The Agency must require a CWS supplier to demonstrate under
Section 611.201 whether it uses
"groundwater under the direct influence of surface water". Based on the
information the supplier provides, the Agency must determine whether a PWS uses
"groundwater under the direct influence of surface water". The Agency must base
this determination on specific factors:
a) Physical Characteristics of the Source.
Whether the source is obviously a surface water source, such as a lake or
stream. Other sources possibly subject to influence from surface waters include
springs, infiltration galleries, wells, or other collectors in subsurface
aquifers.
b) Well Construction
Characteristics and Geology with Field Evaluation
1) The Agency may use the wellhead protection
program's requirements, which include delineation of wellhead protection areas,
assessment of sources of contamination, and implementation of management
control systems, to determine if the wellhead is under the direct influence of
surface water.
2) A well less than
or equal to 50 feet deep is likely under the direct influence of surface
water.
3) A well more than 50 feet
deep is likely under the direct influence of surface water, unless it includes
specific features:
A) A surface sanitary seal
using bentonite clay, concrete, or similar material;
B) A well casing penetrating consolidated
(slowly permeable) material; and
C)
A well casing that is only perforated or screened below consolidated (slowly
permeable) material.
4)
A source less than 200 feet from any surface water is likely under the direct
influence of surface water.
c) Any structural modifications to prevent
the direct influence of surface water and eliminate the potential for Giardia
lamblia cyst contamination.
d)
Source Water Quality Records. Specific factors indicate that a source is under
the direct influence of surface water:
1) A
record of total coliform or fecal coliform contamination in untreated samples
collected over the past three years;
2) A history of turbidity problems associated
with the source; or
3) A history of
known or suspected outbreaks of Giardia lamblia, Cryptosporidium, or other
pathogenic organisms associated with surface water attributable to the
source.
e) Significant
and relatively rapid shifts in water characteristics, such as turbidity,
temperature, conductivity, or pH.
1) A
variation in turbidity of
0.5 NTU or more over one year is
indicative of surface influence.
2)
A variation in temperature of nine Fahrenheit degrees or more over one year is
indicative of surface influence.
f) Significant and relatively rapid shifts in
water characteristics, such as turbidity, temperature, conductivity, or pH,
closely correlating with climatological or surface water conditions indicate
surface water influence.
1) Evidence of
particulate matter associated with the surface water; or
2) Turbidity or temperature data that
correlates with that of a nearby surface water source.
g) Particulate Analysis. Significant
occurrence of insects or other macroorganisms, algae, or large-diameter
pathogens, such as Giardia lamblia, indicates surface influence.
1) "Large-diameter pathogens" are those over
seven micrometers.
2) The supplier
must measure particulates as the Guidance Manual for Filtration and
Disinfection (91), incorporated by reference in Section
611.102, specifies.
h) The potential for contamination
by small-diameter pathogens, such as bacteria or viruses, does not alone render
the source "under the direct influence of surface water".
