RAINWATER
HARVESTINGRETURN ON INVESTMENT
BENJAMIN SOJKARAINWATER MANAGEMENT
SOLUTIONS
Benefits of rainwater
harvesting1 inch of rain on a 1,000 ft2 roof yields 620
gallons of collected rainwater
• Decreases use of municipal water --- worldwide
consumption is growing at double the population
growth rate
• Reduces reliance on energy-intensive, aging water
infrastructure
• Decreases stormwater runoff, which is a major source
of pollution
Why Reduce Stormwater
Runoff
• Urban infrastructure increases the imperviousness of
the environment and pollutes and concentrates
stormwater. DC is 43% impervious.
• In cities, like Washington, DC, with combined sewers
the stormwater can overburden the combined sewers
and sewage treatment capacity. About two billion
gallons per year overflows to the Anacostia and
Potomac rivers.
• Combined sewer overflow events result in cities being
sued by the EPA for violations of the clean water act.
What DC is Doing to Avoid
Violating the Clean Water Act
• DC Clean Rivers Project is in the process of digging
large tunnels to be used to divert the CSOs from the
receiving waterways and retain that water to be treated
by Blue Plains WWTP.
• Cost of DC tunnels - $2.6 Billion
• Cleveland - $3 Billion
• Kansas City - $2.48 Billion
• New stormwater regulations aimed at making DC
“spongier” to reduce the amount of stormwater
entering the combined sewers.
Changes to DC Stormwater
Regulations
• New construction over 5000 sq. ft. must retain first 1.2”
of rainfall (90% of storm events).
• Major renovations must retain first .8” (80% of events)
• Retained water must be disposed of on site. Infiltrate,
fixture flushing, cooling tower, evaporate, etc…
• At least 50% of required detention must be done on
site. Remainder can be purchased as credits.
• Credits can be purchased from DDOE for $3.50 per
gallon per year or in the private marketplace.
Rainwater harvesting for
Stormwater Management•Sizing guidelines and
regulations per DDOE
•Stormwater can be detained
and reused on site
•New emphasis is on runoff
reduction
•Works best as part of a
treatment chain 0
10
20
30
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60
70
80
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100
0 5 10 15 20
Per
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dem
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et b
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wate
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Tank size ( thousands of gallons)
Where to Capture Rainwater
Best Practice• Rooftops – The best and cleanest water comes off the roof.
Handle with Care•Green Roofs and Planted Areas – Water from green roofs is
often high in dissolved solids from the growing media.
• Not good for toilet flushing
• May work for irrigation or cooling tower makeup
•Parking Lots – Often contains oils and dissolved salt.
• Salt is difficult to remove and detrimental to plants
Possible Uses of Rainwater
•HVAC cooling systems
•Commercial laundries
•Water closets and urinals
•Irrigation
•Pool and pond Filling
•Other non-potable uses (fire suppression; floor and vehicle
washing)
Rainwater Harvesting and LEED
11 Possible Points
• Reduce or eliminate pollution from stormwater runoff
• Limit disruption and pollution of natural water flows by
managing stormwater runoff
• Limit or eliminate the use of potable water for landscape
irrigation
• Use only captured rain or recycled site water for site irrigation
• Reduce potable water use for building sewage conveyance by
50%
• Reduce water use for building by 20%
• Maximize water efficiency within building to reduce the
burden on municipal water supply & wastewater systems
No matter how big the job is, the concepts are
the same
You just have to choose the
right tools
Size Matters!Larger Tanks – Usually below grade
•Tend to utilize the captured rainwater more efficiently
•Rainwater Harvesting – Want the tank full
•Stormwater Management – Want the tank empty
• Control systems can help manage tank capacity
Smaller Tanks – Architectural Feature•Tend to be much cheaper
•Can reduce the cost of the rainwater system
•Some clients want them above grade to show off system
4 Steps for Rainwater Harvesting
•Self-cleaning filters
•Smoothing inlet
•Floating filter intake
•Multifunction overflow
Storage tank
Grade
Putting it all together1
2
34
Two Ways to Build a Rainwater System
A La Carte Skid System
A group of parts
and pieces are
sourced and
assembled on site
usually following a
project specific
scenario.
The system is pre-
designed and pre-
packaged with
minimal on-site
construction.
Some Considerations for A La Carte Systems
• Increased possibility that the installing
contractor might not assemble the components
in the order that the designer intended.
• Liability concerning installation must be clearly
defined and understood between all parties.
• Some of the equipment may be delicate and, if
poorly understood, may be damaged and or
broken during installation. This will fall on the
contractor.
