The USAEC provides support to Army Headquarters, Army commands and Army installations relating to Natural Resource Trustee and Natural Resource Injury issues.

The Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), the Oil Pollution Act, and the Clean Water Act (CWA) all contain provisions on natural resource injuries and damages (NRI/NRD). These laws allow natural resource trustees to assess damages to natural resources resulting from a discharge of oil or a release of a hazardous substance covered under CERCLA or the CWA. Specifically, under CERCLA 107(a)(4)(C), DoD, like any other responsible party, may be liable for "damages for injury to, destruction of, or loss of natural resources, including the reasonable costs of assessing such injury, destruction, or loss resulting from [the release of a hazardous substance]."

Natural Resources are broadly defined to include "land, fish, wildlife, biota, air, water, groundwater, drinking water supplies and other such resources". When oil or hazardous substances (but not pollutants or other contaminants) enter the environment, they may harm natural resources, reduce the public's use or enjoyment of them and/or degrade an ecological function that they provide. When the changes to the resource are adverse and measurable, the affected resource is said to be injured. Injury to natural resources serves as the basis for a damage claim.

CERCLA Sec. 104(b)(2) requires the lead agency to promptly notify the appropriate Federal and State natural resource trustees of potential damage to natural resources resulting from releases under investigation. In the case of DoD, the "responsible party" side of DoD should notify all applicable trustees, including its own internal trustee representative. DoD shall seek to coordinate their plans, assessments and investigations with both Federal and State trustees.

By Executive Order 12580 and in the National Contingency Plan, the President has designated certain executive officers as Federal trustees for natural resources. These Federal trustees include the Secretaries of Defense, Interior, Commerce, Agriculture and Energy. Each State Governor has designated one or more State agencies to serve as Trustee for resources under State management or control. Tribal Chairmen, or their designees, serve as Trustees for tribal interests.

The Secretary of Defense has trusteeship over all lands owned or managed by the DoD, including facilities operated by the Navy, Army, Air Force and Defense Logistics Agency. Where DoD facilities contain hazardous waste disposal sites, the agency managing the property may have responsibilities as a natural resource trustee, lead response agent and be held accountable as a responsible party. The latter two roles may often conflict with the natural resource trustee role.

The NCP lays out the following trustee responsibilities:

Coordinate and cooperate with other trustees at sites where there are multiple trustees
Designate appropriate contacts to receive notification about potential injuries to natural resources
Upon notification or discovery of injury to, destruction of, loss of, or threat to natural resources, trustees should take the following actions:
Conduct a preliminary study to determine if trust resources under their jurisdiction are, or potentially may be, affected
Cooperate with the lead agency RPM in coordinating assessments and investigations
Carry out damage assessments
Prepare and implement a plan for restoration, rehabilitation, replacement, or acquisition of equivalent natural resources

When an injury occurs, the trustees seek to restore the injured resources to a baseline condition. The baseline condition is defined as the condition that would exist except for the hazardous substance or oil release. Replacement or acquisition of equivalent resources may be substituted in appropriate circumstances. Additional measures may also be appropriate to address lost uses of resources (referred to as lost services) during the period of injury. Responsible parties may either restore the injured resources and address the loss of services, or they may simply make a payment (i.e., pay damages) to the natural resource trustee(s) equal to the sum of the baseline restoration program cost and the value of lost services.

The Secretary of Defense has delegated trusteeship of Army property to the Deputy Assistant Secretary of the Army for Environment, Safety and Occupational Health [DASA(ESOH)]. As Army Trustee, he/she may further delegate trusteeship duty, if warranted. As of Aug 2013, trustee responsibilities at two Army installations have been delegated down to the USAEC (Massachusetts Military Reservation and Twin Cities Army Ammunition Plant). USAEC has personnel available who are knowledgeable in this area and are available to support higher headquarters. Installation inquiries concerning NRI or NRD issues, above and beyond regular notification and coordination, should be relayed up the chain of command to DASA(ESOH), with a copy furnished to AEC.

On 2 May 00, DoD published guidance on the Integration of NRI Responsibilities and Environmental Restoration Activities. The policy's stated purpose is to provide guidance to each of the Components regarding their responsibilities to address NRI at sites where DoD is both a natural resource trustee and, as a responsible party, the lead response agency for environmental cleanup actions. DoD stresses, wherever possible, the Services should redress NRI as part of the site assessment, investigation and remedy selection and implementation. DoD notes that while an Ecological Risk Assessment (ERA) and a Natural Resource Damage Assessment study are intended to address different concerns, they both address injury. In appropriate situations, DoD suggests to expand the ERA to collect additional information regarding NRI and to coordinate this idea with the other trustees during the design of the ERA.

On 11 Jul 02, the Army published its Interim Policy for Integrating Natural Resource Injury Responsibilities and Environmental Response Activities. The policy required the Army to consider and, if applicable, eliminate or reduce the potential for Natural Resource Injury (NRI) as part of the site assessment, investigation, remedy selection, and implementation process for cleanup actions. The policy was intended to ensure that the Army carried out its Lead Agent responsibilities in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), the National Contingency Plan, the Defense Environmental Restoration Program, and Army Regulation 200-1.

On 24 Jan 06, the Army published its Natural Resource Injury Guidance for Active and Base Realignment and Closure (BRAC) Installations. This guide provided supplemental guidance to AR 200-1 and the Army Interim Policy for Integrating Natural Resource Injury Responsibilities and Environmental Response activities.