Decision Requested

Approve sending DRB Referral Letter to initiate formal Dispute Review Board proceedings.

• Recommendation: Proceed to DRB on one question
• Cost Exposure: $450K–$7.8M (two countermeasure options); excludes CLOMR, permitting, reconstruction
• Risk Level: Low-to-moderate — strong contract language, but two bridges already constructed

DRB Question

Does Section 2.30.5.2.1 require the Design-Builder to apply the “not low” lateral migration determination to Sammamish River structures, or does it permit the Design-Builder to reach a different determination through independent analysis?

Section 2.30.5.2.1 provides: “The Sammamish River ‘not low’ lateral migration determination discussed in the Sammamish River Migration Risk Assessment (Appendix H) shall apply to the new structures within the river flow limits defined by the 500-year flood elevation.”

“Shall apply” mandates the “not low” determination as a contract requirement. H26 concludes: “The risk of channel migration… is NOT LOW and therefore will require further analysis during final design.” The word “therefore” shows further analysis is a consequence of the NOT LOW determination, not a license to revisit it.

Three bridges are affected: the Ramp Bridge (constructed), Mainline Bridge (in construction), and DAR Bridge (design phase, April 2026 construction). Skanska’s supplemental (LTR 322) presents two countermeasure cost scenarios: Option 1 ($7,809,741) — vertical steel sheet pile walls; Option 2 ($450,032) — rock and log vanes per HEC-23. Both exclude CLOMR, extended general conditions, permitting, and reconstruction.

Skanska/AECOM’s Table 2.30-B argument—that the Sammamish bridges are “fish passage structures” subject to a “low” standard—fails because Table 2.30-B identifies specific fish passage structures by name and does not include the I-405 bridges. Two key submittals are directly affected: the Draft FHD (CRE-00888, rejected January 2025) and the Zero Rise Report (CRE-01059, blocked). Between August 2024 and January 2025, WSDOT and Skanska/AECOM engaged in 8+ documented OTS review interactions without reaching agreement on the classification.

Per Section 1-03.5, the IED interprets existing requirements and creates no entitlement to cost or time adjustment. The Design-Builder had six months’ notice before contract award. H26 was added via Addendum 9 (Jan 2023); Section 2.30.5.2.1 via Addendum 14 (Mar 2023). Section 2.14.6.11 zero-rise certification is blocked pending resolution.

Defense Layers

#	Defense Layer	Authority	Strength
1	“Shall apply” is dispositive	Section 2.30.5.2.1	Strong
2	IED authority, no entitlement	Section 1-03.5	Strong
3	Pre-award notice (Form A, 6 months)	Addendum 9, 14	Strong
4	Silent deviation — no DBIC filed	Section 1-04.4(2)	Strong
5	LTR 322 deficiencies	Section 1-04.5	Moderate
6	WSDOT demonstrated good faith	Partnering record	Favorable
7	H26 rebuttal — even under 1-03.1, H26 says “NOT LOW”	H26	Reserve

DRB Considerations

• Two bridges already constructed. Sympathy factor, but the contractual question is unchanged regardless of construction status.
• DAR Bridge may already comply. AECOM’s draft analysis suggests current shaft design accommodates “not low” scour — Skanska may call the dispute “academic.” WSDOT response: low-cost compliance makes the silent deviation less defensible.
• DAR Bridge schedule pressure. Design blocked pending resolution (April 2026). WSDOT response: requirement has been in the Contract since award; WSDOT first flagged Aug 2024.
• CLOMR is conditional. 12–18 month timeline applies only if BFE rises. Countermeasure approaches may avoid a BFE rise entirely.
• Sophisticated Skanska/AECOM position. Multiple legal theories (addendum sequencing, harmonization, 1-03.1 reclassification, Table 2.30-B) require careful, layered rebuttal.
• Section 1-03.1 argument. Double-edged sword — even under Skanska’s own reading, H26 says “NOT LOW.” Keep rebuttal in reserve.
• Collaborative resolution possible. DAR Bridge negotiation could narrow the dispute scope.
• DRB may lean toward compromise. Cost disparity ($450K vs. $7.8M) may reinforce tendency toward practical resolution.
• Cost disparity ($450K vs. $7.8M). Wide range suggests LTR 322 cost analysis is preliminary and may not reflect the most efficient compliant solution.

Fallback Position

If DRB recommends compromise: accept countermeasures for DAR Bridge only if it preserves the “shall apply” framework as precedent. Resist any recommendation that the Design-Builder may override contractual design classifications through independent analysis — this precedent affects all IEDs on this project.

Skanska’s Cost Estimates (LTR 322)

Scenario	Cost	Schedule Risk	Notes
Option 1: Sheet Pile Walls	$7,809,741	Unknown	352 fifty-foot steel sheets ($2.0M) + pile driving ($2.6M) + 20% markup ($1.3M). Excludes CLOMR, extended GCs, permitting, reconstruction
Option 2: Rock/Log Vanes (HEC-23)	$450,032	Unknown	Design ($127K) + FHD update ($106K) + construction. Bioengineering approach. Excludes CLOMR, extended GCs, permitting
DAR Bridge RFC	—	April 2026 at risk	Design blocked pending dispute resolution. 6+ months potential delay

Key Considerations

• Interior pier prohibition: BDM Section 7.1.7.B states countermeasures “shall not be placed at interior piers.” The only compliant path is foundation design accommodating full scour depth.
• AECOM draft analysis (Feb 2026): DAR Bridge shafts (100–135 ft) already accommodate “not low” scour — oversized for landslide demands. Only Piers 3 and 4 within 500-year flood limits. Ramp Bridge and Mainline Bridge not analyzed. Draft in WSDOT review.
• Zero-rise certification: CRE-01059 submitted August 2024 but blocked per Section 2.14.6.11. Lateral migration classification affects scour countermeasure design, which affects the hydraulic model and BFE analysis.
• CLOMR timeline: 12–18 months per SL 178, but conditional — only applies if BFE rises. Countermeasure approaches may avoid BFE rise entirely.