PERMFILE46869 - Laserfiche WebLink

Home Browse Search

approved for the White Rocks project will be conducted in nine stages over a 10-year period, with each stage yield- ing from 200,000 m 250.000 tons of gravel. Once reclamation is completed. the 300-acre aria will consist of lakes, riparian woodlands, wzt sedge mzad- ows, and dry grassland. Mining is carried out during the months of October through March with the restoration process, which includes grass and tree planting, cartied on con- currently with mining so that revegeta- tion is done during the same season that mining is completed in an area. Much of the planting is done during March and April so that the only human activ- ity in the area from May to October is haulin, gravel from the stockpiles. The goal of the restoration process is to create an area of biological diversity much like that which existzd prior to man's disturbance of the land. With the reclamation being carrried on concurrent to mining. the removed overburden will be placed in its uhi- mate location to a contour and elevation according to the master plan. This overburden is used m build islands, sounds, and lake banks. Perimeter plantings of cottonwood and willow trees, plus nmive grasses will be made prior to the growing season. When the final portion is excavated, the perimetzr planting will he nine to ten years old. Coring of cottonwood and willow species made at Sawhill ponds, another Flatiron reclamation project nzar White Rocks showed that these species arz from 10 to 20 fzet tall at six to seven years of age, and are expzcted to grow from 3 to 5 feet a year aftzrward. By the time all of thz area has bzen mined, the eastern portion of the site will have been producing natural habitats for approximately fivz years. Also, ;tfter the first four stages are mined and restored, the access road to the area will be moved from an eastern to a western route to minimize the dis- turbance of natural processes in the re- claimed areas. The gravel is being mined by dq• methods. Prior to mining, a dewatering trench is excavated around the area to be mined and thz ground water col- lected in the trench by means of perco- lation through the gravel strata. This water will be pumped from the lowest point in the trench into Boulder Creek allowing front end loadzrs to excavate the gravel from the unmined face. A 600-tph capacity portable crush- ing-screening plant is moved into the site in October and positioned near the excavation site. The pit run gravel is transported to the crushing plant by the front znd loader and processed imo stockpiles of finished products. The operation will produce two types of aggregates: I'/: and '/a-in. rock (or as- phalt, and. '/a and 1'/z-in. rack for road base. Currently, only road base mate- rial is being produced, and is stock- piled near the crushing site until the construction season at which time it is hauled to the construction sites. Once the operating season is over in the spring, pumping of the dewatering trench is stopped anJ the water table is allowed to rise. Noise produced during the crush- ing-screening operations is han- dled primarily by proper location and orientation of the equipment. The orientation of the smckpiles is such that they function as an effective sound bartier and the portablz plant and as- sociated equipment is kept at a mini- mum 1400 fl distance from the nzarest dwellings. In addition, operating hours for the plant are held to between 7:00 a. m. and 6:00 p.m. Although the Boulder city noise ordinance is not ap- plicable at White Rocks, the noisz Izvel expzctzd al White Rock is "many times" lower than the allowablz Izvel in thz city during working hours. To date, thz fiat and second stages of mining and reclamation have been completed, accounting for the removal of approximately 20 percent of the gravel. Work on the third stage began in October. 1975. According to Ed McDowell, community acceptance of the project is excellent, partly due to feature articles on reclamation progress that have appeared in local newspapers and on Dznver television stations. The project was awarded one of ten national Engineering Excellence Awards of 1974 by the American Consulting En- gineers Council For the water manage- ment plan which was developed by the company's consultant Leonard Rice, Water Engineers. However, all of this success did not come cheaply. The $250.000 expended for planning, approval, design and re- clamation amounted to approximately $I .00 a ton for every ton mined during the first year. During the second year, according td McDowell, an additional $25,000, or $0.10 a ron was spew on reclamation. However, the Flatiron exzcutive added that in the future the company hopes to amortize the $I .00 a ton cost over future production to insure that costs go down. m This portable scale, used to weigh loaded trucks leaving the area, will be moved from the eastern access route to the western access of the property aner the first lour stages of mining are completed