Wyoming Administrative Code
Agency 020 - Environmental Quality, Dept. of
Sub-Agency 0011 - Water Quality
Chapter 17 - STORAGE TANKS
Part F - MINIMUM SITE ASSESSMENTS
Section 17-29 - MSA Requirements

Universal Citation: WY Code of Rules 17-29

Current through September 21, 2024

(a) When a MSA is Required. MSAs are utilized to determine whether a regulated substance has been released from a storage tank system and, if so, to determine if soil and/or ground water contamination is present in exceedance of applicable standards. The MSA results will determine the site's eligibility for the corrective action fund. MSAs are required when any of the following conditions are met:

(i) Unless the site is already listed as a contaminated site, all owners and/or operators of regulated ASTs shall, by October 1, 2007, provide a MSA to the department. This MSA shall be done at the owners and/or operators expense and shall meet all of the requirements of this part.

(ii) Unless the site is already listed as a contaminated site, all UST owners and/or operators which have not previously performed a MSA shall perform a MSA. This MSA shall be performed no sooner than eighteen (18) years, and no later than twenty (20) years, after the tanks were installed, at the owners and/or operators expense. This requirement applies to all USTs installed after September 22, 1988.

(iii) After the effective date of this chapter, owners and/or operators who remove storage tanks without obtaining the required department inspection shall complete a MSA at their own expense and within forty-five (45) days of the tank removal.

(iv) After the effective date of this chapter, owners and/or operators who change the use of a regulated tank to a non-regulated use in accordance with Section 31 of this chapter, or change the use of a non-regulated tank to a regulated use shall complete a MSA at their own expense and within forty-five (45) days of the change of use.

(v) Any owner and/or operator of a storage tank system which was abandoned prior to the program and who now elects to participate in the state program, shall:
(A) Provide written documentation that the site actually had a storage tank system at some time;

(B) In the case where the storage tank was an AST, provide documentary evidence that the storage tank was used to dispense gasoline and diesel fuels to the public;

(C) Complete an MSA in accordance with this part and prove that the site has been contaminated by a storage tank system; and

(D) Pay one year's storage tank fee for all storage tanks on the site at the time of the initial site registration. If all of the tanks were removed and it is not possible to determine how many storage tanks were on the site, pay the fee for one tank.

(vi) Owners of former storage tank sites that are not on the contaminated site list shall perform a MSA any time that soil and/or ground water contamination is discovered on the property or adjacent properties.

(vii) A MSA shall be accomplished by an owner and/or operator before permanently closing a storage tank in place in accordance with the procedures contained in this part.

(b) MSA Work Plan. At least thirty (30) days prior to performing a MSA, the owner and/or operator shall submit a Work Plan to the appropriate Water Quality Division Storage Tank Program District Office for review and approval. The department will review the work plan to insure that the proposed MSA will meet the requirements of this part. The Work Plan shall include at least the following information:

(i) Facility name, address and identification number, if applicable.

(ii) Name, address and telephone of person(s) who will be conducting the MSA;

(iii) Number of storage tanks, whether they are AST or UST, and how many are regulated versus unregulated;

(iv) Description of MSA methodology to be utilized for storage tanks and connected piping, including borehole and/or soil excavation installation and closure and monitor well installation and closure, equipment decontamination, contaminated soil and ground water disposal;

(v) Soil and ground water Sampling and Analysis Plan, including proposed sample collection and shipment protocols and analytical methods. ;

(vi) A plan map showing the location of property lines, drainages, buildings, tanks, connected piping and proposed boreholes/monitor wells and/or soil excavations. All maps shall be to scale and provide a north arrow.

(c) MSA Performance and Information Requirements.

(i) The MSA shall be inclusive for all storage tanks located on a site.

(ii) MSAs for Storage Tanks.
(A) The MSA for storage tanks shall consist of boreholes and/or soil excavations accomplished within five (5) horizontal feet of the UST basin or AST secondary containment structure. For USTs, these boreholes/ soil excavations shall extend to a minimum of three (3) feet below the bottom of the tank. For ASTs, the boreholes or soil excavations shall extend to a minimum of fifteen (15) feet below the bottom of the AST. USTs with secondary containment shall have the above distances measured from the outside and bottom of the secondary containment.

(B) To the extent possible, the boreholes/soil excavations shall surround the tank area and provide an adequate representation of any potential contamination that may have been released from the storage tank system(s). The total number and locations of the boreholes or soil excavations will vary dependant upon the number of storage tanks and the total storage tank capacity at any location.

