Situated on the east bank of the Mississippi just south of 694, the Saint Paul Regional Water Service’s Fridley pump station has the aesthetic appeal common to well-maintained public buildings dating from the 1920s. With its trim grounds, banks of tall windows and freshwater scent, the station could pass for an old-fashinoned yacht or sculling club.
Articles in our water quality series:
PFCs from 3M: an ongoing source of debate by Anna Pratt
Measuring water quality in Minneapolis, St. Paul lakes by Anna Pratt
St.Paul water: good to the last drop?
Drinking across the river in Minneapolis by Rich Broderick
Water as an economic resource by Rich Broderick
Savage water by Rich Broderick
On this warm day, two of the utility’s point-men are showing off the now-automated facility; once-upon-a-time, the pumping station had a live-in manager who resided in a house on the top of the bluff, but now it is run from the central office. Jim Bode is the utility’s water quality manager. Dave Schuler, who used to have Bode’s job, is the organization’s chief engineer. Nonchalant and jocular, the pair keep up a banter of inside jokes and technical jargon; nonetheless, they are keenly aware of how seriously citizens take what comes out of the tap.
“One of the downsides of my job,” jokes Bode, “is dealing with people who’re convinced I’m trying to kill them.”
|Talking about water |
aquifer – a layer of permeable, sand or gravel that contains large amounts of water
groundwater – water that is underground, as opposed to surface water in lakes and rivers
potable – fit for drinking
point source –specifically site of contamination, such as a wastewater outlet
non-point source – diffuse source of pollution, such as run-off from lawns
watershed – a region that drains into a particular river or body of water
Inside the pump station, a pair of intake valves greedily suck water from the Mississippi. Three giant pumps push the murky fluid – the river’s turbidity averages more than 500 times the acceptable limit for drinking water – 40 feet up the bluff into a surge tower where the water pressure is stablized before the water is released into a pair of 60-inch underground conduits, also dating from the 1920s, for its roughly eight-mile trip east to Charlie Lake in North Oaks. From Charlie Lake, the water passes on to Pleasant, Sucker, and finally Vadnais Lake – a natural reservoir system of more than three billion gallons. From Vadnais, the water sluices down a pair of 90-inch conduits for its three mile trip to the utility’s treatment plant on Rice Street in Maplewood. Though backup water is available if needed from the Rice Creek basin and a series of wells located along the route of the Lake Vadnais conduit, the Mississippi River, which is to say the Upper Mississippi watershed, is responsible for supplying St. Paul and several surrounding suburbs with their daily ration of water, some 46 million gallons per day on average, a total that has actually dropped slightly in the past several years.
|And then, there’s Lambert Creek |
A series of sloughs and wetlands that stretch from White Bear Lake to Vadnais Lake, Lambert Creek is also known as Ditch 14, dug during the 1930s to transform “useless” bog into dry land for houses and development. On its own, the ditch increases erosion by speeding the passage of water down the natural drainage system. On top of that, it has been a major pipeline for material once deposited in Goose Lake, a small pond off the western shore of White Bear Lake. At the turn of the century, White Bear Township impounded Goose Lake and used it as a dumping ground for the refuse from its new municipal sewage treatment plant.
About such practices, Schuler is philosophical “It’s nobody’s fault,” he shrugs. “Nobody knew any better back in those days.” Today, of course, we do, and for the past 17 years the utility has been impounding erstwhile wetlands along Ditch 14 and turning them back into wetlands. Water that once might drain all way down Lambert Creek in a matter of three hours now might take three months to make the same journey, thus reducing erosion – and the depositing of nutrients in St. Paul’s water supply.
Despite all these efforts, the utility faces a virtually impossible challenge in trying to return the lakes to anything like their original pristine state, according to University of Minnesota limnologist Amy Myrbo.
“There are studies from Europe, in particular a lake in Switzerland that was for a long time used by shepherds to water and graze their flocks, that it can take 75 years for a lake to return to its natural state,” she observes. “When you are speaking of lakes in the middle of a dense population density and urban sprawl, the problems become almost impossible to remediate.”
“That’s because of conservation devices on new appliances and the loss of some industry,” Bode explains, pointing out that the east metro has seen Whirlpool depart, Gopher State Ethanol shut down, and 3M announce it is closing its sandpaper plant on St. Paul’s east side.
Even so, the utility’s capital investments are up, driven in large part by demand for a product that is not only safe but also free of any off-odors or tastes. Water, in other words, that comes from a less-than-pristine source, travels through a chain of nutrient-rich lakes, but comes out of the tap tasting like springwater from the foot of an Alpine glacier. For SPRWS, as for other water services in urban areas around the country, trying to please the public’s ever-more discriminating palate is at best a catch-up game.
At the moment, that catch-up game finds the water service in the midst of a nearly $10 million project that includes changes to the underground storage facility at the treatment plant and conversion of 24 of the plant’s filter beds from powdered activated charcoal to granular activated carbon; the latter is capable of filtering out geosmin molecules, a by-product of excess algae growth – itself a by-product of excessive nutrients, principally phosphorus and nitrogen – entering the water supply.
“The whole project has been driven by taste and odor concerns,” Bode concedes. “Geosmin is one we know about, but there are others, I’m sure, that we don’t know about.”
In addition to changes at the treatment plant, the water service is also completing a major wetlands restoration project, and digging new wells, up to a total of 10. The wells will serve as a safe source of water in case of any interruption in surface water supplies (think terror attack). They will be used when necessary to dilute the water in the Vadnais chain of lakes in order to keep algae concentrations below 25 parts-per-billion, the level at which it starts causing taste and odor problems.
Meeting that last mark can be tough. Nutrients enter St. Paul’s water supply from the river itself, as well as from sediment that settles on the bottom of the lakes. Our mania for lawns that look like putting greens – and thus in need of massive doses of artificial fertilizers – has contributed some to the overload of phosphates and nitrogen, but the real culprits lie elsewhere.
“We sit in rich farmland and the problem is increased erosion, which is the result of urbanization,” Schuler says. Which is to say, the spread of soil compaction and impermeable surfaces that are part-and-parcel of urban sprawl. Since the days when the land around the Vadnais chain was either fallow or farmland until today, the region’s “run-off co-efficient” – a measure of how much sedimentation enters a watershed – has increased by a factor of 10.
“Rain falls and storm water rushes into streams and the streams empty into the lakes,” Schuler explains matter-of-factly.
The utility tackles the problem of nutrients from the river by treating that water with ferric chlorate, a harmless form of liquid iron that binds with phosphates and strips them from the water supply. It has also installed specialized devices called hypnolimnetic aerators in the lakes to oxygenate their bottoms and inhibit algae blooms.