River Friendly Landscaping - UCANR
Transcript of River Friendly Landscaping - UCANR
River Friendly Landscaping Low Impact Development Stormwater Management:
Permeable Paving, Stormwater Swales and Detention Wetlands
Presented by:
Ed Armstrong, RLA
Foothill Associates
“...because we no longer traveled in the wilderness as a matter of course,
we forgot that wilderness still circumscribed civilization and persisted
in domesticity. We forgot, indeed, that the civilized and the domestic
continued to depend upon wilderness -- that is, upon natural forces
within the climate and within the soil that have never in any meaningful
sense been controlled or conquered. Modern civilization has been built
largely in this forgetfulness.”
Wendell Berry, The Unsettling of America
LID Techniques
• Permeable Paving
– Pavers
– Permeable Asphalt
– Permeable Concrete
• Stormwater Swales
• Detention Wetlands
Permeable Paving
Stormwater Management Objectives
• Retain/infiltrate
stormwater runoff
• Capture “First Flush”
(typ. first ½ inch of rainfall)
• Control specific pollutants & metals
• Reduce amount of impervious cover
• Capture high percentage of storms
Brian McThorn, Calstone & the Interlocking Concrete Pavement Industry (ICPI)
Basic Permeable Paver Components
(optional)
Benefits of Permeable Pavers
• Help meet national/state stormwater regulations
• Conserves space: Usable pavement above detention facility
• 100% runoff reduction for low intensity storms
• Filter and reduce pollutants & metals
• Increase groundwater recharge
• Lower peak flows = reduce downstream flooding & erosion
• Reduce runoff temperatures
• Can be visually attractive
• Paver patterns can direct traffic
• Relatively easy to repair
• Filters oil drippings & petroleum residue
Paver Types
• Interlocking shapes/patterns
Joint Spacing
Plastic joint spacers
Spacers integral to
pavers
• ADA Compliance: Joints ½” or Less
Infiltration Rates Surface, Joints & Bedding
• Open surface area: varies with paver design/ pattern - 6% to 18%
• Required infiltration rate of openings: – Design storm, inches per hr / 0.06
– Example: 2 inches per hr / 0.06
– Required infiltration rate = 33 in/hr
• Measured infiltration rate of stone in openings: 300 to 500 in/hr
• Assume 10% lifetime efficiency: 30 to 50 in./hr
Base Infiltration Rates Open-Graded Base
• Effective Base Infiltration Rate
• Similar to an infiltration trench design
• Open-graded base stores/releases water
• Initial rate: over 1000 in/hr
• Base infiltration slows over time from sediment
Base Storage Capacity
• Base materials – No. 57 (crushed stone base
1.5 – ⅛ in. aggregate)
– No. 2 (crushed stone subbase 2½ in. – ¾ in. agg. )
• 30% to 40% void space
• Quarry or lab provides % of voids - ASTM C 29
• 3 inches of base stores about 1 in. of water – 60’ x 100’ parking lot w/12” base stores ~ 15,000 gals
• Design for 24 hour storage
Base
Design Options
• Full infiltration – Base stores water & drains to soil
– For sandy soils, typical permeability of > 0.5 in./hr
– No perforated drain pipes at bottom of Base
– Drain pipes for saturated/overflow conditions
• Partial infiltration – an infiltration & detention facility – Base stores water… Some drains to soil, some to pipes at bottom of base
– Most common design approach
– Many soils handle some infiltration
• Detention only, no infiltration – Impermeable liner
– Base filters only and then drains through liner
– Drain pipes at bottom of base
– Conditions for use: • High water table
• High bedrock
• Over fill soils and expansive soils
Full Infiltration
Partial Infiltration
No Infiltration
Areas To Avoid
• Drinking water wells (100 ft. min. distance)
• High water tables (< 1 meter from surface)
• Industrial sites / Fueling stations
• Do not exceed 5% slope (1 – 2% optimum)
Design Steps
• Assess site and soil conditions
• Compute runoff from watershed
• Determine the depth of the base for storage
• Compute the maximum allowable base
depth for drainage in 24 hours
• Determine base thickness for traffic
Performance Monitoring
• Observation well at lowest point
• Min. 6 in. diameter perf pipe w/cap
• Monitor drainage rate, sediment, water
quality
Construction
Construction sequence:
1. Excavation & Sediment control
2. Soil subgrade compaction
3. Geotextile (or impermeable liner if no infiltration)
4. Drain pipes as required
5. Concrete curbs
6. Base installation – Max 4 in. lifts
7. Compaction: initial vibration, 10 T static roll
8. Bedding course: max. 2 in. thick (Geotextile under bedding course not recommended)
9. Pavers placed, joints filled, surface swept and compacted
10. Joints filled, surface swept, pavers compacted again
11. Remove excess stone
Sediment cannot
contaminate base materials!!
