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Page 2 ® • October 4, 1990 - state ]'it M-90-112 Dan Hernandez A:iauming the average gravel thickness is 10 feet and reducing that by a 20Z waste factor, it is estimated an acre of gravel will produce 19,360 tons. With an average annual production of 250,000 tons 12.9 acres of land would be disturbed each year. To allow for thinner gravel and otter disturbances within this category, a 20 acre figure is sufficient to define the major disturbance area. ~ The mined area becomes moderate disturbance almost immediately after dining because the final grade is produced by removal of the gravel. Broderick & Gibbons believes the modera_t_e_diaturbance area (including plant site, access, stockpiles, etc.) should be set at 50 acres ._ It will probably be more like 35 to 45 acres, but setting ~'at ~ 50 acres provides some margin for error. After the first year the amount of land in moderate disturbance should remain quite stable from year to year. The minor disturbance area should be set at five times the major disturbance area. This allows for five years of vegetation development before bond release on any particular parcel of mined land. Hopefully it will only take three or four years under the revegetation program, but considering the vagaries of the weather it would be more comfortable to assuae it will take five years. Therefore, the minor disturbance categor;~ would have 100 acres. Adding ell of these produces a total of 170 acres of bonded land in the thr~3e categories. This total and the respective breakdown should be the basis for the bond calculation. It is not felt that requesting inspections for bond releases two years ahead of time is realistic. FScperience dictates it is almost impossible to determine two years in advance when an area will be ready for bond release. Too many things can happen and this could result in the Div..sion doing inspections of reclamation that is not ready to be released. Furthermore, if the vegetation development is more rapid and is ready for release in three years, this would require Broderick & Gibbons to request a release inspection at the end of the first growing season. That is definitely too early to make any determination of adequacy in the third year. It is suggested that Broderick & Gibbons monitor the acreage, eapecial.ly in the minor disturbance category, and report these acreages in the e.nnual reports. If bond increases are required because of slower vegetation development or other factors then those would be submitted. If a particular parcel of land is believed to be adequately revegetated then the company can request a release and the staff can process that request in accordance with the rules for processing bond releases. i {~';' S~/,~ ~~-I~ /~~ ~,1.~_~~ O- ~ ~ ~Y