Storm Water Management Overview

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Storm Water Management Overview

• Carrie Larson

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Overview

• History of project
• Location
• Development
• Engineering
• Solution

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History

• Minor Subdivision 1980s
• Minor Subdivision 1998
• Major Commercial Subdivision 2006
• Survey
• Preliminary Design
• Preliminary Approval
• Final submittal (DEQ MDT)
• November 2006

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Location
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Major Subdivision
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Development of Project

• Road Design
• Utilities
• Storm Water Management
• Lot Layout

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DEQ Permit

• DEQ Circular 8
• Pre-development Post-development runoff
• 2 year, 1 hour storm
• Flood Irrigated farmland pre-development
• Evapotranspiration rate?
• Runoff from irrigation gtgt DEQ Storm

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Highway Permits

• Very strict with runoff
• Prove irrigation runoff gtgt storm event
• Find management for storm event to minimize
  highway collection
• Deny pre-existing irrigation ditch
• Not on legal survey

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Drainage Map
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Development

• DEQ submittal numbers
• QCiA
• Runoff 0.36 in/hr x 14.69 acres x 1
• Q 5.28 ac-in/hr
• V1hr 0.44 ac-ft 19,200 ft3

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Development

• MDT Submittal Numbers
• Convince DOT that flood irrigation numbers are
  reasonable.
• Use AGRIMET archives and FIRI for data

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Data Development
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Problem Development

• The FIRI computer program was developed by the
  USDA Natural Resource Conservation Service
  (NRCS) to analyze irrigation information.
• Using the FIRI computer program, a seasonal
  efficiency for flood irrigation for the project
  site was determined to be approximately 21 which
  fits within the range of efficiency values (18
  to 30) provided by the local NRCS Office. A 21
  efficiency, therefore, gives an average yearly
  runoff for the site of approximately 23 inches.

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Analysis Comparison

• 28.1 ac-ft gtgt 0.44 ac-ft

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Engineering Solution

• Even with supporting data, DEQ/DOT will not let
  us get away with no storm water management on
  site
• Use first minor subdivision boundary and drain
  into existing outlet
• Crowned Roads
• Pipe Network
• Sediment/Detention Basin

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Drainage (Roads Minor Subdivision Boundary)
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Pipe Network Plan
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Pipe Network Profile
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Major Sediment Basin
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Minor Sediment Basins

• Try to eliminate these with irrigation argument

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Submittal

• Sent to MDT
• Want a traffic study before giving approach
  permits
• Success with irrigation argument!
• DEQ Engineering Report never submitted
• Available upon request
• Never know their response

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Questions?