BMP Training Module 2
Extended Wet Detention Basin
& Extended Detention Wetlands
Sponsored by: MARC
Presenters:
Andy Sauer...
Agenda
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
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8:30-9:20 Lecture 1: Overview of Extended Detention and Wetlands

Review Module 1 and WQv definit...
Best Management Practice
(BMP)






Best – State of the Practice
 No definitive answer
 Past experience, testing, re...
Basic BMP Principles


Plan for stormwater management






Mimic natural hydrology





Sustainable and “be green...
BMP Evaluation Process
PLAN
MIMIC
TREAT
Extended detention
(40 hours) to
increase treatment
and decrease peak
flows

A
TREAT

Detention and Treatment


Structural BMPs
detain runoff


Extended Detention
Basins
• Wet
• Dry







Extende...
Example site
l
ne
n
ha

C
in
Ma
Design Documents
e
i dg
Br

– APWA 5600
– BMP Manual
– Watershed
Master Plans

TREAT

Comm...
Structural BMP Consideration

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




Pollutant removal efficiency
Water quality volume
Site suitability
Tributa...
an
Qu

er

er

Aesthetics/Amenity

y
tit

W
at

at
W

Qu
ali
ty

BMP Evaluation
General Rule

A
BMP Manual

A
Post Development BMP
Selection

A
BMP Selection Flowchart
Level Of Service

BMP Value Rating

Water Quality
Volume/sizing

Placement,
maintenance
A
Water Quality Volume (WQv)


Water Quality Volume
(WQv): The storage needed
to capture and treat 90% of
the average annua...
Kansas City Water Quality
Storm
Young and McEnroe
(http://kcmetro.apwa.net)

Daily Precipitation (in)

A

2.
7

2.
5

2.
3...
Why Use the WQv to size
BMP?


Retain runoff long enough to get
water quality benefits



Reducing erosive flows from
sm...
Water Quality Volume
Calculation


Two methods


Short-Cut Method
•
•



Sites < 10 acres
Only 1 predominant cover type...
WQv Calculation


Short-Cut Method
WQv = P*Rv





P = 24 hour Water Quality Storm (inches)
Rv = Volumetric run coeffi...
WQv Calculation


Small Storm Hydrology Method
WQv = P*Weighted Rv





Weighted Rv = Σ(Rvi*Aci)/Total area (ac)
Rvi =...
Questions?

A
Why the term “Extended”
Detention?
Extended: Designed to release the WQv over a period
of 40 hours




Allows time for ...
Geomorphic Effects of
Uncontrolled Urban Runoff

A
Flow Frequency for
Detention
1000

Developed
Uncontrolled

7-yr
2/yr

6/yr

100

Flow

20/yr

10

Undeveloped

1

0.1
§

·...
40-Hour Drawdown Impacts
1000

Developed
Uncontrolled
100

Flow

0.80 psf
Developed
Controlled
10

0.26 psf

•10-year cont...
BMP Manual
Extended Detention


Water Quality (40-hr)


Pollutant removal through
• Settling
• Biological uptake (more f...
Extended Wet Detention Basin (EWDB)

A
EWDB Littoral Bench

Littoral
Bench

A
EWDB Littoral Bench


Provides water quality
treatment



Mild slope serves as
safety feature around
perimeter of perman...
EWDB Permanent Pool

A
EWDB Permanent Pool







Water quality volume
(WQv) mixes with
permanent pool
WQv released over 40
hours
Minimum de...
EWDB Outlet Structure





Release the WQv over a period of
40 hours
Protected by well screens, trash
racks or grates
...
Extended Detention

A
EWDB Vegetation






Upland area: Native
grasses (preferable) or
turf on berms and side
slopes
Littoral Zone: Native
w...
EWDB Siting Considerations






Off-line, outside of stream corridor
EWDBs can be located within larger flood
contro...
Questions on Extended Wet
Detention Basin (EWDB)?

A
Extended Detention Wetland (EDW)

A
EWD Permanent Pool

Permanent pool extends throughout wetland

A
Extended Detention Wetland
(EDW)
Forebay

A
EDW Forebay




Same function as
EWDB
Should hold at least
10% of the WQv
Separated from the
wetland by a earth
weir, g...
EDW Marsh

Marsh




Pollutant removal through plant root systems
Shallower than EWDB permanent pool
A
EDW Micropool
Micropool

Reverse slope pipe under the surface of the micropool is
used to prevent clogging

A
EDW Micropool





Prevents outlet clogging
Allows further settling of
sediment
Should have a capacity of
at least 10%...
EDW Outlet Structure, Outfall,
and Emergency Spillway

A
EDW Vegetation





Vegetation should cover 50-75% of surface area
3-5 native species are recommended
Select species b...
EDW Siting Considerations




Off-line, outside of stream corridor
Perform water budget analysis to ensure
permanent po...
Extended Wet Detention
versus
Extended Detention Wetlands
Similarities
 Water quality volume mixes with
permanent pool

...
Advantages
and
Disadvantages

A
EWDB Advantages


Settling of suspended
solids



Pollutant uptake by pond
vegetation



Flood control via peak
dischar...
EDW Advantages









Settling of suspended solids
Pollutant uptake by wetland
vegetation
Flood control via peak
...
EWDB Disadvantages


Potential safety concerns



Additional maintenance due to
sediment removal, floating
trash, scum, ...
EDW Disadvantages










Require more space, due
to shallower depth of
water storage
Additional maintenance
due to...
Questions?

Break 10 minute

A
Lecture 2
Design of EWDB  EDW


Discuss key design features



Introduce calculations for each major
component



Perfo...
Extended Wet Detention Basin
Key Design Features


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Water quality storage volume
Permanent pool
Outlet structures


...
Design Example

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26 acre drainage
Land use












1.6 acres of flat
roofs
8.8 acres of parking
lot
3.3 acres...
Water Quality Storage Volume

EWDB Design Procedure Form

i.
ii.

