C - Hanford Site

WHC-SD-EN-TI-136, Rev. 0
Table 1. Tank Identification. ________
Tank Location Contents Size* Date Removed
182-N-1-DT 100-N Diesel Fuel 15,000 Nov. 30, 1990
182-N-2-DT 100-N Diesel Fuel 15,000 Nov. 30, 1990
182-N-3-DT 100-N Diesel Fuel 15,000 Nov. 30, 1990
105-N-LFT 100-N Diesel Fuel 5,000 Dec. 7, 1990
100-N-SS-27 100-N Unleaded 3,000 Dec. 18, 1990
gasoline
100-N-SS-28 100-N Diesel Fuel 2,000 July 17, 1990*
*Denotes volume in gallons.
**This tank last held unleaded gasoline for approximately 1 year prior to
closure.
After the valve caissons had been removed, further site characterization
continued on March 5, 1991. The soil was noted as looking dark and stained
below the valves. Samples were collected from the discolored soils in all
three caisson locations. Analysis of these samples revealed elevated levels
of petroleum hydrocarbons. On September 14, 1991, further remediation of
contaminated soil under valve caissons was attempted. It was determined that
the contamination extended below and beyond several asbestos-wrapped pipes
that prevented access with the backhoe. Work was delayed until the pipes
could be removed for complete excavation.
On March 26, 1992, the asbestos-wrapped pipes had been removed and
sampling activities were continued. Soil was excavated to a depth of 51 to
63 cm (20 to 25 in.) in each caisson location, and samples were taken. The
FTL noted in the field log book (WHC 1991) that all three sample points were
screened with an OVM meter (a pending tradename of Olympus Corporation) and
were less than detectable at the point of collection. Results from sample
analysis were below action levels. For sample summary, refer to Table 2.
4.0 105-N-LFT
Tank 105-N-LFT was removed on December 7, 1990. The tank was surveyed
and determined to be radiologically contaminated. The outer surface of the
tank measured up to 20,000 counts per minute (cpm) on a Geiger-Mueller meter
(GM). Underground piping and cables prevented proper sloping of the
excavation to allow personnel to enter. Therefore, samples were collected
from the bucket of the backhoe. Four locations were sampled, within the
excavation. Radiological contamination levels of the samples measured between
20,000 to 50,000 cpm. Radiological contamination of samples prevented
laboratory analysis before holding times expired.
On March 30, 1992, resampling activities were implemented (Figure 3).
The tank site was excavated to 3.9 m (13 ft) below ground surface. At this
point, plastic markers used to identify the final depth of original sampling
3