2005-07-13_REVISION - M2000016 (41)

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'IWftleApplegate,lec. Consultants for Land, Mineral and Water Development May 19, 2000 Weld County Department of Planning Services 1555 N. 1 T~ Avenue ' Greeley, Colorado 80631 RE: Flood Hazard Development Permit Mobile Premix Concrete, Inc., Riverbend Operation To Whom It May Concern: This application is for a Weld County Flood Hazard Development Permit (PROP) for Riverbend Operation, which is located approximately 3 miles north of Brighton, CO. The property runs along the South Platter River and between some bends of the river channel. Donald and Suzanne Rittenhouse and Steven McWilliams aze leasing the land to Mobile Premix Concrete, Inc., a subsidiary of Lafarge Corporation. The Riverbend Operation is a sand and gravel mining operation along with conaete and asphalt batch plants. It is anticipated that the mining will last for 10 years with an additional 3 years for reclamation work. The total permit azea is 237 acres, with 120 acres being affected by the mining operation. The Riverbend property is found on Community Pane1080266 0983 C of the Weld County Flood Insurance Rate Maps (FIRM). The FIRM revised September 28, 1982, shows the property azea within a Zone A, consequently no Base Flood Elevations (BFE's) are determined. Accordingly this indicates the property is within the Weld County FP-1 Floodprone District. Since the Flood hnsurance Study (PIS) and FIRM were not detailed, it is necessary to determine an Intermediate Regional Flood (IRF) water surface elevation for the South Platte River. In this case, the IRF is the 1-% probability, or 100-year return period, flood event. The proposed operation consists of no permanent structures to remain beyond this use. The only habitable facility would be a scale house, which would be built with its lowest finished floor above the BFE. Given the size of the scale house the impact on the flood capacity of the river would be negligible. Therefore given these unique set of circumstances approximate methods were used to calculate a conservative BFE. The Federal Emergency Management Agency (FEMA) contour interpolation method was used as outlined in the Approximate Zone A manual. Additionally detailed study information from the Urban Drainage and Flood Control District was extrapolated to the site location from approximately 3 miles upstream. The results were found to be in the same range. 5441 Boeing Drive Suite 200 • Loveland, Colorado 80538-8855 • (970) 461-9884 • (Fax) (970) 613-1177 kalliesampish@tuttleapplegate.com