Tributary area = 26 acres
Calculate water quality storag...
Water Quality Storage Volume
ii.

Calculate Water Quality Storage
Volume (WQv)
Two methods


Short-Cut Method
•
•



Sit...
Water Quality Storage Volume
Short-Cut Method
WQv = P*Rv


P = 24 hour Water Quality Storm (inches)
P = 1.37 inches (Kans...
Water Quality Storage Volume

Small Storm Hydrology Method
WQv = (P)*(Weighted Rv)
Weighted Rv = Σ(Rvi*Aci)/Total area (ac...
Rv Table
TABLE 7
VOLUMETRIC COEFFICIENTS FOR URBAN RUNOFF FOR
DIRECTLY CONNECTED IMPERVIOUS AREAS
(CLAYTOR AND SCHUELER 19...
Water Quality Control Volume

Cover Type

Rv

Area (acres)

Flat roofs

0.87

1.6

Parking lots

0.98

8.8

Narrow streets...
Water Quality Storage Volume


Convert WQv from inches to ac-ft by converting
inches to feet and multiplying by the tribu...
Permanent Pool

Permanent Pool

A
Permanent Pool










Average pool depth 4 to
6 feet (not to exceed
12 feet)
A portion of the pool
must be at leas...
Permanent Pool Volume (Pv)
Method 1


Based on the time required for algae to uptake
sufficient phosphorous
VP1 = (C * AT...
Permanent Pool Volume (Pv)
Method 2


Based on the time required for suspended
solids to settle
VP2 = (VB/VR * SD * Ai) /...
Permanent Pool Volume (Pv)
Method 1
Kansas City
From APWA section 5602.3
= 0.3+0.6*.53
= (0.6*26*2.2)/12

A
Permanent Pool Volume (Pv)
Method 2
~93%

VB/R=5
Figure 24

A
Permanent Pool Volume (Pv)
Method 2

5.0

Kansas City

0.6
13.7

= (5.0*0.6*13.7)/12

3.43

Correction: Step 1 should refe...
Permanent Pool Volume (Pv)

= 3.43*1.20

1.
2.
3.

Use the larger volume calculated in the
previous steps and add 20% for ...
Outlet Structure

Single Orifice

V-notch Wei

Perforated Riser or Plate

A
Outlet Structure




Outlet sized to release
WQv (ac-ft) within 40
hours
Locate outlet as far
away from inlet as
possibl...
Single Orifice Outlet

A
Single Orifice Outlet
i.

Depth of water quality volume at outlet (ZWQ)
ZWQ = 3 feet

ii.

Average head of WQv over invert...
Single Orifice Outlet

= 0.5*3.0ft
= (1.62*43,560)/(40*3600)

A
Single Orifice Outlet
iv. Set orifice coefficient
(Co) depending on
orifice plate thickness
u

u
u

Do must be greater tha...
Single Orifice Outlet
v.

Orifice diameter (Do) must be greater than 4
inches, otherwise use weir or riser

Do = 12 * 2 * ...
Single Orifice Outlet

Do=12*2*(0.49/(0.66*π*(2*32.2*1.5)0.5))0.5
A
Perforated Riser or Plate
Outlet

Photo taken by Larry Roesner

Photo taken by Larry Roesner

A
Perforated Riser or Plate
Outlet

A
Perforated Riser or Plate
Outlet


Calculate outlet area per row of
perforations (Ao)
Ao (in2) = WQv / (0.013 * ZWQ2 + 0....
Perforated Riser or Plate
Outlet
3.0

2.4

= 1.62/(0.013*3.02+0.22*3.0–0.1)

1.75

= (4*2.4/π)1/2

1
1.75
NA

9

A
Perforated Riser or Plate
Outlet


Use number of columns to determine exact
perforation diameter
Dperf = (4 / π * Ao / nc...
Perforated Riser or Plate
Outlet
3.0

2.4

= 1.62/(0.013*3.02+0.22*3.0–0.1)

1.75

= (4*2.4/π)1/2

1
1.75

= (4/π*2.4/1)1/...
V-Notch Weir Outlet

Dr. Robert Pitt

Source: Hubbard Brook LTER

A
V-Notch Weir Outlet

= 0.5*3.0ft
= (1.62*43,560)/(40*3600)

A
V-Notch Weir Outlet


Calculate required v-notch weir angle
(calculator in radians)
θ = 2 * (180 / π) * arctan (QWQ/(Cv *...
V-Notch Weir Outlet



If θ is 20º set θ to 20º



Calculate top width of v-notch weir
(WV)

θ

Wv = 2 * ZWQ * Tan (θ / ...
V-Notch Weir Outlet

= 2*(180/π)*arctan(0.49/(2.5*1.55/2))
= 2*3.0*tan(8º/2)


Since θ  20º set θ to 20º

A
Pool Shape

W

3W

A
Water Budget





Recommended to
ensure permanent
pool
Chapter 13 the
NRCS Engineering
Hand Book

∆storage
= Qin − Qout
...
Forebay



Volume (VolFB) should be at least 10% of WQv



Depth (ZFB) should be at least 3feet



Sides and bottom pav...
Forebay

= 0.10*1.62
= 0.16/3.0

Topeka KS

A
Littoral Bench







Serves as a planting
surface and safety
feature around
perimeter of permanent
pool
25% to 50% of...
Littoral Bench

Width of Littoral Bench (WLB):

WLB

A LB ( 43,560 )
=
A Pool ( 43,560 )
2π
π
A
Littoral Bench

Min=0.25*0.82, Max=0.5*0.82
Min= (0.21*43560)/(2π*(0.82*43560/ π)1/2)
Between WLBMin and WLBMax

A
Vegetation








Plant berms and
sloped areas with
native grasses
Littoral bench should
be planted with native
wetla...
Questions?

