Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 230 - GROUNDWATER AVAILABILITY CERTIFICATION FOR PLATTING › Section 230.8 - Obtaining Site-Specific Groundwater Data

Current through Reg. 49, No. 28; July 12, 2024
(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
(iv) aquifer
				conditions (e.g., water levels, gradients, etc.) during the previous test were
				approximately the same as they are presently.
(8) Need for additional aquifer testing and
				observation wells. Best professional judgement shall be used to determine if
				additional observation wells or aquifer tests are needed to adequately
				demonstrate groundwater availability. The Theis and Cooper-Jacob nonequilibrium
				equations, and acceptable modifications thereof, are based on well documented
				assumptions. To determine if additional information is needed, best
				professional judgement shall be used to consider these assumptions, the
				site-specific information derived from the aquifer test required by this
				section, the size of the proposed subdivision, and the proposed method of water
				delivery.