Page 149 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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3.20 Groundwater Under the Direct Influence of Surface Water 111
3.20.2 GWUDI Determination: Detailed Evaluation Phase

Once a groundwater source has been selected for further review, as a result of the source
screening phase, the procedure described in Fig. 3.18 should be closely followed.
The detailed evaluation phase has three components, as shown in Fig. 3.18: (a) hydro-
geologic assessment, (b) water quality assessment, and (c) microscopic particulate analy-
sis (MPA). The water supplier makes the decision about whether to begin with option
1 (hydrogeologic assessment), option 2 (water quality assessment), or option 3 (MPAs).
Either the hydrogeologic assessment or water quality assessment is capable of providing
the information required to determine that no surface water influence is present.
Sometimes, for example, when the project time is extremely important, the project
engineer may want to choose option 3 (MPAs) directly or even option 4 (accept GWUDI
determination).
If the hydrogeologic assessment option was chosen, but its results were inconclusive,
the project engineer who represents the groundwater source owner/developer may request
further water quality assessment (option 2) or MPAs (option 3) to complete the detailed
evaluation phase, or simply accept the GWUDI determination (option 4).

From source screening Option 4
Potentially
Option 1 Option 2 GWUDI
Source selected
for further review

Hydrogeologic Inconclusive/positive Water quality
assessment
assessment
Negative Not under No
Significant
the direct correlation?
influence
of surface Yes
water
Adequate seal No Reconstruct
and
construction?
Yes
Hydraulic
connection
Low risk
factor
MPAs High risk
Consult with factor
local dept. of Option 3
Moderate
health
risk factor
Under the direct
influence of
surface water

Figure 3.18 Identification of Groundwater Sources Under the Direct Influence of
Surface Water—Detailed Evaluation Phase Methodology