2013-07-25_REVISION - C1982057 (3)

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1. SCC has proposed the addition of two culverts (PM -3A and HRC -J3A) as supplemental culverts to assist in conveying design flows, and has not included design information for those culverts. The omission of design information is appropriate in this case. However, if at some future date SCC revises the drainage plans to rely on these culverts, design information would be required. 2. SCC provided a SEDCAD Utility Run for Culvert PM -19, using a base flow value of 0.31 cfs. It is not clear how SCC arrived at this base flow value. The approved PM -2 channel design assumes a flow of 24.10 cfs in a 10 year -24 hour precipitation event. The Division understands that the purpose of this culvert is to provide a low water crossing for equipment but needs a better understanding of the design premise to determine if the culvert will convey the typical base flow without siltation /clogging, which would result in an impediment to conveyance of the design flow in the ditch. Please provide additional information on how SCC determined the base flow value to be 0.31 cfs. 3. It is not clear whether SCC intends for these proposed culverts to remain in place on a permanent basis. If the culverts are to remain Map 20 -2 needs to be revised; if they are not, the reclamation cost estimate should be updated. Please revise Exhibit 20 -2 to include Culverts PM -3A, PM -19, and HRC -J3A, or update the reclamation cost estimate to include removal of the culverts. 4. Revised tables 13 -5 and 13 -7 -1 have been updated to include the three proposed culverts. Comparing the proposed tables to the currently approved versions, it appears that SCC also revised the table to delete the "removed" status for culverts HRC -Y3, K -1, and PM -16. Please verify whether these revisions were intentional, and if the culverts have been removed, revise Exhibits 13 -2 and 20 -2 to reflect the current status of the culverts.