An updated Rivanna Water & Sewer Authority capital improvement plan would cut the one adopted last year by 23 percent to $155.3 million, officials said Tuesday.

The five-year capital improvement budget covering fiscal years 2013-17 would reflect a “nice windfall” that would positively impact one component of both wholesale water and sewer rates, said authority Executive Director Thomas L. Frederick Jr. New bond financing has taken advantage of lower interest rates.

The authority board is scheduled to approve the plan at its Feb. 26 meeting.

Savings would total about $1.7 million annually, said Lonnie Wood, the authority’s director of finance and administration.

Wholesale water rates will decrease more significantly over five years than expected for both the city of Charlottesville and the Albemarle County Service Authority, while wholesale sewer rates will not increase as sharply as previously estimated.

Projected city wastewater rate increases, for example, have been slashed from 38.5 percent to 17.1 percent over five years.

It’s too early to say whether the decrease in rates at the wholesale level would trickle down to customers; those rates would be determined by the city and the service authority at later dates.

“Urban wastewater is higher in very large measure due to the size of the Rivanna Pump Station,” Frederick said in reference to the sewer pump station being moved in Woolen Mills.

When the capital improvement plan was reviewed a year ago, the authority’s intention to use chloramines as a water treatment method garnered public scrutiny. In July, local officials dropped chloramines in favor of using granular-activated carbon to filter local drinking water and comply with tougher federal standards.

The capital plan includes $24.7 million in new or expanded projects, the largest, $10.2 million for the granular-activated carbon project. When combined with the prior budget for chloramines, the total “placeholder” for granular-activated carbon is $16.2 million.

“One thing we haven’t focused a lot on in recent years is water treatment plant infrastructure renewal,” Frederick said. “We have water plants built in the 1950s and 1960s and they reflect that old technology.

“Not everything that was requested by our operating managers is in the budget for water treatment. We need to put some investment there, and that’s where some of our new money in the CIP is [allocated].”

The five-year capital improvement plan is updated annually, Frederick said.