11/21/2007
1
Michael Dietz, Ph.D.Assistant Professor/Extension Specialist in Sustainable Living
Utah State University
November 16, 2007Harvesting Water in the Landscape: Implementing Low Impact Development
University of Nevade Cooperative ExtensionReno, NV
Point Source PollutionPoint Source Pollution
11/21/2007
3
Polluted Runoff is the #1 Water Quality Problem in the U.S.*
Polluted Runoff is the #1 Water Quality Problem in the U.S.*
* USEPA* USEPA
INTENSITY OF LAND USEINTENSITY OF LAND USEINTENSITY OF LAND USEINTENSITY OF LAND USEINTENSITY OF LAND USEINTENSITY OF LAND USEINTENSITY OF LAND USEINTENSITY OF LAND USE
WATER QWATER Q UANTITY/QUALITY PROBLEMSUANTITY/QUALITY PROBLEMSWATER QWATER Q UANTITY/QUALITY PROBLEMSUANTITY/QUALITY PROBLEMS
Amount of IMPERVIOUS SURFACESAmount of IMPERVIOUS SURFACESAmount of IMPERVIOUS SURFACESAmount of IMPERVIOUS SURFACES
11/21/2007
4
8080
7070
6060
5050
4040
3030 DEGRADED
HED
IM
PERV
IOU
SNES
SH
ED I
MPE
RVIO
USN
ESS
(%)
(%)
ADAPTED FROM SCHUELER, ET. AL., 1992
2020
1010
00
STREAM IMPACTSTREAM IMPACT
WAT
ERSH
WAT
ERSH
PROTECTED
IMPACTED
Low Impact Development (LID) Site Planning and Design Concepts
□ The Goal: To preserve pre-development □ The Goal: To preserve pre development hydrology □ Runoff volume and rate□ Groundwater recharge□ Stream baseflow□ Runoff water quality□ Runoff water quality
11/21/2007
5
…”so our biggest problem is water supply…”
Supply is a bigger issue in arid climates, but nonpoint pollution still is a problem and LID can help maintain pollution still is a problem, and LID can help maintain supply
Bioretention/Rain Gardens
Ponding area
Flow entrance
Ponding area
Overflow pathSoil, mulch and plants
Vegetated areas designed to infiltrate and process stormwater
11/21/2007
6
Bioretention/Rain Gardens
Rain Garden, Glen Brook Green, Waterford, CTRain Garden, Glen Brook Green, Waterford, CT
Rain Garden, Suburban MarylandRain Garden, Suburban Maryland
11/21/2007
8
I filt t d Infiltrated 99% of roof runoff!!
Bark mulchlayer
Bark mulchlayer
Flow entrance Overflow
2.5 cm roundstone w/ pea gravel blanket
Perforatedunder-drain
Bioretention soil mixture
2.5 cm roundstone w/ pea gravel blanket
Perforatedunder-drain
Bioretention soil mixture
8-10” of crushed stone (1-2”)
Dddd d d
11/21/2007
9
Underdrain (not always necessary) and stonenecessary) and stone
Typically 4” corrugated, perforated black pipe surrounded by crushed stone, run out to grade or connected to catch basin
Avoid geotextile fabric!!Avoid geotextile fabric!!
Commercial applications‐usually engineered systems
Prince George’s County, MD
Wisconsin design manual
UConn design manual**Geared towards homeowners**
11/21/2007
10
More than 10 feet from foundation with basementAvoid placing over septic system or close to wellAvoid placing in wet areas of yard‐don’t forget, a
rain garden IS NOT a water garden!Site to most effectively catch storm runoffC id flConsider overflow
11/21/2007
11
Avoid areas with:Shallow (<3 feet) depth to bedrockSeasonal high water table
Be aware of the infiltration capacity of native soilssoils
UnderdrainOnly necessary in some situations
Quick percolation testDig hole 6 inches deep, and fill with water.Ideally, infiltration rate should be more than 1 inch per hourIf there is still water in the hole after 24 hours, the site is not suitable for a rain garden
*S i l t f t ti*Special note for new construction…Soil compaction is common
11/21/2007
12
50‐60% sand20 30% topsoil 20‐30% topsoil
Low clay content20‐30% leaf compost
Low phosphorus
Sandy loam, loamy sand, loam soils usually OK as is
Source: The Bioretention Manual (PGC, 2002)
Calculate area of roof feeding to garden
30 ft
50 feet
11/21/2007
13
50 feet x 30 feet = 1500 square feet1500 feet / 2 = 750 square feet
