Unless remedial action is initiated in accordance with WAC 173-360A-0750(4), owners and operators must immediately investigate and confirm all suspected releases of regulated substances requiring reporting under WAC 173-360A-0700 or investigation under WAC 173-360A-0710 using the following steps, except as otherwise directed by the department.

(1) System test. First, all tanks and underground piping suspected of a release must be tested to determine whether a leak exists or whether a breach exists in either wall of the secondary containment. The tests must be completed within seven days of identifying a suspected release or receiving notice that the department requires investigation of a suspected release.

(a) Performance. For each tank or pipe suspected of a release, one of the following tests must be performed:

(i) A tightness test of the tank or piping in accordance with WAC 173-360A-0635 or 173-360A-0650; or

(ii) A tightness test of the secondary containment area of the tank or piping used for interstitial monitoring in accordance with WAC 173-360A-0490 (4)(c) and, for piping, a tightness test of any containment sumps used for interstitial monitoring in accordance with WAC 173-360A-0450.

(b) Next steps.

(i) If the test results do not indicate there is a release and environmental contamination is not the basis for suspecting a release, then no further investigation is required.

(ii) If the test results do not indicate there is a release but environmental contamination is the basis for suspecting a release, then a site check must be performed in accordance with subsection (2) of this section.

(iii) If the test results confirm there is a leak into the interstice but do not indicate a release, then the defective UST system components must be repaired, replaced, or closed immediately. No further investigation is required.

(iv) If the test results indicate there is a release, then:

(A) The defective UST system components must be repaired, replaced, or closed immediately; and

(B) A site check must be performed in accordance with subsection (2) of this section.

(2) Site check. Second, if required based on the results of the system test in subsection (1) of this section, a site check must be performed to determine whether regulated substances have been released from the UST system into the environment. The site check must be completed within thirty days of identifying a suspected release or receiving notice that the department requires investigation of a suspected release.

(a) Performance. Site checks must be performed in accordance with WAC 173-360A-0730.

(b) Next steps.

(i) If the results of the site check do not indicate there is a release from the UST system that may pose a threat to human health or the environment, then no further investigation of the suspected release is required.

(ii) If the results of the site check confirm there is a release from the UST system that may pose a threat to human health or the environment, then the confirmed release must be reported, investigated, and cleaned up in accordance with WAC 173-360A-0750.