A
Extended Detention Wetland
Key Design Features


Permanent
pool









Low marsh
High marsh
Forebay
Micropool

O...
Extended Detention Wetland
Permanent Pool Volume


Use Method 1 or Method 2 – same as in Extended
Wet Detention Basin Des...
Extended Detention Wetland
(EDW)

0-6 in

4-6 ft
4-6 ft
6-18 in

A
Permanent Pool
Design Volume Allocations

20%

20%

20%
40%

A
Permanent Pool
Design Volume Allocations

= 4.1*0.2
= 4.1*0.2
= 4.1*0.4
= 4.1*0.2

A
Forebay Considerations


Pre-sedimentation at entry to EDW




Capacity to contain 5 years of
sediment

Separated from ...
EDW Forebay



Use VForebay from step II and SAForebay from step III to
find forebay depth (ZForebay)
ZForebay = VForebay...
EDW Forebay

A
Micropool Considerations




Prevents clogging of outlet
4-6 feet deep
Should be surrounded by a safety shelf

A
EDW Micropool



Using the same method used to calculate the
forebay:
ZMicropool = VMicropool/SAMicrpool



Depth should...
EDW
Water Quality Outlet


Depth of water quality volume above permanent
pool






Consider survivability of plant s...
Shape
Flowpath length (L) to permanent pool width (W)
ratio must be greater than 3:1
 Place berms or high marsh wedges at...
Vegetation


Wetland vegetation should occupy 50-75% of surface
area



Develop a landscaping plan, which places appropr...
Questions?
15 minute break

A
Design Activity

UMKC Rain Garden Project

A
Activity
Design an extended wet detention basin to capture
runoff from a 42 acre drainage area with mixed land
use. Size t...
Activity - Design an EWDB

A
Activity Results

A
Lecture 3
Other Consideration




Vegetation
Operations and maintenance
Implementation






Planning
Design
Constr...
Vegetation




Process

Design

Review

Standards

Construction

Adaptive Management 
Maintenance
Buy-in

Project ...
Vegetation



Use plants listed in the BMP Manual Appendix A
“Recommended Plant Materials for BMPs”
Narrow down from thi...
Vegetation


Narrow down from this list by (cont):


Speaking with local nursery or botanists
•
•
•



What plants are ...
Wetland Species

A
Nuisance Species

A
Nuisance Species

A
Native versus Non-native
Plants


Native plants are
recommended
 Larger root system

Increase infiltration

More droug...
Native Plants-Advantages and
Disadvantages
Advantages
 Indigenous to the area and able to thrive in the local climate wit...
Vegetation – Design
Consideration










Local and regional planning initiatives
Public involvement/public rel...
Vegetation Resources
http://plants.usda.gov






Appendix A in the MARC BMP manual
Local nurseries
www.kansasnativepl...
Other Sources


Tallgrass Restoration Handbook for Prairies Savannas and
Woodlands (Packard  Mutel, 1997)



The Nationa...
Vegetation Examples


Banks


Butterfly Milkweed,
Asclepias tuberosa

Clarence A. Rechenthin @ USDA-NRCS PLANTS Database...
Vegetation – Other Design
Consideration


Setting





Built Environment







Urban
Rural
Commercial
Residentia...
Vegetation – Installation 
Maintenance




Installation

Oversight

Contractor Experience

Plant availability
Mainten...
General Maintenance








Event Inspection ( 0.5 inches)

Inspect facility operation, especially outlet structure
...
Other Maintenance
Consideration







Maintenance access - 15
feet wide strip around
the perimeter of the site
May n...
Designer
Review Team

Planning Phase
– Environmental Site
Assessment
– Select Post
Construction BMPs
– Flood Control Study...
Upcoming Training Sessions


Module #3 – Rain Gardens  Bioretention





Date: January 23, 2009
Location: Helzberg Aud...
Questions?
Comments.
Suggestions.

A
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MARC BMP Manual Training Module 2

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  • Green to gray?
  • Best Management Practices (BMPs) is a familiar term we use when talking about water quality, NPDES Phase II permits, and education to the public. We all have are own understanding of the term and use it maybe more than we should and too often forget the true meaning and intent of the acronym. The action word in the acronym is PRACTICE. Practice if you go to a dictionary is defined as to carry out, apply, or to do or perform often. Therefore what should w carry out regularly (often) to improvement water quality in our region? This and other BMP manuals often focus on the actions that are BEST not the ones that should be perform regularly. Therefore this primer is a discussion on what we should do regularly to improve water quality. Other items in this manual will focus on specific structural practices that can be implement for a specific site. This section will focus on regular practices that should be consider as key part in a stormwater management program to improve water quality.
  • Add pic of wqv
  • Add a pic or figure of settling cross-section
  • Picture
  • Picture
  • Split up and use same figures as eddb
  • Picture
  • Changed tile from “Extended wet detention BMPs”
  • Bad standing water pic
  • Pic of dead plants or dry basin
  • PIC
  • This slide is not finished last two bullets have XXXX
  • Added method description
  • Added method description
  • Changed fish statement
  • Changed fish statement
  • Photos need permission to be used
  • Same as single orifice
  • Same as single orifice
  • For larger Zwq values the angle is over the table, the angle doesn’t change that much with the range of Cv values
  • For larger Zwq values the angle is over the table, the angle doesn’t change that much with the range of Cv values
  • Added chart
  • MARC BMP Manual Training Module 2

