(a) When an MSA is Required. MSAs are used to determine if a regulated substance has been released from a storage tank system and, if so, to determine if soil and/or groundwater contamination is present in excess of applicable standards. The MSA results will determine the site's eligibility for the Corrective Action Account. MSAs are required when any of the following conditions are met: - (i) Unless the site is already listed as a contaminated site, all tank owners and/or operators that have not previously performed an MSA shall perform an MSA. This MSA shall be performed at the site owner's and/or operator's expense no sooner than 18 years, and no later than 20 years, after the tanks were installed. This requirement applies to all USTs installed after September 22, 1988, and to all regulated ASTs.
- (ii) Owners and/or operators who permanently close or change the service of storage tanks without obtaining the required department authorization and inspection shall complete an MSA at their own expense within 45 days of the tank closure or change in service. To obtain the required department inspection, the owner and/or operator shall notify the department 30 days prior to tank closure or change in service activities. If tank closure or change in service activities are not sufficient for department personnel to characterize the subsurface conditions at the site, the owner and/or operator shall complete an MSA at his/her expense. The department will assign a priority ranking in accordance with Section 27 based on the results of the inspection or owner's and/or operator's MSA.
- (iii) Owners and/or operators who change a regulated tank to a non-regulated use in accordance with Section 31, or change a non-regulated tank to a regulated use shall complete an MSA at their own expense regardless of whether or not the site is listed as a contaminated site. The MSA shall be completed within 45 days of the change of use.
- (iv) Any owner and/or operator of a storage tank system abandoned prior to the program that now elects to participate in the state program shall:
- (A) Provide written documentation that the site actually had a program-eligible 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 or diesel fuels to the public;
- (C) Complete an MSA in accordance with this Part and prove that the site has been contaminated by a program-eligible 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 tanks were removed and it is not possible to determine how many storage tanks were on the site, pay the fee for one tank.
- (v) Unless the site is already listed as a contaminated site, an MSA shall be completed by the owner and/or operator, in accordance with this Part, before permanently closing a storage tank in place.
- (vi) When a storage tank system is temporarily closed for more than 12 months, the owner and/or operator shall complete a minimum site assessment in accordance with this Section unless the site is already listed as a contaminated site or a time extension has been granted, in writing, by the department.
(b) MSA Work Plan. At least 30 days prior to performing an MSA, the owner and/or operator shall submit a Work Plan to the appropriate Storage Tank Program (STP) District Office for review and approval. The STP will review the Work Plan to ensure the proposed MSA will meet the requirements of this Part. At a minimum, the Work Plan shall include the following: - (i) Facility name, address and identification number, if applicable;
- (ii) Name, address and telephone number of person(s) who will be conducting the MSA;
- (iii) Number of storage tanks, whether they are ASTs or USTs, and how many are regulated versus unregulated;
- (iv) Description of MSA methodology to be used for storage tanks and connected piping, including borehole and/or soil excavation installation and abandonment, temporary monitoring well installation and abandonment, equipment decontamination, and contaminated soil and groundwater disposal;
- (v) Soil and Groundwater 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/monitoring wells and/or soil excavations. All maps shall be to scale and provide a north arrow; and
- (vii) Proposed construction for any permanent monitoring wells being installed. Well construction shall be approved by the STP.
(c) MSA Completion Requirements. - (i) The MSA shall be inclusive for all storage tanks, associated piping, and dispensers located on the site.
- (ii) MSAs for Storage Tanks.
- (A) The MSA for storage tanks shall consist of boreholes and/or soil excavations completed within 5 horizontal feet of the UST basin or AST secondary containment structure.
- (B) To the extent possible, the boreholes and/or 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 depending on the number of storage tanks and the total storage tank capacity at the location. The number and location of the boreholes shall be provided in the Work Plan and approved by the District Office reviewing the Work Plan. In addition to the soil borings/excavations, any site that is permanently closing by abandoning USTs in place or removing ASTs shall install at least three temporary groundwater monitoring wells. The wells shall be drilled at least 5 feet into groundwater or 40 feet deep, whichever comes first. The location, depth, and exact number of wells to be installed shall be determined by actual site conditions and construction requirements for monitoring wells. The wells may be abandoned after sampling. This requirement is intended to provide data on the condition of the groundwater at the site and allow the STP to evaluate site closure without further work.
