The City of Sandy’s stormwater management program defines one Equivalent Residential Unit (ERU) as 2,750 square feet of impervious area, or the equivalent impervious area of a typical single-family home site. Non-single-family-residential properties with more than one ERU of impervious area are charged the monthly stormwater management fee ($3.25) multiplied by the number of ERUs.
The impervious surface area of each commercial, industrial, and multi-family site was determined in one of three ways:
The calculation of area mitigated by the various recommended methods is shown in the spreadsheet below. The determination of the discount is shown below:
An eco-roof is a vegetated roof system that consists of lightweight soil and plants adapted to survive both the western Oregon wet winters and dry summers. Eco-roofs reduce or eliminate runoff from roofs, and filters pollutants. Additionally, eco-roofs provide habitat and food for insects and birds. Benefits to the building include increased insulation on the roof, mitigation building and roof temperatures, and potentially longer lifespan than traditional roofs.
Grassy swales, like vegetated swales, are long, narrow, channels that are used to filter and infiltrate stormwater from parking lots, sidewalks, streets, and other impervious surfaces. Grassy swales are landscaped solely with a grass seed mix, and may be mown occasionally, depending on aesthetic and stormwater filtering requirements.
The primary goal of the Neighborhood Traffic Management Program is to improve the livability and environment on neighborhood streets. With that goal in mind, the following program objectives were identified:
Pervious paving is a catch-all category for a variety of paving materials that allow water to infiltrate into the ground and prevent runoff. All rely on pervious material placed over an open-graded base material underlain by a minimally compacted subgrade. Examples of pervious paving include paving blocks (numerous shapes and sizes), plastic grids that allow grass growth between the plastic, pervious concrete, and pervious asphalt. The numerous different types of pervious paving materials provide flexibility in choosing the most appropriate system for the usage.
Planters are structural landscaped reservoirs used to collect and filter stormwater runoff. Infiltration planters allow water to infiltrate through the planter soil and into the ground. Flow through planters include the use of a waterproof lining, and include an overflow to an approved stormwater conveyance system. Both types of planters may be used to help fulfill site landscaping requirements.
Project plans must be submitted electronically with the Permit Application Form for review and approval. Plans will be returned to the applicant electronically with any redlines/corrections and a permit approval letter. For simple crossings or service laterals/drops serving single-family dwellings or small commercial/industrial sites a simple sketch may be submitted if project plans have not been prepared for the work.
