By Dennis Box-The Courier-Herald

Members of the Bonney Lake City Council are trying to figure out how much water people in the area will be drinking during the next 20 to 40 years, and it looks like the best guess is, simply, a lot.

RH2, a Tacoma engineering firm, was contracted by the city to put numbers together estimating the area's consumption over next four decades. The firm also compared the cost of purchasing more water from Tacoma Water or the Lakewood Water District, which is offering about four million gallons per day (MGD).

RH2 is estimating the city will need to add another two MGD by 2016 to service the growth in the water district. Another two MGD will be needed around 2025.

The firm is estimating by about 2050 the city will need to purchase 28 percent of its annual water needs from wholesale sources like Tacoma Water or Lakewood.

The council's plan was to begin debating whether to purchase from Tacoma Water or Lakewood at workshop this week.

&#8220This is all based on buying water for customers who don't live in the city today,” Councilman Mark Hamilton said. &#8220Ultimately we are looking at if we will have the ability to set rates and maintain costs.”

Purchasing from Tacoma Water appears more straightforward. The water hookups are in existence and the city is already a customer of the utility.

The Lakewood Water proposal would mean building a pipeline from Salmon Springs near Puyallup to Bonney Lake.

&#8220Some of the factors we have to consider is Tacoma Water may not be able to lock in the rates,” Hamilton said. &#8220With Lakewood we know basically what the cost is. It's higher, but we may be able to manage the cost better.”

Hamilton is concerned if the city purchases Tacoma Water and is not able to lock in rates, the Tacoma City Council would have control of the rates.

&#8220I'm not sure I want to hand that control over to another jurisdiction,” Hamilton said.”

Deputy Mayor Dan Swatman said the &#8220Lakewood deal looks more complicated than Tacoma Water. We are already hooked in on the eastside and they may add one more near Falling Water. Lakewood would require wheeling (the water) through multiple water districts.”

Swatman said he is not &#8220necessarily in favor of purchasing more water because it gives the city the ability to build more homes. Our water district is already much larger that our city.”

Hamilton pointed out overtures were made to Cascade Water Alliance to find out if the city could purchase water from the eastside water wholesaler. Cascade it attempting to purchase Lake Tapps from Puget Sound Energy, converting the reservoir into a drinking water reservoir.

&#8220Cascade Water Alliance is off the table,” Hamilton said. &#8220We talked to Cascade, but what we got back would not make sense economically.”

RH2 reported purchasing four MGD from Tacoma Water would cost about $60 million and from Lakewood about $57 million spread over 40 years.

The second plan analyzed by RH2 compared buying only two MGD from either Tacoma or Lakewood. In this plan the cost of Lakewood water is considerably higher because of the cost of building a pipeline is spread over two MGD rather than four. The Lakewood plan would cost nearly $36 million over 40 years and Tacoma Water about $24 million.

Dennis Box can be reached at dbox@courierherald.com.