    1. 1. BMP Training Module 2 Extended Wet Detention Basin & Extended Detention Wetlands Sponsored by: MARC Presenters: Andy Sauer, P.E. (CDM) Natalie Postel, P.E. (CDM) December 12, 2008 A
    2. 2. Agenda        8:30-9:20 Lecture 1: Overview of Extended Detention and Wetlands  Review Module 1 and WQv definition  Define “Extended Detention”  Define Extended Wet Detention and Extended Detention Wetlands 10 minute break 9:30-10:30 Lecture 2: Design Examples  Extended Wet Detention Basin  Extended Detention Wetland 15 minute break 10:45 – 11:30 Design Activity 11:30 – 11:45 Design Activity Results 11:45 – 12:00 Lecture 3: Other considerations  Implementation  Operations and maintenance  Vegetation  Lessons learned A
    3. 3. Best Management Practice (BMP)    Best – State of the Practice  No definitive answer  Past experience, testing, research,  Unique to site Management – Responsible Parties  Improve water quality, meet NPDES Phase II  Jurisdictional specific  Meet specific requirements of a regional Practice – Action or Implementation  Practice = defined to carry out, apply, or to do or perform often. A
    4. 4. Basic BMP Principles  Plan for stormwater management     Mimic natural hydrology    Sustainable and “be green” Provide a level of service Improve water quality Increase initial abstraction Promote infiltration, retention & ET “Treat” the stormwater runoff   Natural processes Treatment trains A
    5. 5. BMP Evaluation Process PLAN MIMIC TREAT Extended detention (40 hours) to increase treatment and decrease peak flows A
    6. 6. TREAT Detention and Treatment  Structural BMPs detain runoff  Extended Detention Basins • Wet • Dry    Extended Detention Wetlands Infiltration basins Typically used as larger, centralized facilities Topeka KS A
    7. 7. Example site l ne n ha C in Ma Design Documents e i dg Br – APWA 5600 – BMP Manual – Watershed Master Plans TREAT Commercial Building BioFilters Wet Pond Grass Swale Streambank Biostabilization Culvert Roa d w ay A
    8. 8. Structural BMP Consideration          Pollutant removal efficiency Water quality volume Site suitability Tributary area Dimensions (depth, length-width ratio) Outlet Emergency spillway Maintenance easement Routine and non-routine maintenance A
    9. 9. an Qu er er Aesthetics/Amenity y tit W at at W Qu ali ty BMP Evaluation General Rule A
    10. 10. BMP Manual A
    11. 11. Post Development BMP Selection A
    12. 12. BMP Selection Flowchart Level Of Service BMP Value Rating Water Quality Volume/sizing Placement, maintenance A
    13. 13. Water Quality Volume (WQv)  Water Quality Volume (WQv): The storage needed to capture and treat 90% of the average annual storm runoff volume  Water Quality Storm: The storm event that produces ≤ 90% volume of all daily storms in a year  WQv Extended detention and wetlands sizing is based on the WQv A
    14. 14. Kansas City Water Quality Storm Young and McEnroe (http://kcmetro.apwa.net) Daily Precipitation (in) A 2. 7 2. 5 2. 3 1. 9 2. 1 1. 5 1. 7 1. 1 1. 3 0. 5 0. 7 0. 9 45 40 35 30 25 20 15 10 5 0 0. 1 0. 3 Water Quality Storm = 1.37 in # of days > or= 2003 Kansas City Precip events
    15. 15. Why Use the WQv to size BMP?  Retain runoff long enough to get water quality benefits  Reducing erosive flows from smaller runoff events A
    16. 16. Water Quality Volume Calculation  Two methods  Short-Cut Method • •  Sites < 10 acres Only 1 predominant cover type Small Storm Hydrology Method • Larger or more heterogeneous drainage areas A
    17. 17. WQv Calculation  Short-Cut Method WQv = P*Rv    P = 24 hour Water Quality Storm (inches) Rv = Volumetric run coefficient = 0.05+0.009(I) I = % site Imperviousness A
    18. 18. WQv Calculation  Small Storm Hydrology Method WQv = P*Weighted Rv    Weighted Rv = Σ(Rvi*Aci)/Total area (ac) Rvi = Volumetric runoff coefficient for cover type (table) Aci = Area of cover type i (ac) A
    19. 19. Questions? A
    20. 20. Why the term “Extended” Detention? Extended: Designed to release the WQv over a period of 40 hours    Allows time for more particles and associated pollutants to settle out Reduces the downstream velocity and erosive conditions More closely imitates natural release rates and duration A
    21. 21. Geomorphic Effects of Uncontrolled Urban Runoff A
    22. 22. Flow Frequency for Detention 1000 Developed Uncontrolled 7-yr 2/yr 6/yr 100 Flow 20/yr 10 Undeveloped 1 0.1 § · q· more frequent than 1-yr B 1-yr 2-yr Storm Return Interval Ú 10-yr 100-yr y· A
    23. 23. 40-Hour Drawdown Impacts 1000 Developed Uncontrolled 100 Flow 0.80 psf Developed Controlled 10 0.26 psf •10-year control •1-year control •WQv – extended detention with 40 hr drawdown 1 Undeveloped 0.1 0.01 0.1 more frequent than 1-yr 1 1-yr 2-yr Storm Return Interval 10 10-yr 100 100-yr A
    24. 24. BMP Manual Extended Detention  Water Quality (40-hr)  Pollutant removal through • Settling • Biological uptake (more for wetland) • Permanent Pool • WQv = Volume above the permanent pool  Stream Sustainability (40-hr)   Mimic undeveloped conditions for full range of hydrology Can meet flood control objectives A
    25. 25. Extended Wet Detention Basin (EWDB) A
    26. 26. EWDB Littoral Bench Littoral Bench A
