Gaia Place, Tucson AZ 85745


CoHousing "Rainwater Harvesting" "urban food production"

Date:  7/16/2008

Inspected By:  Matthew Bertrand

Site Representative(s) Interviewed:  Jackie Day and Bob Gilby

Type of Space: Cohousing community.

Tours/visits ok?  Yes.  Arrange tours through website:

The 28-home Milagro Cohousing development in Tucson illustrates the effectiveness of integrating infiltration basins throughout a site.  There are no conventional detention or retention basins at the bottom of the Milagro development.   Instead dozens of small infiltration basins are grouped and scattered throughout the site's landscape.  They are the dominant landform throughout the common area landscape, and in the majority of backyards.

Raised pathways break the landscape into an integrated series of large basins.  Small earthen berms divide these large basins into smaller infiltration basins, which hold both the rain that falls within them and roof runoff.  Diverse arrays of food-producing, wildlife-attracting plants are planted within the basins to utilize this rainwater.  Mulch then covers the soil's surface to make the rainwater go further.

Some of the homes direct their roof runoff to above-ground cisterns first, which then direct their overflow to the basins.  The cistern water is then doled out in the dry seasons to irrigate more water-needy vegetables and such.

In the unlikely event the basin system overflows, each basin overflows to the next to manage the excess water.  The concrete sidewalks of the raised paths act as stabilized spillways between the basins and dip slightly where surplus water is meant to pass.  The final overflow exits from the lowest basins into a natural drainage, which is alive with undisturbed, established vegetation that is enhanced by a series of small water harvesting check dams.  And just that rainwater and wastewater are enough to enable the designed landscape to produce 100 pounds (45kg) of organic produce per resident per year.  (Taken from Brad Lancaster's Rainwater Harvesting for Drylands and Beyond, Volume 2.  Used by permission).

1.      Average annual rainfall at site: 10 inches

2.      Longest days without rain at site: 90 +- 30 days

3.      Do you register your site's rainfall with  no.

4.      Site elevation (feet above sea level): 2,365 feet.

5.   Please estimate the cost of the Rainwater Harvesting work done on site $____

Cistern $1500 x 16 = $24,000

Gutters $

Earthworks $_____

Greywater Wetlands cost less than sewer hookup would have.

6.                  How often do you water your landscape using municipal and/or well water?  Please estimate quantity used.

Awaiting data.

7.      What benefits, problems, or lessons have you experienced with your system?

·        The buried irrigation lines have been a problem, as no records were made of their locations.  It's hard to tell how much water goes to each basin, and to each plant in that basin.  Maintenance will thus be quite expensive.

·        Challenges with constructed wetlands: At first it was not maintained properly.  There were also problems with the type of reeds planted - it used far too much water during the summer time, a time when residential water output reduced due to residents leaving on vacation.  As a result, it required significant supplemental irrigation using city water.  To make matters worse, the plants often died during the wintertime.

·        The community hesitated for some time over whether to begin installing cisterns, with many dissatisfied with the aesthetics of the culvert style.  Finally, one member installed one, and the rest went for it.  "Just do it."

·        Many have found that they have not been able to capitalize on the passive heat entering through south facing windows when it falls on concrete slab, which absorbs the heat instead of radiating it out into the living area. 

·        More trees, more water harvesting done outside developed area and on vacant lot higher in the watershed.

·        Better initial communication between members regarding vision before beginning development.  Community currently experiencing turbulence as individual members disagree over long-term site goals.



8.         Who was involved in the development of the features? Designers, consultants, implementers, maintenance folk, vision holders, etc...

Brad Lancaster, Mayne Moody, David Coutter, Chuck Durette, 20 members of CEL.


9.      Description of Site Aesthetic (well-groomed look vs. a naturalized look vs. a homegrown DIY)

Much of the site evinces a planned naturalism, with regular and carefully planned forms, yet with elements of a natural aesthetic with mulched basins, some of which abound with growth.  Other sites demonstrate more of a well-groomed appearance, with natural mulch replaced with rock mulch, and vegetation trimmed or removed entirely.  The majority of the site remains undeveloped, or undeveloped but augmented with fishscale swales, basins, and check dams to enhance the natural landscape.



What water harvesting features are present on site?

10.  Rainwater Harvesting


infiltration basins: Between the sidewalks reticulating through the center of the complex, with each basin spilling over into the next one in the case of a large storm event. 

swales: Fish scale swales high on the watershed above development to slow             water entering the site from above.

terraces: One or two isolated examples in front of homesites of low key terracing.

permeable pavement:  Parking lot covered with Gravelpave system. 

other: Entry road consists of polymer stabilized granite

Cistern(s) harvesting water  (Exterior use) (above ground)

Additional Notes: Community has approximately 20 culvert style cisterns in use.  Cisterns vary in size and capacity, but all are gravity fed and top-filling.


