SFUND RECORDS CTR 0048-91654 Apache Powder EPA Superfund Site R0003

U.S. Environmental Protection Agency, San Francisco, CA 94105

St. David, Arizona May 1999 STATUS OF APACHE CLEANUP ACTIVITIES

The purpose of this fact sheet is to shaded areas show where nitrate major reason is that in February 1995, provide new information on investiga­ concentrations may have exceeded this ANP ceased discharging the nitrate- tive and cleanup activities at the standard of 10 parts pet million contaminated plant process waste Apache Powder Superfund site. The (ppm, also known as milligrams per waters to the unlined evaporation site study area is located in Cochise liter), but where current data only ponds in the southern area of the site. Sounty in southeastern Arizona, indicate concentrations below 10 Since the construction of a $5 million Ibout seven miles southeast of the ppm. dollar brine concentrator in 1994, an incorporated town of Benson and estimated two million gallons per approximately 50 miles southeast of The reasons for the reduction in month of the plant's wastewaters are Tucson. Bordered to the east by the nitrate concentrations and the corre­ being recycled for reuse in the plant's San Pedro River, the site includes sponding reduction in the size of the operations. A second reason is that approximately 1,000 acres of land nitrate-contaminated plume may be contaminated water in the northern owned by Apache Nitrogen Products, attributed to several factors. One area is being extracted and used to Inc. (ANP), formerly known as the Apache Powder Company. The site cm h- was listed by the U.S. Environmental o Protection Agency (EPA) on the Superfund National Priorities List in 1990. UJ S XTENT OF NITRATE § 00 LUME IN \U ttmm. m smxcm AOWFIR pcccEDS va. U- mGROUNDWATE R The extent of the nitrate-contami­

nated groundwater plume in the ST. OHM shallow aquifer has decreased consid­ erably from the extent of contamina­ tion estimated in 1996. Figure 1 shows the extent of the nitrate con­ (xssas>-i wa tamination as of November 1998. In comparison. Figure 2 shows the extent of nitrate contamination as of Novem­ ber 1996. The dark shaded areas on each map show where nitrate was detected in the shallow aquifer at concentrations known to exceed the federal and state drinking water standard, referred to as the maximum contaminant level (MCL). As a conservative approximation, the light

Figure 1: Extent of Nitrate Plume in November 1998 PAGE APACHE POWDER SUPERFUND SITE

establish the wetland vegetation. An treatment and disposal options for this that ANP sample the shallow aquifer estimated 34 million gallons have TNT and DNT-contaminated soil groundwater for perchlorate. Sampling been extracted from the contaminated will be included in the Supplemental was conducted in November 1998, shallow aquifer since October 1997. FS currently being drafted. and the analytical results were received in December 1998. Unexpectedly, TRINITROTOLUENE RECENT DISCOVERY - perchlorate was detected in several CONTAMINATED SOIL PERCHLORATE IN monitor wells located in the perched DISCOVERED NEAR SOILS AND SHALLOW zone and in the southern area of the PLANT PRODUCTION AQUIFER shallow aquifer near the production AREA GROUNDWATER IN area of the facility. As a result, confir­ SOUTHERN AREA matory sampling of the groundwater In Fall 1997, during a routine obser­ was conducted in January and Febru­ vation of stormwater runoff, some dark In mid-November 1998, as a result of ary 1999 to confirm if the extent of brown, stained soil and unidentified the recent detection of perchlorate in perchlorate was limited to the south­ debris were discovered in an arroyo the groundwater adjacent to several ern area of the site (see Figure 4). adjacent to a dirt road, just a short explosives manufacturing facilities in Additionally, some initial soil sam­ distance to the west of the plant's the western United States, EPA and pling in the vicinity of the former operating area. After further sampling, the Arizona Department of Environ­ nitric acid plant detected low concen­ laboratory analysis, and consultation mental Quality (ADEQ) requested trations of perchlorate in the sur- with mining and explosives experts during 1998, the dark brown waste materials were determined to contain trinitrotoluene (TNT), an explosive waste material, with some metal fragments. The sample results indi­ cated high concentrations of TNT in the range of 53% to 56% and lesser quantities of dinittotoluene (DNT). Because these contaminated materials had not been identified prior to EPA's 1995 Record of Decision (ROD), EPA instructed ANP to include this area in a Supplemental Feasibility Study (FS) for fmal cleanup of the soils contami­ nation at the site. (See Figure 3 for location of TNT contaminated soil.)