Skid System On-Site Hook Up
Inlet from
Cistern
To End
Use
Filter
blow-
down
Domestic
Water
supply
line
SYSTEM CONTROLLER
Urban farm
Charlottesville Public Works
Charlottesville Area Transit
Jefferson Houston Elementary
School – Skid System
Jefferson Houston Elementary
School – Skid System
Home Depot
Boeing – Crystal City, VA
Boeing – Crystal City
Boeing – Crystal City
No Pre-Filter
Kellum High School, Virginia
Beach
701 2nd Street, Washington, DC
450 Unit Apartment
ICC Bethesda
High Security Office Building
Oscar Smith Middle School
A two-tiered approach
Two “clean” tanks are
used for indoor use –
toilets and urinals
The other two tanks are
used for irrigation
Manassas Park Elementary
61,500 sf of additional roof area (12,000
pre-k; 49,500 upper elementary)
Estimated project budget $33 million
Manassass Park Elementary School
Effect of system Eighty-two percent of the precipitation that falls on the roof is used in the
building or for irrigation (1.1 million gallons). Any additional runoff is routed
to the constructed wetland for infiltration or evaporation or in extreme
events, detention and release. The initial estimates used in sizing the
system were based on monthly rainfall data. This difference in time interval
is why the signs and other early estimates predict an annual water savings
of 1.3 million gallons.
The school uses about 356,000 gallons of water per year; the neighboring
school (Cougar Elementary) uses 2.2 million gallons of water per year.
LEED Gold certified
Numerous awards including
K-12 Project of the Year, Mid-Atlantic Construction magazine
Platinum Design Award and People's Choice Award, 2009 Virginia
School Board Association
Exhibition of School Architecture; 1st place in the 2007 Go Green
Competition, USGBC James River Chapter
AIA/COTE Top Ten Green Projects
Manassas Park Elementary
School- Education component
Western Virginia Regional Jail Regional partnership between the counties of Franklin,
Montgomery, Roanoke and the city of Salem
264,000 sq. ft. with a rated capacity for 605 inmates
Seeking LEED certification
Includes a siphonic roof drainage system
Payback analysis Total system cost = $258,000
3.9 million gallons of water saved
Current water rate $3 per 1,000 gallons
Annual savings from water = $11,675
Total payback time = 22 years
But does that really include everything?
Payback analysis Offsetting capital costs – the rainwater harvesting
system has the same water quality benefits for storm
water as a bioretention area that would cost about
$240,000 plus take up space on the site
Increasing water rates – if water rates increase 4% per
year, in twenty years, the water savings will have more
than doubled ($24,599 per year)
-400,000
-200,000
0
200,000
400,000
600,000
800,000
1,000,000
1,200,000
0 10 20 30 40 50
Sys
tem
re
turn
on
in
ve
stm
en
t ($
)
Years
Payback with no offsetting costs
and no increase in water rates
Payback with offsetting costs and
increase in water rates
Benjamin Sojka
Rainwater Management Solutions
434-531-0381 -direct
The Joyce Agency
3933 Avion Park Court, Suite B102B
Chantilly, VA 20151
www.thejoyceagency.com
1-800-291-9298
Experience Matters!
• All Souls Church – Washington, DC
• Car Barn Training Facility – Washington, DC
• Wounded Warriors Dorm Facility – Bethesda Naval
Hospital, MD
• PH2SO Apartments – Washington, DC
• Patterson House Apartments – Washington, DC
• 800 New Jersey Avenue – Washington, DC
• 880 New Jersey Avenue – Washington, DC
• Park Chelsea Apartments – Washington, DC
• 2001 Clarendon Apartments – Arlington, VA
• 9th Street Office Building – Richmond, VA
• Fairfax Public Safety Building – Farifax, VA
Experience Matters!
• I.C.C. Government Security Complex – Bethesda, MD
• St. Elizabeth’s Rehab and Renovations (2) –
Washington, DC
• H.D. Woodson High School – Washington, DC
• Brookland Middle School – Washington, DC
• University of the District of Columbia Greenhouse –
Washington, DC
• Anacostia High School – Washington, DC
• Arlington Mills Community Center – Arlington, VA
• Kempsville High School – Virginia Beach, VA
• Gunston 9 Secure Facility – Lorton, VA
Experience Matters!
• Mathias Research Center (Smithsonian) – St. Mary’s
County, MD
• Monument View Center (Boeing) – Crystal City, VA
• 82 Eye Street – Washington, DC
• Caffie Building – Arlington, VA
• Manassas Elementary School – Manassas, VA
• University of Maryland Knight Hall – College Park,
MD
• Hillen Street Fire Station – Baltimore, MD
• National Business Park – Baltimore, MD
Experience Matters!
Rainwater Management Solutions
• Over Ten years of rainwater harvesting experience
each
• Have made many of the mistakes and have learned
from them
• Have the financial backing and resources to stand
behind their systems