GENERAL46748

• Permit No: M1994117
• IBM Index Class Name: General Documents
• Doc Date: 12/1/1995
• Doc Name: FAX COVER
• From: DMG
• To: DUFFORD & BROWN
• Media Type: D
• Archive: No

`J

iection II. GUIDELINES TO DEVELOP ASECOND-LEVEL SITE ASSESSMENT
REPORT
A second-level site assessment is intended to provide more detailed support data as
requested by CDH or by regulation, in order to allow for proper assessment and for
corrective actions at the site. Two (2) copies of this report must be submitted to the CDH.
As a minimum, the following information will be provided:
A) Site Geoloev
This section should contain a detailed discussion of the local geology, including a
description of the lithology of the subsurface as determined from soil borings,
excavations, or other sources. Include a copy of all available boring logs showing
drillers name, drilling date, drilling method, lithology, sampling intervals, field
screening measurements, blow counts, and all other pertinent information. If the site
geology is complex or if topography is an important consideration, then it is
suggested that a geologic profile be included in the report.
B) Site Hydrogeology
I) The depth to the uppermost saturated zone beneath the site should be
determined through the use of monitoring wells and/or piezometers, or other
means approved by the CDH;
2) The local ground-water flow direction and gradient should be determined
using a sufficient number of monitoring wells; and
3) The lithologic and hydrologic characteristics (e.g. permeability, conductivity)
of the saturated interval should be described in this report.
C) Contamination Extent
1) A sufficient number of representative soil samples must be collected to
adequately determine the horizontal and vertical extent of soil contamination
to less than or equal to 20 mg/Kg total petroleum hydrocarbons and 5 mg/Kg
total BTEX (see Section III). If background soil contamination is found to
be above the levels previously described, then the background levels can be
used as a guide for determining the extent of soil contamination.
Consideration must be given to impact or possible future impact to ground
water from the soil contamination.
2) A sufficient number of representative ground-water grab samples must be
collected to determine the extent of ground-water contamination. This must
include an upgradient (upstream) sample for background water quality and
a sufficient number of downgradient (downstream) samples to define the
extent of ground-water contamination in accordance with Colorado ground-
water standards (5 CCR 1002-8).
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