Cedar Rapids officials say drinking water is safe, even amid nitrate spike in some Iowa rivers

CEDAR RAPIDS — The Des Moines metro area has been experiencing the highest nitrate levels in the Des Moines and Raccoon rivers in more than a decade — prompting an unprecedented ban on lawn watering so Central Iowa Water Works can keep up with the treatment process that reduces nitrate concentration in the water supply.

While Cedar Rapids has not implemented such drastic measures, nitrate levels in its source water have risen. Still, officials say drinking water in the city is safe.

The City of Cedar Rapids has two water treatment plants — the Northwest and J Avenue Water Treatment Plants — that pull water from the Cedar River to be filtered into drinking water.

The U.S. Environmental Protection Agency limits nitrate levels in drinking water to 10 milligrams per liter.

As of Friday, Cedar Rapids’ Northwest plant’s nitrate level was 9.0 mg/L. At the J Avenue plant, the nitrate level was 7.2 mg/L, up from 6.8 mg/L earlier in the week, according to the city.

The Cedar River’s nitrate level is currently 12.9 mg/L.

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Utilities Director Roy Hesemann said that until the EPA changes the nitrate limit from 10 mg/L — or the city exceeds that limit — it will be “business as usual.”

Hesemann said the last time Cedar Rapids saw nitrate levels this high was this past spring. He believes the spike is partly due to recent significant rainstorms, which flush nitrogen fertilizer from farms into streams and rivers.

Hesemann said about 1.5 million pounds of nitrogen flow down the Cedar River daily.

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“We're cautiously optimistic that it will hang around that low nine level,” Hesemann said of the nitrate level.

The highest nitrate level reported in Cedar Rapids was 9.4 mg/L in April 2006.

According to the city’s water testing lab, the nitrate levels in January hovered around 2.5 mg/L at the J Avenue plant, and 3.9 mg/L at the Northwest plant.

Hesemann said the demand for water has increased with Iowa’s recent heat wave.

Whereas on a typical summer day the city runs 41 to 42 million gallons per day to its two treatment facilities before it’s sent to customers, lately, it’s been running 48 to 51 million gallons each day.

In Iowa City, Jonathan Durst, water superintendent in the Public Works department, said the nitrate level in the Iowa River is at 14 mg/L and the treated water is at 8 mg/L, as of Wednesday.

Iowa City draws water from wells of varying depth, including shallow alluvial wells along the Iowa River and deep wells that tap into the Silurian Aquifer 300 feet below ground.

This allows the city to use more water from deep wells when nitrate levels are high closer to the surface. This dilution approach has, so far, allowed Iowa City to keep nitrate levels in finished drinking water below the EPA standard of 10 milligrams per liter.

How does Cedar Rapids’ filtration process work?

When it comes to public water supplies, treatment processes differ depending on factors like the water source, the location of facilities and the resources available to purchase and maintain infrastructure.

Cedar Rapids gets its drinking water from 52 shallow wells stationed along the Cedar River that suck up groundwater percolating through the riverbed, The Gazette has previously reported.

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For nitrate filtration, Hesemann said the water is naturally filtered when it is pulled through layers of sand, gravel and clay. As the water passes through each layer, there are microorganisms in the river that consume some of the nutrients in the water, including nitrate.

Hesemann said the City of Cedar Rapids utilizes two kinds of wells: horizontal collection wells and vertical wells, which are smaller.

The horizontal wells have lateral pipes right above the bedrock in the river. Hesemann said the river water goes down into the lateral pipes, up into the wells after passing through the sand and gravel filtration layers in the river.

Hesemann said the J Avenue water plant has historically seen lower levels of nitrate in its water, partly because the plant uses more vertical wells that do not have the lateral pipes that go out into the river.

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He said the city is planning to incorporate one or two more horizontal collector wells, as well as an aquifer storage recovery well into the Northwest plant.

An aquifer storage recovery well — or an ASR — is a well that can store excess surface water underground in an aquifer when there is a surplus of water.

Hesemann said Des Moines and West Des Moines also have installed ASR wells.

“The nice thing about those, you can take your finished, treated water and pump that into the ASR and use that ASR as a storage facility,” Hesemann said. “There are multiple benefits of us putting an ASR well in, so that's one of our first things that we're looking at doing here in the short term.”

One of those benefits, Hesemann said, is if an existing Cedar Rapids well suddenly started testing high for a contaminant and had to be temporarily shut down, the water stored in the ASR well could be mixed with other wells’ water to dilute it and bring the contaminant levels down.

He said it likely will take 18 months to two years for the ASR well to come online.

