HomeMy WebLinkAboutNotes Applicant 12/9/2024 (4) Favreau EngineeringFavreau EngineeringFavreau EngineeringFavreau Engineering
2206 Country 2206 Country 2206 Country 2206 Country Haven DrHaven DrHaven DrHaven Dr
Eugene, OR 97408Eugene, OR 97408Eugene, OR 97408Eugene, OR 97408
(541) 556(541) 556(541) 556(541) 556----4425442544254425
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503 17th STREET, SPRINGFIELD STORMWATER NARRATIVE
August 1, 2024
SITE CHARACTERISTICS
The subject tax lot, identified as TL 17-03-36-24-03300, is currently a vacant lot. A single-family residence previously
existed on the site prior to demolition. NRCS soil classification maps identify this site as having Class C and D soils. The site
is generally flat with only a couple of trees on site. According to available records, there is an existing 12” storm mainline
in 17th Street.
INFILTRATION TESTING
An infiltration test was performed on 7/31/2024. A single test pit was dug near the approximate location of the proposed
stormwater facility. No groundwater was encountered. After testing, it was determined that the soil had an infiltration
rate of 3”/hr. For sizing, an infiltration rate of 1.5”/hr will be used, applying a factor of safety of 2.
FACILITY SIZING
There are two proposed facilities with this development. A stormwater planter is proposed to treat the runoff generated
from the driveway and parking area. This facility has been sized only for the water quality storm and utilized the SIM Form
from the City of Eugene Stormwater Management Manual. For larger events, an overflow structure will direct runoff via
pipe to a weephole in the curb in 17th St, where it will ultimately discharge into the public stormwater system. Additionally,
an underground soakage trench has been designed to detain runoff from the roof of the proposed building, sized for the
10-year storm. An overflow is proposed to connect to the public stormwater mainline within 17th St for larger events. See
the attached calculations and details for further information regarding facility construction.