The City of Sandy has initiated a stormwater management incentive program to encourage multi-family, commercial, and industrial property owners to reduce runoff by treating and disposing of stormwater on-site. The resulting decrease in runoff entering the stormwater system will reduce capital and maintenance costs to the City and the decrease in runoff and pollution loading will improve the water quality of streams in and around Sandy.
More detailed descriptions of the credit program, method for determining stormwater fee discounts, and stormwater mitigation techniques are found below.
Sandy’s incentive program is intended to encourage property owners to utilize source control facilities on new development or redevelopment, or to make improvements to existing properties to mitigate stormwater discharges. The simplest way to reduce stormwater runoff is to reduce or eliminate impervious surfaces, (roofs, parking areas, etc.).
Credits may be given up to 1/3 of the total number of ERUs; therefore, a property owner must have at least 3 ERUs (8250 square feet of impervious surface) to qualify for a credit. Additional credit may be given to property owners who completely eliminate impervious surfaces on their property.
Trees can be used to mitigate for ground level impervious surfaces due to their ability to intercept stormwater and allow it to evaporate, as well as dissipating the energy of runoff. They also provide shade, which helps keep surface temperatures lower, and they facilitate stormwater infiltration and groundwater recharge.
Vegetated swales are long, narrow, landscaped channels that filter and infiltrate stormwater runoff from parking lots, sidewalks, streets, and other impervious surfaces.
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.
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.
Vegetated Infiltration Basins
A vegetated infiltration basin is a landscaped depression that accepts stormwater runoff from impervious surfaces, and is similar to a planter box. The basins allow pollutants to settle and filter out, and also provide the opportunity for infiltration. A vegetated infiltration basin can help fulfill site landscaping requirements
Sand filters, like planter boxes, are structural reservoirs that filter pollutants from stormwater and slow water runoff. Infiltration sand filters allow water to infiltrate through the sand and into the ground. Flow through sand filters include the use of a waterproof lining, and include an overflow to an approved stormwater conveyance system.
A soakage trench is a shallow trench in permeable soil that is backfilled with sand and coarse stone, and lined with filter fabric. Water from rooftops is diverted into the trench, where pollutants are filtered from the water and groundwater is recharged through infiltration. The trench surface may be covered with grating, stone, sand, grass, or plantings.
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.
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.