PERMFILE49711

• Permit No: M2005066
• IBM Index Class Name: Permit File
• Doc Date: 4/6/2006
• Doc Name: Adequacy Response
• From: Banks and Gesso LLC
• To: DMG
• Media Type: D
• Archive: No

Ms. Erica Crosby
Division of Minerals and Geology
April 5, 2006
Page 19 of 21
ranges from approximately 4- to 5- feet at the western edge of the site to
approximately 10-feet in the WIA well vicinity. The general gradient for the alluvial
water table in the area is from south-southwest to north-northeast, and generally
trending towards the South Platte River. The gradient is extremely low, being about
0.0035 to the north, northeast in the Wattenberg vicinity. The velocity of flow is
likewise extremely low, estimated to be in the range of 5- to 6-feet per day, based on
the 0.0035 gradient, a hydraulic conductivity of 500 feet per day and a estimated
porosity of 30-percent.
8. In accordance with Rule 6.4.4(1](1), please verify the maximum depth of excavation
and the substrate at the pit bottom, ie: shale, clay, claystone, sandstone, etc. In
addition, please provide a representative cross-sectional diagram which shows the
width and depth of slurry wall installation relative to the pit excavation(s) and verified
the slurry wall will be `keyed into" competent bedrock. Please respond.
At least 9 borings have been performed at this site for various purposes (including
monitor well installation). In each borehole, bedrock consisting of claystone was
encountered at depths ranging from 18 feet (on the west part of the property) to 40.5
feet (on the eastern side). A representative cross section of the slurry wall is
included as Attachment 11. As described in response #12 above, the maximum pit
depth is approximately 40 feet, and the slurry wall will be keyed into the underlying
shale 2-5 feet or as necessary based on the future geotechnical evaluation study.
9. The May 3, 2005 "Ground Water Modeling Study" provided by Martin and Wood
Water Consultants, Inc. focuses primarily on expected impacts to the Town of
Wattenberg's well. In accordance with Rule 3.1.6(1), please quantify the horizontal
and vertical extent of mounding (up-gradient) and shadowing (down-gradient)
expected following completion of the slurry wall surrounding Phase 2 & 3. Based on
the above results, please provide a Map or Exhibit which shows the location of any
groundwater users (wells, springs) and/or structure owners (septic tanks, leach
fields, sewer lines, basements) within the extent of mounding or shadowing; and
provide an assessment of the impact to each water user or structure owner.
Exhibit C-1 provides the approximate location and owner of all registered wells and
known structures within the extent of mounding and shadowing. It is likely that
occupied buildings in this area are served by septic systems; however, their
approximate locations are unknown. Houses in the vicinity without registered wells
may be served by unregistered wells and/or the Wattenberg municipal well.
(Response from Martin and Wood Water Consultants, Inc.)
The modeling carried out previously for the combined proposed pits (Asphalt Paving
and Aggregate Industries) and presented in the May 3, 2005 report, indicates that
the mounding will extend out some 2000-feet from the slurry wall boundary. The
magnitude is predicted to range from approximately 1.5-feet at the wall edge down
to less than 0.25-feet at the 2000-foot distance. For the shadowing, a somewhat
reduced extent and magnitude is predicted, with 0.5 feet predicted at a distance of
approximately 750-feet and 0.75 feet at the wall edge.