    27. 27. EWDB Littoral Bench  Provides water quality treatment  Mild slope serves as safety feature around perimeter of permanent pool  25% to 50% of permanent pool surface area  Helps control geese access Topeka, KS A
    28. 28. EWDB Permanent Pool A
    29. 29. EWDB Permanent Pool      Water quality volume (WQv) mixes with permanent pool WQv released over 40 hours Minimum depth of 6-ft Residence time of 14 days Significantly more water quality benefit than EDDB Topeka, KS A
    30. 30. EWDB Outlet Structure     Release the WQv over a period of 40 hours Protected by well screens, trash racks or grates Located as far from inlet as possible Various outlet structure options    Single Orifice Perforated Riser or Plate V-notch Weir Source: Hubbard Brook LTER A
    31. 31. Extended Detention A
    32. 32. EWDB Vegetation    Upland area: Native grasses (preferable) or turf on berms and side slopes Littoral Zone: Native wetland species Recommend 3-5 native species Kansas City, MO Soft Rush, Juncus effusus A
    33. 33. EWDB Siting Considerations      Off-line, outside of stream corridor EWDBs can be located within larger flood control facilities Minimum 20 feet setback Not on fill sites or steep slopes (unless enhanced) Use fences and landscaping to impede access areas to address public safety concerns  Outflow structure shall be fenced A
    34. 34. Questions on Extended Wet Detention Basin (EWDB)? A
    35. 35. Extended Detention Wetland (EDW) A
    36. 36. EWD Permanent Pool Permanent pool extends throughout wetland A
    37. 37. Extended Detention Wetland (EDW) Forebay A
    38. 38. EDW Forebay    Same function as EWDB Should hold at least 10% of the WQv Separated from the wetland by a earth weir, gabion or loose riprap wall Topeka, KS A
    39. 39. EDW Marsh Marsh   Pollutant removal through plant root systems Shallower than EWDB permanent pool A
    40. 40. EDW Micropool Micropool Reverse slope pipe under the surface of the micropool is used to prevent clogging A
    41. 41. EDW Micropool     Prevents outlet clogging Allows further settling of sediment Should have a capacity of at least 10% of WQv Surrounded with a safety bench A
    42. 42. EDW Outlet Structure, Outfall, and Emergency Spillway A
    43. 43. EDW Vegetation     Vegetation should cover 50-75% of surface area 3-5 native species are recommended Select species based on stress tolerance and ability to handle variations in water availability Consult local experts Lenexa, KS Topeka, KS Topeka, KS A
    44. 44. EDW Siting Considerations    Off-line, outside of stream corridor Perform water budget analysis to ensure permanent pool Soils should be suited for wetland species    Hydric soils with high phosphorous affinity Not on fill sites or steep slopes (unless enhanced) Use fences and landscaping to impede access areas of public safety concern  Outflow structure shall be fenced A
    45. 45. Extended Wet Detention versus Extended Detention Wetlands Similarities  Water quality volume mixes with permanent pool  40 hour drawdown of water quality volume (WQv) Differences  Depth of permanent pool (18 inches in wetland vs. 6 to 12 feet in basin)  Vegetation types and planting configurations A
    46. 46. Advantages and Disadvantages A
    47. 47. EWDB Advantages  Settling of suspended solids  Pollutant uptake by pond vegetation  Flood control via peak discharge attenuation  Control of channel erosion by reducing downstream flow velocities  Creation of wildlife habitat  Recreational and aesthetic benefits Topeka, KS A
    48. 48. EDW Advantages        Settling of suspended solids Pollutant uptake by wetland vegetation Flood control via peak discharge attenuation Control of channel erosion by reducing downstream flow velocities Creation of wildlife and aquatic habitats Recreational and aesthetic benefits Some groundwater recharge A
    49. 49. EWDB Disadvantages  Potential safety concerns  Additional maintenance due to sediment removal, floating trash, scum, and algal blooms  Potential odor problems  Need conditions to sustain permanent pool  Resident waterfowl can become a source of fecal coliform and nutrients  Vector issues may result in additional maintenance requirements A
    50. 50. EDW Disadvantages      Require more space, due to shallower depth of water storage Additional maintenance due to vegetation overgrowth Requires larger drainage area to sustain permanent pool Vector issues can result in increased maintenance requirements Site limitations in urban areas A
    51. 51. Questions? Break 10 minute A
    52. 52. Lecture 2 Design of EWDB EDW  Discuss key design features  Introduce calculations for each major component  Perform example calculations A
    53. 53. Extended Wet Detention Basin Key Design Features    Water quality storage volume Permanent pool Outlet structures         Orifice Perforated riser or plate V-notch weir Pool shape Basin shape Forebay Littoral bench Vegetation Topeka, KS A
    54. 54. Design Example   26 acre drainage Land use       1.6 acres of flat roofs 8.8 acres of parking lot 3.3 acres of narrow streets 12.3 acres of silty soil 53 % impervious Outlet Structure designed for 40 hour release of WQv New Development Site A
    55. 55. Water Quality Storage Volume EWDB Design Procedure Form i. ii. Tributary area = 26 acres Calculate water quality storage volume A
