HOLGATE TO KING ST. STAGE 3 (H2K3) VALUE ENGINEERING STUDY

BASIC OUTLINE

  • Introductions
  • Project Background and Overview

The formal name of the structure to be built by the H2K3 project is Alaskan Way S. and Colorado S over SR99. This structure, often referred to as “little h”, is an overhead bypass bridge that will serve to connect port activities to SR 519 and to maintain continuity of Alaskan Way S. The little h structure will allow freight and other users in the area a bypass option when tail track blockages occur on S. Atlantic Street. Sidewalks will be provided on the structure to allow a pedestrian bypass as well.

The visual significance and gateway role of the overpass are important design considerations which need to be integrated with the structural design and architectural treatment of the overpass structure. Because of commitments made regarding the visual appearance of the structure, evaluation of other bridge types will not be investigated during this VE Study.

Construction of the Stage 3 project will take place during the construction of (and also within the project limits of) the Holgate to King Stage 2 project. Most of the surface street configurations, SR99 ramps, and mainline alignments that the Stage 3 project will need to be designed around do not currently exist. They will be constructed during the Stage 2 project.

  • Structure Overview (by Tim Moore)
  • Discussion of Other Project Element (by Brian Glas)
  • Basic Overview of Design and Construction Schedules (by Brian Glas)
  • Staging and Construction Access discussion (by Kurt Caton)
  • Focus of the VE Study

The primary focus of this study is to evaluate the project site (its limitations and constraints), and develop a construction and staging strategy (using the preliminary bridge plan configuration) that will allow the completion of the project within the allotted time frame. Consideration shall be given to the limited amount of staging area available, as well as the restrictions to access for construction equipment this unique construction site imposes.

  • Project Constraints
  1. Construction may begin in July 2012 and the project must be operationally complete by December 23, 2013.
  2. It shall be assumed that the WOSCA staging and construction area (vicinity of Piers 11 thru 15) will not be available to the Stage 3 contractor until February 1st, 2013.
  3. The contractor shall be required to provide and maintain a shared use path (12 ft minimum width) through or immediately adjacent to the construction site. This path is intended to maintain the continuity of the existing path located on the west side of Alaskan Way, and to also allow a through route for bicyclists currently using Alaskan Way .
  4. The new structure will need to maintain 23.5 feet of vertical clearance over the tail track. During construction, a minimum of 21.0 feet of clearance over the tail track shall be maintained. Lateral clearance of 8.5 feet from the centerline of the tail track shall be maintained at all times. See Attachment for additional details.
  5. No lifting of objects over the tail track will be permitted when a train is present.
  6. No pile driving shall be permitted at night. Pile driving typically shall be limited to the hours of 8:00 am to 5:00 pm weekdays, and 9:00 am to 5:00 pm on weekends and legal holidays. We anticipate the extension of these hours to 10:00 pm (under a variance) for pile driving in critical areas.
  7. In addition to SR 99 mainline, a northbound site access road (for the tunnel contractor) and a SB mainline off ramp will pass through the middle of the construction site for the duration of the project. The current alignment of the haul road crosses the east leg of the little h alignment in the vicinity of Atlantic Street. The contractor will be required to work around these facilities. A limited number of closures for mainline lanes, the ramp, and the haul road will be allowed. Permitted closures of the southbound ramp and the access road (as specified in the Technical Requirements of the SR 99 Bored Tunnel RFP) are as follows:

Construction of drilled shafts

Anticipated durationOct. 2012 – Jan. 2013

Closure of southbound off-ramp/northbound

site access road: 4 Complete weekends

Construction of falsework piling

Anticipated durationApril 1, 2013 – April 30, 2013

Closure of the southbound off-ramp/northbound

site access road:8 consecutive 24 hour days

(beginning on Friday evening)

Construction of columns and sub-deck

Anticipated durationJan. 2013 – April 2013

Closure of the southbound off-ramp/northbound

site access road:Periodic evening closures

Removal of falsework and project demobilization

Anticipated durationNov. 2013 – Dec. 2013

Closure of the southbound off-ramp/northbound

site access road:Periodic evening closures

The number and duration of lane closures needed on main line SR 99 has yet to be determined. All of these closures (ramp, access road, and mainline lanes) will have to be coordinated with the Stage 2 and Bored Tunnel contractors.

  1. Any proposed changes to the preliminary bridge design shall be in compliance with the “PORTAL AREA DESIGN GUIDELINES” prepared for the SR99 Bored Tunnel Alternative. A brief summary of pertinent guidelines is a follows:

It is important that the visual design of the elements of the South Portal not seek to demand a great deal of attention in themselves. Rather, a simple and elegant minimalist approach would allow for a clarity of purpose and respect for what is already a dramatic setting.

