Infiltration System Design and Installation

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Infiltration SystemsComponents of Installation
Presented by Eben Swain Resource
Conservationist Tahoe Resource Conservation
District
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Overview

• Chapter 4
• Background
• Conveyance Systems
• Infiltration Techniques
• Common Systems
• Installation and you!
• Maintenance

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Conveyance Systems

• Convey runoff to infiltration system
• Good building practice to convey concentrated
  runoff at least 10 feet away from foundation
• Gutter downspouts, valleys
• 2 slope needed to move water

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Mistakes in the Field
Borders blocking the conveyance of runoff
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Function of Infiltration Systems

• Slow Runoff
• Maximize storm water infiltration
• Collect and Convey Runoff
• Provide Runoff Retention.
• Easy to Maintain

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Infiltration Techniques

• Spread runoff across vegetated areas on property
• Infiltrate into an area armored by drain rock
• Underground storage and infiltration
• Above ground storage and infiltration

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Common Infiltration Systems

• Underground
• Infiltration Trenches
• Infiltration Systems
• Prefabricated or Drain Rock
• (aka drywells, gravel pits)
• Above Ground
• Relatively Flat Vegetated areas
• Infiltration Basins
• Rock lined or Vegetated
• (aka mini basins, retention areas)
• Drain Rock Armoring
• Berms

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Infiltration Systems Locations

• Under roof drip lines
• Under gutter downspouts
• Armoring under open elevated structures
• decks, stairs, walkways
• Adjacent to parking areas
• At the end of conveyance structures

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How to Install .

• Infiltration Systems (aka Drywells, Pits)
• Drain rock filled
• Prefabricated
• Drip Line Infiltration Trenches
• Drain Rock Armoring
• Infiltration Basins
• Rock lined / Vegetated swales (aka dry creek
  beds, mini basins, retention areas)
• Level Spreader

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Infiltration DrywellsStart to Finish
Step 1 Step 2 Step 3
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Filter Fabric (Geo-textile)
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Filter Fabric
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Sediment Traps

• Sediment Traps
• Are made up of several components
• and come in a variety of sizes and materials
• Allows for periodic clean out and
• removal of debris
• Will greatly reduce maintenance
• of infiltration system
• Are required!!

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Sediment Traps
Conveyance system directs water through a
sediment trap and into adjacent infiltration
system
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Prefabricated Infiltration Systems

• 7.Insert Units
• 8.Install Borders
• 9.Backfill with drain rock

Prepare Pit
Prep Units
Install System

• Dig Hole
• Level Bottom
• Install 2 -3 drain rock

4. Stack Rainstores 5. Attach Tendrain 6. Wrap
or Place Filter Fabric
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Prefabricated Infiltration SystemsRainstore
Arrangement and Associated Capacities
Storage capacity based on rapid soil
permeability 40.6 cubic feet
Rainstore units alongside driveway
Storage capacity based on rapid soil
permeability 28.6 cubic feet
Rainstore units under lawn
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Drip Line Infiltration Trenches (Components)
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Drip Line Infiltration Trenches (Installation
Guidelines)
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Drip Line Infiltration Trenches
Stabilize Excavated soil on property
Border required to reduce Maintenance
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Drip Line Infiltration Trenches
Extend Treatment under Roof Valleys
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Drip Line Armoring
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Vegetation Under Drip Lines

• Use of vegetation is dependent on
• soil characteristics
• available space

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Level Spreader
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Infiltration On Steep Slopes(Baffled Systems)

• Install filter fabric, border system according to
  appropriate dimensions
• Baffles set at 90 degree angle, perpendicular to
  system
• System is backfilled with drainrock and
  maintained as necessary

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Infiltration On Steep Slopes(Rip Rap and Native
Materials)

• Use drain rock in conjunction with rip rap
  applications
• Use rip rap as alternative to terracing
• systems on steep slopes
• Apply low fire risk native or adapted seed
• to the slope prior to rock placement

• Use native materials found on site for
• Border materials
• Slope Stabilization
• Armoring

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Infiltration On Steep Slopes(Terracing)
( gt 15 slope, install riprap or subsurface drain
to convey runoff )
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Infiltration On Steep Slopes(Terracing)
No terraces (Conveyance only)
Terraces
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Elevated Structures

• Helps to control wind and water erosion
• Border system for containment and
• to exclude encroaching sediment/debris
• Finish grade should be 6 below
• wood siding to maintain wood/earth separation

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Elevated Structures
Jog border around footprint of elevated structure
Combination of drain rock armor and vegetation
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Swales and Basins(Rock Lined)

• Construction of rock lined swales should
• Be installed at a 21 ratio
• Have level bottom to ensure
• even water spreading
• Created along contour of slope
• Incorporate rock armored spillway
• for potential overflow

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Swales and Basins(Vegetated)

• Construction of vegetated swales should
• Be well irrigated to establish vegetation
• Have level bottom to ensure
• even water spreading
• Created along contour of slope
• Be at least 2wide at bottom of swale if
  
  area is
  expected to be mowed

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Subsurface Conveyance Systems
Subsurface conveyance should be used if
Space is limited
Uphill slope directs water to
foundation Site conditions
allow for natural infiltration
rather then excavation of soil

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Subsurface Conveyance Systems
Steep slope leading to structure will mean it is
necessary to convey water to more appropriate
area.
Perforated pipe incorporated into trench
backfilled with drainrock
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Berms
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Site Constraints

• Proximity to Stream Environment Zone (SEZ)
• High Ground Water
• Depth to Bedrock
• Utility Placement
• Retaining Structures
• Property Boundaries
• Encroachment Permit
• Steep slopes / Cut banks
• Tree roots/Large boulders

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Maintenance Recommendations Requirements

• Underground vs. Above Ground Systems
• Install soil stabilization BMPs
• Filter Fabric
• Borders
• Sediment Traps/Clean out devices

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System Maintenance

• Test system for capability
• Remove sediment by sifting drain rock
• Place sediments removed from system on property
  and stabilize with veg/mulch
• Replace or clean filter fabric
• Replace washed drain rock into system

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Thank You