Bringing Experience and Innovation to Your Project
City of Olympia, Washington
The City of Olympia, Washington utilizes a variety of methods to deal with stormwater runoff from urban and suburban areas. In addition to utilizing a variety of porous paving materials, the City is also evaluating the potential for infiltration under public roads. The pilot project on Decatur Street utilizes a geogrid stabilized gravel infiltration gallery under the street with three different pretreatment methods. These include porous asphalt pavement, a stormwater cartridge treatment system, and a linear rain garden. More information about this project can be found at the City's website: Unique features of this project include:
Utilization of area under streets for infiltration
Ability to infiltrate 100% of most storms, despite low subsoil infiltration capacities (~0.15"/hr)
Full size manhole/observation pit to provide an educational look at how the system is constructed and how it works
Multiple LID practices in one location (infiltration, porous pavement, rain garden, permeable block pavers)
Stormwater is introduced into the rain garden via a "bubble-up" design (runoff from the street enters a conventional drop inlet, flow to the rain garden through a pipe, then "bubbles-up" into the rain garden through a second manhole structure)
Permeable block paver sidewalk section uses WaterPerm tiles rather than conventional porous block paver design. Infiltration occurs through the paver blocks, rather than through the porous material between the blocks
Olympia is also utilizing porous concrete bike lanes to infiltrate street runoff. These look great, clearly mark the bike lanes, and provide the benefits of porous pavement installation without having to design for full-scale traffic loadings. The concrete mix design used in Olympia proves a much tighter surface (compared with conventional porous concrete). This reduces the accumulation of debris in pore spaces and (theortically) less maintenance.
