Iowa Cities Track, Wage War On High Nitrate Levels in Drinking Water

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It took nearly three months and $525,000, but Des Moines Water Works (DMWW) in late July prevailed over record-setting nitrate levels in the Des Moines and Raccoon rivers, two of the Iowa capital’s primary water sources. The 85-day battle to return to levels considered safe by the U.S. EPA raised issues ranging from drought to land management and even touched Cedar Rapids. 

The EPA established nitrate levels of 10 mg/L for drinking water. At one point this summer, Des Moines experienced levels at 18.62 mg/L, highs it hadn’t seen before. In fact, the area’s last nitrate problem occurred in the late 1980s and early 90s, when Des Moines built its $3.6 million state-of-the-art Nitrate Removal Facility, one of the world’s largest. DMWW operates three water treatment plants: Fleur Drive, L. D. McMullen Treatment Plant at Maffitt Reservoir and Saylorville Water Treatment Plant. It also operates Water Works Park and Maffitt Reservoir and maintains seven water storage facilities. 

Nitrate contributors 

“Nitrates can get into water from a number of different sources,” explains Bill Stowe, CEO and general manager of DMWW, who was appointed to the position in August 2012. “However, research data point to chemical agricultural fertilizers as the largest single contributor to our high nitrate levels.” 

Stowe, who previously served as Assistant Manager – Public Works/Engineering for the City of Des Moines, says monitors up river indicated that a plume of nitrates was headed toward the metropolitan area. 

“Fortunately, we were able to divert our water intake from the rivers to alternate water resources that were lower in nitrate levels, including Maffitt Lake, Crystal Lake, aquifer storage recovery wells and our underground infiltration gallery,” he says. “As the weather became drier, usage ticked up, so we asked our customers to cut back on irrigation and engage in smart water management, which they did. Some lucky weather breaks, in the form of substantial rain, helped us make it through.” 

Health risks 

High nitrate levels can pose a risk to health and drinking water. The primary risk group is infants and small children. Though this is a relatively narrow group, the bigger issue is that once there is a violation of federal requirements and people are notified, residents begin to doubt the integrity of their tap water, finding it hard to distinguish between organic contaminants and carcinogens. This became a business issue when Stowe’s team urged reduced demand because DMWW couldn’t denitrify the water quickly enough for the hot, dry conditions, thus chasing away revenue. 

Chemical fertilizers used heavily in row-crop farming up river from Des Moines are seen as the root cause of high-nitrate concentrations. Nitrate contaminants make their way into the rivers as a result of stormwater runoff. Since the 1930s, primary nitrates have gone up, largely because of widespread agricultural fertilizer use. 

According to Stowe, there are several approaches that can be taken to prevent these high nitrate levels. One of them is greater use of technologies that are currently available in terms of stormwater management, crop use, and buffer areas to remove nitrates before they leave fields and flow into the waterways. Another approach calls for restrictions on the use of chemical fertilizers or that they be used with a stabilizer so they’re time-released rather than immediately rushed into the waterways when stormwater hits. 

For his part, Stowe remains guarded in his outlook for controlling nitrates long-term. “I’m optimistic that this crisis is behind us, but I am pessimistic because I think these causes will continue to haunt us,” he says. 

“We believe we’re an excellent example of why source waters should be protected through regulation, but the EPA and our state have been reluctant to come up with any regulatory process to protect these public assets. Without systemic protection for source waters, we’ll have nitrate problems again and potentially not be able to meet the safe drinking water standards.” 

About 100 miles away in Cedar Rapids, water officials report seeing the highest nitrate levels in years. The city monitors the Cedar River, adjacent to its well fields, and has seen nitrate levels as high as 18 mg/L in the river. While the situation is serious, Cedar Rapids hasn’t had to ask customers to restrict water use and its water remains safe to drink. The city has two water treatment plants: J Avenue with a 40 mgd processing capacity, and the Northwest Plant, which has a 20 mgd processing capacity. The water utility maintains 45 vertical shallow wells and four horizontal collector wells, 660 miles of pipeline, nine pump stations and 11 storage tanks. 

“There is some reduction in nitrate levels as the water passes through the aquifer and makes its way to our well sites,” explains Water Plant Manager Tariq Baloch. “But we know that rising nitrate levels have been caused primarily by the runoff of agricultural chemicals, and we have several thousand square miles of agricultural land in our watershed area. To change the equation, we need to rely on land managers to continually incorporate best management practices in their operations.” 

Steve Hershner, Cedar Rapids Utility director, points to last year’s drought as a contributing factor to the high nitrate levels. “A lot of nitrogen-based fertilizers that were applied to farm fields just sat there unused because there was no rain. When heavy downpours occurred earlier this spring, those chemicals moved into tile lines that flowed into the waterways, causing nitrate levels to rise. By analyzing individual wells, the water utility was able to blend water from them so the finished water would contain less than 10 mg/L.” 

Both Baloch and Hershner say that in terms of upstream practices, there are several things that can be done to protect source waters. These include field edge bioreactors, tile drainage wetlands, buffer strips, and other practices that reduce nitrates in the Cedar River. Still, they’re thankful that Cedar Rapids is fortunate to have access to good source water, and to this point have not had to take special steps to remove nitrates.


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