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3.4.2 Flood Plain <br />Approximately one-third of the Site is in the 100 year floodplain of the South. Platte <br />River, but none of the property is located in the floodway portion of the South Platte <br />River. The proposed filling of the Site is sequenced such that the portions of the Site in <br />the floodplain will be filled further in the future. Filling in the floodplain to elevations <br />consistent with the elevations prior to the gravel mining, and below the present day 100 <br />year floodplain elevations, will require obtaining a Floodplain Use Permit from Adams <br />County that will be subject to comments by UD&FCD prior to issuance of the Floodplain <br />Use Permit. Filling in the floodplain above the present 100 year floodplain elevation will <br />also require a Floodplain Use Permit from Adams County, after relevant comments by <br />UD&FCD prior to issuance of the Floodplain Use Permit, but also require approval of a <br />CLOMR prior to filling in the floodplain being undertaken by FEMA and then approval <br />of a LOMR by FEMA after filling to revise the relevant FEMA map. <br />3.4.3 Wetlands <br />There are no obvious or designated wetlands within the Site's boundaries. <br />3.4.4 Seismic Impact Zones <br />The United States Geologic Survey (USGS) Open-file Report was reviewed to determine <br />if the Site is in a seismic impact zone as defined in the current State and Federal <br />Regulations. The report indicates that the Site is not defined as a seismic impact zone. <br />Placement of inert materials does not require a barrier layer of liner material either (clay <br />or synthetic) and is not subject to seismic impact zone requirement. <br />3.4.5 Fault Zones <br />• <br />The Site boundary is not located within 200 feet of any fault experiencing displacement <br />in the Holocene time. The nearest reported fault is the Rocky Mountain Arsenal Fault <br />located approximately 3 to 4 mile to the east of the site. Placement of inert materials <br />does not typically require a barrier layer of liner material and although this Site is lined <br />with clay, it is not subject to the fault zone requirement. <br />3.4.6 Unstable Areas <br />There are no unstable geologic areas on the Site. Man-made features on Site will be <br />maintained to be stable. Permanent constructed slopes will be a no steeper than 3:1. <br />3.5 Site Topography <br />The Site topography prior to re-contouring is presented on the map in Appendix I. The <br />Site is located in area along the South Platte River basin. Prior to gravel mining the Site <br />topography was relatively flat and generally sloping up from the South Platte River. The <br />topography of the Site has changed due to the sand and gravel mining, and then the <br />AFS Frei-Henderson Inert Fill <br />MOLEN & ASSOCIATES, LLC <br />Page 7 of 23