Installing Geotextile
Adding Base
Compacting Base
Installing Bedding Course
• Screeding bedding layer over stone base
Installing Pavers
• Edges cut, placed
then compacted
Compacting Pavers
Filling Joints
• Filling the openings with No. 9 stone before
second compaction
Excess stones removed, then final compaction
Maintenance
• Annual
– Inspection of observation well after
major storm, vacuum and sweep
surface – improves infiltration
• True vacuum sweeper
– Very powerful
– Restores clogged
surfaces
PICP Costs
• Assumptions:
– 80mm (3.2”) thick pavers
– 2 in. leveling course
– 12 in. open graded base
– 10,000+ sf
• $12 to $17/sf (Union / Prevailing wages)
• Larger projects may be mechanically installed to lower unit costs
Permeable Asphalt
University of New Hampshire,
Stormwater Center
SECTION FOR STORAGE & INFILTRATION
Permeable Asphalt
University of New Hampshire, Stormwater Center
SECTION WITH FILTER COURSE FOR WATER QUALITY
Permeable Asphalt
• Effectiveness
– Infiltration up to 80% of annual runoff (with proper installation and maintenance)
– Can remove between 65 and 85 percent of undissolved nutrients and up to 95% of sediment
Sierra College Boulevard @
Miner’s Ravine
Permeable Asphalt
• University of New Hampshire, Stormwater
Center research has found:
– Water quality performance is strong to
excellent, depending upon design
– Hydraulic performance is excellent
– Little removal of nitrogen
– No removal of many common ionic forms
Permeable Asphalt
Design Considerations:
• Soil permeability/infiltration rate – EPA recommends 0.5”/hour
– 0.1”/hour still OK
• Depth to bedrock > 2’
• Depth to high water > 3’
• Fill – not recommended
• Frost – Pavement section should exceed frost depth
• Slope – Limit surface slope to 5%
– Terrace when necessary
– Use conventional HMA for steeper slopes
Permeable Concrete
• Concrete with little or no sand and sufficient cementious material to bind aggregates.
• Contains 15% and 25% voids
• Can be used in most locations concrete pavement is used.
• Limitations:
– Less strength than standard concrete.
– Not for heavily travelled roadways due to surface raveling.
Permeable Concrete
• Effectiveness:
– Flow rates are
typically around 480
in./hr, although they
can be much higher.
