The Sebastopol Demonstration Energy
Garden, an initiative of Post Carbon Institute, has begun constructing a
wetland water catchment system capable of treating grey water. The system
reflects the goals of Post Carbon Institute by demonstrating reduced
consumption and facilitating localized production. It allows for extended
retention of runoff water on the property so that it may be diverted to areas
of necessity during times of scarcity. In addition, it demonstrates sustainable
urban methods of treating contaminated water and low impact techniques for
re-integrating it with groundwater. This project aims at establishing a tool
that allows for the investigation of constructed wetlands in the remediation of
contaminated waters as well as providing literature on the replication of such
systems.

The selected site, at 327 Murphy
Avenue in Sebastopol, California lies within the Laguna de Santa Rosa
Watershed. It is characterized by the moderately slow permeability of its soil,
and the relatively high annual rainfall it receives. Onsite are three separate
buildings, of which the system utilizes only a fraction of one, an 8.5x24’
portion of the 1500 square foot house capable of collecting 5,205.825 gallons
of rainfall over the course of an average year. Due to the seasonal differences
in precipitation and soil permeability on site, the system was designed such
that it could receive grey water (pending approval from local authorities) during summer months when water is scarce but
sunlight is ample, and rainwater during winter months when soil permeability
and bioremediation are reduced.

The system currently consists of a
surge tank that receives water from the roof of the house, two constructed
wetland tanks, and an outlet tank containing a solar powered effluent pump,
each connected to the next with 1 ¼” PVC. Once water is allowed entrance to the
circuit from the surge tank it travels through each constructed wetland tank as
well as the outlet tank many times over until it is manually released into a
branched drain that empties at fruit tree mulch basins. The system was designed
such that it can accommodate the estimated 30.5 gallons of daily grey water
input during summer months and 35.6 gallons of daily rainwater input during the
winter.

Implementation of the system began
in November of 2007 and shall continue through 2008, with maintenance
continuing indeterminately. Construction of the system began with excavation of
the selected site, followed by the setting and plumbing of the tanks, and
development of the surrounding landscape. Upon establishing the hydraulics of
the system as well as the stability of the wetland flora and fauna, the system
will be ready for the integration of grey water components. Monitoring of the
water quality, sediments, and biota has begun and will continue as the wetland
develops. The data produced will allow for investigation of constructed
wetlands in the remediation of contaminated waters, and assist in pursuing Post
Carbon Institute’s goals of demonstrating reduced consumption and facilitating
localized production.

PROJECT
GOALS:

It
is the goal of Post Carbon Institute to demonstrate reduced consumption and
localized production. In this project we are focusing primarily upon the use
and conservation of water in the garden and surrounding landscape. One purpose
of this project is to prolong the retention of runoff water on the property so
that it may be diverted to areas of necessity during times of scarcity. Another
purpose is to demonstrate practices on the compact scale for the treatment of
used water so that it may be safely recycled into the ground. By reducing our
consumption of water, we consequently reduce our consumption of energy.

It
is the goal of Post Carbon Institute to provide information on actions that
enhance regional sustainability to the scientific community as well as the
local community. This project serves as a tool for the investigation of
constructed wetlands in the remediation of contaminated waters as well as a
replicable model for future systems.

SITE ANALYSIS:

Post
Carbon Demonstration
Energy Garden

327
Murphy Ave

Sebastopol,
CA, 95472

WATERSHED

The
Energy Garden belongs to the Laguna de
Santa Rosa watershed, the largest tributary of the Russian River, capable
of storing over 80,000 cubic feet (99,000,000 m³) of stormwater. Soil types
within the Laguna vary depending upon location; those onsite have been
classified as Sebastopol Sandy Loam, characterized by moderate to rapid runoff;
and slow permeability. During the winter months the soil remains moist and the
water table high, with summer conditions being very dry.

Month: J F M
A M
J J A S
O N D
Moisture: M M M M MD MD D D D MD MD M

M = Moist
all parts
MD = Moist some parts
D = Dry all parts

(National Cooperative Soil Survey, U.S.A.)

