Stormwater, Floodplain and Drainage Memo - Tamsin Ridge
3. Floodplain
FEMA's effective Flood Insurance Rate Map (panel 39019C0135D, effective September 14, 2018) maps Zone
AE, with a regulatory floodway, along Sallow Creek through the middle of the site. About 62 acres of the parcels
are in Zone AE, of which about 21 acres are floodway. Base flood elevations are 1,012 to 1,019 feet (NAVD 88).
Layout. Quote starts. No arrays, inverters, the substation, the BESS yard or fill are placed in the floodway. Quote ends. About 14 acres of
array rows are in the flood fringe (Zone AE outside the floodway) on Parcels 9 and 10, set so that the lowest
module edge at full tilt is at least 2 feet above the base flood elevation; inverters and electrical equipment are at
least 2 feet above it and outside Zone AE. The two collection line crossings of Sallow Creek are directional
bores. Piles in the flood fringe displace a negligible volume.
Permits. Carroll County's floodplain regulations exempt major utility facilities permitted by the OPSB, but OPSB
staff expect the application to show compliance with them. A no-rise certification would be needed for any work
in the floodway; none is planned.
Flooding history. Landowners report that Sallow Creek overtopped Linnet Road at the county bridge during the
flash flood of June 2019 and that the floodplain fields flood for a day or two most springs. The flood fringe array
rows on Parcels 9 and 10 should be checked against a local hydraulic model before final design; if flood levels
prove higher than mapped, those 14 acres may need to be dropped.
4. SPCC
The main power transformer holds about 14,000 gallons of mineral oil, so the substation needs a Spill
Prevention, Control and Countermeasure (SPCC) plan under 40 CFR Part 112, with secondary containment
around the transformer.
5. Water supply and private wells
Construction water, about 4 million gallons for compaction and soil conditioning, will be bought from the Village
of Carrollton public water system and trucked in; no water well will be drilled. The operating facility needs no
process water, and any panel washing would use trucked water. The nearby residences and farmsteads rely on
private water wells in the shale and sandstone aquifer. Ohio EPA source water protection mapping shows no
drinking water source protection area within the parcels. Northfold should offer pre-construction testing of private
wells within 1,000 feet of pile driving.
Tessmer Coyle Engineering, Inc. - Job 2317 Page 2 of 3
The page
The outline marks where the quote begins on the page.
Flood fringe array rows should be checked against a local hydraulic model; if flood levels are higher than mapped, those 14 acres may need to be dropped.
