Section 30.905 - Cost Estimation for Post-closure Care(1) The owner or operator shall, within the applicable time period prescribed in 310 CMR 30.901(3) or (4), prepare and submit to the Department a written estimate, in current dollars, of the cost of post-closure monitoring and maintenance of the facility pursuant to 310 CMR 30.590 through 30.595. This cost estimate shall be calculated by multiplying the annual post-closure cost estimate by the number of years of post-closure care required in 310 CMR 30.592. This cost estimate shall be certified by an independent Massachusetts registered professional engineer.(2) Within 60 days prior to each anniversary of the date on which the first post-closure cost estimate was prepared, the owner or operator shall prepare and submit to the Department an adjustment for inflation of the post-closure cost estimate. The adjustment shall be made as specified in 310 CMR 30.905, using an inflation factor derived from the annual implicit Price Deflator for Gross National Product as established by the U.S. Department of Commerce in its Survey of Current Business. The inflation factor shall be calculated by dividing the latest published annual Deflator by the Deflator for the previous year. (a) The first adjustment shall be made by multiplying the post-closure cost estimate by the inflation factor. The result shall be the adjusted post-closure cost estimate.(b) Subsequent adjustments shall be made by multiplying the latest adjusted post-closure cost by the inflation factor.(3) The owner or operator shall revise the post-closure cost estimate whenever a change in the post-closure plan increases the cost of postclosure care. The revised post-closure cost estimate shall be adjusted for inflation as specified in 310 CMR 30.905(2). The Department may authorize or require the use of an adjusted inflation factor if the Department determines that the inflation factor calculated pursuant to 310 CMR 30.905(2) does not accurately reflect change in the cost of post-closure care of the facility.(4) During the operating life of the facility, the owner or operator shall keep in the facility's records all post-closure cost estimates prepared pursuant to 310 CMR 30.905.