Bob Spencer Seattle Public Utilities wwwseattlegovutilgreeninfrastructure wwwseattlegovutilRainWise SPUs CSO System 87 outfalls 300 overflows per year on average for 20102011 ID: 186071
Download Presentation The PPT/PDF document "Detention Cisterns for CSO Control" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Detention Cisterns for CSO Control
Bob SpencerSeattle Public Utilitieswww.seattle.gov/util/greeninfrastructure www.seattle.gov/util/RainWise Slide2
SPU’s CSO System
87 outfalls 300 overflows per year on average for 2010-2011134 million gallons into Seattle lakes, streams, and Puget Sound 2Slide3
Realtime CSO website
Long Term Control Plan SiteRainWise Home PageRainWise Tools
Seattle Public Utilities
3Slide4
What is
RainWise
?
General technical
information
Rebates for property owners in target CSO basins Slide5
The Rain Wise Toolbox
Rainfall:
- slow it
- spread it
- filter it
- soak it in.Slide6
6
RainWise Eligible BasinsTilDecember 2016Slide7
Locating and Planning Cistern Installations
for Stormwater Management
Downspout
Screened inlet
Overflow
Drain to garden hose
For more information,
see the Cistern factsheet and other resources at
www.seattle.gov/util/rainwise
Slide8
Seattle Public Utilities
8Is this a good site for a cistern? A cistern installation needs:
A level location
near a downspout, outside (not inside building)
A solid base
(6” of packed 3/8 crushed rock)
To allow ingress and egress for people
Don’t block doors, windows, vents, or utilities accesses
A safe place to
discharge the overflow
, a
minimum
of:
5 feet from your home (with no basement)
10 feet from your home, if you have a basement
5 feet from a property line, and 10 feet from neighboring buildings
or
connect overflow to sewer
(requires side sewer permit – call DPD at # on
RainWise
factsheet)Slide9
Constructing Cistern Installations
for Stormwater Management
www.seattle.gov/util/rainwise
Downspout
Screened inlet
Overflow
Lowflow
orificeSlide10
Example
Cistern LayoutFollow manufacturer’s instructions!
Gutter
(ideally with leaf screens)
Downspout
Self-cleaning leaf filter
Screened inlet
Finer screens keep
more dirt out.
Overflow
–
3-4 inch pipe, with ”P” trap
Cistern
– typically heavy plastic or fiberglass
Disperse overflow into landscape
A
minimum of:
- 5 ft. from house, or 10 ft. with basement
- 5 ft. from property line,
- 10 ft. from neighboring buildings
Level foundation
– 6 inches of packed 3/8” crushed rock, or concrete block, over packed subsoil
Drain
– 3/4 inch pipe with faucet
Connect garden hose to drain to
yard in winter. Close faucet in May
to store water for summer.
screen
Cleanout plug
(3 to 4 inch diameter)
Clean tank annually by squirting hose into inlet and cleanout, and scrubbing with long-handled brush.Slide11
Seattle Public Utilities
11What makes a cistern work for storm water detention?
The “low-flow orifice” In this case, a faucet that’s left open October-May,
to allow tank to drain out between storm events, so there’s space to store and slowly release the next rainfall.
Cisterns must have a ¼-inch orifice plumbed to the landscape or sewer.
For non-rebate homeowner projects,
a faucet & garden hose works fine.
If the cistern is full when it rains hard,
it provides
no
stormwater
benefit
–
it must be able to drain between storms.Slide12
Low-flow orifice plumbing for Code-permitted cisterns (example from Lakewood project)
Seattle Public Utilities12Slide13
Seattle Public Utilities
13Slide14
Modeling % Reduction for Rebate Value
Seattle Public Utilities14Slide15
15
Step 1: Build a level foundation to support a cistern full of waterExcavate topsoil at least 3 inches: create hard a level surface – don’t place on un-compacted fill
Pack subsoil with hand tamper or mechanical compactorPlace a level foundation:
Ground-contact-treated lumber box, filled with 6 inches of 3/8 crushed rock,
well compacted
. May top with 1 inch of sand or fine gravel to get smooth
level
surface under cistern.
Concrete blocks or heavy (min. 3-inch thick) pavers – perfectly level on top
Existing concrete pad, if level.
