2000-12-11_GENERAL DOCUMENTS - C1981015 (2)

Home Browse Search

" has shown how slope transition areas are subjected to higher erodibility from flow velocity and that the transition zone should located higher up -slope as possible. Field Directive #2 authorized additional machine time, Additive Alternate #1 (track -hoe), to be used for additional side channel work from the east and at the toe of the slope. It also directed that machine time could be used to pull out the drainage to the west, to start the access road recontouring, and for sediment pond spillway work. Field Directive #2 also allowed for diviting with the hoe bucket as being an acceptable surface roughening instead of the specified dozer blade furrowing. The punchlist for the channel work included: the need for filling the voids between the larger rock; the need to address side slope riprap placement in places lacking the 48" minimum height; a few side slopes not adhering to the 3:1 specification and; the upper portion checkdam elevation difference was not at 24" needing additional rock up both sides of the side slopes. All the Komatsu machinery was demobed. Shortly after, a Case 1080 track -hoe with thumb was mobilized onto the site and all the punch list items were corrected. The first 40 hours of additional machine time (track -hoe) had completed: the side drainage construction from the east tying into the main slope channel; recontouring the drainage to the northwest and related access roads; and had started the upper access road recontouring. Field Directive #3 was issued for additional machine time to complete access road recontouring and to perform work on the sediment pond spillway. All recontouring performed by the track -hoe resulted in approximate original contours to the extent possible with a extremely rough surface desirable for revegetation. Extremely large rock was left in. place. While access road recontouring work was being performed west of the northwest drainage, buried lime was encountered. All the lime was placed to the best extent possible first against the slope cut and then was buried with overcast material. The spillway construction for the sediment pond had followed the staked location which was based on a 24" higher elevation than the standpipe inflow. Concern was made as to if the spillway elevation was higher than the southwest corner elevation of the sediment pond. After critical review, it appears that there is an approximate 12" of difference between the two elevations. Revegetation operations were delayed (5 days given) due to late spring wind and rain. The steep sloped 0.5 acre area associated with Additive Alternate #2 regarding revegetation using BIOSOL was divited, seeded and mulched without incident. Mulch consisted of Western Wheatgrass and Galleta grass bales from Southwest Seed of Dolores, Colorado. Mulch transport was not included in this contract and was billed separately. The Galleta mulch was used exclusively on the BIOSOL area. A very late season seeding (late May) coupled with extreme high temperatures and a poor precipitation season to follow resulted in revegetation failure. Realizing the late season seeding and the assumed need for an additional seeding, Field Directive #4 was issued to provide the additional costs for reseeding based on the submitted bid revegetation cost, Additive Alternate #3, of $500.00. The site was reseeded by broadcast methods in late November. V. FUTURE WORK The site should be monitored for revegetation success as well as for the affects of erosion on the reclaimed areas.