Section 18 AAC 78.090 - Site characterization and assessment(a) When performing permanent closure or a change-in-service, the owner or operator shall complete a site characterization, and depending on the results of the site characterization, perform a site assessment or a released investigation.(b) A site characterization must include one or more of the following: (1) a visual inspection of the site;(2) photographs documenting the site;(3) surface or subsurface soil and water sampling and analytical testing;(4) personal interviews; and(c) If the results of the site characterization indicate that a release of petroleum has (1) not occurred, the owner or operator shall perform a site assessment in accordance with (d) of this section; or(2) occurred, or is likely to have occurred, the owner or operator shall proceed with corrective action under 18 AAC 78.200 - 18 AAC 78.280, including release notification and release investigation.(d) A site assessment, if conducted, must be conducted as follows: (1) the site assessment must include an evaluation of the UST site to (A) check for obvious leaks at the dispensers and at exposed pumps and piping;(B) check for obvious soil or water contamination caused by a release or leakage from a UST;(C) review the UST inventory control and repair records for indications of a release; and(D) determine the (i) general nature of the stored substance;(ii) general nature of the subsurface soils; and(iii) estimated depth to groundwater; and(2) the site assessment must include the collection of soil samples; the number and location of samples collected is determined as follows:(A) for an in-place assessment(i) of an individual tank that occupies a surface area less than 250 square feet, at least two borings or test pits must be placed within five feet of the tank, each at the midpoint along two sides of an imaginary rectangle drawn around the tank, with one of the borings or pits located on the side parallel to the end of the tank that has the fill point and the second boring or pit located on the side parallel to the length of the tank where contamination is most likely to be present, as determined by field screening conducted as required by the UST Procedures Manual;(ii) of an individual tank that occupies a surface area equal to or greater than 250 square feet, at least two borings or test pits must be placed within five feet of the tank, as required under (i) of this subparagraph; one additional sample must be collected for each additional 250 square feet of surface area, or portion thereof over the initial 250 square feet, at points where contamination is most likely to be present, as determined by field screening conducted as required by the UST Procedures Manual;for example, if the total surface area is 1270 square feet, five additional samples are required;(iii) of multiple tanks, the borings or test pits for each tank must be placed according to (i) or (ii) of this subparagraph, as applicable; the same boring or test pit may be used to satisfy the requirements applicable to more than one tank, if that boring or test pit meets the requirements for each tank separately;(iv) of dispensing areas, at least one boring or test pit must be placed adjacent to any UST dispensing equipment; if multiple dispensers exist on a common dispensing island, then one boring or test pit may be placed at the midpoint between the dispensers; if multiple dispensing islands exist, then additional borings or test pits are required at each island; if a canopy exists in a configuration that prevents excavating or boring equipment from operating adjacent to the dispensers or dispenser islands, samples may be collected as close as possible to the dispenser islands;(v) of in-place piping, at least one boring or test pit must be placed adjacent to the piping at points where contamination is most likely to be present, as determined by field screening conducted as required by the UST Procedures Manual;(vi) soil samples for assessments under this subparagraph must be collected from each boring or test pit at an elevation that is below, and within two feet of, the tank bottom and that is within two feet below the lowest point of the piping for the UST dispensing equipment; and(vii) in this subparagraph, "surface area" is the sum of the tank length plus five feet multiplied by the sum of the tank diameter, or width for square tanks, plus five feet;(viii) all excavated soil must be assessed for levels of contamination to include field screening and analytical samples taken and tested in accordance with the UST Procedures Manual;(B) for assessment of a closure by removal (i) of an individual tank with an excavated pit area less than 250 square feet, at least two samples must be collected from two different positions in the pit area, with position one on the longitudinal axis, centered between the ends of the tank, underneath where the tank was located, and position two on the longitudinal axis, underneath where the tank was located, where contamination is most likely to be present, as determined by field screening conducted as required by the UST Procedures Manual,but not including position one;(ii) of an individual tank with an excavated pit area equal to or greater than 250 square feet, at least two samples must be collected from the pit area, as required under (i) of this subparagraph; one additional sample must be collected for each additional 250 square feet of pit area, or portion thereof over the initial 250 square feet, at points where contamination is most likely to be present, as determined by field screening conducted as required by the UST Procedures Manual;for example, if the total pit area is 1270 square feet, five additional samples are required;(iii) of multiple tanks, by taking the samples for each excavated pit area according to (i) or (ii) of this subparagraph, as applicable; the same sample location may be used to meet the requirements applicable to more than one tank, if