Third Five-Year Review Report, Cornhusker Army Ammunition Plant, Grand Island, Nebraska

1139 Pages·2015·34.8 MB·English

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
%
REGION 7
* 11201 Renner Boulevard
Lenexa, Kansas 66219
MEMORANDUM
SUBJECT: Request for Approval of the Third Five-Year Review Report, Cornhusker Army
Ammunition Plant, Grand Island, Nebraska
FROM: Bill Gresham, Remedial Project Manager fall GAM/A—
Iowa/Nebraska Remedial Branch
THRU: Jim Stevens
Office of Regional Counsel
Diana Engeman, Acting Chief
Iowa/Nebraska Remedial Brand
TO: Mary Peterson, Director
Superfund Division
This memorandum is to transmit the Third Five-Year Review Report on the Former Cornhusker Army
Ammunition Plant, Hastings, Nebraska, prepared by the U.S. Army Corps of Engineers, Kansas City
District. This report was prepared in accordance with section 121 of the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980 and 40 Code of Federal Regulations
§ 300.430(f)(4)(ii).
The triggering action for this review was the completion of the Second Five-Year Review Report on
September 14, 2010. The Five-Year Review is required because the selected remedies do not allow for
unlimited use and unrestricted exposure. This review evaluates protectiveness of the remedies for OUs
1,2, 3 and 4. Pursuant to Records of Decision in 1994, 1998,1999, and 2000, an Explanation of
Significant Difference in 1996, and a ROD Amendment in 2001, the remedies included: extraction and
treatment of explosives-contaminated groundwater with discharge to onsite streams; excavation of
contaminated soils at OU3; monitored natural attenuation of volatile organic compound contamination
in groundwater; institutional controls to prevent residential use of groundwater; and deed restrictions to
prevent residential use of OU4 areas of concern.
A draff version of the report was previously reviewed by the EPA and NDEQ, and comments were
forwarded to USACE. USACE and the EPA revised the report to address the EPA's comments.
The EPA concurs with USACE that the remedies are protective. During the review process, there was
significant attention given to the fact that institutional controls have been inconsistently
applied/enforced, which could theoretically affect the long-term protectiveness of the remedy. USACE
maintains they have "no authority to take an enforcement action for deed restriction violations" and that
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such action "is a regulatory function and if requested or required will have to be addressed by the EPA
or the State". The EPA disagrees with USACE on this issue, and states that the transferring agency
which creates the restrictions has the authority and responsibility to enforce deed restrictions (absent
language in the deed to the contrary), and reiterates that USACE has responsibilities to ensure that the
land use controls are maintained over time. However, both organizations have agreed to jointly develop
a memorandum which will address ICs and LUCs specifically, ensuring consistent future enforcement.
Also during the review process, the EPA brought up the fact that there has never been sampling for
perchlorate at the Cornhusker site. Perchlorate is associated with the kinds of munitions produced at
Cornhusker, in the timeframes during which munition production occurred. Although there is no record
of its use at Cornhusker, the EPA considers it prudent to conduct some sampling to confirm whether
perchlorate is present as a contaminant. USACE disagrees, stating that it does not intend to conduct
such sampling. Given USACE's resistance to agreement on perchlorate sampling, the EPA is
considering options for conducting such sampling ourselves. For the purpose of this document, the lack
of perchlorate data should not be considered an issue preventing acceptance.
Attached is a copy of the report for your consideration and approval. The final signed report and the
supporting information will be added to the Administrative Records file for the site.
Attachment
Third Five-Year Review
For
Cornhusker Army Ammunition Plant
Grand Island, Nebraska

June 2015

Prepared By:

U.S. Army Corps of Engineers
Kansas City District
Kansas City, Missouri
TffiRD FIVE-YEAR REVIEW REPORT
CORNHUSKER ARMY AMMUNITION PLANT
GRAND ISLAND, NEBRASKA
Approved by:
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Executive Summary