In February 1999, EPA approved an ANP workplan for conducting addi­ tional soil sampling and unexploded ordnance survey work in the TNT area during the spring of 1999. In addi­ tion, ANP's contractors have been researching various technologies, including biological treatment meth­ ods, for treating these explosive materials. Additional research appears to indicate that these waste materials may have resulted from a post-World War I salvage operation to recover materials for reuse. A full range of Figure 2: Extent of Nitrate Plume in 1996 MAY 1999 PAGE'S

rounding soils. discovered that from the 1920s to the aquifer drinking watet wells contain­ 1980s the company purchased ing nitrate above EPA's drinking water In the initial groundwater sampling Chilean sodium nitrate for manufac­ standard were provided deep aquifer rounds, the concentrations of perchlo­ turing processes. These nitrate depos­ replacement wells. Since the late rate ranged from less than four parts its contain a small percentage of 1980s and prior to the installation of per billion (ppb) to a high of 670 naturally-occurring perchlorate. these deep aquifer wells, residents ppb. Figure 1, which shows the Chilean sodium nitrate was used at using the shallow aquifer were pro­ location of the monitor wells, depicts ANP for the ptoduction of nitric acid vided bottled water by ANP. Addi­ what is currently known about the (a process discontinued in the 1950s) tionally, based on the sampling extent of the perchlorate contamina­ and, to a lesser extent, in the manufac­ conducted in November 1998, tion in groundwater at the southern turing of dynamite and blasting January 1999, and February 1999, area of the site. agents (processes discontinued in the perchlorate has only been detected in 1980s). the groundwater in the southern area The occurrence of perchlorate at the of the shallow aquifer. In the sampling ANP site was unexpected as perchlor­ NO KNOWN EXPOSURE conducted to date, no perchlorate has iate compounds were never directly TO PERCHLORATE AT been detected in groundwater wells at ised or manufactured on-site. How- APACHE the northern area of the shallow evet, upon this recent discovery, ANP aquifer (see Figure 4). Based on researched old shipping records and In 1995, residents with shallow current information, there is no indication that anyone in the vicinity

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Figure 3: Location of TNT-Contaminatci PAGE APACHE POWDER SUPERFUND SITE of the ANP facility is drinking been detected in groundwater at currently being conducted by EPA to groundwater with perchlorate. various manufacturing sites and in determine an appropriate health well water and drinking water advisory level for exposure to this WHAT IS supplies. There currently are 14 states compound. EPA has not established a PERCHLORATE? with confirmed detections of perchlor­ National Primary Drinking Water ate in ground or surface water. There Regulation (NPDWR) for perchlorate. Perchlorate (ClO^ ) is a chemical anion are 44 states with confirmed perchlor­ that may exist as a contaminant in ate manufacturers or users based on HEALTH BASED ground and surface waters from the EPA data. CLEANUP STANDARDS solid salts of ammonium, potassium, magnesium, or sodium perchlorate. WHAT ARE THE Although EPA is still conducting Most of the perchlorate compounds HEALTH CONCERNS? research on the appropriate drinking manufactured in the United States are water standard, the California Depart­ used for solid rocket fuel, with a Perchlorate affects the thyroid hor­ ment of Toxic Substances Control minor amount used for explosives, mone function by inhibiting iodine (DTSC) has established an interim fireworks, car airbags, and other uptake by the thyroid, resulting in health-based standard of 18 ppb of applications. Perchlorate is very reduced thyroid hormone production. perchlorate in drinking water. In mobile in water and can persist for Thyroid hormone deficiencies can March 1999, the State of Arizona many decades under typical ground affect normal metabolism, growth and adopted a provisional Human Health- and surface water conditions. Follow­ development. Severe disruption of the based Guidance Level (HBGL) for ing the development of new laboratory thyroid can also result in the forma­ perchlorate in drinking water of 31 analytical methods in April 1997 tion of thyroid tumors and othet ppb. For soils cleanup, the Arizona which can detect petchlorate at levels effects of impaired metabolism. provisional residential and non­ as low as four ppb, perchlorate has Human and ecological assessments are residential Soil Remediation Levels (SRLs) for ammonium perchlorate are 38 parts per million (ppm) and 850 ppm respectively.

