SPOKANE, Wash. -- Several Spokane County residents filed a lawsuit Thursday against the City of Spokane for $30 million.

They claim the city is overcharging county residents who use city water. The city has 60 days to respond to the lawsuit.

Attorney Bob Dunn said he filed the lawsuit after receiving dozens of phone calls from Spokane county residents who said they have been overcharged for using city water.

"On 57th and I think that's the city limits on the south side. I had a lady called me who said, ‘I live on 57th on the county side of the road, 30 feet away my neighbor in the city pays half of what I'm paying right now,’" Dunn said, giving an example of one of the issues.

A city map of the water service lines shows there are places where one side of the street is being charged one rate, while the other is being charged significantly more. Dunn wants to know how much it actually costs to move the water to the other side of the street.

"So what's the extra service cost that you're providing to this lady living 30 feet across the street on 57th, versus what you're charging a city user? Just show us," Dunn said.

Here is how the $30 million claim was calculated: Dunn said there are about 6,000 county residents using city water. He said they figured out each County resident is paying $500 more a year than City users. So multiply 6,000 residents by $500 and you get $3 million. He said they have been overcharged for about 10 years. So multiply $3 million by 10 and you get to $30 million. Dunn wants the city to stop overcharging and set reasonable rates based on the actual added cost to supply the water to county residents.

"If there's a charge, then yes the city's entitled to increase the water rate, but it's got to be a reasonable increase. It's got to be a reasonable charge and they just pulled a number out of the hat, there's no basis for these numbers that they've been charging," Dunn explained.

The City of Spokane released a statement Thursday afternoon saying:

“City of Spokane residents, over the past 100 years, have paid to expand, update, and maintain their complex water system. Today that system is the second largest water system in the state with 1,000 miles of water main, wells, pumps, and reservoirs necessary to provide reliable drinking water. The City’s citizens rightfully benefit from their long-term investment with inside City rates. State law and court decisions support this approach, which has been in place in the City for more than 50 years and in cities around the state including Tacoma, Seattle, Kennewick. It would be unfair to ask City residents to pay more now to accommodate lower rates for outside developments.”

When KREM 2 asked the city about the different rates for a story back in May, we were told that county residents are paying more because they do not pay city taxes but are using a city service. Dunn disagrees with that argument and points to the fact that county residents cannot vote in the city and have no say over ordinances that impact their water bills.