Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Wind Modeling topic
No spam. Unsubscribe anytime.
Model disagreement clouds wind‑safety findings for proposed Tenth & Market tower
Summary
Staff and independent consultants reported conflicting wind‑tunnel and computational model results for a high‑wind threshold at the Tenth & Market project site, prompting calls for method comparison, possible code guidance on repeatability/error margins, and a plan for cumulative impact analysis.
City staff and outside consultants told the Planning Commission that repeated wind‑tunnel tests can yield divergent counts of 'hazardous wind' hours at the same test points, and that computational (digital) modeling can help visualize flow patterns that explain differences.
Why it matters: For projects near Fox Plaza and other high‑wind locations, small differences in measured wind velocity can change whether a design meets the planning code's hazard threshold (26 mph for one hour/year). RWDI (computational consultant) presented flow visualizations showing the Fox Plaza wake dominates local flows and concluded the 2006 tests did not materially increase hazard hours compared with earlier studies. RWDI's Colin Williams summarized: "the wind flows are similar with the proposed 2006 Hellermanis Building and with the 2003 building," and said the computational flow visualization helps explain tunnel differences.
Public and commission concerns: Residents and some commissioners pressed for cumulative analyses covering approved and proposed towers (Trinity Plaza, Fox Plaza additions, other projects) and asked that any new methodology be validated with field (post‑construction) measurements. Commissioner comments and public testimony emphasized that recreational, pedestrian, and open‑space comfort thresholds differ from the hazard standard and urged staff to specify which numeric criteria apply to which uses.
Staff response and next steps: Planning staff outlined short‑term options: (a) allow the zoning administrator to grant variances using both tunnel and digital evidence; (b) amend code to include an explicit margin of error; (c) convene technical experts to establish repeatable standards. Commissioners asked staff to rerun or compare models on representative projects (e.g., Trinity Plaza) and to report back with recommended procedural guidance and, if appropriate, code amendments.
