PERMFILE105327

• Permit No: C1992081A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: TAB 7 HYDROLOGICAL DESCRIPTION
• Media Type: D
• Archive: Yes

• TAB 7
HYDROLOGICAL DESCRIPTION
Regional Hydrogeology and Surface Water Chazacteristics
The Hayden Gulch Terminal, Inc.'s (HGT) loadout facility (LOadout) is principally situated
(coal storage, tipple and majority of the railroad apur)in the Dry Creek drainage basin
(tributary to the Yampa River) . A small portion of the railroad spur exists in the Yampa
River drainage basin. A regional hydrological description of this area is presented in detail
in Attachment 7-1.
Site Specific Ground Water Characteristics
The coal storage and tipple area of HGT'e Loadout is situated in alluvial and collwial
materials overlaying the Loris shale of upper Cretaceous age. Two alluvial/shallow Lewis
shale walls ware constructed in the loadout area prior to 1993 by the previous operator H-G
Coal Company. One wall, identified ae HGDALI, is located upgradient of the loadout Brea and
the second well, identified ae HGDAL2, is located dorngradient of the Loadout. During
October 1993, a new downgradient alluvial vrell, identified as HGDAL3, was constructed along
Dry Creek to assure all potential ground water impacts from the Loadout could be assessed.
The nex dotmgradiant well was installed to alleviate Colorado Division of Minerals and Geology
• (DM-s) concerns regarding the possibility that walls HGDALI and HGDAL2 ware pa~:ally completed
in the Lewis shale. The locations of the three alluvial relle are shown on Exhibit 12-2 in
Tab 12. Completion information for the new cell (HGDAL3) is presented in Attachment 7-2.
Seasonal Vaziability and Trends. Tables 7-1, 7-2, and 7-3 present the water level and
chemistry data for wells HGDALI, HGDAL2, and HGDAL3, respectively. Water levels ranged fr®
1.6 to 8.4 feet below ground surface (bgs), 0.7 to 13.5 feet bgs, and 0.9 to 7.5 feet bgs at
sells HGDALI, HGDAL2, and HGDAL3, respectively. On 5/4/95, the water level in well HGDALI was
reported as -0.42 feet, which indicates the water level in the casing was above ground
surface. Generally, no water level trends or seasonality are evident at the wells, however,
water levels tend to be higher during spring anowmalt months which indicates that snormalt may
ba recharging the alluvium.
Total dissolved solids (TDS), magnesium (Mg), sodium (Na), and sulfate (SOS) concentrations in
well HGDALI ors generally trice those measured in well HGDAL2. Folloring the completion of
wall HGDAL3 in Nov®ber 1993, the ground rater quality data demonstrates that a similar ground
water chemistry pattern exists between HGDALI and HGDAL3 as what existed between HGDALI and
HGDAL2. TDS, Mg, Na, and 90. concentrations in roll HGDALI were generally three times
the corresponding concentrations measured in wall HGDAL3. However, the TD9, Mg, Na, and
SO. concentrations in well HGDALI were generally only twice those measured in well
HDGAL2. TDS concentrations at wall HGDALI range from 15,000 mg/1 to 68,000 mq/1 while
TDS concentrations at cell HGDAL2 range from 2,000 mq/1 to 28,000 mg/1 and the TDS
concentrations at well HGDAL3 range from 14,000 to 19,000 mq/1. The TD9 value at HGDAL2
for 08/13/90 appears to be an erroneous as the S04 concentration ie 13 times the
reported TDS value.
/Q/l/- D /
1 Revised 2/98