COMMISSION_MINUTES_1978-09-28 - Laserfiche WebLink

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_2_ Necessary Preparations The City property, which now drains in all directions, should be graded flat with an earthen mound around its perimeter, a minimum of one £oot high. The straw bales would then be placed within this earthen mound and staked. At a point in the SW corner, another ring of bale is required to double filter the runof£ water. The existing storm sewer is estimated to be able to carry the 2,000 gallons per minute. Temporary fencing of this area should also be required, as it could be a public nuisance. Estimated Amounts o£ Solids The following figures and calculations are sta`f's estimates and, due to the information at hand, could be in error as much as t258. Figuring the pond's average silt depth at 12" will produce 5,646 cubic yards of silt on the pond Ploor. It is believed that the removaL of water will reduce the solid size by one half, givi.ng approximately 2,823 possible cubic yards. (This is felt to be very conservative, as the dumping of the material will be wet and it is believed that it will take from one to two weeks for it to dry, depending on *_he weather.) The staked bales around the £ill perimeter will hold back one foot of solids. Possible fill area is lesa t�an 10 feet around the perimeter of the property, which gives an area of 114' x 342'. The 10 foot area around the perimeter is £or the earthen mound and bales. Taking these measurements, it would be possible to retain 1,444 cubic yards of solids. The machine, pumping 108 solids at 2,000 gallons per minute, can pump approximately one cubic yard per minute. Taking the average work day of ten hours, less 208 for non productive hours, would produce approximately 460 cubic yards a day. Times a five day total, would produce 2,400 cubic yards. Thus, my conclusion is that the total cleaning of the pond could possibly occur in five days, but that there may not be a capacity for all of it. It also may be pointed out that this may cause a rise in the water table in the immediate area, but, due to various conditions, it is impossible to estimate the possible effect. Also, the dumping of this solid material and grading o£ the area will virtually kill all existing vegetation. Removal of the solids at a later date in a dry form should also be required. Recommendations Potential problems which could occur permitting this dredging operation lead staff to recommend against allowing it. \,..