11. Greywater Harvesting

For each system below, note:

Type of system: tankless-gravity fed, tank dependent-pump driven, siphon system, other.

Distribution: branched drain, multi-pipe, diverter valves, infiltration chamber.

If, and how, greywater access/diversion/valving is convenient to person at source of greywater generation (such as multi-pipe greywater- and sewer-pipes both located at washer or a diversion valve located beneath a sink

How is greywater beneficially reused on site? (Irrigating perennial vegetation, other))

#3 Washing Machine: feeds directly to constructed wetlands system.

#all Sink: feeds directly to constructed wetlands.

#all Showers: feed wetlands.

Additional notes: Pipes feed by gravity down to the constructed wetlands at the base of the developed area.  The wetlands uses approximately 20% of the site's total output of greywater to maintain itself.  Once filtered and clean by the wetlands, the remaing 80% is then pumped back up as reclaimed water to support the landscape.  Greywater supports a large turf field, as well as


12.             Stormwater Harvesting

Note quantity, sizes, stacking of functions (passive irrigation, heat island reduction, flood control, food production, native habitat)

Check dams: Present upstream off property on vacant land, to slow entry of water onto Milagro property.  Also present at the bottom of the watershed to manage stormwater leaving property.

Swale network: Present in  vacant lands higher up in the water shed to ensure that water traveling into Milagro is manageable.

13.             On-site "Waste-water" Harvest/Reuse/Reduction

□ constructed wetlands note if constructed wetlands are saving or using more on-site water than conventional systems

With inefficient bulrushes removed, the wetlands no longer require supplemental irrigation.



14.             Inspector Data Sheet

  1. Total site area: 43 acres
  2. Total developed site area in square feet: 300,000 ft2
  3. Total area of catchment surfaces (roofs): 33,800 ft2
  4. Total area of catchment surfaces that is harvested: 7700  ft2
  5. Average yearly rainfall: 10 inches = .83 feet
  6. Volume of rain falling on site in an average year
(7.48 gal./ft3 x B x E)       1,870,000 gal.

  1. Volume of runoff off catchment in an average year (conservative estimate)
(6 gal./ft3 x C x E)       169,000 gal.

  1. Volume of runoff off catchment that is harvesting in an average year
(6 gal./ft3 x D x E)       38,500 gal.

  1. Annual water consumption (according to water bill): 2,044,000 gal./ year
  2. Average water consumption per month (I / 12): 170,033 gal./month
  3. Month of highest water consumption (according to water bill): M June #____ gal.
  4. Average volume of potable water consumed per person per day
(H / 365 / # residents):  100 gal. / person / day

  1. Square footage of building per person to encourage smaller living space: 903 ft2
                (1 drop lost if indoor living space exceeds 600 ft2 per person; 2 drops lost if indoor living space exceeds      1,200 ft2 per person)

15.             Estimate the following with Site Rep

Percentage of landscape irrigation needs met by non-potable, harvested water: 75%

Percentage of greywater reused on site: 100%.  20% of greywater lost to support wetlands. 

Percentage of wastewater reused or treated on site: 100%




Integration of Sustainable Features

(Check features which are present)


16.             Passive heating and cooling

o       East-West Building Orientation

o       South-facing windows having good-sized roof overhang or awning: ____

o       Percentage of floor area equaling surface area of south-facing windows (strive for 12 to 15% of floor area): 30-50% of southern exposure consists of windows to let winter sunlight in.

o       Trees on east, west, north - NOT direct south

o       What percentage of hardscape is shaded in summer - strive for 75%

§         Approximate percentage: ___________

o       Other Features? Low-E glass - highly reflective.

17.       Active on-site renewable energy production

o       solar hot water

o       No solar power - roofs not installed correctly.  Community researching alts.

o       solar oven - one large for the community, and some houses have them.

o       Other? Solar powered path lights.


18.       Community building

o       shared use with neighbors - Shared 3,000 ft2 community area with games, tv, kitchen, pool, and laundry facilities.  Shared garages, fruit trees throughout the community, and playground.

o       is it in view and celebrated

o       workshops for installation

o       Other? Community building mural project near the common house.

