Lot coverage is limited to no more than 50% impervious surface area. Impervious surfaces include driveways, building footprints, sidewalks, paved parking, compact gravel, and other surfaces that do not allow rain to percolate into the soil.
NOTE: Un-compacted gravel surfaces or pervious pavers may be demonstrated to be partially pervious using a professionally accepted methodology. If this calculation is prepared by the applicant's engineer and approved by the City Public Works Director, the graveled or permeable paved surface shall be counted in the lot coverage figure in accordance with its relative permeability (e.g., if a graveled path is demonstrated to be 15% permeable then 85% of the graveled path area would be counted in the impervious surface calculation).
The purpose of this requirement is to help ensure that surface and stormwater are contained on site. Stormwater low impact development techniques that encourage the natural treatment and infiltration of stormwater to mimic pre-development site conditions shall also be employed. Examples of low impact development techniques include directing stormwater to landscape areas with amended soils or into improved drainage areas under porches or eaves, green or living roofs, the use of pervious pavers, and retention of existing mature trees. Aggressive employment of stormwater low impact development techniques may allow for additional lot coverage if an applicant develops a project design that demonstrates the ability to handle surface and stormwater in common areas without limiting the community or public benefits of the established common areas. Private areas may also be relied on for stormwater infiltration if determined to be adequately protected by easement to ensure the continued availability of these areas as infiltration areas.
A qualified, Oregon-licensed professional engineer, considering at a minimum a 25-year storm event of 15 minutes duration, shall perform an on-site stormwater analysis. The stormwater control plan shall be approved by the Director of Public Works or Director's authorized designee and shall provide for the on-site collection, containment, and release of stormwater such that it will not have a deleterious impact to other properties, public or private. Prior to completion the Public Works Director or Director's authorized designee shall inspect all improvements. The applicant's licensed engineer shall provide a minimum of 2 sets of infrastructure "as built" drawings and confirm that all stormwater infrastructure was constructed according to the approved design.
(Ord. 19-1373; Ord. 23-1400)