![]() Most municipalities report that they can’t afford the costs, so maintenance projects are currently being delayed. Conservative estimates suggest management costs may be measured in the billions of dollars for just these ponds. In the seven-county Twin Cities metropolitan area there are an estimated 15,000 stormwater ponds. It does not include landfill disposal costs if that applies. The equation was developed using 2009 dollars and volume is measured in acre-feet. The cost equation includes 30% for engineering and administration costs and 20% for contingencies. Projects costs to remove and manage uncontaminated sediment (not regulated as a solid waste) are substantially less when transportation and disposal costs are limited and/or not incurred.Ī dredging cost equation was developed for the City of Minnetonka in 2009 as a way to estimate long term stormwater pond maintenance costs. ![]() ![]() Anecdotal information provided by metro-area cities indicates typical costs range from $75,000 to $125,000 per pond when sediments need to be disposed of at an municipal solid waste facility. In some cases costs can be as much as $250,000 per pond when sediment removal projects include sediment contaminated above the industrial and commercial soil reference values. Management costs vary based on the size and location of the excavation, volume of sediment being removed, and laboratory analysis. Other costs include excavation, transportation, and tipping fees if those apply. Neither option is sustainable at the volumes that will likely be generated in the coming decade.ĭisposal costs include testing and laboratory analysis of the sediment to characterize the waste. The cost of the second option depends on whether the sediment is used as daily cover material by the landfill or is disposed of with other municipal wastes. The MPCA doesn't have cost estimates for the first option. Current standards and guidance provide two viable options: The sediment may be used as fill at an already contaminated industrial site, or disposed of as solid waste at a municipal solid waste landfill that has a liner and a leachate collection system. How are PAH-contaminated sediments disposed of, and what does it cost?ĭisposal options depend on the concentration of PAHs in the sediment. They are also accumulating in the sediments of natural lakes, streams, rivers, and wetlands that receive untreated stormwater runoff. PAHs are also accumulating in man-hole sumps, catch basins, rain gardens, ditches, underground treatment systems, street sweepings, and other parts of stormwater collection and conveyance systems where sediment accumulates. Sixty-seven percent of the PAH contamination in stormwater-pond sediments comes from coal tar-based pavement sealants. PAHs have been found in the sediment of stormwater ponds across the state, primarily in urbanized areas. Some PAHs are listed in Minnesota as possible carcinogens. They also come from burning carbon, forest and grass fires, vehicle exhaust, and even char-broiled foods. Polycyclic aromatic hydrocarbons (PAHs) are chemicals that occur naturally in coal, crude oil, and gasoline, and are also present in products made from fossil fuels, such as coal-tar pitch, creosote, and asphalt.
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