Energy Garden Weather Station

The average annual rainfall for the
region is 40.83 in/year; months that express high rainfall correlate with those
in which the soil expresses high moisture content. The wettest month of the
year is January with an average rainfall of 8.65 inches.

Month: J
F M A
M J J
A S O N D

8.65 7.64
6.15 2.25 1.03
0.25 0.08 0.11
0.52 2.01 5.85
6.29

(Graton Weather station, 3.20 miles from Sebastopol)

SITE CAPABILITIES

Onsite
are three separate building, an office that is 216 square feet, a garage that
is 323 square feet, and the 1,500 square foot house, all of which are equipped
with gutters and downspouts. The amount of rainwater that each roof is capable
of collecting can be determined by the following equation.

Area of house (sqft) *
Annual rainfall (in) = Cubic feet of water collected by roof over
course a year

12

Because
7.5 gallons are contained within one cubic foot of water it can be concluded
that the roof of the house on the property has the potential of collecting
38,278.125 gallons/year.

(1500 * 40.83)/12 = 5103.75 * 7.5 = 38,278.125
gallons water/year

During a 62 day period
(6/30/07-8/31/07) the household and the garden consumed 160 cubic ft. of water.
This includes the needs of the household and the irrigation needs for the 3,500
square foot garden. By projecting these summer meter reading, in which no
rainfall occurred, upon the whole year it can be predicted that no more than
7,181.298 gallons are consumed by the household each year. Considering that the
roof alone is capable of collecting 38,278.125 gallons per year, there should
be no reason that the garden cannot be irrigated on collected rainwater alone.

160 cubic ft * 7.5 gallons/cubic ft = 1196.883
gallons
1196.883 gallons * 6 = 7181.298 gallons used

The
amount of grey water produced by the household can be estimated using proposed
calculations. Art Ludwig, author of The Grey Water Builder’s Manual and Create
an Oasis with Grey Water, has projected volumes of grey water output upon
plumbing fixtures, based on their weekly use and the number of occupants. It
has been estimated that for each occupant a top loading washing machine
produces 45 gallon/week, a bathtub 30 gallon/week, a shower 65 gallon/week, and
a bathroom sink 10.5 gallon/week. The reason that other potential sources for
grey water output have not been considered is due to the legality of their implementation
in grey water systems. The household onsite functions as both a place of
residence and business and therefore the amount of grey water output must
reflect a more frequent usage.

Occupants: 2 adult residents,
1 child

4 onsite
employees

Top loading washing machine:
3 * 45GPW = 135GPW/7 = 20GPD

Public bathroom Sink: 7 *
10.5GPW = 73.5GPW/7 = 10.5GPD

Private bathroom sink: 3 *
10.5GPW = 31.5GPW/7 = 4.5GPD

Shower: 3 * 65GPW = 195GPW/7
= 28GPD

Grey water produced = 345GPW
= 50GPD

So
as to determine the rate of absorption by the soil, the irrigation demand of the fruit trees was calculated.
The site selected for water deposit is more
than capable of holding the amount of treated grey water that the system will
emit each week.

Irrigation Demand = Regional
Evapotraspiraton value * Plant water usage factor * Irrigated area * 0.62

Irrigation
Efficiency

ID = (1.0) * (0.8) *
(300sq ft) * (0.62) = 186 gallons water/week

0.8 *
All values can be found in Art Ludwig’s, Grey water
Builder’s Manual. (0.62 is conversion from inches/sq.ft. to gallons.

DESIGN

Upon
evaluating the water consumption of the property, the capabilities for
rainwater catchments, and grey water output, as well as having researched the
biological and environmental potential of phytoremediation, we have selected a
location for a seasonal grey water system. The selected location falls within
zone one of the energy garden, close enough to the house to collect grey water,
but not too close to violate the law as presented by CPC/UPC, which states that
the minimum distance of 5 feet from buildings and structures is required.

