As noted in the attached referral memo, the item sponsor would like the PSNQLC to discuss the issue of elevated properties in single family districts and the requirements for retaining walls to ensure that abutting properties are not flooded.

Prior to the adoption of the new Resiliency Code, the single-family development regulations specified the following regarding onsite water retention:

Stormwater retention. In all instances where the existing elevation of a site is modified, a site shall be designed with adequate infrastructure to retain all stormwater on site in accordance with all applicable state and local regulations, as determined by the public works department.

In addition to the above language, the Resiliency Code also includes the following new requirement as it pertains to retaining walls:

• For properties in which the required yard elevation is greater than the yard elevation of the neighboring lot, either a retaining wall at the perimeter of the property or a slope maximum of 5:1, or a combination of both, shall be provided.

 
• Retaining walls shall be finished with stucco, stone, or other high quality materials, in accordance with the applicable design review or appropriateness criteria.

Additionally, the maximum height of a retaining wall along an interior side property line shall not exceed seven (7) feet, as measured from future adjusted grade. The portion of the wall above four (4) feet is required to consist of an open picket fence, so that the wall does not have an overbearing appearance on a lower, abutting neighbor.

For reference, future adjusted grade is defined as follows:

Future Adjusted Grade means the midpoint elevation between the future crown of the road, and the base flood elevation (BFE) plus minimum freeboard (1’) for a lot or lots.