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.

[video]

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.

[video: index=1]

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.