FEMA mapping, water modeling and a Sept. 18 public hearing on sign rules noted at commission meeting

Planning staff member Laurie told the commission on Sept. 3 that a recent FEMA study will not focus on the city’s alluvial fans — including a large alluvial fan near Rocky Ridge — even though those features can produce rapid flows that threaten houses along the fan. Laurie said FEMA staff will consider how these features are labeled on maps and that she asked the agency to correct any stream-name inconsistencies (Willow Creek was cited as an example).

Commissioner Jack and a technical speaker (water system modeler) discussed the limits of the FEMA materials and then described municipal water modeling for planning. The engineer explained that a water model uses elevation, pipe sizes and network nodes to estimate pressures and flows under different conditions, including fire-flow analyses. They noted that static pressure depends on elevation (2.31 feet of head equals 1 psi) and that tank surface elevation and tank height affect available pressure. They said that while model outputs are useful, many software packages use proprietary file types; the planning office might request a copy of a model from Johnson DeMille for future reference.

The commission also discussed recent high-intensity rainfall that caused basement flooding at one Main Street residence; staff and commissioners noted sandbagging and suggested property-level mitigation such as grading or a diversion ditch. Laurie said Chuck reviewed water-study materials and reported them sufficient for the current application and that questions remain about who will pay for needed road extensions.

Laurie announced that the planning department will post a public hearing for proposed sign regulations and lighting on Sept. 18 and asked commissioners to submit comments before then.

No formal action was taken on FEMA mapping; commissioners asked staff to follow up with FEMA and Johnson DeMille and to post the public hearing notice.