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The Addendum to the Baseline Risk Assessment (RA) has been prepared for the U.S. Army Environmental Center (USAEC), to discuss the results of additional investigations at existing RI study sites at Umatilla Depot Activity (UMDA), Hermiston, Oregon. The Addendum to the Baseline RA is prepared in support of the Remedial Investigation/Feasibility Study (RI/FS) of the follow-up field program at 16 UMDA RI/FS study sites to verify and characterize environmental contamination at the study sites in terms of potential impacts on human health under current and future land use conditions. This addendum assesses the potential present and future health risks and hazards posed by contaminants in soil and groundwater in the absence of remediation, and develops preliminary remediation goals for these media if remediation is determined to be required.

The Report on the Treatability Test of Groundwater by Ultraviolet (UV)/Oxidation has been prepared for the U.S. Army Environmental Center (USAEC), to document the results of the treatability test performed at Umatilla Depot Activity (UMDA), Hermiston, Oregon, during the Site 4 (Explosive Washout Lagoons) pumping tests. It has been prepared for the USAEC under the Base Realignment and Closure (BRAC) Program, and is part of the Remedial Investigation/Feasibilty Study (RI/FS) activities being performed at UMDA. The objective of the treatability test was to gather data to evaluate whether UV/ozone is a feasible alternative for effectively removing explosives from groundwater at Site 4. The report presents discussions on the treatment technology, field setup, sampling/analyses, results, and useability. The results indicate that most explosives were effectively treated by UV/ozone, but that I ,3,5-trinitrobenzene (1 ,3,5-TNB) was difficult to treat. Projected costs for a full-scale treatment system are provided. In addition, an evaluation of a field method for analyzing explosives in groundwater-which was performed in conjunction with the treatability test-is presented.

The Underground Storage Tank (UST) Investigation Report has been prepared for the U.S. Army Environmental Center (USAEC) to present the results of the UST field investigation at Umatilla Depot Activity (UMDA), Henniston. Oregon. It has been prepared for USAEC under the Base Realignment and Closure (BRAC) Program. Although the UST investigation was performed in conjunction with the Remedial Investigation/Feasibility Study (Rl/FS) activities at UMDA, it was not part of the Rl/FS. The purpose of the UST investigation report is to document the results of the UST field investigation, which included sampling and chemical analysis of the unknown contents of five tanks, tank leak testing of 30 active tanks, geophysical surveys at 14 potential UST sites, soil gas surveys at 17 potential UST and fuel oil spill sites, and soil sampling and analysis. The information gathered is used to assess the potential for contamination and to present recommendations for further action.

This document is the Risk Assessment (RA) for the Explosive Washout Lagoons (Site 4) at Umatilla Army Depot Activity (UMDA). The purpose of this RA is to address the potential future health risks posed by explosives-contaminated soil and groundwater associated with Site 4 in the absence of remediation, and to identify safe residual explosives concentrations (remedial action criteria) in soil if remediation is determined to be a requirement. This RA is not intended to address the remediation of contaminated groundwater; contaminated groundwater is addressed only to the extent that contaminants in Site 4 soil are affecting groundwater quality. The potential remediation of contaminated groundwater will be addressed in the installation-wide Baseline RA for UMDA. Based on the available data, explosives contamination appears to be widespread in soil near the lagoons and in groundwater at distances of over 650 yards from the lagoons. Three future land use scenarios-residential, light industrial, and military-and four potential future exposure pathways-soil ingestion, dust inhalation, dermal contact with soil, and groundwater ingestion-were evaluated in the RA to estimate potential future carcinogenic hazards. The results of RA indicate that remediation may be a requirement for soil at Site 4; therefore, remedial action criteria for soil were developed. Risk Assessment.

Sponsored in part by Grant NSF-MPS75-04118.