If the grass is always greener in Woodbury, here’s one reason — it has the cheapest water in the metro area.

Drop by drop, the average water bill for a Woodbury home is a mere $8.32 per month. In St. Paul, it’s more than four times as much: $34.70. And in Maplewood, it’s $33.81.

“Our rates are remarkably cheaper,” said Woodbury City Engineer John Bradford.

Woodbury city officials at a July meeting discussed surrounding cities’ water costs, based on a 2016 Metropolitan Council report that says Woodbury has the cheapest water of 182 cities in the Twin Cities area.

Bradford said price differences are overwhelmingly attributable to one factor — whether the water comes from wells or from the Mississippi River.

Consistently, cities relying on well water have lower rates, Bradford said, because the water needs to be pumped a shorter distance and is usually cleaner, requiring fewer chemical treatments.

Yet there are some advantages to river water. It will not draw down aquifers and is immune to the kind of groundwater pollution now plaguing cities such as Cottage Grove.

Bradford admits that Woodbury’s low prices are largely a matter of luck. The city was built over aquifers that have high-quality water, he said. The city only has to pump it up and add fluoride to prevent tooth decay and chlorine to kill germs.

Then it’s ready to be flushed, guzzled, boiled or sprinkled.

Woodbury has another cost advantage. Cities often incorporate the cost of water-system repairs into their water bills. Woodbury’s repair bills are low because most of the city’s infrastructure is relatively new. “We do not have the same age deterioration as others,” said Bradford.

The Woodbury survey assumed that the average residential use is about 7,666 gallons a month — comparable to 100 bathtubs-full.

WATER THAT COSTS MORE

In Maplewood, water comes from St. Paul Regional Water Services and is about 75 percent from the Mississippi River, said City Manager Melinda Coleman.

That water travels farther. Most of the St. Paul water is pulled from the Mississippi, then runs through nine miles of pipe to Pleasant Lake in North Oaks, then south through Sucker and Vadnais lakes. It is augmented by water from the lakes.

Then the processing starts.

According to spokeswoman Jodi Walin, the treatment includes adding:

Ferric oxide to prevent algae growth.

Lime to soften.

Aluminum sulfate to get rid of minerals and bacteria.

Fluoride and chlorine, and ammonia to help kill germs.

Sodium hydroxide to prevent corrosion of water pipes.

The water is then tested for flavor and purity before it finally flows into homes and businesses.

That much treatment is expensive.

The bills are also higher because an aging system means more repair bills. “We have old infrastructure,” said Maplewood’s Coleman.

The river water has its advantages.

The softening done by St. Paul Regional Water Services means minerals that could build up in pipes and fixtures are removed. Customers can save the cost of buying and installing a home water softener, plus the cost of salt pellets.

Also, the Mississippi River is basically an inexhaustible source of water. That’s not true with well water, which can lower the water tables. Local wells were blamed for the recent low water in White Bear Lake.

River water does contain some forms of pollution, but not usually pollution dumped on the ground. River water would not be polluted the way groundwater has been in Washington County, where minute traces of chemicals dumped by 3M are still in the water about 40 years after the dumping stopped.

Cottage Grove is on track to spend an estimated $15 million to remedy that pollution, which it would not have to spend if it were using river water as its primary source.

Overall, said Woodbury’s Bradford, local water has been good for Woodbury — especially for the property owners paying the bills.

“It’s not like Maplewood is doing anything wrong,” he said. “But we are lucky to have different circumstances.”

WHO PAYS WHAT FOR WATER?

Cost for average residential use of 7,666 gallons a month, as of January 2017.

Source: Metropolitan Council