Runoff calculation sheet (free)
- Drainage area and outlet
- Design storms and rainfall depths
- Soils and curve numbers
- Time of concentration
- Peak flows before and after
- Notes for the engineer of record
Small civil firms, surveyors and land planners
Where is the drainage area?
Free TR-55 and rational-method runoff sheet for a small site, with Atlas 14 rainfall and soil groups filled in. Your engineer checks and signs the design.
- Free to read
- No sign-up until the draft
- Hands off to the right door
ePlan fills in
- Design rainfall
- Soil groups
- Land cover
- Slope
How it works
Runoff calculation sheet, from one answer
- Pin the outlet and outline the drainage area.
- ePlan fills Atlas 14 rainfall, soil groups and land cover.
- Read the free calc sheet. Disturbing an acre or more? Start a SWPPP draft.
What you get
Runoff calculation sheet and 1 more document
The check is free. The paperwork after it is drafted at the SWPPP door.
Construction SWPPP
- Site and receiving water
- Erosion and sediment controls
- Inspections
From public data
What ePlan fills in, and from where
- Design rainfall depthsNOAA Atlas 14 (Precipitation Frequency Data Server)
- Hydrologic soil groupsUSDA NRCS Web Soil Survey (SSURGO)
- Land coverUSGS/MRLC National Land Cover Database
- Slope and flow pathsUSGS 3D Elevation Program
1 acre
of land disturbance is where federal construction stormwater permit coverage, and a SWPPP, starts
Source: 40 CFR 122.26(b)(15), eCFR
Ready for the paperwork?
Disturbing an acre or more? Answer four questions and get a site-specific SWPPP draft with BMPs, an inspection form and NOI notes. Free to read.
Questions
TR-55 Runoff Calculator: what people ask
Where do the design rainfall depths come from?
From NOAA Atlas 14 through NOAA's Precipitation Frequency Data Server, which gives precipitation frequency estimates for a point you pick on a state map.
When does a site need a construction stormwater permit?
When construction disturbs 1 acre or more, or less than 1 acre that is part of a larger common plan of development that will disturb 1 acre or more.
Do towns regulate runoff after construction?
Towns under a small MS4 permit must run a program for new development and redevelopment that disturbs 1 acre or more, using an ordinance or similar tool, and must ensure long-term operation and maintenance of the controls.
The rules this door follows
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Where is the construction site?
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What equipment are you qualifying?
Shops and contractors welding or cutting on site
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Where will the hot work happen?
Raw land and building lot buyers
Land Due Diligence Report
Which parcel are you thinking of buying?
Old-house buyers, historians and site researchers
Property history source list
What address do you want history for?
Contractors and owners · grading
Grading and erosion control plan
Where are you grading?
TR-55 Runoff Calculator: check it free
Answer it and ePlan opens the SWPPP door with your answer filled in.