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Ms. Erica Crosby <br />March 30, 2007 <br />Page 4 <br />• Test the integrity of the A-Pit water line during the next scheduled plant shut <br />down. <br />• Prepare a report summarizing the results of the inves-dgations. <br />Task 1.0 Site Visit/Field Mapping/Planning <br />Brown and Caldwell will conduct a site visit to confirm piezometex and well locations, walk <br />the Boulder Feeder Canal and Swede Ditch along their reaches to the west of C-Pit to <br />confirm gauging locations, and to map local conditions, See the attached Figures 1 and 2 <br />Fox preliminary locations of the gauging stations, piezometers and wells. <br />Historical aerial photography of the C-Pit area will be reviewed and summarized to clarify <br />the mining and operational history of the C-Pit area, the two irrigation ditches to the west <br />and the area between them. Preliminary contact with ait photo vendors has confirmed that <br />good coverage exists fox this area through the 1980s and 1990x. Brown and Caldwell will <br />review their holdings and obtain the relevant photos that will fill in the gaps in our present <br />understanding of site history. <br />Task 2.0 Irrigation Ditch Investigation <br />Brown and Caldwell has contacted the owners of the irrigation ditches that may potentially <br />be impacting C-Pit. The Boulder Feeder Canal is owned by the Northern Colorado Water <br />Conservancy District (NCWCD), and reportedly carries 200 cubic feet per second (CFS) of <br />flow during the irrigation season. The District has indicated that the canal may see some <br />low level flows (5-10 CFS) as soon as April 15, but the heavier irrigation flows will not <br />occur any sooner than May 1, 2007. Flows last until October 1. The Boulder Feeder Canal <br />was relocated to the west from its original alignment, away from C-Pit toward B-Pit, in the <br />1980x. Conversations with NCWCD and CEMEX Lyons Plant personnel have confirmed <br />that the area between the Boulder Feeder Canal and the Swede Ditch was reined out and <br />backfilled with shale prior to reclamation. <br />All available NCWCD records for the Boulder Feeder Canal, including any engineering <br />drawings, maps, specifications, and construction photographs, will be reviewed for <br />information that may be relevant to whether the canal may be a significant source of inflow <br />to C-Pit. <br />The Swede Ditch can reportedly carry up to 30 CFS. This ditch was placed in a corrugated <br />metal pipe (CMP) by CEMEX in 1998 to eliminate seepage that had been observed on the <br />western highwall of C-Pit. Flow is anticipated to commence in this ditch from mid-April to <br />May, and will continue through mid-September to October 1. <br />The Highland Ditch suffers from limited access to water due to junior water rights, and in <br />recent years has not carried significant flows. In good mn-off years, flow can reach a <br />maximum of 80 CFS, and typically ranges from 30 to 50 CFS. <br />Brown and Caldwell proposes to gauge the flow in the Boulder Feeder Canal and Swede <br />Ditch through standard open channel Elow measurements taken both upstream and <br />downstream of their reaches west of C-Pit, to determine if any discernable seepage can be <br />measured. Even though some measurement error is expected, it ma}' be possible to assess <br />whether any significant losses axe occurring. Such losses may be occurring due to possible <br />increases in the permeability of the shale from the blasting of the canal when it was moved <br />-05946S6.doc <br />