Biofiltration Plant selection for these projects is driven by:
A) Site conditions - sun exposure, soil depth, physical and chemical properties and moisture holding capacity
B) Intended function of the project
i. Performance - infiltration, pollutant removal, evapotranspiration
ii. Safety- hedging, protection
iii. Aesthetics - visibility, recreation, amenity
C) Degree of maintenance expected on the project
D) Water regime that will naturally occur at the site - such as the depth, frequency and duration of soil saturation, which can vary daily, seasonally or annually. Rain Gardens - collect rainfall from roofs, sidewalks, driveways and other urban surfaces. The plants and soil prevent erosive run-off, remove pollutants and allow the water to slowly soak in and replenish the groundwater. This means that our wetlands, lakes, streams and drinking water are all improved. Thus less money must be put into cleaning the water for use. The plants selected for these projects must have seasonal interest and the ability to perform well in a variety of conditions:
1) standing water in winter, abundant water in summer supports plants such as:
i. Juncus effusus
ii. Scirpus microcarpus
iii. Carex obnupta
iv. Oenanthe sarmentosa 2) standing water in winter, dry in summer:
i. Philadelphus lewisii
ii. Osmaronia cerasiformis
iii. Polystichum munitum
iv. Blechnum spicant 3) abundant moisture in winter, dry in summer:
i. Mahonia nervosa
ii. Rosa nutkana
iii. Rosa gymnocarpa
iv. Arctostaphylos uva ursi 4) Hedges:
i. Spiraea douglasii
ii. Symphoricarpus albus
iii. Rubus Spectabilis
iv. Holodiscus discolor 5) Shrubs/Small Trees:
i. Malus diversifolia
ii. Acer circinatum
iii. Osmaronia cerasiformis
iv. Rhamnus purshiana Bioswales Grass Channel - most similar to a drainage ditch, with flatter slopes and longitudinal slopes and a slower design velocity for water quality treatment of small storm events. Dry Swale - similar to bioretention areas where existing soil is replaced with a sand/soil mix meeting minimum permeability requirements. A gravel layer surrounding a perforated pipe is placed under the soil bed. The treated Stormwater flows through to the underdrain to the drainage system. Wet Swale - intersect the ground water with a shallow, permanent pool and wetland plants which filter the water. There is a potentially high level of pollutant removal. Vegetated Buffer Strip - designed to prevent erosion, areas are seeded with grasses, often between strips of cultivated crops. Filter Strip - vegetated to remove sediment, organic matter and other pollutants from runoff and wastewater. Plants for bioswales: 1) Abundant and standing moisture during all seasons
i. Calamagrostis stricta
ii. Carex kelloggii
iii. Glyceria grandis
iv. Scirpus microcarpus
v. Salix scouleri
vi. Sambucus racemosa
vii. Alnus rubra
viii. Acer macrophyllum 2) Standing water in winter, dry in summer
i. Cornus sericea
ii. Amelanchier alnifolia
iii. Cratageous douglasii
iv. Lonicera involucrata 3) Abundant moisture in winter, dry in summer
i. Prunus emarginata
ii. Acer glabrum
iii. Amelanchier alnifolia
iv. Mahonia nervosa
v. Polystichum munitum
vi. Rosa nutkana
vii. Symphoricarpus albus
viii. Arctostaphylos uva ursi
ix. Fragaria chiloensis Creeks - restored creeks or riparian habitat with off-channel Stormwater ponds for treatment and detention of surface runoff
o Pseudotsuga menziesii
o Thuja plicata
o Acer circinatum
o Acer macrophyllum
o Rhamnus purshiana
o Salix hookeriana/scouleriana/sitchensis
o Cornus sericea
o Lonicera involucrata
o Osmaronia cerasiformis
o Physocarpus capitatus
o Rosa nutkana
o Rosa pisocarpa
o Sambucus racemosa
o Spiraea douglasii
o Symphoricarpus albus Ponds - aquatic habitat
o Carex rostrata
o Carex sitchensis
o Carex stipata
o Juncus effuses
o Juncus ensifolius
o Oenanthe sarmentosa
o Typha latifolia
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