Viruses in Madison s Deep Wells: The Unexpected Effect of Heavy Precipitation

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1 Viruses in Madison s Deep Wells: The Unexpected Effect of Heavy Precipitation Mark A. Borchardt, Susan K. Spencer Marshfield Clinic Research Foundation Kenneth R. Bradbury, Madeline Gotkowitz Wisconsin Geological and Natural History Survey University of Wisconsin-Extension Randall J. Hunt U.S. Geological Survey

2 Take Home Message Groundwater in deep, confined aquifers is usually assumed to be protected from contamination, but Viruses present in deep wells in Madison shows that surface pathogens can reach deep, confined aquifers, and Water Cycle Heavy precipitation affects more than surface water in Madison it increases virus transport to groundwater affecting the sanitary quality of the drinking water source.

3 Overt Flooding: From the Top Down Cedar Rapids, Iowa Wikimedia photo by Don Becker Des Moines River, Iowa Wikimedia photo by Ted Taber Lake Delton, Wisconsin Wikimedia photo by Paul Gorman

4 Covert Flooding: From the Bottom Up $+ airport field $+ $+ cemetery $+ $+ $+ terrace $+ Photo by Peter Gorman Groundwater flooding in the Spring Green cemetery Photo by Peter Gorman

5 Obvious Potential Health Effects from Overt Flooding WI DNR photos Flooding of the Gays Mills, WI sewage treatment plant 2007 AND WI communities released untreated sewage during the 2008 flooding

6 Pathogens in Human Wastewater Bacteria (e.g., Campylobacter, Salmonella, E. coli O157:H7, Aeromonas) Protozoa, (e.g., Cryptosporidium, Giardia, Toxoplasma) 1,438 pathogens infect humans of which 32 are waterborne in the U.S. Viruses (e.g., adenovirus, enterovirus, rotavirus)

7 Virus Subsurface Transport Potential Small size ( 50 nm) and negative charge favor movement through soil Survivability favored by low temp, moisture, and absence of UV light Documented transport: penetration as deep as 67 m, horizontal migration up to 1600 m

8 Virus Sources and Infiltration Routes into Groundwater

9 Study Objectives in Madison Obtain a time series of virus, isotopic, and geochemical data from several municipal wells in the confined, deep, Mount Simon sandstone aquifer Evaluate the potential virus sources and pathways to the wells

10 Study Methods Virus samples collected monthly for 11 months, Sep 07 to Jul 08. All samples taken prior to chlorination qrt-pcr/qpcr detection of enterovirus, rotavirus, hepatitis A virus, norovirus, and adenovirus Enterovirus and adenovirus serotype determined by nucleic acid sequencing; infectivity determined by cell culture Isotopes ( 3 H, 2 H, 18 O) analyzed at the University of Waterloo Environmental Isotope Lab

11 Wells sampled We began with 10 wells in a variety of locations to be sure we had virus-positive wells to work with. We later reduced the sampling to 6 wells due to budget and logistic considerations.

12 Municipal Water Supply: Mt. Simon Aquifer Eau Claire Aquitard Mount Simon Aquifer From Massie-Ferch 1997

13 Well Construction in Madison Well Screen in Mt. Simon Cross Connecting Screen aquitard depth (meters below surface) well 5 open hole casing casing well 7 well 24 open hole casing open hole casing Wells 7 and 24 are screened in the Mt. Simon aquifer Well 5 is screened in the upper aquifer, the Eau Claire aquitard, and the Mt. Simon aquifer not to scale glacial materials Wonewoc sandstone Eau Claire aquitard Mt. Simon aquifer crystalline rock water table potentiometric surface

14 Overall findings We found viruses in every well sampled in , though not every time sampled Summary of virus detections by water source Water source Wells Lakes Sewage Virus detection (gc/l) Percent positive min max ,600 2,078,000 mean ,000

15 was an unusually wet period; large storms in August 2007 and June 2008

16 Sewer flows, lake levels, and groundwater levels in /1/07 8/1/07 9/1/07 10/1/07 11/1/07 12/1/07 1/1/08 2/1/08 3/1/08 4/1/08 5/1/08 6/1/08 7/1/08 8/1/08 9/1/08 flow at Spring Harbor storm sewer, CFS date 856 elevation of Lake Mendota feet above msl water table elev, DN-83 ft above msl hydraulic head, upper sandstone Nine Springs site, ft above msl DN-83 water table upper aquifer water level Lake Mendota elev Spring Harbor storm sewer flows

17 9/1/07 10/1/07 11/1/07 12/1/07 1/1/08 2/1/08 3/1/08 4/1/08 5/1/08 6/1/08 7/1/08 8/1/08 9/1/08 Coincidence with time wells (number sampled) sewage L Wingra L Monona L Mendota sample date virus concentration (gc/l) overall percentage of virus-positive wells The coincidence of virus detections in wells, lakes, and sewage is surprising.

18 Well Virus Concentrations - Coincidence with Time

19 Several different virus serotypes were identified in wells, sewage, and lake water and in many cases wells and sewage contained identical virus serotypes. Detected viruses include enteroviruses echovirus 3, echovirus 6, echovirus 11, Coxsackie A16 and B4, Adenoviruses 2, 6, 7, 41, as well as G1 norovirus and rotovirus.

20 Sewer Locations Relative to the Water Table Figure. Cross sections showing the possible locations of a sewer relative to the water table. A: gravity-drain sewer below water table; B: gravity-drain sewer above water table; C: force main above water table; D: force main below water table. H 1 and H 2 represent hydraulic head inside and outside the sewer. Arrows show directions of potential sewer leakage. Sewers are a potential virus source. Some Madison sewers are in hydraulic positions that allow them to leak to groundwater.

21 Summary Human viruses can be commonly present in groundwater in deep bedrock wells. The percentage of virus-positive samples ranged from 60% in multi-aquifer wells with shallow casings to 18% in well 30, a new, deep well deeply cased across a regional aquitard. Several lines of evidence suggest that transport is rapid on the order of months or weeks rather than years. Leaking sanitary sewers are the most likely virus-source to the wells; the Madison lakes are NOT a likely virus-source Virus levels in the wells increased after rapid melting of heavy snowfall and after heavy rainfall Groundwater supplies for drinking water, even very deep supplies, are not immune to changes in sanitary quality stemming from heavy precipitation.