Page 99 - Materials Chemistry, Second Edition

82 Practical Design Calculations for Groundwater and Soil Remediation

Discussion:
1. In part (a), 0.041 is the conversion factor to convert the hydraulic
conductivity from gpd/ft to m/day. The factor was taken from
2
Table 3.1.
2. Calculations in part (a) have demonstrated that the results would
be the same by using two different systems of units.
3. The (h − h ) term can be replaced by (s − s ), where s and s are
1
2
1
2
2
1
the drawdown at r and r , respectively.
2
1
4. The same equation can also be used to determine the radius of
influence, where drawdown is equal to zero. This topic is dis-
cussed further in Chapter 6.
Example 3.8: Estimate Hydraulic Conductivity of a Confined
Aquifer from Steady-State Drawdown Data
Use the following information to estimate the hydraulic conductivity of a
confined aquifer:

• Aquifer thickness = 30.0 ft (9.1 m)
• Well diameter = 4 in. (0.1 m)
• Well perforation = fully penetrating
• Groundwater extraction rate = 20 gpm
• Steady-state drawdown
= 2.0 ft observed in a monitoring well 5 ft from the pumping well
= 1.2 ft observed in a monitoring well 20 ft from the pumping well

Solution:
Inserting the data into Equation (3.11), we obtain:
528 r r/) (528)(20)log(20/5)
K = Qlog( 2 1 = = 397 gpd/ft 2
bh( 2 − h ) (30)(2.0 1.2)
−
1
Discussion:
The (h − h ) term can be replaced by (s − s ), where s and s are the
2
1
1
1
2
2
drawdown at r and r , respectively.
1
2
Example 3.9: Estimate Hydraulic Conductivity of a Confined
Aquifer Using Specific Capacity
Use the drawdown data of the pumping well in Example 3.7 to estimate the
hydraulic conductivity of the aquifer: