Despite worries it might not be made public, yesterday afternoon the City of Bellevue posted their $670,000 East Link study phase 1 online. A controversial expenditure at the time, it was intended to compare the B7 alignment that Sound Transit studied in its EIS with B7 “revised”, which was conceptually reputed as improved over B7 and named B7R. Although the study did not address Sound Transit’s preferred B2M alignment directly, observers widely construed the study as an attempt to show that B7R, which largely follows I-405 through South Bellevue, is superior to B2M, which would serve the South Bellevue Park and Ride. All “B” alignments refer to the segment between Mercer Island and Downtown Bellevue, exclusive.
There are several differences between B7 and B7R, the most salient of which is a new Park and Ride “A-2” at the Bellevue Way/I-90 interchange. Assuming that downtown Bellevue gets a tunnel, choosing B7R would leave the cost of Segment B about the same at $515m, because the cost of the A-2 P&R is canceled out by the elimination of the 118th Ave SE station. It would increase overall East Link boardings in 2030 from 49,000 to 50,500.
There are additional costs for bus operations (up to $1m** a year), plus some money to enable sharing of the BNSF tracks with other rail operators, if desired. B7R also incurs a further $9m in costs in segment C, because the approach to the tunnel is more expensive. Crucially, there are cost and schedule risks associated with the Mercer Slough crossing (pg. 3):
The crossing of the Mercer Slough is challenging as a result of: the environmentally sensitive nature of the Slough; the poor foundation materials; the movement of the peat as documented by WSDOT; and WSDOTs concerns regarding protection of their existing I-90 structures. While two construction methods have been developed, further analysis will be required to define the appropriate solution and to satisfy WSDOT concerns. This could potentially delay the project and add construction cost.
By comparison, Sound Transit’s supplemental EIS reported that under the same assumptions, B2M would attract 50,000 riders to the line in 2030, vs. 48,000 for B7. It prices B2M at $480-550m and B7 at $515-595m.
The B7 figures do not match those from the supplemental EIS because the City of Bellevue instructed Arup, who did the study, to use a different (“BKR”) traffic model for both, and “the BKR Model has greater detail for the localized road network and traffic analysis zones.” (page 6)
Although some of these differences make it hard to compare things directly, it is evident to me that the ridership difference between B7R and B2M is basically a wash, but B7R is approximately $40m more expensive*.
*$40m accounts for the gap in segment cost, but is likely to be significantly more when factoring in the costs for the C9T tunnel since a connection to B2M is roughly $100m cheaper.
**The $1m figure only accounts for additional costs with Sound Transit bus operations and leaves out Metro routes. According to the report, ST would have to procure two additional vehicles just to maintain bus headways.