Driveway Paving

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Driveway Paving Runoff Conveyance
Jessica Schwing TRPA - Erosion Control
Team
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Why Pave Driveways Parking Areas?

• Compacted soil
• (soft coverage)
• Stormwater carries sediment to Lake
• Snow removal
• Dust Control

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Retrofit 1 Unpaved Driveway

• Review Site Evaluation
• Contact local jurisdiction or TRPA for allowable
  coverage
• County minimum is typically 400 ft2
• Select paving material
• Obtain permits
• paving
• encroachment

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Permitting Process
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Local Rules Regulations

• All roads, driveways and parking areas
  
• must be paved with an approved material.

• No private property runoff can flow into the
  street.
• Know jurisdictions requirements.

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Permitting Process for Unpaved Driveways

• Determine how much you are going to pave
• Site Evaluation Prescribes BMPs, NOT Coverage
• Site Assessment - Verifies Coverage

This is not a permit!
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Once you know how much you are paving. . .

• You need TWO Permits
• Local Jurisdiction Encroachment Permit
• TRPA Paving Permits

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Two Possible TRPA Permits

• Paving Permit
• Can be issued by Jurisdictions
• 237 fee
• Will not verify coverage may need site
  assessment

• BMP Retrofit Permit
• Issued by TRPA
• Free
• Verifies driveway coverage only
• Will only allow paving of reasonable area

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What type of material is right for your property?

• Cost
• Aesthetics
• Maintenance Commitment

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Asphalt

• Lower cost
• Standard grading
• Quick installation
• Oil based product
• Maintenance intensive
• Easily formed (swales)

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Concrete

• More durable than asphalt
• Less maintenance
• Less temperature fluctuation than asphalt
• Inert material
• Color texture choice

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Paving Stones

• Not 100 infiltration
• Compacted and/or pervious base
• Many styles colors
• Considered hard coverage
• Typically not allowed in public rights-of-way
• Tough to plow

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Pervious Concrete

• As durable as standard concrete
• Allows water to pass through
• ¾ crushed gravel base for drainage
• Works better on flat sites
• Many colors textures
• Allows roots to breathe
• Limited testing in Tahoe Basin
• Maintenance intensive

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Driveway Design Elements
1. Capture 2. Convey 3.
Infiltrate
1. Capture 2. Convey 3.
Infiltrate
1. Capture
3. Infiltrate
2. Convey
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Basic driveway BMP Grading is Everything!
Grade towards infiltration system
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Grade towards infiltration system
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Swale
Grade towards infiltration system
?
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Driveway Infiltration Trench
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Retrofit 2 Existing Paved Driveway
You must capture, convey infiltrate the volume
of a 20 yr / 1 hr. storm onsite
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Driveway Conveyance Structures

• Often needed to capture divert runoff for
  infiltration
• Source Control
• Placed at right-of-way
• Should NOT direct runoff to street
• Must direct runoff to infiltration system

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Types of Conveyance Structures

• Slotted Channel Drain

Swale
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Slotted Channel Drain

• Grated structure
• Flush with driveway
• Effective on steep driveways
• Good for snow removal
• Requires Removable grates for maintenance
• Pre-sloped
• Higher cost

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Slotted Channel Drain - Schematic
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Installing a Slotted Channel Drain

• Step 1 Plan where to install channel drain
• Note Should be as close to right-of-way as
  possible

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Installing a Slotted Channel Drain

• Step 2 Cut and Remove Existing Asphalt

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Installing a Slotted Channel Drain

• Step 3 Excavate material, hang slotted channel
  drain and form for concrete

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Installing a Slotted Channel Drain

• Step 4 Pour a minimum of 4 of concrete around
  channel drain and finish

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Install a Sediment Trap for easy maintenance
Sediment Traps are REQUIRED!
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Whats Missing?
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We Do Not Recommend Slotted Drains Without
Removable Grates

• They are difficult to maintain

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Asphalt/Cement Swale

• Linear depression or Vee channel
• Not effective on steep driveways (over 5)
• Installed at an angle (Not perpendicular to flow)
• Must be wide and shallow
• Less expensive
• Snow removal difficult if improperly installed

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How to Install a Swale

• Select swale location
• Plan infiltration system
• Remove existing asphalt
• Grade compact area for swale shape and constant
  slope
• Pour asphalt or concrete and finish

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Remember the Infiltration System

• Required at outflow of conveyance structure
• Infiltrate runoff onsite
• Flat area preferable
• Placed downslope of conveyance structure

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Parking Barriers

• Prevent vehicular access to unpaved areas
• Examples Natural vegetation, large boulders,
  posts, fences, bollards

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Are you building a slotted drain to nowhere?
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Difficult DrivewaysChallenging to Retrofit
Consult with local professionals
Due to

• Retaining walls
• Steep slopes
• Boulders
• Vegetation/trees
• Underground utilities
• Limited infiltration area
• Structures

Slotted channel drain
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Retaining wall, stairs and slopes limited
treatment area
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Limited infiltration areas
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Steep Slope
?
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Retrofit Options for Difficult Driveways Get
Creative!

• Break up the flow
• Reduce coverage
• Re-slope the driveway
• Install sub-pavement infiltration system
• Work with an adjacent landowner or municipality
• Install pervious concrete driveway

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Remove asphalt to install sub-pavement
infiltration system
Dont forget to install a clean out!
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Install drywell and stabilize slope above
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Slotted Channel Drain with Elbow Pipe Conveying
Runoff to Drywell
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Common Installation Mistakes

• The devil is in the details
• Ensure grades are correct
• Design for functionality
• Design for durability
• Design for ease of maintenance

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Missing or Insufficient Parking Barriers
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Pervious Strips are Not Recommended
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Cold Patch Berms Do Not Work!
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Commercial Industrial Parking Areas
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BMPs for Commercial Parking Areas The Solutions

• Better site design innovative planning
• Reduce coverage
• Vegetated Detention Basins
• Mechanical Treatment Systems (sand/oil
  separators)
• Source Control
• Good Housekeeping Practices
• Maintenance of BMPs
• Monitoring

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Maintenance of Parking Area BMPs

• Source Control consistent with Living with Fire
  is 1
• Visually check BMPs often
• Sweep parking lots
• Clean out basins drop inlets

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Questions?