(C) Whenever a groundwater table is encountered, the depth of the borehole or soil excavation shall be accomplished to a depth necessary to provide for the collection of a groundwater sample.

(iii) MSAs for Connected Piping and dispensers. The MSA for connected piping shall consist of boreholes or soil excavations accomplished within three (3) horizontal feet of the piping and shall extend to a minimum of three (3) feet below the bottom of the piping. For dispensers, boreholes or soil excavations shall extend to ten (10) feet below the bottom of the dispenser sump. The total number and locations of the boreholes or soil excavations will vary dependant upon the length of the piping and the number of dispensers.

(iv) Borehole/Soil Excavation Completion Requirements.
(A) Either borehole drilling or soil excavation are acceptable techniques for accomplishing the MSA as long as the results meet the purpose of the MSA in (a) above. The particular MSA technique shall be proposed in the work plan for review and approval by the department.

(B) For boreholes, at least one borehole shall be advanced to the ground water table or a maximum of thirty (30) feet below ground surface, whichever is first. At least one borehole shall be completed as a monitor well whenever groundwater is encountered during the drilling. For soil excavations, the maximum excavation depth shall be fifteen (15) feet below ground surface.

(C) An accurate log of subsurface conditions shall be provided for all boreholes and/or soil excavations. This documentation shall be provided by a person qualified and experienced to describe soils based on the Unified Soil Classification System.

(D) All boreholes shall be abandoned in accordance with the approved work plan. Shallow boreholes that do not penetrate the ground water table may be abandoned with uncontaminated drill cuttings to within two (2) feet of the surface. The upper two (2) feet of the borehole shall consist of a hydrated bentonite plug. All other boreholes shall be abandoned with a bentonite slurry from the bottom of the borehole up.

(E) Soil excavations shall be closed in accordance with the approved work plan.

(v) Monitor Wells.
(A) All boreholes that penetrate the ground water table shall be completed as monitor wells or abandoned in accordance with this part and the approved work plan.

(B) Any monitor wells installed as part of a MSA are exempt from the requirements of Chapter 11, Part G, Wyoming Water Quality Rules and Regulations.

(C) All monitor wells shall be constructed in accordance with the approved work plan and the issued State Engineer's permit. Monitor wells shall be capable of providing a representative sample of formation ground water for chemical analysis.

(D) All monitor wells shall be abandoned in accordance with the approved work plan.

(vi) Soil Sampling.
(A) All borehole and/or soil excavation samples shall be collected in a manner to ensure that the soil collected is representative of the in-place soil at the sampling location.

(B) Based on field instrument measurements, the most heavily contaminated soil sample will be properly packaged and submitted to a chemical laboratory for analysis. If field instrument measurements do not indicate a contaminated soil layer, the soil sample submitted to the laboratory shall be from three (3) feet below the base of the storage tank or the connected piping and dispenser.

(vii) Ground water Sampling.
(A) Ground water samples shall be collected in accordance with the approved work plan and in a manner that ensures that the samples are representative of the in-place formation ground water.

(B) All ground water samples shall be properly preserved and packaged prior to submitting to the analytical laboratory.

(d) Documented contamination. Any contamination documented during this MSA process requires the owner of the contaminated site and/or the owner and/or operator of the storage tanks to implement Part E of this chapter, if the storage tank system is currently in use.

(e) MSA Report. Within forty-five (45) days after the completion of the MSA, the owner and/or operator shall submit two (2) copies of a summary report of the MSA to the department on a form provided by the department or a consultant's report which at a minimum includes the following information:

(i) Facility name, address and ID number , owners name and address and name of person(s) performing the MSA;

(ii) Date assessment was accomplished;

(iii) Storage tank(s) information, including tank number, capacity, regulated substance stored and depth to top and bottom of tank(s);

(iv) Borehole and/or soil excavation information, including borehole/soil excavation identification, total depth, depth to ground water and description of soils and/or ground water;

(v) Discussion of any contamination noting depths encountered or lack of contamination discovered;

(vi) All analytical results.

(vii) Plan map of the location indicating structures, drainages, property lines, location of boreholes or soil excavations, monitor wells tank(s), piping and dispensing pumps. Drawings shall include title, north arrow and scale;

The summary report shall be submitted to the appropriate Water Quality Division Storage Tank Program District Office for review and approval.

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