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From what little research time I have spent, I 've been able to glean <br /> the following rather sketchy "facts": Application rates for sludge <br /> can differ from as little as 20 dry tons per acre to as much as 100 <br /> dry tons (as long as salts in the sludge don't start affecting plant <br /> growth) . Generally, one can think of 40 dry tons per acre to be about <br /> the equivalent of one-fourth inch over an entire acre. , If all the <br /> sludge material is considered to be organic matter and were <br /> incorporated into the top six inches of cover material, this would be <br /> the equivalent of about 4 percent organic matter in the growth medium <br /> (probably typical of the surrounding forest surface soils) . Depending <br /> on the quality of the sludge, maintenance applications may be needed <br /> to get higher organic matter in the surface soils since a heavy <br /> initial. application may expose plants to salts or other toxic elements <br /> in the sludge. <br /> Lime application rates are hard to determine until the nature of the <br /> cover material is more well known. Application of limestone may be <br /> cheaper but the risk of armoring of the particles by metals in the <br /> cover material may preclude the use of limestone. One method that may <br /> be used is to apply the limestone on the surface and let it sit there <br /> for at least a year to get high pH water to flow through the top <br /> portions of the cover material. After some time, the limestone and <br /> applied sewage sludge could be incorporated into the top six inches of <br /> cover material. Incorporation of these materials to greater depths <br /> may not be necessary since many subalpine and alpine plant species are <br /> shallow rooted anyway. A light topical application of lime or <br /> limestone just before or following seeding would be suggested. <br /> As you may have determined from this memo, I would suggest that DMG <br /> reopen the question of the requirements necessary to provide a <br /> suitable growth medium over the tailings ponds at Climax since all the <br /> above mentioned factors are interrelated. Given the expense to <br /> Cyprus/Amax of providing this growth medium, it seems prudent to give , <br /> some careful thought and review to all factors involved in getting the <br /> best product possible so revegetation efforts have the best chance of <br /> success the first time. <br /> I do believe that the sewage sludge (and perhaps lime/limestone) <br /> application rates needs to be a technical revision to the permit since <br /> DMG would have to review the information above and make a judgement on <br /> whether the proposed revegetation plan (growth medium enhancement) <br /> would have a reasonable chance of success. <br /> I have contacted Mr. Phil Hegeman at the Colorado Department of Public <br /> Health and the Environment and he indicated a willingness to allow a <br /> higher rate of biosolids application than presently allowed in the <br /> "Notice of Authorization for the Use and Distribution of Biosolids" <br /> dated December 15, 1994 so long as the rate did not conflict with the <br /> DMG permit. <br /> I also think that Gregg should handle this from now on, given the <br /> amount of time involved. <br /> C:M77493 .MEM <br />