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Classes of Dams <br />The following gasses of dams have been established by policy and repeated <br />here for convenience of the user. <br />Class (a). -Dams located in rural or agricultural areas where failure may <br />damage farm buildings, agricultural land, or township and country roads. <br />Class (b). - -Dams located in predominantly rural or agricultural areas where <br />failure may damage isolated homes, lain highways or minor railroads or cause <br />interruption of use or service of relatively important public utilities. <br />Class (c). --Dams located where failure may cause loss of life, serious <br />damage to homes, industrial and commercial buildings, important public <br />utilities, main highways, or railroads. <br />We added the dam criteria at the end of the report in Appendix 2.05.3(4) -1. They are all <br />Class (a) dams. <br />c) As required under Rule 4.05.9(8)(a) or (b), please revise the permit application after <br />construction of the three sediment ponds to include the appropriate geotechnical <br />demonstrations that the applicable factor of safety required under Rule 4.05.9(8)(a) or <br />(b) had been achieved for each sediment pond embankment. <br />Response — The slope stability analysis for the three sediment ponds is included in <br />Appendix 2.05.3(4) -2A. <br />d) Appendix 2.05.3(4) -1, "Arcadis Report on Sediment Control ", contains cross sections <br />for the three sediment ponds. The cross sections show that ponds NHN -001 and NHN - <br />003 will have 10 foot wide embankment tops. However, the cross section for pond <br />NHN -002 shows that it will have a 5 foot wide embankment top. The Division is <br />concerned, especially since a public road is adjacent to the length of the pond, that such <br />a narrow embankment may not be stable enough to achieve the applicable factor of <br />safety. The Division requests that the permit application designs be revised to show that <br />the embankment top width for pond NHN -002 will be at least 10 feet. <br />Response — Expanded the footprint of NHNO02, allowing 10 feet for the top of the <br />embankment as suggested. <br />e) The proposed sediment pond embankment heights, measured from the pond bottom to <br />the emergency spillway bottom, are listed in Table 3 and shown on the cross sections, in <br />Appendix 2.05.3(4) -1. The proposed embankment heights for ponds NHN -001 and <br />NHN -003 are less than 10 feet but for pond NHN -002, the proposed embankment <br />height is 11.5 feet. Rule 4.05.9(6) requires a foundation investigation for those pond <br />embankments that exceed 10 feet in height. Please provide the foundation investigation <br />required under Rule 4.05.9(6) or lower the height of the pond embankment for NHN - <br />002 to 10 feet or less. <br />Response —Pond NHN -002 has been revised to have an embankment height not exceeding <br />10 feet; no foundation investigation is required. <br />f) The certified pond cross sections in the Arcadis report in Appendix 2.05.3(4) -1 show <br />that the pond embankment inslopes and outslopes for sediment ponds NHN -002 and <br />NHN -003 are both 2H:1 V. However, Rule 4.05.9(7)(e) requires that the combination of <br />the inslope and outslope of a pond embankment not be steeper than 5H:1V unless a <br />demonstration is provided to show that the steeper slopes will be stable. Please provide <br />Page 16 <br />