Due to the elevated ground water table
that occurs in Sebastopol during winter months in which rainfall is most
frequent, and also due to the impeded rate of phytoremediation during this
season, we have chosen to employ a seasonal grey water system. During the
summer months when water is scarce but sunlight is ample we will allow grey
water from the nearby bathroom sink and washing machine into our constructed
wetlands to be filtered by the growing flora, and during winter months the
system will function as storage for rainwater that runs off the asphalt
roof.

The designed system consists of a
surge tank that receives water via a rain chain from the asphalt roof of the
house, two constructed wetland tanks, and an outlet tank containing a solar
powered submersible pump. Each tank is connected to the next with 1 ¼” PVC
within which we have installed manual on/off valves to allow flexibility in the
hydraulics of the system as well as to provide a means for future maintenance.
Once water is allowed entrance to the circuit from the surge tank it travels
through each constructed wetland tank as well as the outlet tank many times
over until it is manually released into a branched drain that dumps it at the
base of the fruit trees in zone three of the property.

The tanks were sunk level with the
surrounding walkways and have been secured with a 6 inch layer of gravel
beneath and around them. The surrounding landscape was designed so as to
compensate for any potential overflow that might occur. Native plant pockets
have been incorporated into the design as well as a perennial wetland pocket
and xeriscape pockets. Each micro-habitat has been developed with the intention
of demonstrating possible bunker flora for grey water systems as well as to
investigate the most successful method of utilizing the space surrounding grey
water systems. The selected plants are
neither root crops nor low growing edibles, but rather plants that exhibit
phytoremediating capabilities as well as function as pollinator attractants so
as to benefit the ecology of the surrounding garden and constructed wetlands.

The
rainwater that feeds the system during winter months is diverted from an 8.5x24’
section of the roof (capable of capturing 5,205.825 gallons of rainfall over
the course of a year. The system was intentionally designed to account for
January, the wettest month of the year, in which the average daily input of
rainwater into the system is 35.6 gallons per day.

8.65 monthly in. rainfall/31
days = 0.279 daily in. rainfall

0.279 * 204sqft = 4.7 daily
cubic feet water * 7.5 gallons/cubic ft = 35.6 daily gallons of water

12

During
summer months, the system was designed to receive grey water from the washing
machine and public bathroom sink. Using the proposed grey water output values
per person per week, we can estimate that 30.5 gallons of grey water will enter
the system each day. For phyotremediation to occur it is recommended that the
water be allowed 2-4 days circulation within the constructed wetlands. With a
360 gallon system we could afford an input rate of 90 gallons per day. This
compensates for the projected 30.5 gallons of daily grey water input during the
summer and 35.6 gallons of daily rainwater

input during the winter.

Upon
circulating through the system for 2-4 days, a portion of the water is removed
and replaced with the contents of the grey water surge tank or the rain water
catchment surge tank. The proposed area in which treated grey water shall be
distributed lies within zone 3 of the property; it is distributed through
branched drains which deposit into mulch basins surrounding fruit trees. The trees
receiving the treated water are located 55 feet away from the system. So as to
comply with legal requirements stated in CPC/UPC, all pipes involved in the
disposal of treated grey water are buried at depths lower than 9 inches.

IMPLEMENTATION

Throughout the
implementation of the system, aerial photographs have recorded each procedure,
step by step. These provide us with both documentation of the procedure
involved in building a grey water system and serve as to-scale diagrams of the
system. We have intentionally recorded the construction pictorially as well as
through written report so as to meet the requirements laid out by CPC/UPC.

Because the system will not operate in the
phytoremediation of grey water until permits allow, we have not yet installed
the tanks associated with that process, but rather focused our efforts on the
rain water catching components of the system. Although the design and
construction of the system is site specific, we have created what we consider
to be a general implementation plan. It outlines the steps that were required
through the progression of implementation.

