(a) Applicability of section. This section is applicable
only if the proposed method of water distribution for the proposed
subdivision is individual water wells on individual lots. If expansion
of an existing public water supply system or installation of a new
public water supply system is the proposed method of water distribution
for the proposed subdivision, site-specific groundwater data must
be developed under the requirements of Chapter 290, Subchapter D of
this title (relating to Rules and Regulations for Public Water Systems)
and the information developed in meeting these requirements must be
attached to the Certification of Groundwater Availability for Platting
Form (TCEQ-20982).
(b) Location of existing wells. All known existing,
abandoned, and inoperative wells within the proposed subdivision must
be identified, located, and mapped by on-site surveys. Existing well
locations must be illustrated on the plat required by the municipal
or county authority.
(c) Aquifer testing. Utilizing the information considered
under §230.7(b) of this title (relating to General Groundwater
Resource Information), an aquifer test must be conducted to characterize
the aquifer(s) underlying the proposed subdivision. The aquifer test
must provide sufficient information to allow evaluation of each aquifer
that is being considered as a source of residential and non-residential
water supply for the proposed subdivision. Appropriate aquifer testing
must be based on typical well completions. An aquifer test conducted
under this section utilizing established methods must be reported
and must include, but not be limited to, the following items.
(1) Test well and observation well(s). At a minimum,
one test well (i.e., pumping well) and one observation well, must
be required to conduct an adequate aquifer test under this section.
Additional observation wells must be used for the aquifer test if
it is practical or necessary to confirm the results of the test. The
observation well(s) must be completed in the same aquifer or aquifer
production zone as the test well. The locations of the test and observation
well(s) must be shown on the plat required by the municipal or county
authority.
(2) Location of wells. The test and observation well(s)
must be placed within the proposed subdivision and must be located
by latitude and longitude. The observation well(s) must be located
at a radial distance such that the time-drawdown data collected during
the planned pumping period fall on a type curve of unique curvature.
In general, observation wells in unconfined aquifers should be placed
no farther than 300 feet from the test well, and no farther than 700
feet in thick, confined aquifers. The observation well should also
be placed no closer to the test well than two times the thickness
of the aquifer's production zone. The optimal location for the observation
well(s) can be determined by best professional judgement after completion
and evaluation of the test well as provided in paragraph (4) of this
subsection.
(3) Lithologic and geophysical logs. The test and observation
wells must be lithologically and geophysically logged to map and characterize
the geologic formation(s) and the aquifer(s) in which the aquifer
test(s) is to be performed.
(A) A lithologic log must be prepared showing the depth
of the strata, their thickness and lithology (including size, range,
and shape of constituent particles as well as smoothness), occurrence
of water bearing strata, and any other special notes that are relevant
to the drilling process and to the understanding of subsurface conditions.
(B) Geophysical logs must be prepared which provide
qualitative information on aquifer characteristics and groundwater
quality. At a minimum, the geophysical logs must include an electrical
log with shallow and deep-investigative curves (e.g., 16-inch short
normal/64-inch long normal resistivity curves or induction log) with
a spontaneous potential curve.
(C) The municipal or county authority may, on a case-by-case
basis, waive the requirement of geophysical logs as required under
this section if it can be adequately demonstrated that the logs are
not necessary to characterize the aquifer(s) for testing purposes.
(4) Well development and performance. The test and
observation well(s) must be developed prior to conducting the aquifer
test to repair damage done to the aquifer(s) during the drilling operation.
Development must ensure that the hydraulic properties of the aquifer(s)
are restored as much as practical to their natural state.
(A) Well development procedures applied to the well(s)
may vary depending on the drilling method used and the extent of the
damage done to the aquifer(s).
(B) During well development, the test well must be
pumped for several hours to determine the specific capacity of the
well, the maximum anticipated drawdown, the volume of water produced
at certain pump speeds and drawdown, and to determine if the observation
well(s) are suitably located to provide useful data.
(C) Water pumped out of the well during well development
must not be allowed to influence initial well performance results.
(D) Aquifer testing required by this section must be
performed before any acidization or other flow-capacity enhancement
procedures are applied to the test well.
(5) Protection of groundwater. All reasonably necessary
precautions must be taken during construction of test and observation
wells to ensure that surface contaminants do not reach the subsurface
environment and that undesirable groundwater (water that is injurious
to human health and the environment or water that can cause pollution
to land or other waters) if encountered, is sealed off and confined
to the zone(s) of origin.
(6) Duration of aquifer test and recovery. The duration
of the aquifer test depends entirely on local and geologic conditions.
However, the test must be of sufficient duration to observe a straight-line
trend on a plot of water level versus the logarithm of time pumped.
Water pumped during the test must not be allowed to influence the
test results. Aquifer testing must not commence until water levels
(after well development) have completely recovered to their pre-development
level or at least to 90% of that level.
(A) At a minimum, a 24-hour uniform rate aquifer test
must be conducted. Testing must continue long enough to observe a
straight-line trend on a plot of water level versus the logarithm
of time pumped. If necessary, the duration of the test should be extended
beyond the 24-hour minimum limit until the straight-line trend is
observed.
(i) If it is impractical to continue the test until
a straight-line trend of water level versus the logarithm of time
pumped is observed within the 24-hour limit, the test must continue
at least until a consistent pumping-level trend is observed. In such
instances, failure to observe the straight-line trend must be recorded.
(ii) If the pumping rates remain constant for a period
of at least four hours and a straight-line trend is observed on a
plot of water level versus the logarithm of time pumped before the
24-hour limit has been reached, the pumping portion of the test may
be terminated.
(iii) The frequency of water level measurements during
the aquifer test must be such that adequate definition of the time-drawdown
curve is made available. As much information as possible must be obtained
in the first ten minutes of testing (i.e., pumping).
(B) Water-level recovery data must be obtained to verify
the accuracy of the data obtained during the pumping portion of the
test. Recovery measurements must be initiated immediately at the conclusion
of the pumping portion of the aquifer test and must be recorded with
the same frequency as those taken during the pumping portion of the
aquifer test. Time-recovery measurements must continue until the water
levels have recovered to pre-pumping levels or at least to 90% of
that level. If such recovery is not possible, time-recovery measurements
should continue until a consistent trend of recovery is observed.
(7) Use of existing wells and aquifer test data.
(A) An existing well may be utilized as an observation
well under this section if sufficient information is available for
that well to demonstrate that it meets the requirements of this section.
(B) The municipal or county authority may accept the
results of a previous aquifer test in lieu of a new test if:
(i) the previous test was performed on a well located
within a 1/4-mile radius of the subdivision;
(ii) the previous test fully meets all the requirements
of this section;
(iii) the previous test was conducted on an aquifer
which is being considered as a source of water supply for the proposed
subdivision; and
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