In August 2008, the cities of Lake Oswego and Tigard formally endorsed a partnership agreement for sharing drinking water resources and costs. Lake Oswego's water supply facilities were undersized, aging and seismically weak. Tigard has long sought ownership in a secure, dependable water source and both cities wanted to keep water rates affordable for their residents. By sharing the cost of planning, designing and constructing a new supply system, each city secures its long term water supply needs at a cost neither could afford alone.

The project  created a reliable water system that delivers high-quality drinking water from the Clackamas River to the communities of Lake Oswego and Tigard. The new water supply system replaces aging, vulnerable, at-capacity infrastructure with an innovative system designed to the highest seismic resiliency standards. The new system also enhances emergency water supply reliability regionally by providing access to Lake Oswego's and Tigard's combined storage as well as other supply sources. Tigard customers benefit by obtaining access to a high-quality water source and ownership in a state-of-the-art, seismically safe water supply system. Lake Oswego customers also save millions of dollars by sharing water system improvement costs with Tigard.

The cities of Lake Oswego and Tigard completed a comprehensive study in 2007 to evaluate possible formation of a joint water supply system to serve the two communities. The evaluation compared financial and other impacts of different water supply options for each city - from Lake Oswego "going it alone," to fully developing Lake Oswego's Clackamas River water rights in partnership with Tigard. In a follow-up study in 2008, Tigard also considered other water supply options including the Tualatin Basin Water Supply Project, the Willamette River Project, and continuing to purchase water from the City of Portland.

These studies determined the partnership approach as the preferred supply option for both cities based on a variety of factors: cost, permitting, governance, design and financing.

The water facilities are jointly owned by Lake Oswego and Tigard, except for the Bonita Road Pump Station that is wholly-owned by Tigard. Under the Partnership agreement, the City of Lake Oswego is the managing agency responsible for the design, construction, and ongoing operation of the new facilities. An Oversight committee composed of elected officials from Tigard and Lake Oswego provide guidance and oversight, ensuring that both communities are represented.

Since 1968, Lake Oswego's drinking water source has been the Clackamas River. In the early 1970's, Lake Oswego began supplying water to Tigard under a surplus water agreement, but as Lake Oswego's demands grew, the availability of surplus water decreased and Tigard began purchasing water from Portland. With the Partnership's expanded water supply system now complete, Tigard ended its supply agreement with Portland and receives all of its water from the Clackamas River.

The Clackamas River is one of Oregon's high-quality drinking water sources and is afforded special protection under state law. The 950 square mile Clackamas River watershed provides drinking water for 400,000 Oregonians in several other communities in North Clackamas County.

The City of Lake Oswego was granted rights, by the State of Oregon, to use water from the Clackamas River for municipal purposes. Those rights are documented in two water right permits, one issued in 1967 for 32 million gallons per day (mgd) and one issued in 1973 for 6 mgd. Half of the 1967 water right is certificated – meaning Lake Oswego has demonstrated beneficial use of the water and has completed the state required claim process. Once certificated, a water right is considered a property right which cannot be revoked. The undeveloped portions of the permits will remain in permit status until the City can demonstrate beneficial use and completes a second claim process.

A third permit on the Willamette River allowing use of up to 3.88 mgd was secured for emergency purposes only and is not expected to be used for the foreseeable future.

The new water supply system was designed for the ultimate supply of up to 38 million gallons per day (mgd), but currently is limited to a maximum delivery capacity of 32 mgd. Combined demands of the two cities during a typical peak summer season is anticipated to be 20-26 mgd.

Lake Oswego's Clackamas River water rights provide enough water to meet Lake Oswego's needs for the foreseeable future and Tigard's needs for the next 20 years.

In 2003, Lake Oswego applied to the Oregon Water Resources Department (WRD) for an extension of time to fully develop the remaining undeveloped portions of its 1967 and 1973 Clackamas River water permits.

The water rights involved in this permit extension process are not new water rights. The permit extension process allows Lake Oswego more time to complete construction of facilities necessary to beneficially use the undeveloped portions of its permits. The ability of municipalities to extend the time available to develop their water rights is vital to their ability to engage in long term planning to meet the projected needs of their growing populations.

To ensure stream flows and protect fish, the Partnership is required to reduce their withdrawals during certain months of the year, if natural stream flows fall below certain levels.

The Oregon Water Resource Department's conditions establish a method to calculate the reductions. In the event reduced withdrawals are required, Lake Oswego and Tigard have backup plans in place and can rely on more than 450 million gallons of water stored in underground and above ground reservoirs, to supply water to Lake Oswego and Tigard residents.

Lake Oswego and Tigard are committed to preserving, protecting and enhancing water quality and fish habitat in the Clackamas River. Both cities continue to implement their robust, state-approved water management and conservation plans which, along with water rates, have already reduced historic consumption and peak per-capita water demand by almost 20 percent.

These plans are intended to reduce water use and to maintain flows for fish passage, particularly during summer periods of low stream flows and drought. Reducing demands during the summer means the Partnership can rely on use of water stored in underground and above ground reservoirs and minimize withdrawals from the Clackamas River.

