Stormwater Calculator

Rational method runoff, detention/infiltration sizing, orifice and overflow pipe sizing, 72-hr drain-down, and system elevation checks.
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Development Type

Newark Ordinance §41:17. Minor development uses the 10-year storm; major uses the 100-year storm.

System Type

Storm Event

Intensity (in/hr)

Duration Tp (min)

Site Areas

Total Lot Area (SF)

Existing

Building (SF)

Paved (SF)

Seeded (SF)

Leave blank = Lot - Bldg - Paved

Proposed

Building (SF)

Paved (SF)

Seeded (SF)

Leave blank = Lot - Bldg - Paved

Runoff Coefficients

C — Building

C — Paved

C — Seeded

Seepage Pit — Peerless Concrete

Pit Model

# of Pits

Gravel Ring (ft)

Gravel Below (ft)

Void Ratio

Percolation

Perc Unit

Perc Rate

HDPE Detention Pipe

Pipe Diameter

Length per Row (LF)

# of Rows

NDS Flo-Well Drywell

24" dia × 24" tall, 50 gal (6.68 CF) per unit. Stackable up to 4 high or side-by-side 18" apart. Gravel around at ~40% void.

# of Units

Gravel Ring (ft)

Gravel Below (ft)

Void Ratio

Stack Height (units)

Percolation

Perc Unit

Perc Rate

NDS EZflow French Drain

Bundle Size

Total Length (LF)

NDS StormChamber

Chamber Height

# Start

# Middle

# End

# Closed

ADS StormTech

Chamber Model

# of Chambers

Installed storage assumes 40% stone porosity per ADS specifications.

Outflow Pipe Sizing

Pipe Type

Slope (in/ft)

Selected Pipe

Outlet Control Structure

Orifice Type

Sharp-edged orifice in a thin plate is the standard assumption for most outlet control structures.

System Elevations

Grade at System Location

Finish Grade at System (ft)

Inlet Pipe — Farthest Inlet to System

Grade at Inlet (ft)

Min. Cover (ft)

Pipe Length (ft)

Min. System Cover (ft)

High Water Table

HWT Elevation (ft)

Outflow Destination

Outflow to Sewer

Sewer Invert (ft)

Pipe Length to Sewer (ft)

Results

These calculations provide preliminary estimates for stormwater management design. Verify all outputs against current adopted codes, local amendments, and project-specific conditions. This tool does not replace professional engineering analysis. Green Stories LLC is a building design and consulting firm. All projects requiring a licensed architect are completed in collaboration with registered design professionals.