This is because only half the roof contributes to the garden750 square feet / 6 = 125 square feet
This just sizes the garden to hold 1 inch of water from the roof in a 6 inch deep rain gardenp g
In the East and Midwest, 90% of storms are 1” or less
Wisconsin design guide
UConn design guide
11/21/2007
14
Precipitation Frequency Estimates (inches)Precipitation Frequency Estimates (inches)
ARI* 5 10 15 30 60 120 3 6 12 24 48 4 7 10 20 30 45 60
(years) min min min min min min hr hr hr hr hr day day day day day day day
1 0.09 0.13 0.16 0.22 0.27 0.36 0.43 0.58 0.73 0.89 1.05 1.22 1.43 1.58 1.87 2.09 2.48 2.82
2 0.11 0.16 0.2 0.27 0.33 0.45 0.53 0.73 0.92 1.11 1.32 1.54 1.81 2.01 2.37 2.65 3.15 3.59
5 0.14 0.22 0.27 0.36 0.45 0.57 0.67 0.9 1.16 1.42 1.68 1.98 2.33 2.6 3.06 3.4 4.04 4.6
10 0.18 0.27 0.33 0.45 0.55 0.68 0.77 1.03 1.35 1.66 1.97 2.34 2.75 3.06 3.58 3.98 4.7 5.32
25 0.23 0.35 0.44 0.59 0.73 0.84 0.91 1.2 1.58 2 2.38 2.84 3.34 3.7 4.28 4.74 5.56 6.22
50 0.28 0.43 0.53 0.71 0.88 0.97 1.02 1.32 1.76 2.27 2.7 3.25 3.81 4.2 4.81 5.32 6.19 6.87
100 0.34 0.52 0.64 0.86 1.07 1.13 1.17 1.44 1.94 2.55 3.04 3.67 4.3 4.72 5.36 5.91 6.81 7.48
200 0.41 0.63 0.78 1.05 1.29 1.32 1.35 1.57 2.12 2.84 3.39 4.12 4.82 5.25 5.9 6.49 7.41 8.04
500 0.53 0.8 0.99 1.34 1.66 1.7 1.71 1.76 2.36 3.24 3.88 4.76 5.54 5.98 6.63 7.26 8.17 8.74
1000 0.63 0.96 1.19 1.6 1.98 2.04 2.06 2.08 2.54 3.55 4.27 5.27 6.12 6.55 7.17 7.85 8.71 9.2
From: http://hdsc.nws.noaa.gov/hdsc/pfds/index.html
1.80
2.00
Days with precipitation, Reno, NV, 1977-2007
0.80
1.00
1.20
1.40
1.60
80
ecip
itatio
n (in
ches
)
0.00
0.20
0.40
0.60
0 10 20 30 40 50 60 70 80 90 100
Pre
1-Probability of Exceedance
11/21/2007
15
Not necessary to use 1” storage sizeNot necessary to use 1” storage size
Size rain garden to contain ½ inch of runoffCut previous size calculation in half, so instead of 125 ft2, make it 63 ft2
If soils are slow to infiltrate, make the garden bigger or reduce the area of roof that contributes to the garden
125 square feetGarden can be shaped in a variety of waysGarden can be shaped in a variety of ways
10’10’
12.5’12.5’
10
11/21/2007
16
Call hotline to locate underground utilitiesCall hotline to locate underground utilities
Smaller gardens can be dug by hand (friends+beer=rain garden), or equipment can be rented for larger gardens
Mark area to be dug
Dig out 8‐9 inches of il k i th b tt soil, keeping the bottom
fairly levelA string or board can be used as a guideBerm the bottom end, if necessaryP id d l l t Provide a gradual slope to the sides
11/21/2007
17
Avoid compaction/sealing of bottom with bucket
AVOID COMPACTION!!!Compacted soil will causea rain garden to fail
11/21/2007
18
SOIL COMPACTION before, during construction
Make sure flow paths and storage areas are properly constructed (per plan details)properly constructed (per plan details)
11/21/2007
19
Don’t allow runoff from an open, unstabilized construction site to enter the garden
Surface of garden will become clogged
Make sure storage depth is correct at installation
11/21/2007
20
“Over‐Engineering”
See the UConn or WI publications for a plants to publications for a plants to use in Midwest or East
USU Extension plant list
Apply about 3 inches of pp y 3shredded hardwood mulch (not pine bark‐it floats)
11/21/2007
21
Has open flow paths, overflow and an d t l i d t g ( l )adequately sized storage area (per plan)Has proper materials installed (per plan)Has NON‐COMPACTED soils!Is only used after the surrounding site is
stabilizedHas proper plantings/ground coverHas a provision for short term care
(watering), and in arid climates irrigation
11/21/2007
22
Similar to other landscaped areasSimilar to other landscaped areasYearly mulch, if desiredPrune plants, if desiredIrrigate/water as necessary
MOST IMPORTANTLY: Maintain flow paths and storage areastorage area