    56. 56. Water Quality Storage Volume ii. Calculate Water Quality Storage Volume (WQv) Two methods  Short-Cut Method • •  Sites 10 acres Only 1 predominant cover type Small Storm Hydrology Method • Larger or more heterogeneous drainage areas A
    57. 57. Water Quality Storage Volume Short-Cut Method WQv = P*Rv  P = 24 hour Water Quality Storm (inches) P = 1.37 inches (Kansas City)   Rv = Volumetric run coefficient = 0.05+0.009(I) I = % site imperviousness A
    58. 58. Water Quality Storage Volume Small Storm Hydrology Method WQv = (P)*(Weighted Rv) Weighted Rv = Σ(Rvi*Aci)/Total area (ac) • • Rvi = Volumetric runoff coefficient for cover type (table) Aci = Area of cover type i (ac) A
    59. 59. Rv Table TABLE 7 VOLUMETRIC COEFFICIENTS FOR URBAN RUNOFF FOR DIRECTLY CONNECTED IMPERVIOUS AREAS (CLAYTOR AND SCHUELER 1996) Rainfall (inches) Flat roofs and large unpaved parking lots Pitched roofs and large impervious areas (large parking lots) Small impervious areas and narrow streets Silty soils HSG-B Clayey soils HSG-C and D 0.75 0.82 0.97 0.66 0.11 0.20 1.00 0.84 0.97 0.70 0.11 0.21 1.25 0.86 0.98 0.74 0.13 0.22 1.37 0.87 0.98 0.75 0.14 0.23 1.50 0.88 0.99 0.77 0.15 0.24 Note: a reduction factor may be applied to the Rv values for disconnected surfaces, consult the BMP hydrology section A
    60. 60. Water Quality Control Volume Cover Type Rv Area (acres) Flat roofs 0.87 1.6 Parking lots 0.98 8.8 Narrow streets 0.75 3.3 Silty soil 0.14 12.3 Rvi × Aci WQv = ∑ ×P= Total Area ∑ ( .87 × 1.6 + .98 × 8.8 + .75 × 3.3 + .14 × 12.3) × 1.37 = 0.749in 26 A
    61. 61. Water Quality Storage Volume  Convert WQv from inches to ac-ft by converting inches to feet and multiplying by the tributary area = (0.749in)*(1ft/12in)*26ac A
    62. 62. Permanent Pool Permanent Pool A
    63. 63. Permanent Pool      Average pool depth 4 to 6 feet (not to exceed 12 feet) A portion of the pool must be at least 10 feet if the pool is to contain fish At least 5.5 acres of tributary area per ac-ft of permanent pool At least 10.3 acres of tributary area per acre of pool surface area 14 day residence time A
    64. 64. Permanent Pool Volume (Pv) Method 1  Based on the time required for algae to uptake sufficient phosphorous VP1 = (C * AT * R14) / 12     C = Runoff coefficient = 0.3 +0.6*I or APWA section 5602.3 I = Fraction of impervious area R14 = 14-day wet season rainfall At = total tributary acreage A
    65. 65. Permanent Pool Volume (Pv) Method 2  Based on the time required for suspended solids to settle VP2 = (VB/VR * SD * Ai) / 12    VB/VR = ratio of design water quality volume to runoff volume (should be at least 4 for adequate TSS removal) SD = mean storm depth Ai = impervious tributary acreage A
    66. 66. Permanent Pool Volume (Pv) Method 1 Kansas City From APWA section 5602.3 = 0.3+0.6*.53 = (0.6*26*2.2)/12 A
    67. 67. Permanent Pool Volume (Pv) Method 2 ~93% VB/R=5 Figure 24 A
    68. 68. Permanent Pool Volume (Pv) Method 2 5.0 Kansas City 0.6 13.7 = (5.0*0.6*13.7)/12 3.43 Correction: Step 1 should refer to Figure 24 A
    69. 69. Permanent Pool Volume (Pv) = 3.43*1.20 1. 2. 3. Use the larger volume calculated in the previous steps and add 20% for sedimentation Average pool depth: 4 to 6ft Surface area = VP / ZP A
    70. 70. Outlet Structure Single Orifice V-notch Wei Perforated Riser or Plate A
    71. 71. Outlet Structure   Outlet sized to release WQv (ac-ft) within 40 hours Locate outlet as far away from inlet as possible    Avoid short-circuiting The facility must bypass 1% storm event Provide at least 1ft of freeboard above WQV stage A
    72. 72. Single Orifice Outlet A
    73. 73. Single Orifice Outlet i. Depth of water quality volume at outlet (ZWQ) ZWQ = 3 feet ii. Average head of WQv over invert of orifice, HWQ (ft) HWQ = 0.5*ZWQ iii. Average water quality outflow rate, QWQ (cfs) QWQ = (WQV * 43,560) / (40 * 3,600) A
    74. 74. Single Orifice Outlet = 0.5*3.0ft = (1.62*43,560)/(40*3600) A
    75. 75. Single Orifice Outlet iv. Set orifice coefficient (Co) depending on orifice plate thickness u u u Do must be greater than 4 inches in the following step C0 = 0.66 if plate thickness is Do C0 = 0.80 if Do A
    76. 76. Single Orifice Outlet v. Orifice diameter (Do) must be greater than 4 inches, otherwise use weir or riser Do = 12 * 2 * QWQ / Co * π * ( 2 * g * HWQ ) g=32.2 ft/sec2 π = 3.14 A
    77. 77. Single Orifice Outlet Do=12*2*(0.49/(0.66*π*(2*32.2*1.5)0.5))0.5 A
    78. 78. Perforated Riser or Plate Outlet Photo taken by Larry Roesner Photo taken by Larry Roesner A
    79. 79. Perforated Riser or Plate Outlet A
    80. 80. Perforated Riser or Plate Outlet  Calculate outlet area per row of perforations (Ao) Ao (in2) = WQv / (0.013 * ZWQ2 + 0.22 * ZWQ – 0.1)  Assuming a single column, calculate the diameter of a single perforation for each row D1 = (4 * Ao / π)1/2  If D1 is greater than 2 inches add more columns nc = 4 A
    81. 81. Perforated Riser or Plate Outlet 3.0 2.4 = 1.62/(0.013*3.02+0.22*3.0–0.1) 1.75 = (4*2.4/π)1/2 1 1.75 NA 9 A
    82. 82. Perforated Riser or Plate Outlet  Use number of columns to determine exact perforation diameter Dperf = (4 / π * Ao / nc)1/2  Using a 4” center to center vertical spacing and ZWQ, determine number of rows (nv) nv = ZWQ / 4 nv = 5 A
    83. 83. Perforated Riser or Plate Outlet 3.0 2.4 = 1.62/(0.013*3.02+0.22*3.0–0.1) 1.75 = (4*2.4/π)1/2 1 1.75 = (4/π*2.4/1)1/2 = (ZWQ*12in)/4 NA 9 A
