Proposal for woodash application to Mud Lake within the "waste management area" at the abandoned South Bay Mine site / For David Porter, Talisman Energy Inc

Abstract

Wood ash has long been recognized as a valuable and safe additive to agricultural soils. Composed primarily of calcium- and potassium-oxides, it also contains major and minor elements common in the environment and yet essential to plant growth. Field and greenhouse research have shown that it has a liming effect of up to 90% of the total neutralizing power of lime. Almost by definition, since ash is derived from the combustion of clean and virgin woods, it is not offensive to the environment. In summer 2000, 4 t of wood ash, generated in Ear Falls by Weyerhaeuser sawmill, was applied on an experimental basis to the slopes of the recently enlarged Backfill-Raise Ditch at the Abandoned South Bay Mine Site, which provides a pathway for seepages from the underground workings. Lacking a ground cover, the contaminated slopes were vulnerable to erosion. Experiments in the previous year, with one truck load of wood-ash indicated that the wood ash would both raise the pH of the waste rock, and provide nutrients to stimulate the growth of a terrestrial moss. In fact, this was accomplished. The resulting carpets of moss in the cracks between the rocks stabilized the ground and reduced the infiltration of the contaminated run-off into the waste rock of the mill site. During the summer of 2001, with the approval of the MOE, approximately 100 tonnes of wood ash were spread over Mill Pond, Mine site and on the Backfill Raise ditch slopes. The results will be documented by fall 2002 but so far are very promising. Concurrent with those terrestrial experiments, in May 2000, wood ash was added to samples of acidic water taken from Mud Lake and Boomerang Lake, both of which lie within the waste management area. The pH of Mud Lake is presently at 2.5; Boomerang Lake is 3.0. The object of the experiment in two 1 m3 containers was to determine the amount of wood ash required to raise the pH to 4.5, at which level phytoplankton and microbial activity accelerate, to counteract acidification and promote biological polishing, mainly for the removal of zinc. Wood ash has two reaction components; it contains potassium oxide (1.6 % wt/wt), which reacts immediately, and calcium oxide (11.4 % wt/wt), which settles with the remaining inert materials in the ash, which is about 80% by weight, to the sediment of the lake to be treated. From there it gradually releases its neutralizing capacity.