Board finds Cascade Road dome application substantially complete; questions remain on lighting, deflation and emergency response

The Planning Board voted 3–1 to find the application for an athletic complex and dome on Cascade Road substantially complete and set a public hearing for June 17, while directing the applicant to provide additional technical information on a set of safety and neighborhood-impact questions.

Project changes and board action Applicant representatives said they removed the previously proposed outdoor turf field from the application, are now providing a pumped sewer connection and force main (rather than an on-site septic), and have supplied geotechnical design and details to support a requested slope waiver for steep fills within the 75-foot shoreland setback. The applicant also supplied manufacturer information about the dome’s strength and winter performance and added evergreen buffering along the closest property line.

Why the board found it incomplete on some points Board members said they wanted more detail on several items specific to the dome structure and operation: - Lighting and dark-sky compliance: Board members asked whether the dome material is translucent at the top and, if so, how much light will transmit at night; they requested photometric values for light emission through the dome surface in order to apply the city’s dark-sky and lighting trespass standards. - Noise and acoustics: Members asked for measured or rated sound levels for the primary inflation blowers and backup generators, plus any acoustic-dampening measures inside the dome; the applicant agreed to provide blower and generator noise specifications and to document any sound mitigation in the dome’s construction (the manufacturer had said the dome uses two membrane layers with an insulation layer between them). - Deflation and egress: Board members requested a manufacturer calculation for the rate of deflation and an evacuation-time estimate assuming all emergency egress doors are opened, so the board can assess occupant safety in catastrophic failure scenarios (a manufacturer representative had described a long hold time with some configurations, but the board asked for a firm calculation under emergency egress conditions). - Fire response and environmental runoff: Given industry experience that many thermal-runaway battery incidents occur during charging, board members asked staff to request a memo from the deputy fire chief on expected response procedures and on containment of potential runoff to the nearby waterways.

Board vote and next steps The board ultimately approved a motion to find the application complete by a 3–1 vote (one member opposed). Staff and the applicant agreed to file the technical clarifications (lighting photometrics, blower/backup-generator sound ratings, membrane reflectivity, deflation/egress calculations and fire/runoff contingency plans) before the scheduled June 17 public hearing. The board also asked staff to check whether a slope waiver is within the board’s authority and to request a legal opinion if necessary.