C - Hanford Site

WHC-SD-EN-TI-136, Rev. 0
56, and 199-N-57 (See Figure 1). They have been monitored for total petroleum
hydrocarbons (TPH) and for benzene, toluene, M+P-xylene, and 0-xylene (BTEX)
from 1988 to present. Records back to 1988 indicate that no organic carbons
(other than chloroform) have been detected in any of these wells.
6.0 CLOSURE RECOMMENDATIONS: TANK 100-N-SS-28
The WAC 173-340 "Model Toxic Control Act--Cleanup" and WAC 173-360
"Underground Storage Tank Regulations" are the established guidelines. These
guidelines specify the means and degree for any corrective/cleanup action. If
contaminated soil is found in contact with the groundwater or if soil
contamination appears to extend below the lowest soil sampling depth, testing
shall include the installation of groundwater monitoring wells to test for the
presence of possible groundwater contamination. The minimum testing will be
for BTEX and TPH constituents. Based upon these guidelines, recommendations
of Site Remediation Management (SRM) are as follows:
Option 1: Excavate the area in question using an excavator capable of
reaching depths of at least 12 m (40 ft).
(a) If contamination is not present after excavating to 40 ft BGS, SRM will
consider the site to be clean from petroleum product.
(b) If contamination is determined to be present, excavation will continue
until contaminated soils are removed, or Option 2 will be used.
Option 2: Install monitoring wells as required by the regulations. Because
there are some wells already in close proximity, a compromise could possibly
be reached with the State of Washington concerning the number of wells needed.
7.0 SUMMARY
This document was created in an effort to summarize the
remediation/characterization activities concerning USTs at 100-N Area and to
compile supporting documentation. The 182-N-1-DT, 182-N-2-DT, 182-N-3-DT, and
105-N-LFT UST's are considered clean closed (Appendix A). The 100-N-SS-27 and
100-N-SS-28 UST site are pending a preferred alternative decision for clean
closure. Tables have been created summarizing analytical results. Maps and
figures of removal sites and sample locations are included. Copies of all
official correspondence letters are contained in Appendix B. Unusual
Occurrence Reports can be found in Appendix C, and validated sample
documentation from the offslte laboratories is included in Appendix D.
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