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Mounds View Planning Commission March 15, 2006 Regular Meeting Page 6 ________________________________________________________________________ their pipes. And with the expected growth over the next 30 years in the Twin Cities, the amount of septage will only be increasing. Commissioner Hegland asked how odor is controlled. Brian Oakley, MFRA, replied odor is controlled with a bio-filter. Commissioner Hegland asked what if the bio-filter becomes inadequate or ineffective and what is done to ensure there are no problems. He also asked what the time frame is to rebuild the filter if they do have a problem. Mr. Oakley replied the bio-filter is simple technology involving the air from the equipment and the building being piped into the bottom of the bio-filter and as it rises, it goes through a layer of woodchips where a biological process happens to remove the odor from the air. The bio-filter does require some maintenance in that it needs to be kept wet. He added segmenting the wood chips would help ensure odor prevention. Commissioner Hegland asked how often the wood chips need to be replaced and what is done with the old chips. Mr. Brisbin replied that the chips do deteriorate over time and about every five years they would be replaced with the old chips going to a landfill. Commissioner Miller asked the location of the bio-filter. She also asked how big the bio-filter is. Mr. Oakley replied it would be outside at ground level. Mr. Brisbin replied there would be two pieces of equipment, with the size being determined later because it needs to be designed to fit the application based on the amount of air being treated. Commissioner Scotch asked why that site was chosen. Mr. Brisbin replied the site is centrally located for all haulers in the north metro area. The center needs to be within a 15 miles radius of the four Met Council sites that they would like to close. Mounds View is within that radius for all four of the sites. Commissioner Zwirn asked what the bio-filter area looks like. Mr. Oakley replied it looks like a garden with no plants; it is all wood chips. Commissioner Miller asked about snow covering the wood chips. Mr. Brisbin replied the air is coming from the building so it is warm and will melt the snow and water will trickle through to keep the chips wet and drain below them. Commissioner Hegland asked where the water will drain to if it is excessive. Mr. Brisbin replied to the sewer. There are pipes in the bottom of the bio-filter to drain excess water out of it in case of heavy rains. Commissioner Zwirn asked if the wood chips could be walked on and, if so, would air be forced up so a person would know they were walking on it. Mr. Oakley replied the chips would be about 3-4 feet deep and could be walked on. Mr. Brisbin replied air is moving upward at only four feet per minute so it is so slow moving that it wouldn’t be noticeable, and it dissipates by the time it reaches the surface.