Nitrate effects on health

Nitrate in drinking water has been linked to blue baby syndrome, a life-threatening condition reducing an infant’s ability to get oxygen through the bloodstream. The U.S. Environmental Protection Agency in 1992 set the upper limit for safe drinking water at 10 milligrams of nitrate per liter of water.

But research since has shown potential harms from drinking water with lower levels of nitrate.

A new Iowa study suggests when pregnant women drink water with nitrate at levels of 5 mg/L or lower they are increasing the risk their baby will be born underweight or prematurely. The study, published Wednesday in the journal PLOS Water, matched Iowa birth records from 1970 to 1988 with nitrate levels in county water supplies where the babies were born.

Of 357,741 births, the average nitrate exposure was 4.2 mg/L. Early prenatal exposure to water with 5 mg/L of nitrate was associated with low birth weight, and early prenatal exposure to as little as .11 mg/L of nitrate was connected to preterm birth, the study reports.

“I would consider talking with your doctor and consider opportunities to make sure you’re drinking healthy water if you’re pregnant, especially in these early periods,” said Jason Semprini, an assistant professor of public health at Des Moines University and the study’s author.

Hesemann, who has been with the city’s utilities department for 25 years, said Cedar Rapids hasn’t considered putting a warning on Cedar Rapids drinking water for pregnant women and young children.

“At least in my tenure, I don't remember us doing that, and we have never exceeded the 10 parts per million,” Hesemann said.

Semprini’s study isn’t the first to show nitrate levels below the EPA’s standard can increase the risk of harm to children, the author said. A 2021 Stanford study of 1.4 million California births found higher levels of nitrate in drinking water during pregnancy were associated with an increased risk of premature delivery — even below the 10 mg/L standard set by the EPA.

Water use restrictions, like those being implemented in central Iowa, can be effective, but sometimes backfire, Semprini said.

“I'm not a fan of mandates,” he said. “But if you're not a fan of these mandates, don't blame public water utilities for trying to keep people safe. Blame the people who are not protecting our waterways.”

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The Iowa study is part of a “growing body of literature on potential adverse health impacts of drinking water nitrate at levels below the current EPA standard suggesting that the existing maximum contaminant level (MCL) of 10 mg/L as N is not sufficiently protective of human health, especially for vulnerable populations like pregnant individuals,” said David Cwiertny, a University of Iowa engineering professor who directs the Center for Health Effects of Environmental Contamination.

The center supplied the water quality data Semprini used for his analysis.

There are some limitations of the study.

The water quality data comes from public water supplies, so does not measure the nitrate in private wells, Semprini said. The study uses older birth records because in 1989 the state no longer made public the county where the mother was living.

“One (limitation) that probably should have been noted is that data from this time period isn’t as reliable as the data that is available after 1993 when EPA started requiring community water systems to report nitrate data in response to the nitrate MCL that was finalized by the EPA in 1991,” Cwiertny said. “Analytical methods for nitrate also greatly improved over the period of the study, particularly the ability to reliably measure lower levels of nitrate like the 0.1 mg/L reference value used in the current study design.”

Sources of nitrate in public water supplies

Farm fertilizer is the largest source of nitrate found in the Des Moines River watershed, which supplies drinking water to more than 500,000 people in Polk County, according to a new report. Other sources include city wastewater treatment plants or industrial plants allowed to discharge into rivers.

“Among the various contaminants that threaten Polk County’s drinking water, nitrate stands out due to its ubiquity and significant human health implications,” according to a Currents of Change scientific analysis developed over two years by a team of scientists and community members for Polk County, and obtained by The Gazette.

Since the 10 mg/L standard was set in 1992, multiple studies have shown connections between consuming nitrate in drinking water and colorectal cancer, thyroid disease and neural tube defects, the report states. The EPA is evaluating whether that “safe” standard should be reconsidered.

“Many of these health impacts arise at nitrate levels below regulatory limits,” the report states. The research team advised Polk County to prepare for a lower nitrate threshold, which could require more extensive water treatment.

Hesemann said without watershed and conservation efforts around Cedar Rapids and throughout the region, the amount of nitrate in the water could be higher.

“A lot of people keep asking the City of Cedar Rapids, why we keep putting money, time and effort into our watershed efforts, and because of times like this, they'll say, ‘Oh, all that work, all that money, doesn't do any good.’ Well, my point is, what if we weren't doing all that effort and helping producers put in buffer strips and all the other edge of field practices?” Hesemann said. Without it “I think we would actually be seeing even higher levels of nitrates coming down the river.”

Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

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Comments: olivia.cohen@thegazette.com