2009-06-08_REVISION - M1997032 ‎(21)‎

• Permit No: M1997032
• IBM Index Class Name: REVISION
• Doc Date: 6/8/2009
• Doc Name: EPP ‎(AM-01)‎ Attachment 1,2,&3 of Attachment A ‎(part 2)‎
• From: Denison Mines
• To: DRMS
• Type & Sequence: AM1
• Email Name: RCO
• Media Type: D
• Archive: No

Secfion 4
Pofenfia/forRock fo be Toxic Forming
• Exhibit 4-1 presents the results of monthly percolation estimates for an average
precipitation year.
Exhibit 4-1. Estimated percolation through develo ment rock areas for average precipitation
Month Potential
ET in. Precipitation
in. Actual
ET in. Runoff
in. Infiltration
in. Percolation
in.
October 3.36 1.51 1.36 0.15 1.36 0.00
November 2.19 1.05 0.95 0.11 0.95 0.00
December 0.48 0.85 0.48 0.09 0.77 0.00
Janus 0.47 0.88 0.47 0.09 0.79 0.00
February 1.94 0.76 1.30 0.08 0.69 0.00
March 2.93 1.04 0.94 0.10 0.94 0.00
April 3.70 1.01 0.91 0.10 0.91 0.00
May 4.93 0.94 0.84 0.09 0.84 0.00
June 5.72 0.47 0.43 0.05 0.43 0.00
Jul 6.34 1.18 1.06 0.12 1.06 0.00
August 5.74 1.35 1.22 0.14 1.22 0.00
September 4.43 1.50 1.35 0.15 1.35 0.00
Annual Total 42.33 12.55 11.29 1.25 11.29 0.00
The estimate summarized in Exhibit 4-1 indicates that potential ET exceeds average
precipitation by a ratio of approximately 3.4 to 1. Under average conditions, available
ET is adequate to evaporate water infiltrating the surface of the rock piles. A
temporary increase in stored soil moisture would occur during the months of January
and February, but this water would be removed from the pile by ET in later months.
Monthly estimated ET exceed monthly precipitation during all months of the year.
Exhibit 4-2 presents a similar estimate using precipitation conditions that occurred
during the wettest year on record, 1997.
Exhibit 4-2. Estimated ercolation throw h develo ment rock areas for wettest year on record
Month Potential
ET in. Precipitation
in. Actual
ET in. Runoff
in. Infiltration
in. Percolation
in.
October 3.36 2.36 2.12 0.24 2.12 0.00
November 2.19 2.16 1.94 0.22 1.94 0.00
December 0.48 1.80 0.48 0.18 1.62 0.00
January 0.47 1.09 0.47 0.11 0.98 0.00
February 1.94 0.48 1.94 0.05 0.43 0.00
March 2.93 0.17 0.30 0.02 0.15 0.00
A dl 3.70 2.41 2.17 0.24 2.17 0.00
May 4.93 1.78 1.60 0.18 1.60 0.00
June 5.72 0.62 0.56 0.06 0.56 0.00
Jul 6.34 1.20 1.08 0.12 1.08 0.00
August 5.74 1.10 0.99 0.11 0.99 0.00
September 4.43 4.70 4.23 0.47 4.23 0.00
Annual Total 42.23 19.87 17.88 1.99 17.88 0.00
The estimate summarized in Exhibit 4-2 for the wettest year on record indicates that
potential ET exceeds precipitation by a ratio of approximately 2.1, and suggests that
water infiltrating the pile also evaporates during the year. During the months of
December and January, the monthly precipitation exceeds the estimated monthly ET.
Therefore, stored moisture within the rock pile would be expected to increase during
December and January. However, excess ET occurring in latter months is estimated to
4-11