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r <br /> IV. CONSTRUCTION SUMMARY <br /> Excavation of the new channel, immediately adjacent to, and east of, the existing Ditch 8 began using a <br /> small track hoe and a very small tracked loader. During initial construction,Contractor was advised to <br /> leave a portion of the existing Ditch 8 open to accommodate summer thunder storm runoff. However, <br /> Contractor determined to fill the existing ditch in order to facilitate access to the under-construction Ditch. <br /> Shortly after placing the topsoil and the upper 75 feet or so of liner, a rain storm virtually washed away all <br /> of the topsoil in the lower portions of the ditch, and seriously compromised the ditch geometry. Contractor <br /> re-shaped the ditch and re-topsoiled portions of the Ditch. Following the rain event, some portions of the <br /> new ditch had been scoured to bedrock. It was determined by Project Manager to not topsoil or line these <br /> portions of the new ditch as the bedrock exposures were very hard and appear to be fairly resistent to <br /> erosional processes. <br /> Following evaluation of liners, a change to the specifications was adopted. The double mat Permamat 200 <br /> F was deleted and a single mat North American Green C-350 with enhanced stapling was adopted. The <br /> number of energy dissipaters within the channel was increased to about 18, and were alternated using both <br /> excelsior logs and stiff geo-membranes. Cursory, initial impressions indicate that the geomembrane may <br /> be a more durable energy dissipater in this environment. <br /> Excess liner materials were purchased from Contractor for later use at the Coal Basin Mine. <br /> V. FUTURE MAINTENANCE <br /> This site will need to be evaluated in the Spring of 2001. Additional seeding may be necessary, and <br /> additional geo membrane energy dissipaters will need to be installed. These are being stored at the <br /> Carbondale Fish Hatchery. <br /> VI. SUMMARY <br /> Initial observations indicate that this channel is more capable of delivering surface runoff from the <br /> southern portion of the Sutey Refuse Disposal Area than the pre-existing channel was. However, this high <br /> energy channel will require frequent observation <br /> Project Manager : Steve Renner <br /> Date : 12-4 -00 <br /> M:\imp\closeout\coalbditch8.doc <br />