At their meeting on May 26, Tigard City Councilors approved an amendment to the city’s 2020 Water System Master Plan, adding King City’s Kingston Terrace Neighborhood. The council adopted the ordinance in a vote of 7-0.
The Kingston Terrace project is slated to span 528 acres across an urban reserve area adjacent to King City. The planned 4,100 properties within the proposed neighborhood are estimated to increase Tigard’s water system by 20%, according to Ross Horton with Tigard Public Works.
“It’s a major change to our water system,” Horton said in his presentation to city councilors on May 26. “Because this was a major change, we wanted to look at how this change would affect our water system using the same lens that we used to evaluate our water system in 2020.”
To adequately service Kingston Terrace during construction, Tigard will install new transmission and distribution piping within its water system, as well as add additional water storage and supply.
Kingston Terrace is proposed to finish final construction in 2053, and Horton estimated that at that time, the subdivision will average a daily demand of 1.12 million gallons and could demand up to 2.2 million at peak conditions.
“At peak day in the summer, we’d be looking at an additional 2.2 million gallons of demand on our system, so not an insignificant amount,” Horton said. “We project that we will have adequate supply until at least 2045, before we will need to start looking at other methods of supply, like a new well or additional supply from Lake Oswego.”
As part of a 1994 intergovernmental agreement between King City and Tigard, Tigard is responsible for supplying water to King City.
The agreement also explicitly states that “Tigard will also serve areas annexed to King City, areas added to the Urban Growth Boundary and any designated Urban Reserves, where King City will be required to provide water service.”
Horton told councilors that addendums had already been incorporated into Tigard’s water plan and cited the River Terrace 1.0 project in 2014.
“Updates to the water system plan are tackled as addendums,” Horton said. “The last addendum that we did was River Terrace 1.0 back in 2014. We’ll be doing the Kingston Terrace addendum this evening, and then coming up in the future, we’ll also be tackling the River Terrace 2.0 water system plan addendum.”
City councilors were inquisitive about the addendum and raised questions about future water supply and storage concerns.
“Looking at Kingston Terrace and River Terrace 2.0, would that be an additional 42% demand on the Tigard water system?” Councilor Faraz Ghodussi said. “That seems like a lot.”
Horton agreed that the addition was “not insignificant” and added that Tigard could be facing a “minor storage deficit” starting in 2030, but that future storage expansion projects, like a “Reservoir 19,” planned to start construction in 2030, which would help Tigard’s system reach adequate levels for the strain of supporting Kingston Terrace.
“From a storage perspective, we are anticipating being able to serve Kingston Terrace without any issue,” Horton said. “We’re currently planning for a seven and a half million gallon reservoir to be built on the southwest side of Bull Mountain, Reservoir 19, and that’s gonna serve Kingston Terrace and River Terrace 2.0.”
Tigard Mayor Yi-Kang Hu asked Horton about funding, reiterating that the exact details of the water system improvements would be decided at a later date and would not be a burden on taxpayers.
“These large system improvements are typically paid for with SDC funds, so we will be updating the SDC rates after we complete our next water system plan,” Horton said. “The water bills that residents pay will not go towards these needed improvements.”
System development charges, or SDCs, are paid for by developers and future property owners, and Horton emphasized at the late May meeting that Tigard would seek favorable SDC rates during its next study, later this summer.
The council adopted the ordinance in a 7-0 vote, and construction on some Tigard water supply expansion projects, like the Lake Oswego water supply extension, are already underway.