19.       Food production (residential - bonus points to public/business sites)

o       Vegetable garden irrigated with rainwater: minimal - on an individual basis

o       fruit trees irrigated with greywater: 80% of water used is grey.  20 trees in total in community, mostly figs, citrus, and pomegranate.

o       stormwater irrigation of native food-producing trees/shrubs: 

20.       Wildlife habitat/ecosystem enhancement  

o       Minimum 10-15% percentage of site area covered with native (vegetation indigenous to a 25-mile radius and within 500 feet of the site and its elevation) plantings: majority of site 100% native.  Developed area mostly native.

21.       Erosion control

o       No signs of erosion problems

22.       Flood control

o       percentage of on-site rainfall used/infiltrated on site

100% of developed area

o       percentage of road runoff infiltrated in public rights-of-way (ROW)


25.       Turning wastes into resources/reusing salvaged materials/on site

o       mulch: Most basins contain vegetative mulch, though some basins contain purchased rocks.

o       urbanite: Broken concrete chunks demarcate parking area.  Broken adobe used to make planters.

o       on-site composting: combination of bokashi and composting by about 50% of residents.


26.       Notes on potential Site Improvements

            Expand water catchment capacity.  Site currently captures a very small percentage (25%) of total roof runoff, which does little to support intensive water needs of non-native plants onsite during summer months before the monsoon season.  Putting that stored rainwater to multiple uses, for example, to be used for wash water, will further reduce reliance on ground water resources.  Expand composting program onsite - 50% of residents not managing their garbage in a sustainable fashion. 

Explanation of "Drops" Ratings
5 Drops:
(o) All or 95% of site's water needs met by rainwater
(o) Integrative sustainable features from all categories present
(o) A 5 bucket site should be a fully developed, fully integrated site living almost entirely within its yearly water budget, demonstrating passive heating/cooling, active on-site renewable energy production, food production, wildlife habitat/ecosystem enhancement, community building, erosion and flood control, and an ethos of salvaging waste resources.  A wide diversity of rainwater harvesting features should be present, including greywater- and stormwater-harvesting (low-energy, passive, gravity-fed greywater- and stormwater-harvesting systems are rated higher than higher-energy, active, pumped/tanked systems).   The site will must be sized appropriately to its number of users.  To achieve this rating, a site will likely have matured for at least 5-10 years, and will emanate a feeling of being far more than the sum of its components.

4 Drops:
(o) 75% of site's water needs met by rainwater
(o) Integrative features from most categories present
(o) A 4 bucket site will demonstrate well-developed rainwater harvesting features that fulfill the majority of the site's water needs.  There will be evidence of many sustainable integrative features present.  Multiple rainwater harvesting features should be present.  The site will be sized appropriately to its number of users.

3 Drops:
(o) 50% of site's water needs met by rainwater
(o) Integrative features from many categories present
(o) A 3 bucket site will show good efforts towards meeting site's water needs with rainwater.  This site will also be on a path towards integration of sustainable features, with multiple features present.  The site should showcase a variety of rainwater harvesting features, though perhaps they are not fully developed.  Alternatively, perhaps this site rates much higher in all categories, except that the site has a proportionally small number of users for its size.  

2 Drops:
(o) 35% of site's water needs met by rainwater
(o) Integrative features from some categories present
(o) A 2 bucket site demonstrates a decent start at rainwater harvesting.  Perhaps this site was recently constructed, with an excellent beginning of basin work but has not been well planted to take advantage of those water resources.  Perhaps only one type of feature present (rainwater/greywater/stormwater).  Signs of a few integrative features beyond rainwater harvesting.  Site not getting much bang for its rainwater budget buck.   

1 Drops:
(o) 20% of site's water needs met by rainwater
(o) Few signs of integrative features present.
(o) Rainwater harvesting features present, but much more work needed to realize site potential.  Still, the rainwater management on this site far surpasses that which is in practiced at the majority of buildings in the Tucson area.  This is a foundation from which to build towards greater things.

0 Drops:
99% of the sites in Tucson fall into this category, which include residences, businesses, right of ways, public parks, governmental buildings, etc.  These sites treat rainwater as a stormwater management problem instead of the precious resource it is here in the Sonoran Desert.   Expect to see drainage pathways shunting water away from existing plants into the streets as quickly as possible, and those same rainwater-starved plants appeased instead with spaghetti irrigation lines that waste our dwindling salty CAP-infused groundwater.  Potable water should never go directly to plants in this manner without having been put through at least one other use first, such as wash water.

admin, HabitatMap, Tucson Rainwater Harvesting



Add1 Add a Marker
Create Create Your Own Map
Share Share This Map
Save Save This Map
Add2 Add to Your Site

Map Key ( 0 )

Marker Key ( 0 )

List of All Markers