1988-04-11_PERMIT FILE - C1981008A

• Permit No: C1981008A
• IBM Index Class Name: PERMIT FILE
• Doc Date: 4/11/1988
• Doc Name: Hydrologic Description ‎(Part 2 of 2)‎
• Section_Exhibit Name: Tab 7
• Media Type: D
• Archive: Yes

Park irrigation water (estimated from samples collected in 1986 from the West Lateral
irrigation ditch) changes substantially in TDS load and water type as the irrigation
return water flows through the mine area. As the Ca-HCO3 type irrigation water
infiltrates into the undisturbed and disturbed (by mining) near surface ground water
system, water type sharply changes to a Ca-SO type as indicated by the stiff
diagrams for the Highwall Spring and the Spoils Spring #1 , respectively. These waters
strongly influence the type of water discharging from the mine area as reflected by the
similarity of these waters to the water discharging from the NPDES 001 discharge point
located immediately upstream of SW-N3. As a result of the above-described process, TDS
concentrations also increase approximately two times that of background concentration
(observed at Site SW-N7) as surface water flows through the mine area and is fed by spoils
ground water. The resultant impact of the quality of the West Return Ditch on the quality
of Tuttle Draw is reflected by the similarity in TDS concentration of SW-N3 to that of
NPDES 001 .
Despite the previously mentioned seasonal fluctuations and despite the fact that this site
is located downgradient of mining, the quality of water at this site has remained
essentially unchanged since monitoring began in 1980. Comparison of the 1980-81 data to
the 1985-86 data presented in Table 7-45 substantiates this conclusion. Table 7-45
presents mean values of select parameters analyzed in samples collected at Sites SW-N1 and
SW-N3 during both seasons (irrigation and non-irrigation) in 1980-1981 and 1985-1986.
West Return Ditch. Site SW-N6 is situated on the West Return Ditch about halfway between
Site SW-N7 and the inflow point at NPDES Pond 001 (see Exhibit 7-1 ). Water quality at
this site has been routinely collected since August of 1980 (see Appendix 7-7). Table
7-46 presents a statistical summary of historic water quality data collected at Site
SW-N6. Figure 7-27 presents a Schoeller diagram of mean milliequivalent values of the
major ions for both the irrigation and non-irrigation season at SW-N6.
The water type at SW-N6 during both seasons (irrigation and non-irrigation) is a
calcium magnesium sulfate bicarbonate (see Appendix 7-8). During the irrigation period,
mean mill iequivalents of bicarbonate and carbonate approach sulfate mean mill iequivalents
(approximately 6.1). During periods of no irrigation, the average milliequivalent sulfate
values greatly exceed bicarbonate and carbonate. For both seasons, the percentage of
these anions in relation to the other major ions results in no difference in water type.
7-132 Revised 04/11/88