Measuring water quality in Minneapolis, St. Paul lakes

By Anna Pratt (June 28, 2007)

Originally published in The TC Daily Planet

Natalie Casemore, a student at the University of Minnesota, was lying on the Lake Calhoun beach on a 90-degree mid-June afternoon. She said she was unaware of the PFCs that have recently raised concerns about Calhoun, but she didn’t think it was a huge deal. For her, the best thing about Lake Calhoun is, "At neck-deep, I can still see my feet.”

Alongside her, Andy Gickling, a student at the University of St. Thomas in St. Paul, a self-proclaimed beach enthusiast, declared “It’s a wonderful beach to come to, better than others in Minneapolis and St. Paul.”

Officials from the MPCA and the Minnesota Department of Health (MDH) say the recently-discovered PFC levels in Lake Calhoun are minimal and the lake is still safe for normal recreation. However, the agencies have issued fish consumption advisories for the upper Chain of Lakes because PFCs collect in bluegills that travel from lake to lake. It cautions people not to eat more than one fish caught in Brownie, Cedar, Lake of the Isles and Harriet lakes in a month’s time.. The guideline also applies to the Mississippi River, in the water between Ford Dam and Hastings, per week.

The Minnesota Pollution Control Agency (MPCA) is conducting an extensive study of fish and sediment samples from about 30 lakes in the Twin Cities, plus others across the state, to find out whether or not some types of pollutants called “perfluorochemicals” (PFCs) are a widespread urban phenomenon. Samples are being analyzed in a specialized lab in Vancouver, British Columbia, and are expected back in July. Also being evaluated on an ongoing basis are municipal and private drinking water wells, landfills, sewage from the metro wastewater plant, Mississippi River discharge and sediment, fish and additional water sources. Marvin Hora, a manager in the MPCA’s environmental analysis and outcomes division, said he couldn’t predict where the PFCs in Lake Calhoun are coming from, whether they’re being swept in from lawn chemicals sprayed on private properties or a chemical spill of some sort, but the possibilities are endless. Regular water quality testing of lakes don’t account for PFCs. “A lot of it could be build up in small amounts," he said. “The tests will tell us if it’s unusual or common to find PFCs in an urban lake. We’ll go out further to Duluth and Rochester, too, to see if it’s associated with being in a city," said Hora.

Evaluating local lakes

Lake Calhoun, an “A” quality lake, has long been an attractive destination for swimming, sunbathing, running, biking, walking and Rollerblading, among other summertime activities that can be observed along its sandy shores on a nice day. Since 1998, it has maintained a “B+” to “A” average, according to reports from the Minnehaha Creek Watershed District (MCWD).

Lakes receive letter grades from “A” to “F,” on a spectrum that goes from “crystal clear” to severe algae problems in yearly report cards from the MCWD. An “A” lake, for instance, can be enjoyed without hesitation, according to the MCWD. Poor quality lakes can’t sustain much activity. The Met Council, which monitors and collects information for lakes across the metro area, defines “impaired waters” as those brimming with too much phosphorous, which leads to eutrophication, or a vicious cycle of plant growth that blocks sunlight and kills fish.

Diamond Lake, which is part of the same watershed as Lake Calhoun, received an “F” last year. According to MCWD administrator Eric Stevenson, Lake Calhoun has luxuries the shallow Diamond doesn’t. For example, it’s deep, with a series of ponds that were carved out in 2000, to sift out contaminants before they enter the lake. Two years ago, 31 truckloads of sediment were removed from the ponds, he said. In contrast, Diamond is closer to being a wetland than a lake, where,"You expect the water quality to be poor. It is nature’s way of dealing with things," he said. Even before people arrived in the area, Diamond’s waters were inferior, compared to Lake Harriet and Cedar Lake, both of which enjoy “A” and “B” ratings. Lake Hiawatha and Lake Brownie maintain a consistent “C+," while Powderhorn Lake, Lake Nokomis, Grass Lake and Lake of the Isles fall behind. In general, “Lakes in the Minneapolis area are remarkably clean, a credit to the history of how the city developed parkland around them," said Stevenson.

In St. Paul, there have been numerous efforts to improve Lake Como, which belongs to the Capitol Region Watershed. The district has dug underwater infiltration ditches and installed rain gardens, because Como suffers some of the same problems as Diamond. Basically, it lacks the depth to cope with a heavy load of runoff, said district administrator Mark Doneux. As a result, sediments get trapped at the bottom of the lake, which prevents sunlight from penetrating the waters. Last year, Como’s phosphorous level, .15 milligrams per liter, was well over the standard even for shallow lakes, he said. Como is also very murkey, with a Secchi transparency reading of less than one foot. (In the Secchi test, a round disk is lowered from a cord into the water as someone monitors when it disappears from view.) Como's chlorophyll-a level is .04 milligrams per liter, which is double the typical figure for similar lakes.

Last year, nearly one-fifth of 141 metro lakes for which sufficient data is available from the Met Council, achieved an “A” or a “B.” About 38 percent got a “C," while another 38 percent were given a “D” or “F," according to Met Council data. While the majority of lakes didn’t see much of a change from the previous year, 11 percent improved and 25 percent got lower grades. Although there’s no observable pattern across the whole region, many of the lakes have seen a dip over the past couple years.

Activity around Lake Calhoun

Frank Hornstein, who serves on the state’s House of Representatives (DFL District 60B), led a community meeting about Lake Calhoun in southwest Minneapolis in May, which attracted a large crowd on short notice. “The real issue, or the overwhelming concern, is that people are uneasy about not knowing the source of the PFCs," said Hornstein..

Minneapolis resident, Shannon Plourde, said she’s been reluctant about letting her children swim in the lakes in the area. Recently, she gave into the pleas from her two young children, about splashing around in Lake Harriet, but, still, speaking for herself and her husband,"We’re definitely worried about it," she said.

Tracy Nordstrom, a Park Board commissioner (District 4), testified that Lake Calhoun’s beaches continue to be packed. She lives close to Lake Calhoun, in a house without air conditioning. Her family has been swimming in Lake Calhoun sometimes multiple times a day, during hot weather. “I think the Park Board has done a good job explaining that the PFOS and other PFCs are more about fish consumption, kind of like mercury, and don’t affect swimming," she said.