As members of the Clackamas River Water Providers (CRWP), and in partnership with the Clackamas River Basin Council, US Geological Survey, PGE, and Clackamas County Water Environment Services, Lake Oswego and Tigard are actively making a difference in watershed conditions. Over the last decade, Lake Oswego has contributed more than $500,000 dollars to improve water quality and fish habitat within the Clackamas River basin. Tigard is also a member of the CRWP and contributes toward these same efforts.

No. To comply with the federal Endangered Species Act, the Partnership undertook a rigorous scientific study of historic river flows and their relationship to fish habitat in the lower three miles of the river. This study, which the National Marine Fisheries Service agreed with, found that during low streamflow periods, the Partnership's maximum water withdrawal of 38 million gallons per day would reduce water depth below the intake by less than one inch.

The Partnership project expanded the water treatment plant capacity from 16 million gallons per day (mgd) to 38 mgd. A total of 20 mgd is allocated to Lake Oswego and 18 mgd for Tigard. The Partnership agreement allows the leasing of excess capacity between the partners if necessary.

Lake Oswego's previous system was capable of reliably delivering 12 million gallons per day (mgd) of drinking water—barely enough to serve the community during summer peak use. The system was old and could not continue to function without significant upgrades. The Partnership allows Lake Oswego to address service, capacity and reliability issues and deliver a total of 20 mgd per day in addition to 18 mgd for Tigard. This offers Lake Oswego significant cost savings over making upgrades alone and builds in capacity to serve anticipated needs into the future.

The Lake Oswego Tigard Water Partnership project expanded Lake Oswego's existing drinking water infrastructure so that it can serve both communities.

1. Lake Oswego withdraws water from the Clackamas River at the Clackamas River Intake as it has done for almost 50 years. A new river intake pump station was constructed next to the previous intake located in Gladstone approximately 3/4 of a mile upstream from the confluence with the Willamette.
2. From the intake, water travels in a large, steel pipe through Gladstone and then under the Willamette River to the water treatment plant in West Linn.
3. At the water treatment plant, the water is treated to meet or exceed safe drinking water standards.
4. The treated water is then pumped through another pipeline through West Linn to Lake Oswego's Waluga reservoir complex.
5. Water is stored in the new Waluga reservoir and an existing reservoir near the city's western boundary.
6. From there, water flows through pipes to Lake Oswego customers and to Tigard's Bonita Road pump station.

The $249 million Partnership project upgraded, upsized and expanded these six facilities.

Lake Oswego's key water supply facilities - the water intake on the Clackamas River, the water treatment plant in West Linn, and the pipes that connect these facilities - were almost 50 years old. These facilities suffered from a variety of ailments despite years of maintenance and upgrades.

In addition to age and condition, new information gathered during the design phase revealed that some facilities were vulnerable to failure during a strong earthquake. Seismologists predict this region is at risk of a major earthquake within the next 50 years.

Yes, the new facilities were designed and constructed to remain operable even after a major earthquake.

For more information about the resiliency features of the new system, see Built to Last: a new, resilient water system. 

The final cost for the program was $249 million. The Partnership Agreement allocates 38.2% of this cost to Lake Oswego and 61.8% to Tigard. Both cities issued revenue bonds to finance their respective shares of total program costs.

Upgrades are paid for by selling bonds, which are then paid off by customer utility rates (you may have noticed changes to the water portion of your utility bill). If you are a water customer of Lake Oswego or Tigard Water, you can find helpful information about your bill at the following locations:

• City of Lake Oswego Finance Department, Rate Changes Impacting Bi-Monthly Utility Bills.
• City of Tigard, Water Rates and Information.

As part of the upgrade and expansion of the system, a new treatment process was recommended by a panel of experts in drinking water treatment and public health. In spring 2017, the new plant started utilizing a state-of-the-art water treatment process, conventional filtration plus ozone. Ozone, a powerful oxidant, destroys taste and odor causing compounds and removes more impurities from the water supply. Ozone treatment offers multiple benefits:

• Provides an additional treatment barrier to protect public health
• Consistently produces water that is pleasant tasting
• Is capable of meeting emerging concerns for pathogens, algal toxins, disinfection by-products, pharmaceuticals, and personal care products
• Represents proven technology, with the number of ozone installations increasing in Oregon and across the U.S. due to its ability to provide multiple water quality benefits

To learn more about the water treatment process, visit or watch 'The Path to Pure Water'.

Ozone is oxygen (O₂) with an extra atom (O₃). Ozone treatment works through a process called "oxidation." During oxidation, the extra atom oxidizes, or destroys, odor-causing material and microorganisms, leaving only pure oxygen in the water. A generator uses energy to produce ozone from oxygen for the water treatment process. Lightning storms naturally produce ozone; that is what creates the clean, "after-rainstorm" smell.

For more information call the water treatment plant at 503-635-0394 or email us. You can also visit the project archive.