| (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 shall 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
shall be attached to the form required under §230.3 of this title (relating
to Certification of Groundwater Availability for Platting).
(b) Location of existing wells. All known existing, abandoned,
and inoperative wells within the proposed subdivision shall be identified,
located, and mapped by on-site surveys. Existing well locations shall 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 shall 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 shall be based on typical well completions. An aquifer test
conducted under this section utilizing established methods shall be reported
as specified in §230.3(c) of this title and shall 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, shall be required to conduct
an adequate aquifer test under this section. Additional observation wells
shall be used for the aquifer test if it is practical or necessary to confirm
the results of the test. The observation well(s) shall be completed in the
same aquifer or aquifer production zone as the test well. The locations of
the test and observation well(s) shall 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 shall be located by latitude
and longitude. The observation well(s) shall 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 shall 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 shall 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 shall be prepared which provide qualitative
information on aquifer characteristics and groundwater quality. At a minimum,
the geophysical logs shall 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) shall be developed prior to conducting the aquifer test
to repair damage done to the aquifer(s) during the drilling operation. Development
shall insure 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 shall 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 shall
not be allowed to influence initial well performance results.
(D) Aquifer testing required by this section shall 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 shall 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 shall 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 shall not be allowed to influence the test results. Aquifer
testing shall 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 shall
be conducted. Testing shall 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 shall continue at least until a consistent pumping-level
trend is observed. In such instances, failure to observe the straight-line
trend shall 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 shall be such that adequate definition of the time-drawdown curve
is made available. As much information as possible shall be obtained in the
first ten minutes of testing (i.e., pumping).
(B) Water-level recovery data shall be obtained to verify the
accuracy of the data obtained during the pumping portion of the test. Recovery
measurements shall be initiated immediately at the conclusion of the pumping
portion of the aquifer test and shall be recorded with the same frequency
as those taken during the pumping portion of the aquifer test. Time-recovery
measurements shall 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
Cont'd... |
