Sewerage Proposal Allows 6 Overflows
NOTE: The Deparment of Natural Resources has scheduled a public hearing on the proposed discharge permit beginning at 1 p.m. July 26 in the department's southeast region headquarters, 2300 N. King Drive, Milwaukee.
[excerpted from the Milwaukee Journal Sentinel]
A draft state discharge permit for the Milwaukee Metropolitan Sewerage District does not reduce the number of combined sanitary and storm sewer overflows to local waterways it is allowed each year - the total remains at six - though the district has not reported more than that in any year since the deep tunnel began operating in 1994.
Six such overflows were recorded in 1999 and five in 2000, the most on record since the tunnel started capturing most combined sewer overflows during heavy rain. There was one overflow of combined sewers in central Milwaukee and eastern Shorewood in 2011 and none so far this year.
The district's discharge permit for the first time prohibits more than an average of four combined sewer overflows a year over a 20-year period as a step toward tightening the number, a state environmental official said.
But this step likely will not carry much threat of enforcement because there has been an average of 2.5 combined sewer overflows a year from 1994 through 2011.
One significant change in the new permit is the elimination of a 60-million gallon a day limit during wet weather on the volume of wastewater that can be pumped out of the deep tunnel and disinfected with chlorine at the Jones Island sewage treatment plant before being pumped into Lake Michigan, said Ted Bosch, wastewater engineer with the state Department of Natural Resources in Milwaukee.
This emergency measure has been called blending and in-plant diversions in the past because it diverts wastewater from full treatment. With the new permit, this remains an emergency measure, but it is described as combined sewer overflow treatment.
Such treatment of wastewater pumped directly from the tunnel will be limited by the 100-million gallon a day capacity of the plant's diversion channel, Bosch said.
This option can be used early in extreme storms - when the deep tunnel is filling and the district's Jones Island and South Shore plants are treating wastewater at capacity - to prevent a combined sewer overflow, MMSD Executive Director Kevin Shafer said.
Pumping wastewater out of the tunnel to a diversion channel at Jones Island provides more space in the tunnel to store sewage and storm water flowing into it. So this emergency option reduces total overflow volume if one occurs.
This emergency measure is better for water quality, too, because diverted wastewater gets some treatment, according to permit documents. Settling of solids out of wastewater stored in the tunnel is equivalent to the primary treatment step at the plant, state and federal environmental regulators have determined. Disinfection kills bacteria and is another step at the plant.
The DNR has scheduled a public hearing on the proposed discharge permit beginning at 1 p.m. July 26 in the department's southeast region headquarters, 2300 N. King Drive, Milwaukee.
The five-year permit must be approved by the U.S. Environmental Protection Agency before it could take effect on Oct. 1, Bosch said.
Copies of the draft permit and a summary fact sheet can be read at the DNR office between 9 a.m. and 3 p.m. Monday through Friday. Permit information will be available Monday at the department's website: dnr.wi.gov/org/water/wm/ww/drafts/pubnot.htmhttp://dnr.wi.gov/org/water/wm/ww/drafts/pubnot.htm.
The district's Jones Island and South Shore plants treated a total average of 164 million gallons of sewage a day in 2011 during dry weather, permit documents say.
Jones Island discharges treated wastewater to the outer harbor. The South Shore plant in Oak Creek discharges to Lake Michigan through a pipe that extends more than 500 feet from the shore.
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