HomeMy WebLinkAboutWPO201300068 Assessment - Environmental 2013-10-28 sHimp PROJECT MANAGEMENT
CIVIL ENGINEERING
LAND PLANNING
December 10, 2013
Albemarle County Community Development Department
Regarding: Houndstooth
Downstream Channel Adequacy Analysis
On December 5, I conducted a field inspection to determine the condition and adequacy of the channel
downstream from the Houndstooth site. Photos from the visit are attached to this document, preceded by a
photo key showing a satellite image of the area.
The site currently drains into a wide flat field covered with thick grass(Images 1-4). No signs of erosion
were observed, indicating that the grass effectively disperses flows from major storm events and provides a
stable vegetative cover.
From the field, water flows through a small wooded area (Images 5-8). Since the flows entering this area
are not concentrated, no eroded channels were observed. Water flows across this wooded area towards
the culvert under the driveway just north of the site.
The area near the culvert is thickly vegetated (Image 9)and shows no indications of erosion. The culvert
was measured at 36 inches with approximately three feet of freeboard to the driveway(image 10). The
outfall of the culvert is thickly vegetated (Image 11) and flows into another wide, grassy field (Image 12).
The inspection ended at the culvert that flows under Silas Jackson Drive. It appears that no properties or
homes downstream of the Houndstooth site will be affected by potential increased flood volumes due to
development.
Since the current conditions disperse flow and prevent erosion,the design for the site outfall preserves
existing conditions as much as possible. The biofilter discharges to a 2C' level spreader, simulating the
current wide area of discharge. Approximately 30'of the existing thick grass will be preserved downstream
of the level spreader. Engineered channel stabilization downstream of the site, such as rip-rap extending to
the culvert,would provide a marginal improvement over existing conditions, but would adversely impact the
neighboring property, so it is not the overall best solution.
If you have any questions or concerns about these revisions please feel free to call me at(434) 207-8086
and we can discuss any questions that you may have in further detail.
Best Pe ,ards,
J...stin S°.imp, F.E.
Skimp E -ineering, P.C.
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