River Friendly Landscaping

Transcription

1 River Friendly Landscaping Low Impact Development Stormwater Management: Permeable Paving, Stormwater Swales and Detention Wetlands Presented by: Ed Armstrong, RLA Foothill Associates

2 ...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

3 LID Techniques Permeable Paving Pavers Permeable Asphalt Permeable Concrete Stormwater Swales Detention Wetlands

4 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)

5 Basic Permeable Paver Components (optional)

6 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

7 Paver Types Interlocking shapes/patterns

8 Joint Spacing Plastic joint spacers ADA Compliance: Joints ½ or Less Spacers integral to pavers

9 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

10 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

11 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. ) Base 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

12 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

13 Full Infiltration

14 Partial Infiltration

15 No Infiltration

16 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)

17 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

18 Performance Monitoring Observation well at lowest point Min. 6 in. diameter perf pipe w/cap Monitor drainage rate, sediment, water quality

19 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 Sediment cannot contaminate base materials!! 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

20 Installing Geotextile

21 Adding Base

22 Compacting Base

23 Installing Bedding Course Screeding bedding layer over stone base

24 Installing Pavers Edges cut, placed then compacted

25 Compacting Pavers

26 Filling Joints Filling the openings with No. 9 stone before second compaction

27 Excess stones removed, then final compaction

28 Maintenance Annual Inspection of observation well after major storm, vacuum and sweep surface improves infiltration True vacuum sweeper Very powerful Restores clogged surfaces

29 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

30 Permeable Asphalt SECTION FOR STORAGE & INFILTRATION University of New Hampshire, Stormwater Center

31 Permeable Asphalt SECTION WITH FILTER COURSE FOR WATER QUALITY University of New Hampshire, Stormwater Center

32 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 Miner s Ravine

33 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

34 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

35 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.

36 Permeable Concrete Effectiveness: Flow rates are typically around 480 in./hr, although they can be much higher. From NPR s Science Friday website

37 Permeable Asphalt and Concrete

38 Permeable Pavement Performance

39 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 *Source: Kristopher M. Houle, Master s Thesis, Winter Performance Assessment of Permeable Pavements, University of New Hampshire PA = Porous Asphalt, DMA = Dense-Mix Asphalt, PC = Permeable Concrete

40 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

41 Maintenance Effectiveness

42 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

43 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

44 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

45 LID Effectiveness

46 Detention Wetlands Wetland vs. Basin Detention wetland is meant to handle lowflow, nuisance flow & first-flush Detention basin is designed to detain large flows

47 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% *

48 Detention Wetlands Design Criteria Design for good mosquito management Complex microtopography (also increases treatment effectiveness) Treatment distances of 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

49 Examples - Permeable Paving Nevada Beach Day Use Area, Roundhill, NV

50 Permeable Paving Lowe s Home Center Olympia, WA

51 Permeable Paving Rio Vista Water Plant, Santa Clarita, CA

52 Stormwater Swales Auburn Streetscape, Auburn, CA

53 Stormwater Swales Four Seasons, El Dorado Hills, CA

54 Stormwater Swales South Sacramento Community, CA

55 Stormwater Swales Tempo Park, Citrus Heights, CA Sunrise Boulevard Complete Streets, Citrus Heights, CA

56 Stormwater Swales Village Homes, Davis

57 Detention Wetlands Del Paso Regional Park, Sacramento, CA

58 Detention Wetlands Longview Oaks, Sacramento, CA

59 Detention Wetlands Anatolia Preserve, Rancho Cordova, CA

60 Detention Wetlands Laguna Stonelake, Elk Grove, CA

61 Additional Information Permeable Pavers: Brian McThorn, consulting / installation, main/fax, hardscapes101.com, brian@hardscapes101.com Permeable Asphalt: PorousAsphaltPavements.pdf Permeable Concrete: Swales & Detention Wetlands Ed Armstrong, Foothill Associates, , ed.armstrong@foothill.com