Storm water management assessment memorandum

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Page 8 of 20 Storm Water Management System Assessment Orono Truck Station Table 1 —Vegetation Onsite East Pond Common Name Scientific Name Smooth Sumac Rhus labra Hone Locust Gleditsia triacanthos American Elm Ulmus americana Reed Canary Grass Phalaris arundinacea Common Milkweed Asclepias syriaca Canada Goldenrod Solida o canadensis Cattail T ha S . Common Burdock Arctium minus Vi inia Cree er Parthenocissus a►vensis Common Buckthom Rhamnus cafhartica Smooth Brome Bromus inermis Lea S u e Eu horbia esula Box Elder Acer ne undo Field Bindweed Convovulvus arvensis Basswood Tilia americana Riverbank Gra e V'�tas ri aria Drainage Area The retention ponds receive runoff from the facility's buildings, landscaped areas and paved areas. No new impervious areas are known to have been added to the facility since the ponds'construction in 2002. Inlet Structure East Pond The 2005 technical memorandum noted that a side bank near the inlet of the east pond had experienced erosion problems. Vegetation has filled this area and the erosion issue is no longer apparent. Due to snow cover at the time of MFRA's first site visit, an inspection of the both ponds' inlet structures could not be completed.At the time of the second inspection, the 15 inch HDPE inlet pipe was being encroached upon by vegetation. This vegetation should be cleared to allow for better flow and maintenance access. The inlet pipe was in otherwise good condition and no erosion was noted. West Pond The west pond inlet structure appears to be an 18 inch flared end section that receives runoff from the truck station facility(the west pond also appears to receive runoff from the east pond through a culvert crossing under the road). At the time of the second inspection, the 18 inch flared end section and riprap were in good condition. A small amount of vegetation has begun to grow inside the flared end section and should be removed to prevent clogging of the system.