Guardrail on top of walls will not be allowed.

The overpass bridge structure needs to maintain 23.5 feet of clearance over the tail track. As it goes across the highway, it should remain level over both the north and southbound lanes of the highway.

A 54-inch barrier shall be utilized for pedestrians and vehicles on the bridge. The 54 inches should be measured from the top of the sidewalk which shall have a 6-inch curb to the roadway. At select locations, a 30 inch high throw fence will be installed on top of the barrier.

Lighting of the bridge structure shall be aligned with the columns below and no light fixtures shall be located in the midspan. All light fixtures shall be located on the outer edge, that is on the northern, western and eastern edge of the barrier, to minimize their visibility in the northbound direction of travel.

Sidewalks shall be provided on the overhead bypass bridge for pedestrian access on the west, east and north sides of the structure from East Marginal Way to Atlantic Street. These sidewalks will be ADA compliant and incorporate frequent landings (rest intervals) within the walkway (see the preliminary bridge plans for landing locations). In addition, a stairway may be provided for more direct and convenient pedestrian access to Royal Brougham Street on the east side of the overhead bypass bridge.

  1. Throughout construction, an unobstructed access route to the Terminal 46 substation needs to be maintained 24/7 for Port of Seattle maintenance crews. Their primary access gate is on the southeast corner of the substation facility. A “daisy chained” gate would be permitted to maintain security of the contractor’s staging area.
  2. Throughout construction, an unobstructed access route to the King County regulator building needs to be maintained 24/7 for King County maintenance personnel. The primary access for this facility is on the north side of the building. A “daisy chained” gate would be permitted to maintain security of the contractor’s staging area.
  3. Offsets from back of type 2 traffic barrier to any adjacent falsework will be 2 feet minimum if the barrier is not anchored. If the barrier is pinned or otherwise securely anchored, the acceptable offset is 6 inches.
  4. A BNSF flagger will be needed on the tail track under the following conditions:

a) When a tracked piece of equipment crosses the track (even if at a designated public crossing).

b) When an object is being lifted in the vicinity of the tail track (via crane or other device) creating a situation in which an object can fall within 5 feet of a rail.

c) When a crane is positioned in such a way that if its boom support mechanism failed, and the boom could fall to within 5 feet of a rail.

d) When working within 25 feet of the centerline of the tail track.

e) When people and or equipment are crossing the track at a location that is not a designated public crossing.

  • VE Study Goals
  1. Development of two viable construction schedules. One schedule would follow the time line provided in the constraints listed above recognizing there will be a premium resulting from this timeline (due to poor access, limited staging areas, staging area restrictions, etc.). The second schedule would be developed with a project end date beyond the December 23, 2013 date specified in the constraints. This second schedule would extend the project as needed to eliminate the premium.
  2. Develop a rough estimate of the construction cost savings the second (less aggressive) schedule mentioned above would provide.
  3. Evaluate the proposed staging and construction areas and determine their adequacy. Is there sufficient space to allow the contractor to work efficiently enough to complete the work within the stated timeline?
  4. Evaluate the space available for the SB off ramp and haul road in the vicinity of piers 7 and 16 and determine the optimum temporary traffic barrier scenario at this location that will meet the falsework offset requirements and can still be installed within the allowable ramp and haul road closure hours. Anchored barrier will be needed at this location. Pinned barrier may not be an option in all areas. Ramp and closure constraints may make installation of alternate anchored barrier options a challenge.
  5. Evaluate the specified number of closures provided for the access road and the southbound ramp and determine if they are sufficient.
  6. Identify any additional contract requirements that will need to be specified to complete key items of work (e.g. maximum number and or duration of closures).
  7. Evaluate the feasibility of constructing a portion of the SR99 NB on ramp (basically the portion within the H2K3 project limits) during the Stage 3 contract. See item “8” on sheet 17 in the Tunnel Contractor’s Staging Plan.

ITEMS TO BE PROVIDED AND OR MADE AVAILABLE DURING THE STUDY:

  • Preliminary bridge plans
  • Stage 2 right of way plan
  • Design Schedule
  • Preliminary Construction Schedule
  • Cost Risk Analysis Report
  • Cost Estimate
  • Sampling of geotechnical borings in the area
  • Utility basemap
  • Channelization Plan
  • Layout plots of the site 50 scale showing the structure and staging areas
  • Aerial photo of the site
  • Risk registry
  • Traffic volumes
  • Design Builder’s (Tunnel Contractor’s) conceptual staging plan w/timelines
  • Power Point “kickoff” presentation