2011-08-01_REVISION - M1978210 ‎(15)‎

• Permit No: M1978210
• IBM Index Class Name: REVISION
• Doc Date: 8/1/2011
• Doc Name: Submittal
• From: Weld County
• To: DRMS
• Type & Sequence: TR3
• Media Type: D
• Archive: No

3. SEEPAGE ANALYSIS
The purpose of this section is to document our findings with respect to estimated seepage rates
resulting from various penetration depths of the proposed slurry v'all into bedrock and to
compare them to the allowable seepage rates as defined by the State of Colorado.
Seepage rates from/into reservoirs are limited by the State of Colorado. Design and
performance standards are calculated for each site based on the hc;ight of the slurry wall and the
surface area of the bedrock enclosed in the reservoir. The design standard is 0.03 cubic foot per
day per square foot of slurry wall area plus 0.0015 cubic foot per day per square foot of
reservoir bottom area.
The seepage analysis indicated that if a typical 4 -ft competent bedrock key were used on this
project, the resulting seepage is less than the State Engineer's design standard. This key is
shown on the drawings.
The State requires that the slurry wall design meet the design standard. The performance
standard is three times the design standard and accounts for field conditions encountered during
construction. The 90 -day leak test, to be performed after construction, will compare actual
inflow rates to the performance standard. If inflow is less than the performance standard then
the State will consider Geisert Pit to be a "sealed" reservoir.
G:\PROJECTS \111025 Geisert Gravel Pit Slurry Wall \O \OI \Geisert Sluny Wall Design Repoitdoc
4
Design Standard
Performance Standard
Reservoir Perimeter
=7181 ft x 63.7 ft x 0.03 f /day/ ft
13723 ft /day (71 gpm)
213 gpm
Reservoir Bottom
=56.7 ac x 43560 ft /ac x 0.0015 ft /day/
3705 ft /day (19 gpm)
ft
57 gpm
Total
90 gpm
270 gpm
3. SEEPAGE ANALYSIS
The purpose of this section is to document our findings with respect to estimated seepage rates
resulting from various penetration depths of the proposed slurry v'all into bedrock and to
compare them to the allowable seepage rates as defined by the State of Colorado.
Seepage rates from/into reservoirs are limited by the State of Colorado. Design and
performance standards are calculated for each site based on the hc;ight of the slurry wall and the
surface area of the bedrock enclosed in the reservoir. The design standard is 0.03 cubic foot per
day per square foot of slurry wall area plus 0.0015 cubic foot per day per square foot of
reservoir bottom area.
The seepage analysis indicated that if a typical 4 -ft competent bedrock key were used on this
project, the resulting seepage is less than the State Engineer's design standard. This key is
shown on the drawings.
The State requires that the slurry wall design meet the design standard. The performance
standard is three times the design standard and accounts for field conditions encountered during
construction. The 90 -day leak test, to be performed after construction, will compare actual
inflow rates to the performance standard. If inflow is less than the performance standard then
the State will consider Geisert Pit to be a "sealed" reservoir.
G:\PROJECTS \111025 Geisert Gravel Pit Slurry Wall \O \OI \Geisert Sluny Wall Design Repoitdoc
4