- (C) Whenever groundwater is encountered in a borehole or excavation, a groundwater sample shall be collected for laboratory analysis. If groundwater is encountered in more than one borehole or excavation, up to three groundwater samples shall be collected; one sample from each borehole or excavation.
- (iii) MSAs for Connected Piping and Dispensers. The MSA for connected piping and dispensers shall consist of boreholes or soil excavations completed within 3 horizontal feet of the piping or dispenser. The total number and locations of the boreholes or soil excavations will vary depending on the length of the piping and the number of dispensers. If the dispenser is located less than 20 feet from the storage tank(s), one borehole or soil excavation shall be completed at the dispenser. At sites where the dispenser is located more than 20 feet from the storage tank(s), a borehole or soil excavation shall be completed at the dispenser and every 20 feet along the piping from the dispenser to the storage tank(s).
- (iv) Borehole or 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 this Part. The MSA technique shall be proposed in the Work Plan for review and approval by the STP.
- (B) Boreholes or soil excavations shall be completed to a depth of 5 feet below the bottom of a UST and 5 feet below ground surface of an AST. Boreholes or excavations shall extend to a depth of 5 feet below the bottom of the piping and 5 feet below the bottom of dispenser sumps.
- (C) An accurate log of subsurface conditions shall be provided for all boreholes, wells, 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 and temporary wells shall be abandoned in accordance with the approved Work Plan. Boreholes that do not penetrate the groundwater table may be abandoned with drill cuttings to within 2 feet of the surface. The upper 2 feet of the borehole shall consist of a hydrated bentonite plug. Boreholes or wells that encounter groundwater shall be abandoned with a bentonite slurry from the bottom of the borehole to the ground surface completion.
- (E) Soil excavations shall be abandoned in accordance with the approved Work Plan. Soils may be returned to the excavation with approval from the STP project manager.
- (v) Soil Sampling.
- (A) All borehole and/or soil excavation samples shall be collected in a manner that ensures the samples are representative of the in-place soil at the sampling location. Soil samples shall be submitted to an STP-approved laboratory (A2LA or NELAP certification required; refer to STP website for current list of approved laboratories).
- (B) Based on field instrument measurements, the most heavily contaminated soil sample shall be properly packaged and submitted to an STP-approved analytical laboratory for analysis. If field instrument measurements do not indicate a contaminated soil layer, the soil sample submitted to the laboratory shall be from the bottom of the borehole or excavation.
- (vi) Groundwater Sampling.
- (A) Groundwater samples shall be collected in accordance with the approved Work Plan and in a manner that ensures the samples are representative of the in-place groundwater formation.
- (B) All groundwater samples shall be properly preserved and packaged prior to submission to an STP-approved analytical laboratory (A2LA or NELAP certification required; refer to STP website for current list of approved laboratories).
(d) Documented Contamination. If contamination is documented during this MSA process and the storage tank system is currently in use, the site owner and/or operator site shall implement the requirements in Part E.
(e) MSA Report. Within 45 days after the completion of the MSA, the owner and/or operator shall submit one copy of the MSA summary report to the appropriate STP District Office for review and approval. At a minimum, the report shall include the following: - (i) Facility name, address and ID number; owner's name and address; and name of person(s) or company performing the MSA;
- (ii) Date assessment was completed;
- (iii) Storage tank(s) information, including tank number, type (AST or UST), capacity, regulated substance stored, and depth to bottom of tank(s);
- (iv) Borehole, temporary well, and/or soil excavation information, including borehole, well, and/or soil excavation identification, total depth, depth to groundwater, and description of soils and/or groundwater;
- (v) Discussion of any contamination noting depths encountered or lack of contamination discovered;
- (vi) All analytical results and field measurements;
- (vii) Description of temporary monitoring well installations; and
- (viii) Plan map showing the location of the following: structures, drainages, property lines, boreholes or soil excavations, monitoring wells, tank(s), piping, and dispensing pumps. Drawings shall include title, north arrow, and scale.
020-1 Wyo. Code R. § 1-29