Page 110 - Materials Chemistry, Second Edition

Plume Migration in Aquifer and Soil 93

0
r o = 650 ft
0.2
0.4
Drawdown (ft) 0.8 1
0.6

1.2 ∆s = 1.4 ft
1.4
1.6
1 10 100 1000
Distance (ft)

FIGURE 3.3
Distance–drawdown method for pumping data analysis.

Discussion:
1. As expected, the slope of the straight line in the distance–
drawdown is twice that in Cooper–Jacob’s straight-line plot (for
the same hydraulic conductivity and pumping rate).
2. At t = 90 min (0.0625 day) and r = 300 ft, u is equal to

2
2
1.87 rS 1.87(300 ft)(0.00074)
u = = = 0.11
Tt (18,860 gpd/ft)(0.0625 day)
3. At r < 206 ft, u will be smaller than 0.05.

3.5 Migration Velocity of the Dissolved Plume

As VOC spills enter into the subsurface, the materials may move downward
as free product or be dissolved into the infiltrating water and then move
downward by gravity. This liquid may travel deep enough to get in contact
with the underlying aquifer and form a dissolved plume in the aquifer. This
section will discuss the migration of the dissolved plume, which is relatively
simpler than the transport of the COCs in the vadose zone. This discussion is
applicable not only to VOCs, but to other types of COCs, such as heavy met-
als. Transport in the vadose zone is discussed in Section 3.6.