Remedial Design and Remedial Action Work Plan Remedial Design ...

Draft RD/RAWP
Remedial
Action at IR Site 25
Former NAS Moffett Field
Moffett Field, California
3.0
REMEDIA
AL DESIGN
As previously described, the selected remedy
for IR Site 25 includess excavation of sediment
impacted
by COECs including DDT, PCBs, lead, and zinc. Becausee the remedy
does not entail
traditional construction activities, the RD does not include development of traditional technical
specifications. However, special
considerations regarding sediment chemistry, minimizing
impacts to existing biological resources, and wetland restoration are crucial elements of the RD
and are addressed in the RD/RAWP.
Topics discussed in this RD section include basis of design, including brief descriptions of
previous subsurface investigation
ns at the site; conformance with applicable or relevant and
appropriate requirements (ARARs); list of drawings; andd operation and maintenance (O&M)
requirements.
3.1 BASIS OF DESIGN
The remedy will excavate sediment in areas with COEC concentrations higher than do-not-
will result in
exceed RGs (Table 1). Attainment of the do-not-exceed
RGs at each
selected area
meeting the site-widee average RGs (Table 1) ), which are risk-based and are considered protective
of ecological receptors for conditions at IR Site 25. The selection off areas to be excavated was
based on previous investigations, including the recent pre-design sampling event
(KCH, 2011),
as described below.
3.1.1 Previous Investigations
at IR Site 25
The Navy
has conducted RIs and
FSs at Moffett Field since 1993; several of these studies
addressedd IR Site 25. The IR Site 25 ROD includes a comprehensive list of references of
previous reports and the sources of data that were considered during selection of
the remedy
(Navy, 2010). Information from those sources and the ROD that is pertinent to the RD is
repeated here.
.
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