(Installing a new concrete pad
would require a building permit.)Slide16
Seattle Public Utilities
16Slide17
Seattle Public Utilities
17Slide18
Seattle Public Utilities
18Step 2: Place cistern tankDon’t block opening of doors & windows, emergency egress, vents, utilities access, etc.
Plan for downspout flow to cistern, and overflow routing Consider appearance and consult neighbors
Follow manufacturer’s instructions
If the tank is taller than it is wide,
secure for earthquake safety
(usually impractical, so best
not to use tall, narrow tanks)
Downspout
Screened inlet
Overflow
Drain to garden hoseSlide19
Seattle Public Utilities
19Connect additional tanks, if usedSlide20
Seattle Public Utilities
20Step 3: Install screened inlet,to keep debris and mosquitoes outAt minimum, wrap and secure
aluminum screen over inlet opening Additional protection against clogging:
Gutter screens and wire cages in
gutter outlets to exclude leaves
Self-cleaning leaf excluder in
downspout run to cistern – commercially available or home- assembled – Google “Downspout filters, screens”
Divert dirtier initial flow after dry period: Google “First flush diverters” “Roof washers” or “Cistern Installation” for ideasSlide21
Seattle Public Utilities
21Slide22
Seattle Public Utilities
22Slide23
Seattle Public Utilities
23Slide24
Seattle Public Utilities
24Step 4: Make gutter connections3-4” Aluminum, ABS, or PVC NDS pipeSecure all connections with stainless
steel screws & silicone seal, or glueStrap & support as needed
May put a self-cleaning leaf excluder
in line: typically a sloped screen so
leaves are pushed aside
Arrange so water falls into screened inlet,
with access to clean screenSlide25
Seattle Public Utilities
25Step 5: Install overflow pipe that’s as big as the inlet pipe
Watertight bulkhead fitting at top, or internal overflow riser, or both (if less that 3 inch)
Must be big enough to carry full gutter flow once cistern fills –
Install “P” trap somewhere, to prevent mosquito and rat entrySlide26
Seattle Public Utilities
26Step 6: Extend overflow pipe to a safe discharge point
5’ from house or 10’ if basement5’ from property line, 10’ from neighboring buildings
Rubber “hubless” unions protect against breakage, allow maintenance
Use rocks or gravel to
prevent erosion and
disperse overflow into
landscape
If reconnected
to sewer,
requires a permit
– call DPDSlide27
Seattle Public Utilities
27Slide28
Seattle Public Utilities
28Slide29
Seattle Public Utilities
29Consider appearance
Can screen cistern with fencing, latticework, cedar or bamboo wrap, etc.
Plastic paint works on ABS & PVC pipe
Blend with existing architectural finishes
Consult with neighbors
South Seattle Community College cistern
overflowing to rain garden in a downpour, Nov. 2009Slide30
Seattle Public Utilities
30Slide31
Seattle Public Utilities
31Slide32
Seattle Public Utilities
32Slide33
Seattle Public Utilities
33Slide34
Seattle Public Utilities
34Slide35
Seattle Public Utilities
35Slide36
Million Dollar Idea:
Chia-TankSlide37
I wanna rock!
Seattle Public Utilities37Slide38
Seattle Public Utilities
38Step 7: Install drain valvefor use as “low-flow orifice”
Use oversize (1-3”) bulkhead fitting, so entire fitting can be removed for
cleaning tank. Or install
separate cleanout plug.
“Hose bib” garden hose faucet
Connect garden hose, and run it to safe discharge point to drain cistern slowly between storms
Close faucet in May to store water for summer. Open again in October to detain and slowly drain winter storm waterSlide39
Seattle Public Utilities
39Slide40
Seattle Public Utilities
40Slide41
Installation Statistics
2010: 17 installations2 cistern, 9 rain garden, 6 combo2011: 78 installations7 cistern, 57 rain garden, 14 combo2012: 114 installations14 cistern, 76 rain garden, 24 combo
2013: 123 installations15 cistern, 81 rain garden, 27 combo
Seattle Public Utilities
41Slide42
Questions?
Guide, factsheets, and design tools:
www.seattle.gov/util/RainWise
RainWise
Tools
www.rainwise.seattle.gov
Bob Spencer
David McDonald
Seattle Public Utilities Slide43
Seattle Public Utilities
43