From NPR’s Science Friday website
Permeable Asphalt and Concrete
Permeable Pavement Performance
Permeable Pavement Costs
• DMA $75-100/ton, PA $89-125/ton placed by machine for parking and
residential road and driveways (2009 costs)
• DMA $3,456/parking stall, PA $4,455/parking stall (2008 UNH installation)*
• PC costs approximately 18% greater than PA, 31% greater than DMA;
however, pervious concrete may last up to 40 years before requiring
resurfacing, whereas porous asphalt and conventional asphalt may need to be
replaced after 8 to 10 years*
• Complicated jobs with handwork are more expensive
• Costs offset by lack of stormwater infrastructure
• Cost break even is achieved when designing for quantity management ~Q10-
Q25
PA = Porous Asphalt, DMA = Dense-Mix Asphalt, PC = Permeable Concrete
*Source: Kristopher M. Houle, Master’s Thesis, Winter
Performance Assessment of Permeable Pavements,
University of New Hampshire
Permeable Pavement Maintenance
• PA: Use porous or dense asphalt for
patching
– If using dense, repair should not exceed 10% of
total porous pavement paved area
• Cracks can be repaired using crack sealant
• Regular cleaning
– Flush or jet wash
– Vacuum sweeping
Maintenance Effectiveness
Stormwater Swales
• Types:
– Cobbled or vegetated or both: vegetation adds
benefit of evapotranspiration & filtration, but
requires more maintenance & summertime
irrigation
– Detention or pass-through: defined by at-grade
vs. elevated outflow structure
• At grade can be curb-cut or catch basin grating
• Elevated is typically catch basin grating on riser
Swales
• Can be designed for full infiltration, partial retention or infiltration with subsurface drainage
• Inlet is usually curb cut or flush-curb street
• Carefully control inlet grade if curb-cut to avoid debris accumulation
Stormwater Swale Effectiveness
• Swales are most effective at removal of
Total Suspended Solids (TSS)
• Consider swales as an above-ground
stormwater conveyance system
• Reduce cost of below-ground infrastructure
as well as provide some filtering benefits
LID Effectiveness
Detention Wetlands
• Wetland vs. Basin
– Detention wetland is
meant to handle low-
flow, nuisance flow &
first-flush
– Detention basin is
designed to detain
large flows
Detention Wetland Effectiveness
• Wetlands are effective at removing bacteria, metals, organics, suspended sediment and phosphorus
• Wetlands are less effective at removing nitrogen or improving BOD
• NPS reductions*: – Suspended solids > 60%;
– Total nitrogen ~ 25 to 76%;
– Metals removal ~ variable, but lead generally shows at least 75% reduction; and
– Phosphorus removal ~ 30 to 90%, with an average of 50%
*http://www.water.ncsu.edu/watershedss/info/wetlands/manage.html#cons
Detention Wetlands Design Criteria
• Design for good mosquito management – Complex microtopography (also increases treatment effectiveness)
• Treatment distances of 60-120 feet or more
• Retention times of 5-20 days ideal
• 1 to 3 treatment cells
• Several small wetlands may be better than one large one
• Ideal proportions for stormwater retention are 50% shallow marsh, 30% deep marsh & 20% deep open-water
• Contaminant treatment wetlands should consist of 50-70% very shallow depths
Examples - Permeable Paving
Nevada Beach Day Use Area,
Roundhill, NV
Permeable Paving
Lowe’s Home Center Olympia, WA
Permeable Paving
Rio Vista Water
Plant, Santa
Clarita, CA
Auburn Streetscape,
Auburn, CA
Stormwater Swales
Stormwater Swales
Four Seasons, El Dorado Hills, CA
Stormwater Swales
South Sacramento
Community, CA
Stormwater Swales
Sunrise Boulevard Complete Streets,
Citrus Heights, CA
Tempo Park, Citrus Heights, CA
Stormwater Swales
Village Homes,
Davis
Detention Wetlands
Del Paso Regional Park,
Sacramento, CA
Detention Wetlands
Longview Oaks, Sacramento, CA
Detention Wetlands
Anatolia Preserve, Rancho Cordova, CA
Detention Wetlands
Laguna Stonelake, Elk Grove, CA
Additional Information
• Permeable Pavers: – Brian McThorn, consulting / installation, 209-786-8002 main/fax,
hardscapes101.com, [email protected]
• Permeable Asphalt: – http://www.coastal.ca.gov/nps/lid/Milar-
PorousAsphaltPavements.pdf
– http://www.unh.edu/unhsc/presentations
• Permeable Concrete: – http://www.perviouspavement.org/
• Swales & Detention Wetlands – Ed Armstrong, Foothill Associates, 916-435-1202,