WINTER IMPLEMENTATION
PLAN

Phase 1: Excavating
and Setting Rainwater Catchment Tanks

* Upon determining the necessary
capacity of the system and appropriate tank size, and having already selected a
site

-
Remove topsoil and hard pan

-
Deposit layer of drain rock

-
Determine desired slope of pipes per/foot

-
Design layout for pipes

-
Design layout for garden/constructed wetland pockets

-
Trench for pipes

-
Line garden/constructed wetland pockets with fabric

-
Set tanks and level

Phase 2: Plumbing Rainwater
Catchment Tanks (Hydraulics)

-
Determine desired width of pipe

-
Mark and cut holes for tank adaptors
once tanks are set at level

-
Measure and cut PVC and install manual ball valves for
maintenance

-
Install pump

-
Test the hydraulics of the system and check for leaks

-
Determi

ne the method of flushing system and dispersing
treated water

-
Design layout of branched drain

-
Trench for drain

Phase 3: Softscaping

-
Determine plants to be included in
constructed wetland

-
Deposit layer of drain rock

-
Secure valve boxes around manual ball valves

-
Deposit top layer of pea gravel

-
Fill garden pockets with soil or Wetland pockets w/ lava
rock

-
Cover branched drain with soil and establish community
of plants where water is deposited

SPRING IMPLEMENTATION PLAN

Phase 4:
Establishing Constructed Wetland Ecosystem

-
Plant determined plants within tanks and in surrounding
pockets

-
Slowly integrate mosquito eating fish, and bottom
feeding fish

-
Systematically add beneficial microbes

-
Monitor condition of established ecosystem

SUMMER IMPLEMENTATION PLAN

* To begin upon approval of the proposed grey water system

Phase 5:
Excavating and Setting Grey Water Surge Tank

* Upon determining the necessary
capacity of the system and appropriate tank size,
and having already selected a site close to rainwater catchment system.

-
Remove topsoil and hard pan

-
Deposit layer of drain rock

-
Determine desired slope of pipes per/foot

-
Design layout for pipes

-
Design layout for garden/constructed wetland pockets

-
Trench for pipes

-
Set surge tank level

*
Must be 5’ from house or building

Phase 6: Plumbing
Grey Water Surge Tank

-
Install optional grey water valve into household
plumbing

-
Determine desired width of pipe

-
Mark and cut holes for tank adaptors once tanks are set
at level

-
Measure and cut PVC and install manual ball valves for
maintenance

-
Connect grey water output pipes to grey water surge
tank

-
Connect grey water surge tank and rain water catchment
system

-
Test hydraulics of the system and check for leaks

*
There can be absolutely no leaks

FUNCTION
AND MAITENANCE

The proposed
system functions by employing the remediation capabilities of wetland
ecosystems. The plants selected are hyperaccumulators of the heavy metals and
organic contaminants found in grey water, as well as substrate for promoting
microbial remediation. As the plants grow, toxins are removed from the water,
and it becomes available for reuse. In order for the system to function
properly, certain methods must be employed in the introduction of grey water,
and the removal of treated water to and from the system.

The proposed
system functions as a circuit; into one end grey water and rainwater are
introduced and from the other treated water exits. In order to monitor the
impact of the wetland ecosystem on contaminants in the incoming water, samples
must be taken from the suspended grey water and rainwater runoff prior to entering
the system. Likewise, the treated output must be collected and analyzed.
Quantitative data will provide insight on contaminant levels and microbial
activity of the water at each stage of treatment and serve as an indication of
how long water should remain within the system. So as to eliminate the
possibility of removing untreated water from the system, treated water must be
removed prior to the addition of grey water.

Monitoring of plant tissue is required so as to assess
the health of the system and the accumulation of contaminants. Data produced
from such analyses will indicate when phytoextraction is most productive and
provide information about the capabilities of each plant. Because the removal
of contaminants relies upon the plants and microbes within the system, and they
undergo seasonal changes and winter dormancy, grey water should not be added to
the system during periods of dormancy. At this point, all grey water must be
redirected into city sewer lines and the system switched over to rainwater.

Due to the
importance of maintaining the hydraulics of the system, the submerged effluent
pump must be monitored daily. The addition of grey water must cease at any sign
of pump malfunction. Grey water must not be allowed into the system until the
pump is repaired or replaced. All repairs and
improvements upon the system should be made with caution and in keeping with
the goals of the system.