposal areas including the Bomb and Mine Complex, Explosives Disposal Area,Naval Yard Dump, and South Disposal Area. Selected smaller sites involving secondaryproduction areas, railroad facilities, motor pools, and areas of land disturbance within the formerNAD were also investigated.As the number of, investigations increased; the former NAD was subdivided into OUsbased ongeographical areas of concern or media of interest. The media of interest at the former NAD areshallow soil, vadose zone, and groundwater. Shallow soil is defined as the layers of soil lessthan 10 feet below ground surface (bgs). The. vadose zone is defined as the layers of soil from10 feet bgs to the top of groundwater.The five OUs at the former NAD subsite of the HGC are identified as follows: OU4: HElP - shallow soil OU8: HElP - vadose zone OUI4: Groundwater - entire former NAD OUI5: Remainder of former NAD area - shallow soil and vadose zone (excludesOU4, OU8, and OUI6) OUI6: Bomb and Mine Complex, Explosives Disposal Area, and Naval Yard Dump shallow soil and vadose zoneThe HGCS has other OUs, whiCh are being addressed.byother parties. The geographic locationsof the HElP, Bomb and Mine Complex, Explosives Disposal Area, and Naval Yard Dump areshown on Figure 2.Numerous investigations and response actions have been compl ted for OU4, OU8, OUI5, andOU16 as part of the overall site strategy to remediate the former NAD.2.3.1Operable Unit 15Operable Unit 15 is composed of all areas of the former NAD that are not included in any of theother OUs; Preliminary evaluations ofOU15 conducted in 1993 and 1994 included the review ofprevious investigations, historiCal aerial photographs, and field and aerial reconnaissance. Theseevaluations identified 22 areas of interest (referred to as "sites") as shown on Figure 3, "Operable·Unit 15 Areas ofInterest."RlclrDfl JUI5 RODJ.doc8.23.102-5

1nr"'SII5C "'."*"'AnlWNllllnlla- Or. Jfbira.d C. 1111 o.n- YINNed! Tr"" DepGI,. MIlk II"'"11F.12 MIIk.AIa13F.14SeI* Tr. DtfIIIILegend R Grouna.ter Flow ChctlalCIiniIs fit Former N8w1 ArnmuIIIicn oepcto- y. M8jor ROlid -RailrOild. MaIn lines0.5 1M'NAFigure 3Operable Unit 15Areas of Interest. . CIty Bound8ty- '"County Soundwyrf.iiif.il 0015Ar.s Net Requiring Remechlicn u.s.N MY IlSTRCT001 S Remedillle l,Ar.,Ca PS!:F ENGINEERSKAAlSAS c:rry. UIS O.IRIRkhDP·OU1SROD ldoc8.23.102-6IIIIIIIIIIIIIIIIIII

IIIIIIIIIIIIIIIIIIIBased on additional research, interviews offormer NAD employees, field reconnaissance, andfurther evaluation of the data from previous investigations, six of the sites were'identified as notrequiring'any further investigation. The remaining 16 areas were retained for further evaluationin 1994 resulting in the identification of nine areas that were retained for site investigations aslisted in Table 1, "Sites Retained for Further Investigation."Site investigations for the retained sites wen;: conducted in 1996 through 1999 and: includedsampling and analysis of surface soils and the vadose zone. Groundwater monitoring wells werealso installed at Site 10.,Out of the nine sites retained for further investigation and evaluated in the Baseline RiskAssessment (BLRA), only two, Sites 4 and 10, posed levels of contamination resulting inunacceptable risks to human health and the environment. An Engineering Evaluation and CostAnalysis (EE/CA) was prepared for these sites and removal actions were completed to mitigatethe risks to human health and the environment. As a result of the removal actions at these twosites, the residual risks fell within the generally acceptable risk range. Additional details areprovided in Section 2.S.Table 1Sites Retained for Further InvestigationSiteDescription3Major Caliber Breakdown Facility4Rifle and Pistol Range5Concrete Pads at Nebraska Army National Guard Greenlief Training Site6Railroad Classification and Dunnage Yard7North Transfer Depot10Mark 8a Area12Mark 8b Area14South Transfer DepotSEDASoutheast Detonation Area (SEDA)2.3.2Sitewide Vapor IntrusionVolatile organic compound (VOC) contamination within the vadose zone was limited to various·operational facility locations 3.I,ld waste disposal areas at the site. Vadose zone removal actionswere completed between 1995 and 2005 using soil vapor extraction remediation at source areaswithin OUS, OUI5, and OU16. As a result, the remediated source areas are no longer continuingsources of contamination to groundwater as determined in the Soil Vapor, Intrusion Assessmentsummarized in Sections 2.6.4· and 2.S.3.RJchDP-OUI5 RODJ,docB,23,102-7

