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Grand River Park Project, M-2006.046 Response to Adequacy Letter of August i, 2006 6 September 2006 Page 8 12. Rule 6.4.5(2)(t)(v) requires a description of the anticipated minimum depth or range of depths for those areas where topsoil will be replaced. The applicant has indicated that at least four inches of topsoil will be provided in the reclamation condition however, the applicant should be aware that the Division requires a minimum depth of topsoil replacement of six inches. Please commit to topsoil replacement of this minimum depth. Rule 6.4.5(2)(f) contains requirements to describe various features of the reclamation plan in Exhibit E. The applicant has complied with the requirement of subparagraph (v), concerning a description of the depth of topsoil replacement. Rule 6.4.5 does not contain a requirement of 6-inch minimum topsoil replacement, nor does any other Rule. In fact, Rule 6.4.5(1) states that applicants are encouraged to allow for flexibility in their plans rather than committing to specific figures. As noted in the application (page 2), the site is dominated by "extremely rocky soils, with some places exposed to alluvial sand and gravel and no overlying topsoil layer." In the vicinity of Interstate 70, it is believed that this condition may be a result of construction of the embankment for the highway and associated features, involving the use of the subject site as a source for borrow material. However, regardless of cause, even with extremely shallow topsoil in large areas, the existing condition of the site demonstrates that there is still present throughout a suitable plant growth medium for grasses, shrubs, and trees. As a general performance standard, following from Rule 3 and the performance warranty attaching to a proposed Reclamation Plan {see Rule 4.17.1{1)), the plant growth medium in reclaimed condition must be sufficient in quantity and quality to sustain vegetation. Based on existing conditions, it is evident that the existing matrix of soils and substrate at the subject site provides a suitable plant growth medium, even if the existing topsoil horizon is not uniform and is in large areas less than 6 inches. The applicant has committed, on page 13 of Exhibit E, to providing a topsoil layer at least 4 inches in depth on all disturbed surfaces above the anticipated normal water line. Given the shallow depth to groundwater and extent of proposed groundwater lakes, it is possible that topsoil recovery across the site will far exceed the volume necessary to reclaim disturbed land surface to 6 inches or greater, in which case the applicant will provide a minimum of 6 inches of average topsoil depth for revegetation. However, should salvageable topsoil quantities fail meet the requirement for the preferred 6 inch minimum topsoil depth, it is a reasonable option, supported by Construction Materials Rules, for the operator to reclaim the site with the limited topsoil available.