The United States Army Corps of Engineers (USACE) has conducted the third five-year review
of the remedial actions for the former Cornhusker Army Ammunition Plant (CHAAP) located
near Grand Island, Nebraska. The purpose of this five-year review is to determine if remedial
actions implemented at the site remain protective of human health and the environment. Five-
year reviews are required at CHAAP because hazardous substances, pollutants, or contaminants
remain on-site above levels that would allow unlimited use and unrestricted exposure. The
triggering action for this third five-year review was the completion of the second five-year
review report on September 14, 2010.
CHAAP was a government-owned, contractor-operated (GOCO) facility constructed in 1942 to
produce artillery shells, mines, bombs, and rockets for World War II and the Korean and
Vietnam conflicts. CHAAP was operated intermittently for 30 years, with the most recent
operations ending in 1973. Explosives wastes and residues associated with plant operations have
resulted in soil and groundwater contamination on-site and groundwater contamination off-site to
the northeast of the site. Areas of environmental concern at CHAAP have been designated as
five individual Operable Units (OUs) as described below.

 OU1 includes both the on-site and off-site explosives-contaminated groundwater plumes.
 OU2 includes the Administrative and Base Housing Areas, Abandoned Burning Area,
Drainage Ditches, Magazine Areas, Miscellaneous Storage Areas, and Sewage Treatment
Plants.
 OU3 includes the Pistol Range (three of the four subsites), Nitrate Area, Shop Area, and
Sanitary Landfill.
 OU4 includes the unsaturated zone of Load Lines 1 through 5 and the Gravel and Clay Pit
Area.
 OU5 includes the Pistol Range Area Sites (Firing Range and Static Ejection Test Site), the
Burning Grounds, and the Fuze Destruction Areas on Tracts 19B and 20B. At the end of
fiscal year (FY) 2004, OU5 was reassigned to the Military Munitions Response Program
(MMRP).
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Individual Records of Decision (RODs) were prepared to evaluate and select remedies for OUs 1
through 4. A ROD has not been prepared for OU5, which has been redesignated Munitions
Response Site (MRS) CAAP-005; therefore, OU5 was not evaluated as part of this review. The
selected remedies for OUs 1 through 4 are as follows:

 OU1: Groundwater extraction and treatment for the on-site plume, monitored natural
attenuation (MNA) for the off-site plume, and institutional controls to limit public exposure to
contaminated groundwater both on-site (in the form of deed restrictions) and off-site (in the
form of a City Ordinance).
 OU2: No further action/no response action.
 OU3: Excavation and off-site disposal of contaminated soils, MNA of volatile organic
compounds (VOCs) in groundwater at the Shop Area, and deed restrictions to prevent
residential use in the form of proprietary institutional controls restricting future use of the
property.
 OU4: Institutional controls in the form of deed restrictions to prevent residential use.

