2017-11-29_REVISION - C1981038 - Laserfiche WebLink

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Page 2 of 9 North Fork Farmers Ditch Culvert Inspection occurring. The length of pipe that is in the highest deteriorated condition is approximately 100 feet in length. The bottom of the culvert remains settled, holding over a foot of standing water, approximately 100 feet from the eastern end. Around this location, the culvert invert begins to slope as it was probably originally intended and is in good shape. The eastern end of the culvert has an entrance apron that is in fair condition with no major erosion present. It appears that the portion of the culvert under the detention area has settled, likely due to the presence of water above during storm events and the extra weight of the water on top of and within the overburden soil. The settling has caused a portion of the culvert to hold standing water, which is known to reduce the lifespan of culverts. The pipe failure observed was near the standing water line and appears to be a direct result of that water during the irrigation off-season. Culvert Ratings (Load and Condition) CDOT and other state departments of transportation typically use AASHTO Load and Resistance Factor Rating (LRFR) to determine the safe operating loads for flexible culverts. CDOT has not developed software for the purposes of rating flexible culverts, so we have used the State of Ohio’s rating tool, which mimics the AASHTO requirements that are the basis for both rating programs. We performed two rating scenarios based on the sections of pipe that are in good condition and for the section of pipe that is failing. The results of the rating program are attached to this letter. As expected, rating of the culvert sections in good condition results in no posting recommendations for the culvert, meaning it is operating at full load capacity. The rating of the pipe section that shows sign of failure results in the following load posting recommendations: Recommended Load Posting Sign WEIGHT LIMIT AXLES 2 3 T 3 4 T 4 4 T 5 5 T 6+ 5 T The rating results require some qualifications due to the location of this culvert. First, the culvert is on private land and is not subjected to repeated highway loading scenarios as is assumed for highway culverts. Second, the section of culvert that the recommended loads above apply to is not under a roadway. This rating applies to the section of pipe that was observed under the detention area. Third, the load rating above is in comparison to a full operating 2-axle vehicle of 15 tons. A second rating system that can be used is that of the Federal Highway Administration (FHWA). It uses a matrix for rating the overall condition of a culvert. Using the FHWA matrix, our rating for each of the four criteria is as follows based on the most deteriorated section of pipe: Criteria Rating Description