The Apache Longbow–Hellfire Missile Test at Yuma Proving Ground: Ecological Risk Assessment for Tracked Vehicle Movement across Desert Pavement

ABSTRACT

A multiple stressor risk assessment was conducted at Yuma Proving Ground, Arizona, as a demonstration of the Military Ecological Risk Assessment Framework (MERAF). The focus was a testing program at Cibola Range that involved an Apache Longbow helicopter firing Hellfire missiles at moving targets, that is, M60-A1 tanks. This article describes the ecological risk assessment, using the MERAF, for the tracked vehicle movement component of the testing program. The principal stressor associated with tracked vehicle movement was soil disturbance, and a resulting, secondary stressor was hydrological change. Water loss to desert wash vegetation was hypothesized to result from increased infiltration and/or evaporation associated with vehicle disturbances to surrounding desert pavement, potentially affecting mule deer as well as vegetation. The simulated exposure of wash vegetation to water loss was quantified using estimates of disturbed land area from a digital orthogonal quarter quadrangle aerial photo and field observations, a 30-m digital elevation model, the flow accumulation feature of ESRI ArcInfo GIS, and a two-step runoff process dependent on soil characteristics and the extent of disturbance. In all simulated scenarios, the absolute amount of water lost increased with distance from the disturbance downslope in the washes; however, the percentage of water lost was greatest in land areas immediately downslope of a disturbance. Potential effects on growth and survival of desert wash trees were quantified by comparing water availability from the hydrologic model to water volume thresholds required for wash trees to survive and persist, derived from a local study. For both the incremental risk of the test program and for the combination of test and pretest disturbances, this demonstration of MERAF found no significant risk to either wash vegetation growth and survival or mule deer abundance and reproduction.

Key Words:

• ecological risk assessment
• tracked vehicle
• desert wash
• desert pavement
• surface varnish
• vegetation
• water loss
• soil disturbance

ACKNOWLEDGEMENTS

This research was funded by a contract from the U.S. Department of Defense Strategic Environmental Research and Development Program (SERDP) project CS-1054, A Risk Assessment Framework for Natural Resources on Military Training and Testing Lands, to Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. We thank Bob Holst and John Hall for serving as project sponsors. We also acknowledge the contributions of the following people for data, guidance, manuals, programming advice, text reviews, activity descriptions, and other assistance: Valerie Morrill, Chuck Botdorf, and Junior Kerns from the Yuma Proving Ground Environmental Sciences Division; Sergio Obregon, David McIntyre, and Bruce Goff from Jason & Associates, Yuma Proving Ground Office; Rick Douglas and Bert Evans from Yuma Proving Ground Aviation and Airdrop Systems; Dick Gebhart and Kim Majerus from the U.S. Army Corps of Engineers Construction Engineering Research Laboratory; and Todd Kuiken, Robert Washington-Allen, and S. Marshall Adams from Oak Ridge National Laboratory. Lastly, we acknowledge and thank the many people who conducted and reported field study results at YPG, without which we would not have been able to conduct this risk assessment.

Current address for William W. Hargrove: Eastern Forest Environmental Threat Assessment Center, Southern Research Station, USDA Forest Service, Asheville, NC 28804-3454, USA.

This article has been authored by a contractor of the U.S. Government under contract DE-AC05-00OR22725. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.

Notes

^aOn-road vehicle movement would be expected to generate all of these stressors except for the disturbance of desert pavement.

^bNo evidence for this effect, and not expected to be observed among mule deer.

^aNote that the use of an “initial abstraction” term would result in less runoff.

^bBased on soil survey descriptions by Cochran (1991).

^a1 indicates that all water leaves cell and is potentially available to lower elevation cells; 0 indicates that no water leaves cell (it infiltrates, ponds, evaporates, or is transpired).

^bThe value for disturbed soils in the wash community is not applicable for this test and is not applicable to most test programs at YPG, where wash disturbances are avoided where possible.