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<br />RECOMMENDATIONS <br />1. The bridge in its present condition and r:ith the gravel pit <br />located 200 ft. down... dream must be monitored during any high <br />flow. After any high flow and at least once a yeat• it should be <br />inspected. <br />2. A sediment transport study should be made utilizing IiE%' ti or <br />comparable computer program. 'The study should be prepared by an <br />engineer experienced in the use of the model and shoulri include <br />the amount and rate of a }read .,cut, time fot• stable river <br />recovery, amount of pier and abutment scour, etc. 7'}ris scour <br />determination to be the total expected scour at ttre bridge <br />(local, contraction and long term elevation channel. <br />3. A grade control structure at the correct elev<tion and <br />designed to withstand the hydraulic forces from overtopping and <br />seepage should be constructed dowrstream of Lhe bridge. This <br />structure to go clear across the opening of the bridge and be <br />tied into each .approach to the bridge. ~ The elevation tc be high <br />enough to protect the bridge footings, piles and piers but low <br />enough not to cause backwater higher Lhan FE`•1A regulations. The <br />proposed elevation of~.3608 for the rubble cure is too high. The <br />elevation of this grade control. structure should on 1. ,v be a couple <br />of feet higher titan the present average elevation v[' the stream <br />bed under the bridge. <br />4. If the downstream bridge is replaced the piers should go to <br />bed rock and be designed as a column that is exposed most of its <br />length. The length to be decided by ttre scour study in paragraph <br />2. If a grade control structure is built across the stream a~ <br />described in paragraph 3 then the length of exposed pier would <br />be reduced. <br />r5. Grayel mining operations should out be permitted in the <br />active channel of this river. 7•hat is, the nominal width of 500 <br />to i00 ft. that this river needs to carr3• its normal low, medium <br />and flood flows should not be encroached upon. <br />If the river breaks into the gravel pits a head~cut <br />This head `cut will move up the river and lower the base <br />all tributaries until the river reaches equi.libr•iurrr <br />sediment inflow and its adjusted slope. <br />wi'_1 form. <br />1<~vel for <br />wi t}t the <br /> <br />