PURPOSE: This rule describes the steps needed to verify a release.

1. (1) Unless corrective action is initiated in 10 CSR 20-10.060—10 CSR 20-10.067, owners and operators must immediately investigate and confirm all suspected releases of regulated substances requiring reporting under 10 CSR 20-10.050 within seven (7) days or another reasonable time period specified by the department using either the following steps or another procedure approved by the department:

   1. (A) System Test. Owners and operators must conduct tests (tightness testing of tanks in 10 CSR 20-10.043(1)(C) and piping in 10 CSR 20-10.044(1)(B)) to determine whether a leak exists in that portion of the tank that routinely contains product or the attached delivery piping, or both.

      1. 1. Owners and operators must repair,

replace or upgrade the underground storage tank (UST) system, and begin corrective action in 10 CSR 20-10.060—10 CSR 20- 10.067 if the test results for the system, tank or delivery piping indicate that a leak exists.

1. 2. Further investigation is not required

if the test results for the system, tank and delivery piping do not indicate that a leak exists and if environmental contamination is not the basis for suspecting a release.

1. 3. Owners and operators must conduct

a site check as described in subsection (1)(B) of this rule if the test results for the system, tank and delivery piping do not indicate that a leak exists but environmental contamination is the basis for suspecting a release; or

1. (B) Site Check. Owners and operators must measure for the presence of a release where contamination is most likely to be present at the UST site. In selecting sample types, sample locations and measurement methods, owners and operators must consider the nature of the stored substance, the type of initial alarm or cause for suspicion, the type of backfill, the depth of groundwater and 10 CSR 20-10

other factors appropriate for identifying the presence and source of the release.

1. 1. If the site check indicates that a

release has occurred, owners and operators must begin corrective action in accordance with 10 CSR 20-10.060—10 CSR 20-10.067; or

1. 2. If the results of the site check do not

indicate that a release has occurred, the investigation may stop.

1. (2) Owners and operators shall follow a written procedure. To comply with this rule, the department’s Site Characterization Guidance Document may be used as a written procedure. Other written procedures may be used with prior written approval of the department.

AUTHORITY: sections 319.109, RSMo (Cum. Supp. 1989) and 644.026, RSMo (Cum. Supp. 1993).* Original rule filed April 2, 1990, effective Sept. 28, 1990. Amended: Filed Aug. 3, 1993, effective April 9, 1994. *Original authority: 319.107, RSMo (1989) and 644.026, RSMo (1972), amended 1973, 1987, 1993.