(1) On and after July 30, 1967, an application for a determination of the cost of an existing or newly completed pollution control facility may be filed with the department in such manner and in such form as may be prescribed by the department. The application shall contain the final cost figures for the installation of the facility and reasonable supporting documents and other proof as required by the department. In the event such facility is not already covered by a certificate issued for the purpose of authorizing the tax exemption or credit provided for in this chapter, the department shall seek the approval of the facility from the appropriate control agency. For any application for a certificate or supplement which was filed with the department not later than November 30, 1981, the department shall determine the final cost of the pollution control facility and issue a supplement to the existing certificate or an original certificate stating the cost of the pollution control facility: PROVIDED, That the cost of an existing pollution control facility shall be the depreciated value thereof at the time of application filed pursuant to this section.

(2) When the operation of a facility has commenced and a certificate pertaining thereto has been issued, a credit may be claimed against taxes imposed pursuant to chapters 82.04, 82.12 and 82.16 RCW. The amount of such credit shall be two percent of the cost of a facility covered by the certificate for each year the certificate remains in force. Such credits shall be cumulative and shall be subject only to the following limitations:

(a) No credit exceeding fifty percent of the taxes payable under chapters 82.04, 82.12 and 82.16 RCW shall be allowed in any reporting period;

(b) The net commercial value of any materials captured or recovered through use of a facility shall, first, reduce the credit allowable in the current reporting period and thereafter be applied to reduce any credit balance allowed and not yet utilized: PROVIDED, That for the purposes of this chapter the determination of "net commercial value" shall not include a deduction for the cost or depreciation of the facility.

(c) The total cumulative amount of such credits allowed for any facility covered by a certificate shall not exceed fifty percent of the cost of such facility.

(d) The total cumulative amount of credits against state taxes authorized by this chapter shall be reduced by the total amount of any federal investment credit or other federal tax credit actually received by the certificate holder applicable to the facility. This reduction shall be made as an offset against the credit claimed in the first reporting period following the allowance of such investment credit, and thereafter as an offset against any credit balance as it shall become available to the certificate holder.

(3) Applicants and certificate holders shall provide the department with information showing the net commercial value of materials captured or recovered by a facility and shall make all pertinent books and records available for examination by the department for the purposes of determining the credit provided by this chapter.