3 August 1998
5-11. TREATMENT REQUIREMENTS.
a. Groundwater under the direct influence of surface water. According to 40 CFR 141,
"groundwater under the direct influence of surface water means any water beneath the surface
of the ground with (1) significant occurrence of insects or other macro-organisms, algae, or
large-diameter pathogens such as Giardia lamblia, or (2) significant and relatively rapid shifts
in water characteristics such as turbidity, temperature, conductivity, or pH which closely
correlate to climatological or surface water conditions." Direct influence is determined by the
State or should be determined by the installation's environmental office based on criteria
established by the State. Per Subpart H of 40 CFR 141, groundwater determined to be under
the direct influence of surface water must meet the same source water quality requirements as
surface water and will in most cases require filtration. Disinfection must be provided in all
b. Groundwater not under the direct influence of surface water.
(1) In most of the United States, upper aquifers are directly influenced by surface water
but groundwater from lower aquifers has been filtered by the formation through which it
passes. Water from lower aquifers does not have to meet the specific treatment requirements
of 40 CFR 141 (filtration and disinfection) but must still comply with standards which establish
maximum contamination levels. Other treatment such as softening, iron removal, or pH
adjustment may also be necessary. It should be noted that the natural filtering system can be
short-circuited by sink holes, fractured rocks or shallow soils that provide paths for animal
to occur after heavy storms or snow melts. If the State determines that a groundwater source
is under the direct influence of surface water, the installation must provide treatment within 18
months of written notice from the State.
(2) Guidance from the Office of the Surgeon General is provided to Department of the
Army personnel in TB MED 576. The Office of the Surgeon General advises that all water
used for drinking be disinfected (paragraph 6-1 of TB MED 576). The designer of a well and
treatment system should contact the proper office at the installation to determine if disinfection
is required for a given site. Chlorination is needed to provide residual chloride in the
distribution system. The extent of treatment must be based upon the results of the sampling
program. For a detailed discussion of treatment methods, see TM 5-813-3/AFM 88-10, Vol. 3.