    84. 84. V-Notch Weir Outlet Dr. Robert Pitt Source: Hubbard Brook LTER A
    85. 85. V-Notch Weir Outlet = 0.5*3.0ft = (1.62*43,560)/(40*3600) A
    86. 86. V-Notch Weir Outlet  Calculate required v-notch weir angle (calculator in radians) θ = 2 * (180 / π) * arctan (QWQ/(Cv * HWQ5/2)) CV = V-notch weir coefficient = 2.5 If calculator is set to degrees use θ = 2* arctan (QWQ/(Cv * HWQ5/2)) θ Source: Hubbard Brook LTER A
    87. 87. V-Notch Weir Outlet  If θ is 20º set θ to 20º  Calculate top width of v-notch weir (WV) θ Wv = 2 * ZWQ * Tan (θ / 2) Source: Hubbard Brook LTER A
    88. 88. V-Notch Weir Outlet = 2*(180/π)*arctan(0.49/(2.5*1.55/2)) = 2*3.0*tan(8º/2)  Since θ 20º set θ to 20º A
    89. 89. Pool Shape W 3W A
    90. 90. Water Budget   Recommended to ensure permanent pool Chapter 13 the NRCS Engineering Hand Book ∆storage = Qin − Qout ∆time A
    91. 91. Forebay  Volume (VolFB) should be at least 10% of WQv  Depth (ZFB) should be at least 3feet  Sides and bottom paved or hardened Surface area (AFB):  AFB = VolFB / ZFB A
    92. 92. Forebay = 0.10*1.62 = 0.16/3.0 Topeka KS A
    93. 93. Littoral Bench     Serves as a planting surface and safety feature around perimeter of permanent pool 25% to 50% of permanent pool surface area At least 10 feet wide with a max slope of 6:1 6 to 12 inches below permanent pool water surface A
    94. 94. Littoral Bench Width of Littoral Bench (WLB): WLB A LB ( 43,560 ) = A Pool ( 43,560 ) 2π π A
    95. 95. Littoral Bench Min=0.25*0.82, Max=0.5*0.82 Min= (0.21*43560)/(2π*(0.82*43560/ π)1/2) Between WLBMin and WLBMax A
    96. 96. Vegetation     Plant berms and sloped areas with native grasses Littoral bench should be planted with native wetland species Plant trees and shrubs around perimeter of site Appendix A in BMP manual A
    97. 97. Questions? A
    98. 98. Extended Detention Wetland Key Design Features  Permanent pool        Low marsh High marsh Forebay Micropool Outlet structure Water budget Wetland shape A
    99. 99. Extended Detention Wetland Permanent Pool Volume  Use Method 1 or Method 2 – same as in Extended Wet Detention Basin Design  Choose larger volume as permanent pool volume. A
    100. 100. Extended Detention Wetland (EDW) 0-6 in 4-6 ft 4-6 ft 6-18 in A
    101. 101. Permanent Pool Design Volume Allocations 20% 20% 20% 40% A
    102. 102. Permanent Pool Design Volume Allocations = 4.1*0.2 = 4.1*0.2 = 4.1*0.4 = 4.1*0.2 A
    103. 103. Forebay Considerations  Pre-sedimentation at entry to EDW   Capacity to contain 5 years of sediment Separated from EDW with berm, gabion, or riprap A
    104. 104. EDW Forebay  Use VForebay from step II and SAForebay from step III to find forebay depth (ZForebay) ZForebay = VForebay/SAForebay  Depth should be 4-6feet A
    105. 105. EDW Forebay A
    106. 106. Micropool Considerations    Prevents clogging of outlet 4-6 feet deep Should be surrounded by a safety shelf A
    107. 107. EDW Micropool  Using the same method used to calculate the forebay: ZMicropool = VMicropool/SAMicrpool  Depth should be 4 to 6 feet  Safety bench should be ≥ 12 feet A
    108. 108. EDW Water Quality Outlet  Depth of water quality volume above permanent pool     Consider survivability of plant species Maximum depth should be 2 feet or less Single Orifice, Orifice Plate or Standpipe, and Vnotch outlet examples in Manual Sized for 40 hour drawdown A
    109. 109. Shape Flowpath length (L) to permanent pool width (W) ratio must be greater than 3:1  Place berms or high marsh wedges at 50-foot intervals perpendicular to the flow direction to increase dry weather flowpath length  Wedge-shaped, narrowest at the inlet and widest at the outlet  L W A
    110. 110. Vegetation  Wetland vegetation should occupy 50-75% of surface area  Develop a landscaping plan, which places appropriate species in each EDW zone and the surrounding area  For plantings, use soil from an existing wetland or a designed wetland planting mix Kansas City, MO A
    111. 111. Questions? 15 minute break A
    112. 112. Design Activity UMKC Rain Garden Project A
    113. 113. Activity Design an extended wet detention basin to capture runoff from a 42 acre drainage area with mixed land use. Size the permanent pool and WQv of the basin using a v-notch outlet structure that will release the WQv over a period of 40 hours. A
    114. 114. Activity - Design an EWDB A
    115. 115. Activity Results A
    116. 116. Lecture 3 Other Consideration    Vegetation Operations and maintenance Implementation     Planning Design Construction Lesson’s learned A
    117. 117. Vegetation   Process  Design  Review  Standards  Construction  Adaptive Management Maintenance Buy-in  Project Sponsor  Public/Stakeholders   Education  Aesthetics  Establishment  Benefits and challenges Success  Realistic A
    118. 118. Vegetation   Use plants listed in the BMP Manual Appendix A “Recommended Plant Materials for BMPs” Narrow down from this list by:  Treatment only, habitat creation / biodiversity, aesthetics? • If treatment is most important, then a wetland seed mix may be sufficient. • If habitat creation and biodiversity is desired, specific species with habitat benefits are recommended  Evaluating site conditions - soil quality, climate, wetness, pollution • Hardier plants would work better in areas with poorer site conditions A
