2015-08-26_REVISION - C1981019 (2)

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Mr. Rob Zuber August 25, 2015 Page 3 7/25/07 TR -63, the lower reaches were designed to have a 6 foot wide bottom. In the last adequacy response for this tehcnical revision, the ditch's widths were incorrectly transposed in Table 1. The SEDCAD Streeter Ditch hydrology model attached to this adquacy reponse has the correct design widths for all segments, existing and proposed. The supporting models for both Streeter Ditch and Streeter Pond have been remodeled with the addition of two more stockponds to knock down the peak flows in Streeter Ditch. ii. Also in Table 1, please check the values for the SW and SE tributaries and explain the following. The flows are significantly lower than the values in the SEDCAD runs. Also, the slopes are very different between the two tributaries, but this seems incorrect based on the topography of the map. Response: The two tributaries in question (SW and SE tributaries) were both Phase III released in 2012; therefore, the Division has relinquished jurisdiction on both ditches. Nonetheless, for informational purposes only as discussed in the second paragraph of page Exh. 7-14E-2, the watersheds for Streeter Ditch above Sta. 110+00 and the two tributary ditches SE and SW are all less than one square mile, and were therefore designed for the 10 year, 24 hour storm. This is also indicated in Exh. 7, Item 14, Table 1 where a break from the 100 year flow to the 10 year flow as shown. The average overall slopes on both ditches are approximately 8%, but the bottom portion of SW Tributary has a steep area right before it drops into Streeter Ditch. That segment was, therefore, designated as the controlling segment for SW Tributary, and that segment is the one represented in Table 1. There has been one minor change to Table 1 as a result of this comment. The peak flow for the upper reaches of Streeter Ditch between Sta. 110+187 range from 25.2 cfs to 86.9 cfs, not the 25.2 cfs to 38.68 cfs previously reported. The higher flow rate occurs at Str. 23, upstream of Stockpond 2. The 38.68 value was flow rate downstream of that point. iii. On the maps with Streeter watersheds (Figures 1 and 2 in Exh. 7-14E), explain why Stockpond 1 moved from station 82+00 to 87+00. Response: Stockpond 1, which has yet to be constructed, was relocated from Sta. 82+00 to Sta. 87+00 to avoid having to redisturb areas that have achieved Phase III bond release. iv. In Table 6, the sediment pond summary in Volume 2D, some items under Streeter Pond require explanation. Why did the amount ofundisturbed area change (almost doubled)? Why did the base rate of flow change from 0.00 to 0.15 cfs? Explain the decrease in principal spillway flow T i,C 1w, ite Entt:^ r �. ..