A vapor intrusion assessment, was completed in 2008 to evaluate whether VOC contaminationwithin the groundwater and/or areas of the vadose" zone represent' an unacceptable risk topotential receptors at the formerNAD.2;4Community ParticipationThe Army has maintained an active Restoration Advisory Board (RAB) since 1996. Thepurpose of the RAB is to foster communication between the Army, EPA, NDEQ, and the localcommunity concerning environmental issues at the former NAD. The RAB, is comprised of localcitizens, public officials, and representatives from the Army, EPA, and NDEQ. The RABmeetings are held quarterly and the public is welcome to attend.In addition to the RAB meetings, the Army has held public availability sessions to discussproposed removal actions and public meetings to discuss Proposed Plans for various responseactions at the former NAD. A public' availability session was held' on' October 25, 2000, topresent the recommendations of the OUI5 EE/CA to the public. 'Notices for the publicavailability session and the public comment period were advertiSed in the local print media, theHastings Tribune. No written comments were received during the comment period and no'significant changes were made to the recommended removal action, which was completed in2005.The Proposed Plan for OU15 and Sitewide Vapor Intrusion was made available to the public onJanuary 26, 2010. A copy of the Admiriistrative Record file, which contains the Proposed Planand its supporting documentation (EE/CA, Final Action Memorandum, Removal Action Reports,BLRA, Sitewide Vapor Intrusion Assessment, and other related reports), is available at thefollowing two locations:Hastings Public LibraryFourth and Denver StreetsHastings, Nebraska 68901(402) 461-2346Central Community ColJege LibraryEast U.S. Highway 6Nuckolls BuildingHastings, Nebraska 68901(402) 461-2538The notice ofavailability of the Proposed Plan and date of the public meeting were published inthe HastingsTribune for one week from' January 29 through February 5, 2010, to encourage thepublic to participate in the decision making process by providing comments on the ProposedPlan and attending the public meeting. The public comment period was held from February 1through March 5, 2010. A public meeting was held on February 8, 2010, at the, DawsonRlchDP-OUI5 RODJdoc8.23,102-8IIIIIIIIIIIIIIII'III

IIIII'IIIIIIIIIIIIIIBuilding; Central Community College, East U.S. Highway '6 and South Technical Boulevard inHastings, Nebraska, where representatives ofthe Army, EPA, and NDEQ presented the ProposedPlan and were available to answer questions . There were no questions or comments presented bythe public 'at the public meeting.2.5Scope and Role of Operable Unit 15 and Sitewide Vapor IntrusionOperable Unit 15 addresses contamination of two areas, Sites 4 and 10. The contamination atSite 4, Rifle and Pistol Rang , consisted of lead in the shallow soil. The contaminationaddressed at Site 10, Mark 8a Area,consistedofVOCs in the vadose zo.ne .The Sitewide Vapor Intrusion Assessment evaluated whether vapor intrusion into buildings is apotential exposure pathway and whether such a pathway would present an unacceptable risk topotential receptors.·2.6Site Characteristics'A brief description of general site characteristics is summarized in this section.2.6.1Topography, Soil, and GeologyThe geology and hydrogeology 'of the former NAD· and surrounding area have been studiedextensively through env'ironmental investigations of the site. A briefdescription of the geologyis provided in this subsection; however, more detailed information can be found in theAdministrative Record file.The topography of the region is gently sloping, with the land surface sloping regionally to thesouth-southeast at approximately 5 feet per mile . The principal surface drainages of OU 15 aretributaries of Big Sandy Creek and a small reservoir, which is located in the southeast portion ofthe Roman L. Hruska U.S. Meat Animal Research Center.In general, the unsaturated zone across the site (Le., those soils from the ground surface togroundwater) consists of topsoil, loess (silty clay), and sand and gravel deposits ranging in totalthickness frorri approximately 85 to 110 feet. This zone is comprised of shallow soil and thevadose zone as described in Section 2.3. The groundwater surface is located approximately 95 to120 feet bgs across most ofthe former NAD.The groundwater aquifer underlying' the former NAD is the Pleistocene Aquifer. This aquifer isthe primary source of groundwater used throughout the area for irrigation, industrial andcommercial supplies, and domestic and livestock-uses.RichDP-OUI5 RODjdoc8.23.102-9

2.6.2Site 4 - Rifle and Pistol RangeSite 4 consists of an ,unfenced, bermed area approximately 300 feet long and 140 feet wide thatwas previously used as' the backstop of a firing range. 'The area surrounding the site is nearly flatgrassland. This site is located in the northwest portion ofthe Nebraska Army National GuardGreenlief Training Site ongovemment-owned property managed by the Army. There are noresidences or businesses on'or in the immediate vicinity of the site.Through site investigations, it was determined that Site 4 contained lead ontamination ,abovehealth';'based remediation goals in surface soil. A removal action was identified with the goal ofremoving surface soils from an area measuring 75 feet by 35 feet and 1 foot deep contain'ing leadat levels in excess of established sitewide remediation goals for lead in soil of 400 milligrams perkilogram (mglkg). This remediation goal is considered protective of-area residents, maintenanceemployees, and/or ecological receptors that may come in contact with the remediated soil.A removal action was performed at Site 4 to address the lead contaminated surface soil.Approximately 360 tons of contaminated soil were removed from Site 4 and disposed of in aResource Conservation and Recovery Act, Subtitle C disposal facility located in Peoria, Illinois.Confirmation sampling was conducted to ensure that lead concentrations in the remainingsurface soil were below the remediation goal for lead of 400 mglkg. Site restoration activitiesconsisted of backfilling and regrading the excavation and surrounding area until a relativelyuniform grade was achieved. All disturbed areas were reseeded. The removal action wascompleted'in 2003.2.6.3Site 10 - Mark 8a AreaSite lOis located approximately one-half mile east of the city of Glenvil. This is a fenced site,approximately 190 acres in size that was used by the United States Navy to assemble depthcharge devices. The site includes privately owned buildings, which includes one residence. Theremaining buildings are empty, unusable, or used for storage of grain, 'farm equipment, and/o

Suite 400, The Atrium . 1200 N Street Lincoln, NE 68509-8922 . Subject: Final Record ofDecision, Operable Unit 15 and Sitewide Vapor Intrusion, Former Naval Ammunition Depot, Hastings, Ne1; raska . Dear . Mr. Gresham and Mr. Borovich: This letter transmits the Final Record ofDecision (ROD), Operable Unit 15 and Sitewide Vapor