2018-10-16_PERMIT FILE - M2018039 ‎(2)‎

• Permit No: M2018039
• IBM Index Class Name: PERMIT FILE
• Doc Date: 10/16/2018
• Doc Name: Adequacy Review Response
• From: Blue Earth Solutions
• To: DRMS
• Email Name: JLE
• Media Type: D
• Archive: No

Without specific geotechnical evaluations and sieve analyses from the site, information from the
Treiber Lakes Site (M-2011-049) was used to estimate the hydraulic conductivity for the aquifer
(Table 2). Geotechnical data, including grain-size distributions from the alluvial samples was
collected at the Treiber Lakes Site (approximately one mile west of the Lamb Lakes Site) in
2012 for slurry wall construction (EnviroGroup 2012). Calculated hydraulic conductivity values
from two different methods were used and, if applicable, compared. The Hazen Method (Fetter
1994) is a simple calculation relating the D10 size of the soil to hydraulic conductivity. The
Beyer Equation (Kresic 2006) calculates hydraulic conductivity using the D 10 particle size and
uniformity coefficient of poorly sorted porous media. Results from the bore hole samples
estimate that the hydraulic conductivity of the alluvium is between 9 and 64 feet/day.
Although published data for alluvial hydraulic conductivity is rare, a United States Geological
Survey report (Schneider 1983) found hydraulic conductivities for the northern Front Range
South Platte River alluvium and its tributaries (including the Cache la Poudre River) typically
range from 15 to 300 feet/day. Additionally, during slurry wall construction at Treiber Lakes,
the aquifer conductivity was estimated to be approximately 28 ft/day (Tetra Tech 2015).
Records from the SEO for domestic and agricultural wells near the property generally indicate
low yields during well construction, with saturated thicknesses of 10 to 15 feet and pumping
rates of about 15 gallons per minute, suggesting a relatively low alluvial hydraulic conductivity.
Based on available information, a bulk hydraulic conductivity value of 30 feet/day was used for
potential dewatering impact evaluations. This value is within the bulk hydraulic conductivity
range provided by Schneider (1983) and is consistent with wells yields reported in SEO well
construction documents.
Table 2
Summary of August 2009 Bore Hole Gradation Data (Miller 2009)
D10(t) D50 (2) D60 (3) Uniformity Hydraulic(5)
Bore Hole (mm) (mm) (mm) Coeff.(4) Conductivity
(feet/day)
BH-1 0.15 1.3 2.1 14 64
51
BH-7 0.07 1.2 2.1 30 14
9
BH-9 0.10 2.1 3.5 35 28
17
(1) 10%of the particles in the sample are smaller than this diameter.
(2) 50%of the particles in the sample are smaller than this diameter.
(3) 60% of the particles in the sample are smaller than this diameter.
(4) Uniformity Coefficient=D60/D 10
(5) Method results for estimating hydraulic conductivity: Hazen Method from Fetter 1994
(top)Beyer Method from Kresic 2006(bottom)
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