SECTION 331.164. Cavern Construction Standards

(a) Plans and specifications. Except as specifically required in the terms of the disposal well permit, construction of the cavern shall be done in accordance with all permit application plans and specifications. Any proposed changes to the plans and specifications must be certified in writing by the executive director that said changes provide protection standards equivalent to or greater than the original design criteria.

(b) Standards for cavern construction by controlled dissolutioning. The creation of waste storage or disposal caverns within the salt shall be accomplished by the controlled dissolution of the sidewalls of the well bore to a specified maximum diameter, between selected elevations specified in the permit as the top and bottom of the salt cavern injection interval. The top of the cavern shall be at least 100 feet below the base of the long string casing. The enlargement of a portion of the original well bore to serve as the cavern shall be done according to the cavern construction plans which shall be submitted as a part of the permit application. The cavern construction plans shall demonstrate at a minimum, the following:

(1) the minimum distance between the salt cavern injection zone boundaries and the boundaries of the salt stock, as determined by available geologic data, shall not be less than 500 feet;

(2) adjacent caverns shall be separated by a minimum pillar to cavern diameter (P/D) ratio of 2.0 to ensure a sufficient amount of undisturbed salt for cavern safety and stability. Adjacent salt cavern injection zones shall also be separated by a confining thickness of salt;

(3) that cavern dimensions have been designed by a qualified professional engineer and geologist, to ensure the structural integrity of the cavern;

(4) plans for continual monitoring of the volumes of fluids injected and produced during cavern development;

(5) plans for cavern pressure tests, and sonar surveys to determine the cavern dimensions, volume, geometric shape, and characterization of outbursts or other anomalies;

(6) the cavern construction process shall be conducted under the supervision of a qualified professional engineer, with current registration under the Texas Engineering Practices Act, in accordance with accepted practices in the cavern construction industry.

(7) all cavern solutioning brines shall be disposed of in facilities authorized by the commission for such purpose.

(c) Injection tubing. Except for circulation of drilling fluids during well construction, all injection activities for salt cavern construction and waste disposal in a salt cavern shall be performed through removable injection tubings installed inside of the cemented long string casing and extending from the wellhead at ground surface to the salt borehole or salt cavern below the long string casing seat.

(1) All injection activities during cavern construction shall be performed with the annulus between the outer tubing and long string casing filled with a non-corrosive inhibiting fluid sufficient to protect the bond between salt, cement, and the long string casing seat.

(2) All injection of waste into a salt cavern shall be performed through removable injection tubing with a packer to seal the annulus between the tubing and long string casing near the bottom of the long string casing.

(d) Logs and Tests.

(1) The permit applicant shall submit, as part of its construction plan, information identifying the tests which it will use to verify cavern dimensions throughout the cavern construction process. This information shall include at a minimum, the following:

(A) a description of surveys, logs, and tests to be run and analyzed, including any quantitative performance standards appropriate for any such procedure; and

(B) the frequency of such surveys or logs.

(2) Prior to waste filling, the integrity of the cavern shall be tested in accordance with a test method described in the applicant's cavern construction plan, specified by permit or approved by the executive director in accordance with subsection (a) of this section.

(e) Workovers.

(1) The permittee shall notify the executive director before commencing any workover operation or corrective maintenance which involves taking the injection well out of service. The notification shall be in writing and shall include plans for the proposed work. The executive director may grant an exception of the prior written notification when immediate action is required. Approval by the executive director shall be obtained before the permittee may begin any workover operation or corrective maintenance that involves taking the well out of service. Pressure control equipment shall be installed and maintained during workovers which involve the removal of tubing.

(2) Well mechanical integrity shall be demonstrated following any major operations which involve removal of the injection tubing, recompletions, or unseating of the packer. Cavern integrity demonstration may be required by the executive director in instances where the integrity of the casing seat or cavern may be compromised.

(f) Reports and approval.

(1) Initial cavern integrity report. The operator shall submit a report with the results of all tests regarding cavern integrity, within 30 days of completion of the salt cavern construction stage.

(2) Approval of completion of the cavern construction stage. Within 90 days of completion of cavern construction, including configuration of the well for waste disposal, and prior to beginning waste emplacement, the permittee shall obtain written approval from the executive director which states that the cavern construction is in compliance with the applicable provisions of the permit. To obtain approval, the permittee shall submit to the executive director the following reports and certifications prepared and sealed by a professional engineer with current registration pursuant to the Texas Engineering Practice Act:

(A) final construction, "as-built" plans and specifications, injection and confining zone data, and an evaluation of the considerations under §331.45(2) of this title (relating to Executive Director Approval of Construction and Completion);

(B) certification that the construction of the cavern has been completed in accordance with the provisions of the disposal well permit and with the design and construction specifications of the permittee's application;

(C) certification that actual confining and injection zone data obtained will not result in need for a change in the operating parameters specified in the permit;

(D) certification that the salt cavern injection zone will not be in or above a formation which within 1/4 mile of the salt cavern injection zone contains an underground source of drinking water.

Source Note: The provisions of this §331.164 adopted to be effective June 22, 1992, 17 TexReg 4097; amended to be effective January 2, 1995, 19 TexReg 10099; amended to be effective November 23, 2000, 25 TexReg 11433