The long-term cost of extending light-rail beyond Seattle is about $7 billion less than Sound Transit previously said, according to revised...

The long-term cost of extending light-rail beyond Seattle is about $7 billion less than Sound Transit previously said, according to revised figures the agency issued Friday.

Using numbers supplied by Sound Transit, The Seattle Times last month published a story explaining that proposed transit projects on the November ballot would cost $37.9 billion, if interest and inflation are included until the last bonds are paid off 50 years from now.

The correct figure is $30.8 billion, the agency said Friday.

The larger number, reported in The Times on June 4, reflected the sum of figures provided by Sound Transit.

Sound Transit officials Friday said that some dollars had been included twice — once as payments for construction, and again as principal payments on bond debt.

“We regret we didn’t catch this error,” said Sound Transit spokesman Geoff Patrick.

He says the best figure for the public to use is $10.8 billion, which includes only the capital cost of trains, tracks and other construction, in 2006 dollars.

When inflation, operating costs, finance fees, cash reserves and administration are included, the total for Sound Transit’s plan through 2027 is $23.6 billion, in year-of-expenditure dollars. The $30.8 billion figure includes additional debt payments after 2027.

Voters in King, Snohomish, and Pierce counties Nov. 6 will decide whether to raise taxes for regional road and transit improvements. Sound Transit’s share features light-rail extensions to Snohomish County north of Lynnwood, to Overlake near Redmond, and to Tacoma, to be completed by 2027.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com