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Bradbury, K. R.; Borchardt, Mark A.; Gotkowitz, Madeline B.; Hunt, R. J. / Assessment of virus presence and potential virus pathways in deep municipal wells
[DNR-197] (2008)

Results,   pp. 15-27 PDF (3.9 MB)


Page 15


Results
Precipitation, climate, and water levels during the study period
The Madison area received unusually high precipitation during the study period. Figure 4
shows the distribution of precipitation and air temperature between July, 2007 and
September, 2008. Intense rainfall during August, 2007 caused minor flooding during that
Fall. Record snowfall (over 100 inches) occurred during the winter of 2007-2008.
Finally, June, 2008 was the second wettest month on record, with a rainfall of 10.9 inches
in the Madison area (MMSD, 2008). Very intense rainfall between June 9 and 12, 2008
cause major flooding across southern Wisconsin.
Surface-water and groundwater levels and storm sewer flows responded to the
precipitation events. Figure 5 summarizes storm sewer flows, the elevation of Lake
Mendota, and groundwater levels in two local monitoring wells. Rapid increases in
groundwater levels show that rapid recharge occurred after storm events. The Spring
Harbor storm sewer drains street runoff from west Madison and discharges into Lake
Mendota. It is one of several such storm sewers in the Madison area. Maximum storm
flows occurred after the heavy rains in August 2007 and June 2008. A significant flow
event also occurred during early January, 2008 following an unusually warm "January
thaw".
The June, 2008 precipitation event is also important because it resulted in extremely high
flows in the Madison sanitary sewers (MMSD, 2008). Sewage flows often increase
during precipitation evens due to stormwater infiltration through leaky sewers and
basements. The average flow to the Nine Springs Wastewater Treatment Plant is about 41
million gallons per day (MGD). During the fist significant rains on June 8, flows
increased to 122 MGD, and then declined to about 80 MGD for several days. Several
discharges of sewage diluted with rainwater in the system occurred during this rain event,
on June 9. The largest discharge was into the Cherokee Marsh and the Yahara River
upstream of the Highway 113 bridge (1,080,000 gallons). There was a smaller discharge
into the Cherokee Marsh on the south side on Golf Road (17,200 gallons). There were
also two discharges that would have entered Starkweather Creek (245,000 gallons on the
east side of the Dane County Regional Airport and 48,000 gallons near Milwaukee
Street), a small discharge into Lake Mendota at Carroll Street, and two small discharges
into Squaw Bay on Lake Monona; one on the south shore (50,000 gallons) and one on the
east shore (4,000 gallons) (Jon Schellpfeffer, MMSD, written communication).
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