WHAT'S PLANNED FOR THE FUTURE?

Additiona/ Groundwater Wells to be Instal/ed

Additional groundwater monitor wells will be installed in May 1999 in the southern area of the shallow aquifer to further characterize the extent of the perchlorate contamination. To deter­ mine the appropriate location for these new wells, borings will be installed along transects (see Figure 5). The transects are positioned across the direction of the groundwater flow to detect the flow of contaminants. These new monitor w^ells ^so will help define the relationship berween the perchlorate-contaminated groundwa­ ter and the nitrate-contaminated groundwater. EPA and the ADEQ will MAY 1999 P A G E • 5

levels. The results of these evaluations will be incorporated in the Supplemental FS including other possible alternatives for monitoring or treating the nitrate and perchlorate in the southern area shallow aquifer groundwater.

CONTINUED GROUNDWATER AND SOIL SAMPLING PLANNED

As a result of this new finding, per­ chlorate sampling and analysis will be conducted on a quarterly basis in the existing and new monitor wells. As explained earlier, Chilean sodium nitrate containing perchlorate has not been used at the plant since the 1980s. Therefore, perchlorate is no longer being discharged to soil or groundwater at the ANP facility. However, to assess the residual impact of past releases, ANP will continue comprehensive groundwater monitor­ ing to determine if the perchlorate Figure 5: Proposed Transects for Locating New Groundwater concentrations are constant or declin­ Monitor Wells ing in the perched zone and the adjacent shallow aquifer groundwater. ersee the installation of these new Although constructed wetlands are Additional soils sampling also may be onitor wells. known to be effective for the treat­ conducted. ment of nitrate, it is unknown Additional Studies on Treatment whether the concentrations of perchlo­ SUPPLEMENTAL Alternatives rate now detected in the southern area FEASIBILITY STUDY of the Apache site could also be PLANNED The development of treatment options treated in such a system. In April for perchlorate is still under investiga­ 1999, EPA approved a proposal from In Fall 1999, ANP plans to complete tion because perchlorate was only ANP for experts from Hurriboldt State the Supplemental FS currently in recently identified as a national University in Areata, California, to draft form. The findings from the groundwater problem. One of the conduct a treatability study to deter­ studies and monitoring currently most promising technologies, cui- mine if wetlands can efficiently treat underway wfll be included in this rently being tested at the Aerojet and perchlorate. Research also will be revised document. The Supplemental San Gabriel Superfund sites in Califor­ conducted to determine if perchlorate FS should include alternatives for the nia, is the use of anaerobic bio­ in a wetlands environment could remaining soils cleanup activities reactors. This perchlorate treatment adversely impact wildlife. At the required at the Apache Powder technology is similar to the anaerobic conclusion of these studies, a determi­ Superfund site. If sufficient data are processes that occur in a constructed nation will be made as to whether available, monitoring or cleanup wetlands treatment system. Many of wetland treatment is effective in alternatives for the perchlorate con­ the organisms that reduce nitrate may reducing water contaminated with tamination in the southern area of the also be able to reduce perchlorate. both perchlorate and nitrate to safe site may also be proposed for public review and comment. PAGE APACHE POWDER SUPERFUND SITE

FOR FURTHER INFORMATION ABOUT APACHE POWDER

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