To implement the selected remedies, a groundwater treatment plant (GWTP) was constructed to
treat the on-site portion of the explosives plume at OU-1 along with long-term monitoring
(LTM) of groundwater contamination associated with the off-site portion of the explosives
plume. From December 2006 to the present an optimization effort to include a voluntary
injection program has been conducted at OU1. The injections were initiated in an attempt to
enhance anaerobic in-situ bioremediation and cometabolic biodegradation processes at the
primary OU1 source areas. The injections were expected to reduce the overall timeframe for
closure of the GWTP. Because these injection activities are not a remedial requirement of the
OU1 ROD and have been conducted as an optimization effort, technical evaluation of the
injections was not included in this five year review.
At OU-3 the excavation and removal of contaminated soils has been completed and LTM is in
place to monitor the VOCs in groundwater. Deed restrictions and other institutional controls
specified in the ROD documents for OU1, OU3, and OU4 have been implemented in order to
prevent human exposure to contaminated soil and groundwater.
A site visit was conducted on July 30 and 31, 2014 as part of this five-year review. The OU1
groundwater treatment plant was operating and plant equipment appeared to be in good
condition. The well house for the only operational extraction well (EW-7) was inspected and the
equipment inside appeared to be well maintained. There were no private residences observed at
the site, and the majority of the land was observed to be under agricultural use with a smaller
portion of the land under industrial use.
Based on data from the plant and the monitoring wells, the groundwater treatment portion of the
OU1 remedy is functioning as designed. The OU1 institutional controls portion of the remedy
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require further evaluation as they are not being consistently enforced per the following
observations: domestic and high yield irrigation wells have been installed and screened within
the contaminated aquifer, and well restriction language has not been consistently incorporated
into deeds for excessed property. However, modeling was performed to determine whether the
installation of irrigation wells screened within the contaminated aquifer has introduced risks
associated with this exposure pathway. The model concluded that this exposure pathway was
not a risk and did not impact the protectiveness of the remedy. Furthermore, it was determined
that groundwater from the domestic wells installed within the vicinity of the OU1 plume was not
being used for human consumption. Based on this information the OU1 remedy is functioning as
designed.
No changes in land use patterns have occurred at OU2 since the last five-year review. Thus, the
selected remedy for OU2 is functioning as designed.
The selected soil remedies for OU3 of soil excavation and groundwater MNA are functioning
and achieving the desired results as intended in the associated ROD document. However, the
groundwater use institutional controls do not appear to have been consistently enforced per the
obersvation that domestic and high yield irrigation wells have been installed and screened within
the contaminated aquifer. However, modeling was performed to determine whether the
installation of irrigation wells screened within the contaminated aquifer has introduced risks
associated with this exposure pathway. The model concluded that this exposure pathway was
not a risk and did not impact the protectiveness of the remedy. Furthermore, it was determined
that groundwater from the domestic wells was not being used for human consumption. Based on
this information the OU3 remedy is functioning as designed.
The selected remedy for OU4 of institutional controls to prevent residential use is functioning as
designed. The selected remedy is achieving the desired results as intended in the associated
ROD document.
This third five-year review provides an assessment of these remedial actions to determine if they
remain protective of human health and the environment. Based on the findings of this five-year
review, the remedies at OU1, OU2, OU3, and OU4 are protective of human health and the
environment.

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Five-Year Review Summary Form
SITE IDENTIFICATION
Site Name: Cornhusker Army Ammunition Plant
Region: 7 State: NE City/County: Grand Island/Hall County
SITE STATUS
NPL Status: Final
Multiple OUs? Has the site achieved construction completion?
Yes Yes

REVIEW STATUS
Lead agency: Other Federal Agency Department of the Army
Author name (Federal or State Project Manager): United States Army Corps of Engineers
Author affiliation: United States Army Corps of Engineers Kansas City District
Review period: 04/30/2014 – 9/15/2015
Date of site inspection: 07/31/2014
Type of review: Statutory
Review number: 3
Triggering action date: 09/14/2010
Due date (five years after triggering action date): 09/15/2015

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OU1 Protectiveness Statement
Operable Unit: Protectiveness Determination: Addendum Due Date:
1 Protective n/a
Protectiveness Statement: The remedy at OU1 is protective of human health and the
environment; however, the OU1 institutional controls portion of the remedy require further
evaluation as they are not being consistently enforced per the following observations:
domestic and high yield irrigation wells have been installed and screened within the
contaminated aquifer, and well restriction language has not been consistently incorporated
into deeds for excessed property. It is recommended that the installation generate a
memorandum clarifying the OU1 institutional controls.

OU2 Protectiveness Statement
Operable Unit: Protectiveness Determination: Addendum Due Date
2 Protective (if applicable):

n/a
Protectiveness Statement: The remedy at OU2 is protective of human health and the
environment.

OU3 Protectiveness Statement
Operable Unit: Protectiveness Determination: Addendum Due Date
3 Protective (if applicable):
n/a
Protectiveness Statement: The remedy at OU3 is protective of human health and the
environment.

OU4 Protectiveness Statement
Operable Unit: Protectiveness Determination: Addendum Due Date
4 Protective (if applicable):
n/a

Protectiveness Statement: The remedy at OU4 is protective of human health and the
environment.
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Overall Site Protectiveness Statement
Operable Unit: Protectiveness Determination: Addendum Due Date
1, 2, 3, and 4 Protective (if applicable):
n/a

Protectiveness Statement: The remedy for the site is protective of human health and the
environment.

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