Projected costs to rebuild Portland's Washington Park reservoirs now stand at $190 million, a $20 million increase from eight months ago.

The Portland City Council is set to greenlight the project Wednesday.

Officials for the Portland Water Bureau aren't deterred by the increase. In September, they warned that costs could continue to swell as consultants finalized design plans.

The reservoir project would mark the city's second-most expensive public works effort behind the $1.4 billion Big Pipe. Officials need to cover the open-air reservoirs at Washington Park by 2020 to comply with federal regulations.

The rebuild was originally projected to cost just $62.3 million back in 2009. The estimate climbed to $76.3 million in 2013, only to grow to $170 million in September.

Officials last year explained that building on a hillside location would prove more difficult than expected. They worried about unstable soil and the potential for a landslide during a big earthquake.

Costs continued rising to account for higher labor and material costs tied to inflation, Teresa Elliott, the Water Bureau's chief engineer, said Tuesday.

Although the reservoir project will substantially change how Portland stores its water, it won't look much different to visitors when work wraps up in 2024.

Officials plan to replace the open-air Reservoir 3 with a closed underground reservoir that features a reflective pond on top, similar in appearance to what's there now. Reservoir 4 will be disconnected from the water system but Portland will build a bioswale and reflective pool.

Construction on the new reservoir will finish by December 2019 and it'll go officially online in 2020. Officials plan to wait two years for the soils to stabilize before moving forward with remaining efforts.

The City Council on Wednesday will be asked to approve a $152.2 million construction contract with Hoffman Construction.

Next week, the City Council is scheduled to increase Portland water rates by 7 percent, taking the monthly bill to $33.83 for the typical customer.

-- Brad Schmidt

503-294-7628

@cityhallwatch