I.
Background: The Surface Water Treatment Rule (SWTR)
promulgated by EPA requires that treatment sufficient to produce a three-log (
99.9%) reduction in Giardia lamblia cysts and a four-log (
99.99%) reduction in viruses be provided for all surface water sources and all
ground water sources under the direct influence of surface water. The basic
criteria which determines direct influence of surface water on ground water
sources, within the context of the SWTR, is the possibility of Giardia
cysts being carried into the ground water by infiltrating surface
water. The more recent Interim Enhanced Surface Water Treatment Rule (IESWTR)
and Long Term 1 Enhanced Surface Water Treatment Rule (LT1) add the requirement
for 2-log (99%) removal of Cryptosporidium oocysts for all
surface water sources and all ground water sources under the direct influence
of surface water.
II.
Obvious Surface Water Sources: The Department has
identified ponds, lakes, and streams as obvious sources of surface
water.
III.
Protocol
for Ground Water Under the Direct Influence of Surface Water
Determination: The definitive determination of the influence of
surface water is to perform particulate analyses on water samples collected
from public water sources.
A.
New
Sources: The following screening protocol will identify the
sources for which particulate analysis will be necessary. Department personnel
will examine information on file to determine if a source of water is
potentially at risk to the direct influence of surface water. If any one of the
following conditions is true, then the source of water is potentially at risk
to the direct influence of surface water:
1.
The source of water is a spring, horizontal/radial collector well, or an
infiltration gallery;
2. The top of
the uppermost intake structure of a well is less than or equal to 50 feet from
the ground surface;
3. There is
evidence of E. coli contamination of the discharge of the
source;
4. The source of water is
less than 200 feet from a source of surface water or the sloping margin of, or
the ground bordering a stream that serves to confine the water to the natural
channel during the normal course of flow. It is best marked where a distinct
channel has been eroded in the valley floor, or where there is a cessation of
land vegetation.
5. There are
defects in the condition of the upper terminus (e.g., defective well seals,
grouting, or other defects in the upper annulus);
6. There is inadequate information on file to
assess whether the source of water meets one or more of the conditions in
III.A.1 through III.A.4. In this case, owners of the public water system will
be given the opportunity to provide the required information.
B.
Existing
Sources: Any existing source will be evaluated under the screening
protocol for new sources if any one of the following conditions exists:
1. A waterborne disease outbreak takes place
in the public water system service area and the public water system is
suspected of being the cause;
2.
There is evidence of E. coli contamination in the source water
and the source water meets any of the criteria in III.A above; or
3. The public water system has continuous
disinfection, the source water meets any of the criteria in III.A above, and
the source has not been previously evaluated by the Department using
temperature, pH, turbidity, or microscopic particulate analysis.
C.
Not Under the
Direct Influence: A source of water that does not meet any
of the criteria in III.A or III.B above is not considered to be at risk
to the direct influence of surface water and Title 179 regulations regarding
surface water and ground water under the direct influence of surface water do
not apply.
D.
At
Risk: If a source of water is determined to be potentially at risk
to the direct influence of surface water in accordance with the criteria in
III.A or III.B above, particulate analysis samples must be taken from the
source as follows:
1. A minimum of a set of
two samples must be collected and analyses performed for the presence of green
algae, blue-green algae, diatoms, nematodes, flagellates, and gastrotrichs. The
second sample must be taken a minimum of 24 hours after the conclusion of the
previous sampling. Samples must be collected in accordance with the Consensus
Method for Determining Groundwaters under the Direct Influence of Surface Water
Using Microscopic Particulate Analysis (MPA) which is incorporated herein by
reference. This publication is available from the National Technical
Information Service, NTIS PB 93-180818, U.S. Department of Commerce, 5301
Shawnee Road, Alexandria, Virginia 22161. The toll-free number is 800-553-6847.
This document may be inspected at the Division of Public Health of the
Department of Health and Human Services, 301 Centennial Mall South, Lincoln, NE
68509. Sample collection must be at such times as the ground water source is
most vulnerable to surface water infiltration (e.g., during periods of high
surface water stages, after heavy rainfall or runoff events); however, sample
collection will not be required when the source would not be used due to
abnormal conditions including but not limited to flooding and natural
disasters. Sample volumes must be at least 500 gallons. Analysis must be made
by a certified laboratory that has entered into an agreement with the
Department laboratory as specified in 179 NAC 20.
2. The presence of any of the indicators
given in III.D.1 in both samples will be considered conclusive evidence of
surface water influence and the source is subject to Title 179 regulations
regarding surface water and ground water under the direct influence of surface
water unless the system is able to determine that a structural defect led to
the presence of indicator organisms in the sample(s).
If a structural defect is found and corrected, the system may
sample again in order to determine if the source is under the direct influence
of surface water.
3. If
sample results are inconsistent, an additional set of two samples must be taken
as directed by the Department. If any two of the four samples taken contain any
of the indicators listed in III.D.1, their presence will be considered
conclusive evidence of surface water influence and the source is subject to
Title 179 regulations regarding surface water and ground water under the direct
influence of surface water.
