Site Narrative:
The former Unocal Chemical Distribution Facility is located within the North Industrial Corridor Site in Wichita. Unocal (now Chevron Environmental Management Company) operated the 2.4-acre facility from 1953 until 1992 as a chemical storage and distribution facility. During its operations, Unocal received bulk shipments of containerized liquid chemicals, stored bulk chemicals in aboveground storage tanks, blended bulk chemicals for customers, and packaged and transported bulk and containerized liquid chemicals to customers. The types of chemicals handled at the facility included aromatic and aliphatic hydrocarbons, chlorinated hydrocarbons, petrochemicals, among others.
Contamination at the Site was identified in 1989 when an accidental release of tetrachloroethene (PCE) occurred. Unocal contractors attempted to excavate the release area; however, it was later determined that excavation activities would not completely remediate the contaminated soil, so Unocal installed a vapor extraction system. Additional site characterization activities were conducted in 1990-1991. On the basis of information gained from these investigations, in 1992 KDHE and Unocal entered into a Consent Order for Remedial Investigation (RI) and Feasibility Study (FS) to investigate and evaluate remedial alternatives for the Site.
The RI process was conducted in several phases from 1992-2007. The investigations identified several release areas, each distinguishable by a unique set of chemical constituents. Contaminants of concern include: PCE and its degradation products trichloroethene, cis-1,2-dichloroethene, vinyl chloride; benzene; naphthalene; 1,1,1-trichloroethane; 1,1-dichloroethene; 1,2,4-trimethylbenzene; 1,3,5-trimethylbenzene; toluene; ethylbenzene and xylene. KDHE approved the FS for the Site in July 2009.
Numerous interim measures (IMs) have been implemented including: soil vapor extraction, groundwater pump and treat, soil excavation and off-site disposal, and source area and downgradient enhanced reductive dechlorination. A phytoremediation IM was implemented in April 2010 to address contamination in the western part of the Site. Monitoring was also ongoing in some areas of the Site to evaluate the potential viability of monitored natural attenuation (MNA). In December 2013 a Treatability Study was implemented using Bio-Trap samplers to evaluate the performance of various biostimulants and chemical reductants compared to MNA processes. In July 2014, EHC (electron donor material) was injected into impacted groundwater to increase the rate of biological and/or chemical reductive dechlorination of site contaminants at source areas and downgradient areas. Site-wide and performance/post injection groundwater monitoring events are currently ongoing.
In February 2013, KDHE prepared a Draft Corrective Action Decision (CAD) for the Site which identifies KDHE's preferred alternative to address contamination at the Site. The 30-day public comment period was February 11 through March 12, 2013. The Final CAD was issued July 2015.
A new Consent Order for a Remedial Design (RD) and Remedial Action (RA) for the Site, which outlines requirements for developing a RD and implementing the RA to address Site contamination, was executed in May 2019. The Remedial Action Work Plan has been approved and implemented. |