that sample location meets the requirements for each tank separately;(iv) of dispensing areas, at least one sample must be collected where the dispenser had been located;(v) of piping trenches, at least one sample must be taken at points along the piping trench where contamination is most likely to be present;(vi) soil samples for assessments under this subparagraph must be selected from native soils located at an elevation that is below, and within two feet of the bottom of, the excavated pit area and that is within two feet below the lowest point of the piping for the UST dispensing equipment; and(vii) in this subparagraph, "the excavated pit area" is determined by the amount of ground surface that was excavated;(vii) in this subparagraph, "the excavated pit area" is determined by the amount of ground surface that was excavated;(viii) all excavated soil must be assessed for levels of contamination to include field screening and analytical samples taken and tested in accordance with the UST Procedures Manual;(D) if the borings or test pits cannot be placed or if samples cannot be collected in the manner described in (A) and (B) of this paragraph, any alternative sample location plans must be approved by the department; and(E) if the tank or associated piping will be removed as part of closure activities, the minimum site assessment sampling for the portion of the UST system removed must be conducted as provided in (B) of this paragraph;(3) if groundwater is encountered while undertaking the requirements of this subsection and the groundwater prevents the collection of representative soil samples as required in (2) of this subsection, then(A) soil samples must be collected within the first six inches of the vadose zone above the zone of seasonal water table fluctuation as close as possible to the locations described in (2) of this subsection; and(B) for the removal of an individual tank, soil samples must be collected from the walls of the excavation next to the ends of the tank at the soil/water interface; for the removal of multiple tanks from the same pit area, soil samples must be collected from each of the four walls of the excavation at the soil/water interface;(4) if groundwater or the seasonal high water table is known or suspected to exist at a depth from the surface to within five feet below the bottom of the tank, then(A) at least one boring or test pit must reach groundwater or the zone of seasonal water table fluctuation in an undisturbed portion of the excavation pit area or adjacent to the excavation; and(B) at least one soil sample must then be collected from the first six inches of groundwater-saturated soil or the zone of seasonal water table fluctuation in accordance with the UST Procedures Manual;and(5) within 60 days after closure or a change-in-service, the owner or operator shall provide to the department a site assessment report that includes a compilation of the information collected and results obtained under (1) - (4) of this subsection and (A) the owner's name and address;(B) the operator's name and address, if different from the owner;(C) the location of UST, including the legal description by (i) subdivision lot, block, or tract information; or by section lot, tax lot, or government lot number; or(ii) meridian, township, range, section, and nearest quarter section locations within the section if the location cannot be described under (i) of this subparagraph;(D) the UST registration number assigned by the department;(E) the name and business address of each person who supervised the site assessment;(F) a site sketch that approximately shows (i) the location and configuration of tanks and piping;(ii) the sample locations, including depth below grade;(iii) the proximity to property, buildings, and residences;(iv) any sites where a release has occurred;(v) any sites where free product has been or is located;(vi) the facility and property boundaries;(vii) a bar scale and north arrow; and(viii) any other pertinent information;(G) a narrative description of activities conducted at the site and the dates the activities occurred;(H) any historical information encountered during the assessment regarding a previous release, repair, spill, or corrective action; and(I) the data report required in the UST Procedures Manual,Section 8.4.(e) The collection of field data and the interpretation and reporting of site characterization and site assessment data must be conducted or supervised by a qualified environmental professional in accordance with the UST Procedures Manual.(g) Laboratory analyses submitted to fulfill the requirements of this section must be performed by a laboratory approved by the department under 18 AAC 78.800 - 18 AAC 78.815.(h) The owner or operator shall use the analytical methods set out in Table 1, Chapter 2 of the UST Procedures Manualfor site assessment analysis.(j) Further investigation is not required if (1) the assessment, observations, and investigations of the UST site indicate that a release has not occurred; and(2) the results of sample analysis indicate that(A) groundwater cleanup levels in 18 AAC 75.345 are not exceeded at the UST site;(B) surface water quality standards in 18 AAC 70.020(b) are not exceeded at the UST site; and(C) soil cleanup levels in 18 AAC 75.340 - 18 AAC 75.341 are not exceeded at the UST site.(k) If contaminated soil, petroleum vapor, contaminated surface water, or contaminated groundwater is discovered during a site assessment, or at any other time, the owner or operator shall proceed with corrective action under 18 AAC 78.200 - 18 AAC 78.280, including release notification and release investigation.Eff. 3/25/91, Register 118; am 8/21/91, Register 119; am 11/3/95, Register 136; am 1/22/99, Register 149; am 6/25/99, Register 150; am 1/30/2003, Register 165; am 7/25/2012, Register 203; am 6/17/2015, Register 214, July 2015; am 7/1/2017,Register 222, July 2017Authority:AS 46.03.020
AS 46.03.365
AS 46.03.380
AS 46.03.405