    119. 119. Vegetation  Narrow down from this list by (cont):  Speaking with local nursery or botanists • • •  What plants are available for purchase? Which plants have the best survivability? Which plants would be best candidates for wet areas, variable moisture, poor soils, etc.? Visit at natural wetland in the area • What plants are naturally favored in local area? • Are there specific invasive species that need to be managed?  Check municipal codes to ensure all plant materials are approved for the area A
    120. 120. Wetland Species A
    121. 121. Nuisance Species A
    122. 122. Nuisance Species A
    123. 123. Native versus Non-native Plants  Native plants are recommended  Larger root system  Increase infiltration  More drought tolerant  Disease resistant  Adapted to environment A
    124. 124. Native Plants-Advantages and Disadvantages Advantages  Indigenous to the area and able to thrive in the local climate with less maintenance.  Deep roots enhance stormwater infiltration into the soil.  Able to withstand flooding events as well as extended dry periods.  Reduces flow velocity of stormwater runoff.  Wide range of application (restoration of native prairie, woodland, wetlands, riparian areas)  Attracts wildlife and improves biological diversity.  Requires little to no fertilizer or chemical maintenance  Requires less water to survive.  Provides attractive and natural vegetative scenery. Disadvantages  Can be difficult to establish if some circumstances.  Can be expenses if planted from nursery stock plugs.  Can be considered “weedy” by some people. A
    125. 125. Vegetation – Design Consideration          Local and regional planning initiatives Public involvement/public relations Visibility-Aesthetics Height of vegetation Financial (funding source, budget, property values) Regulatory requirements Function/risk Utility-stormwater management Recreation A
    126. 126. Vegetation Resources http://plants.usda.gov     Appendix A in the MARC BMP manual Local nurseries www.kansasnativeplantsociety.org www.grownative.org A
    127. 127. Other Sources  Tallgrass Restoration Handbook for Prairies Savannas and Woodlands (Packard Mutel, 1997)  The National List of Plant Species that Occur in WetlandsRegion 3 (USFWS, 1988)  The Flora of Missouri (Steyermark, 1963; 1996)  Steyermark’s Flora of Missouri, Volume I, II,…; Yatskeievych; 1999…)  The Flora of the Great Plains (McGregor et. al.)  Ecologist; Landscape Architect A
    128. 128. Vegetation Examples  Banks  Butterfly Milkweed, Asclepias tuberosa Clarence A. Rechenthin @ USDA-NRCS PLANTS Database  Littoral Bench  Blunt Spikerush, Eleocharis obtusa Robert H. Mohlenbrock @ USDA-NRCS PLANTS Database A
    129. 129. Vegetation – Other Design Consideration  Setting    Built Environment      Urban Rural Commercial Residential Mixed Use Stormwater Utility – Stormwater Management Recreation CONTEXT A
    130. 130. Vegetation – Installation Maintenance   Installation  Oversight  Contractor Experience  Plant availability Maintenance Measures  Has a maintenance program/budget been established?  What type of adaptive management will be implemented? • Burning or mowing • Herbicides • Transplanting  Who will do the management-establishment? • Lawn maintenance crews • Native Landscape specialists A
    131. 131. General Maintenance     Event Inspection ( 0.5 inches)  Inspect facility operation, especially outlet structure  Remove trash debris  Document potential problems Monthly Inspection  Inspect repair erosion  Water plant material during dry periods (1st Year)  Perform routine plant maintenance (pruning, weeding, etc.) Semi-Annual Inspection  Remove and replace dead or diseased vegetation  Re-landscape/re-mulch any area areas Annual Inspection  Inspect inlet outlet structure condition  Record assessment of planted species evidence of invasive plant species  A Perform comprehensive safety inspection
    132. 132. Other Maintenance Consideration      Maintenance access - 15 feet wide strip around the perimeter of the site May need to harvest excess plants Erosion issues Sediment removal from forebay when 50% full Sediment removal from micropool and marsh area when 10 to 15% full A
    133. 133. Designer Review Team Planning Phase – Environmental Site Assessment – Select Post Construction BMPs – Flood Control Study – Establish Long-term Maintenance Agreements Plat Approval Planning Engineering Parks Recreation Environmental Specialists Attorney Design Phase – Erosion and sedimentation controls – Post-construction BMPs – Flood control improvements Building Permit Review Team Planning Engineering Code Compliance Inspectors Review Team Planning Engineering Parks Recreation Environmental Specialists Operations Maintenance Construction Phase – Inspect and maintain BMPs for construction activities – Construct Post Construction BMPs – Maintain agreements for post-construction BMPs Occupancy Permit
    134. 134. Upcoming Training Sessions  Module #3 – Rain Gardens Bioretention    Date: January 23, 2009 Location: Helzberg Auditorium, KCPL Module #4 – Extended Dry Detention Infiltration (Pervious Pavements)   Date: February 20, 2009 Location: Helzberg Auditorium, KCPL A
    135. 135. Questions? Comments. Suggestions. A

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