Central Iowa Water Works, Des Moines Water Works Forewarn Outdoor Water Usage Restrictions Could Happen

DES MOINES – Central Iowa Water Works and Des Moines Water Works are advising central Iowa water
users that an increase in customer water usage from lawn watering could make staying in compliance
with the nitrate standard more difficult.

Nitrate concentrations in the Des Moines and Raccoon rivers have been increasing since late March. Des
Moines Water Works (DMWW) has been able to minimize use of river water, which has the highest
nitrate concentrations, because customer demand has been low, but overall demand is starting to
increase with the warmer weather and less rainfall. The Raccoon River and Des Moines River are
exceeding the drinking water standard, measuring nitrates at almost 17.0 mg/L and 14.0 mg/L,
respectively.

Because of the investment in nitrate monitoring and treatment by members of Central Iowa Water
Works (CIWW), finished water continues to meet all drinking water standards. The U.S. Environmental
Protection Agency has set a maximum contaminant level (MCL) of 10 mg/L for nitrate.

Since early April, DMWW has been blending water sources; maximizing water production at treatment
plants that use reverse osmosis filtration; utilizing low nitrate water from reservoirs, lakes and
underground storage wells; and on May 6, began operating the nitrate removal facility. In addition,
CIWW members Ankeny and West Des Moines Water Works (WDMWW) have increased production at
their facilities.

“We are using all of the tools we have available to us, but in order to continue meeting the nitrate
standard for drinking water, we are forewarning central Iowans that in the coming days they may need to
reduce or hold off on lawn watering altogether,” said Ted Corrigan, CEO and General Manager of Des
Moines Water Works.

“While there appears to be plenty of water in our rivers, we cannot rely upon them as the predominant
water source with nitrate concentrations being at the level they are,” Corrigan continued. “High nitrate
concentrations require extensive treatment, which we are currently able to do, but if lawn watering picks
up, Des Moines Water Works may be unable to meet the nitrate standard.”

Developing a resilient water system and jointly responding to water supply challenges such as high
nitrates are part of the reason 12 central Iowa communities, rural water agencies and utilities have
formed CIWW. CIWW is a regional authority responsible for water system planning, drinking water
treatment and wholesale delivery of drinking water to central Iowa.

Average customer demand for customers served by DMWW’s treatment facilities is 55 million gallons per
day. During the warmer months, that number can increase to between 80 million and 85 million, much
of which is attributed to lawn watering and outdoor water use.

Nitrate concentrations in source waters are likely to stay elevated until mid-to-late July, and customer
demand can change rapidly based on weather conditions. CIWW members will continue to monitor this
situation and keep customers informed.

Water from Des Moines Water Works’ treatment facilities serves 600,000 central Iowans, which includes
the communities, utilities and rural water agencies of Ankeny, Bondurant, Clive, Des Moines, Johnston,
Norwalk, Pleasant Hill, Polk City, Urbandale Water Utility, Warren Water District, Waukee, West Des
Moines Water Works, Windsor Heights and Xenia Rural Water District.