21-100325-Traffic Impact Analysis (TIA)-01-29-2021-V1 TENW
Transportation Engineering NorthWest
Transportation Planning | Design | Traffic Impact & Operations
11400 SE 8th Street, Suite 200, Bellevue, WA 98004 | Office (425) 889-6747
MEMORANDUM
DATE: April 6, 2020
TO: Rick Perez / Sarady Long
City of Federal Way
FROM: Jeff Schramm
TENW
SUBJECT: Traffic Pro-Rata at SR 18 WB Ramp Intersection with Weyerhaeuser Way
Woodbridge – Federal Way
TENW Project #5219
This memorandum documents the estimated pro-rata share of traffic from the 3 Woodbridge developments at
the intersection of Weyerhaeuser Way with the SR 18 WB Ramps.
Background & Purpose
This memo documents the proportional-share of traffic of each of the 3 Woodbridge developments at the
intersection of Weyerhaeuser Way with the SR 18 WB Ramps to for the purposes of establishing a pro-rata
share of traffic that can be applied to the cost for intersection improvements.
The Woodbridge development includes the following 3 separate projects:
· Building A – 225,950 sf warehouse
· Building B – 215,350 sf warehouse
· Business Park – 972,700 sf industrial park
The IRG Warehouse A Hearing Examiner Hearing Examiner Reconsideration Decision Pertaining to MDNS
Condition No. 11 (HEX 18-003; 10-001) was replaced and stated, in part, that
„cumulative traffic impacts from Warehouse A and B and the Greenline Business Park to the SR 18
westbound ramp intersection with Weyerhaeuser Way South shall be evaluated and mitigated in a
SEPA analysis addendum and/or revision to the Warehouse A and B TIA. PM peak hour cumulative
impacts shall be included in the TIA analysis, or added to the concurrency review for Warehouse A
as the City finds most consistent with its regulation.‰
The condition further states „All mitigation shall be subjected to RCW 82.02.020 and constitutional
nexus/proportionality.‰
As a result of the reconsideration decision, it is our understanding that mitigation identified at the SR 18 WB
Ramps / Weyerhaeuser Way intersection to maintain acceptable WSDOT LOS standards would be
allocated to each of the 3 developments based on a pro-rata share of traffic generated by each in the PM
peak hour. The following sections describe how the pro-rata share estimate was derived.
Traffic Pro-Rata Memo
Woodbridge Federal Way
TENW April 6, 2020
Page 2
Trip Generation
The trip generation estimates for each of the Woodbridge developments were based on methodology
documented in the Institute of Transportation Engineers (ITE) Trip Generation Manual, 10th Edition. The trip
generation estimates for Building A and Building B were based on Land Use Code (LUC) 150 (Warehousing).
The trip generation estimates for Business Park were based on LUC 130 (Industrial Park). A summary of the
PM peak hour trip generation estimates for each is shown below in Table 1. Note that the trip generation
estimates shown are consistent with what was analyzed in the TIA.
Table 1
Woodbridge Developments
PM Peak Hour Trip Generation Summary
New Trips Generated
Development In Out Total
Building A 25 75 100
Building B 24 73 97
Business Park 82 307 389
Trip Distribution & Assignment
The distribution and assignment of PM peak hour project generated traffic for each of the Woodbridge
developments through the SR 18 WB Ramps / Weyerhaeuser Way intersection was based on anticipated
travel patterns in the area, and EMME/2 traffic model distribution plots provided by the City.
Pro-Rata at SR 18 WB Ramp Intersection with Weyerhaeuser Way
To estimate the pro-rata share of each of the 3 Woodbridge developments, total traffic at the intersection was
estimated and compared with the PM peak hour traffic generated by each of the three.
The anticipated buildout year for the Woodbridge developments is 2022. Future 2022 baseline conditions
without the 3 Woodbridge developments, and traffic volumes at the SR 18 WB Ramps / Weyerhaeuser
Way intersection were estimated by applying a 2 percent annual growth rate to the existing (2019) traffic
counts. In addition to the background growth rate, trips from the following pipeline developments were
included in the future 2022 baseline traffic forecasts:
· East Campus Corporate Park (assuming full occupancy)
· DaVita Federal Way
· Former Weyerhaeuser Headquarters building (assuming full occupancy)
The future 2022 With-Project buildout traffic volumes during the weekday PM peak hour at the SR 18 WB
Ramps / Weyerhaeuser Way intersection were determined by adding the trips generated by each of the 3
Woodbridge developments to the baseline traffic forecasts. The following Table 2 summarizes the future
estimated weekday PM peak hour volumes with the proposed 3 Woodbridge developments and each
projectÊs proportional impact.
Traffic Pro-Rata Memo
Woodbridge Federal Way
TENW April 6, 2020
Page 3
Table 2
Future 2022 With-Project Volumes during PM Peak Hour
SR 18 WB Ramps / Weyerhaeuser Way
Weekday PM Peak Hour
Development
Project
Trips
Total Entering
Volume %
Building A 69 2,979 2.3%
Building B 67 2,979 2.2%
Business Park 137 2,979 4.6%
As shown in Table 2, the future weekday PM peak hour total entering volume at the SR 18 WB Ramps /
Weyerhaeuser Way intersection is estimated to be 2,979 vehicles. Building A is estimated to have a 2.3%
project share (69 total trips). Building B is estimated to have a 2.2% project share (67 total trips). Business
Park is estimated to have a 4.6% project share (137 total trips).
If you have any questions about the information presented in this memo, please contact me at
schramm@tenw.com or 206-396-8286.
cc: Dana Ostenson, Woodbridge
Eric LaBrie, ESM Consulting Engineers