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HomeMy WebLinkAboutSW3181201_Stormwater Narrative_20220407Rob Wallace Park - Phase II Midland, North Carolina Storm Water Management Report Project Description This project involves the construction of a playground, restroom, and picnic shelters near the recently completed Rob Wallace Park Phase 2 improvements. In addition to the structures, a new 23 space parking lot to serve the proposed amenities, as well as several short crushed concrete walking trail connectors. The project will be constructed in a single phase starting with the construction of the structures and playground and ending with the parking lot construction. During construction, there will also be an extension of the private water main that parallels the park road to serve a new hydrant and restroom. Project construction will take place on tax parcel 55447239550000, which is 111.8 acres. The total site area of the park property, combining several other parcels allocated for future park development, is 173.2 acres. The current property owner is Cabarrus County, who will be the financially responsible party. The area to be disturbed is approximately 2.95 acres. Topography/Drainage The site is currently mostly undeveloped and drains to the south. Runoff is undetained and collects in Muddy Creek along the southern portion of the property that drains directly to Rocky River. Rocky River is located 2 miles southeast of the site and is classified as a Class C surface water. Stormwater management for this project is accomplished utilizing vegetated conveyances with low impact methods. The proposed parking lot runoff sheets off the paved surface through a grass road shoulder. The parking lot final grade nearly matches existing grade to prevent the need for deep ditches or re- channelizing runoff. Minimal storm drainage pipe is being installed to convey runoff under road/trail crossings. The site is currently mostly undeveloped and has minimal BUA (Built -Upon Area) from Phase II. The proposed BUA upon completion of this project (including that already constructed in Phase II) is 10.0 acres (9.3 acres existing and 0.7 acres proposed). Therefore, this development is classified as low - density (6.7% BUA). Soi is The soil survey of Gaston County indicates that soils on the site are as follows: • Badin Channery Silt Loam - BaB (Class C) • Chewacla Sandy Loam - ChA (Class B/D) • Kirksey Silt Loam - KkB (Class C) • Misenheimer Channery Silt Loam - MsA (Class C/D) • Udorthents, Loamy - Ud (Class C) Rob Wallace Park - Phase II Midland, North Carolina Model Parameters/Analysis Capacity analysis for proposed storm water conveyance system design was performed using the Rational Method (10 year frequency). Storm conveyance modeling and calculations were completed using the Autodesk Hydraflow Express Extension for Civil 3D software and Benesch's spreadsheets. Refer to the drainage area maps in the appendix section of this report.