Ann Wilde
The construction crew at the Green & Main site enjoyed an extended summer, with temperatures in early October ranging into the 80’s with clear skies. This was an unexpected and much appreciated delay to our typical Iowa autumn. Soon it will be time to batten down the hatches and get ready for sub-zero temperatures when the crew will focus on the interior of the building.
Here’s what they’ve been up to…
Green Roof
Green & Main’s vegetative or green roof was installed on the spectacularly warm day of October 4, provided and delivered by Rooftop Sedums of Davenport, Iowa and installed by Silent Rivers’ staff.
Installation of the rubber membrane.
In preparation for the arrival of over 300 trays of sedum for the green roof, Academy Roofing first installed a membrane to serve as a protective layer between the actual roofing materials and the trays of live plant material, primarily sedum in this case. This membrane, known as a sacrificial membrane, is made of EPDM rubber, a type of synthetic rubber. EPDM roofing does not pollute run-off rainwater, and is an inert material, which has limited environmental impact during its manufacturing process in comparison to other membranes. Additionally, black EPDM is more cost effective as compared to a more reflective white, or TPO, membrane when used with a vegetative roof.
Tim Kepner of Silent Rivers installing the sedum.
Geothermal Energy System
Installing a geothermal energy system is a multi-step process that has taken shape at the Green & Main Pilot Project site over a period of months.
Several critical phases of a geothermal project need to be identified at the onset to assist in the successful installation and operation of the geothermal system. Some of the major phases are:
Loops of tubing.
- Drilling the actual wells, as well as the preparation needed to the soil/grounds to accommodate the loops of tubing which act as supply and recovery lines for the closed system.
- Excavation of the site around the well field, including the removal of the perimeters of a building foundation discovered buried underground, a 500-gallon steam tank and two cisterns.
Looping for the geothermal well system.
- Connecting the well field of lateral supply and return lines to the building, requiring multiple assessments and adjustments. Research and implementation occurred regarding the addition of crushed glass and sand as backfill material, as well as sub-surface meters that will track temperature changes not only in the soil and fill, but also to measure the therms in the supply and return lines. Much of this research was initiated by the SWAP (Solid Waste Alternatives Program) grant in collaboration with the geothermal well installers and engineers, Barker Lemar.
Drilling the well field.
- Backfill, preparation of the site and attention to effectively controlling soil by packing and rolling was essential in order to be ready for installation of the permeable pavers.
- Connecting the well field loops to the mechanical system is yet to occur. This will be accomplished later in the winter.
Geothermal System Gets Buried at Green & Main
For some months, two ends of the geothermal “tubes” have been visibly sticking above ground level at the Green & Main construction site. These were actually part of hundreds of feet of high-density polyethylene pipe, known as “loop”. This continuous system will circulate water through the loop and into the geothermal units, thus providing the geothermal energy system to the building through its underground foundation wall.
Green & Main’s geothermal energy system includes 11 vertical wells that were drilled 300-feet below the surface. After the wells were drilled, the initial tubes were installed to reach above the ground. Then, by exposing the ground about seven feet around the tubes and below the finished grade, the tubes were connected to form the system.
Bottles found while unearthing soil for the geothermal system.
On a historical note, dozens of glass bottles and containers were found during the excavation of the well field site. The bottles have been saved for future showing as evidence of lives past.
Roof on the Building Addition
The addition to the lower and main level of the Green & Main Pilot Project extends out at the back side of the building, pointing to the east. The roof of this addition will someday be the walk-out patio of the upper-level apartment. Once this roof has been completed, it will include additional vegetative roof plants and a decking system, providing an outdoor sanctuary for future second floor residents.
Sedum on the addition’s roof.
Both the roofing system on the main building and the addition will be an aesthetic bridge, creating a connection between the building and the surrounding site through the installation of unique water collection systems that accentuate this relationship.
Landscaping and Stormwater Management on the Grounds
Soil Amendments
The current soil of the Green & Main Pilot Project obviously has been altered in the century or so since it was untouched prairie grasses. To nurture the native plants in Green & Main’s landscaping, the soil was amended, incorporating more organic material into the existing soil. This will help restore the soil back to a more pre-settlement condition and it will help to absorb more water, thus making it more conducive to healthy landscaping. Similarly, combined with the native plants, the site will improve its capacity for ecological regeneration while serving as a pilot project for the Sustainable SITES Initiative.
Soil staging and layering.
Planting of the Site
The extensive native landscaping planned for Green & Main was completed by mid-October. The plants were provided by Allendan Seeds, who grew them from seed – as featured on WHO TV-13 – and installed by Greenbean Landscapes. In order to protect the site and avoid compaction of the amended soils, all construction equipment traffic was relegated to the city right of way and the six-foot perimeter around the building. This will allow the plants to establish themselves and ensure the porosity in the soils that will increase water infiltration and root development.
Plantings on site.
Plantings include such species as: prairie dropseed, big bluestem, blue grama, buffalograss, little bluestem, switchgrass and pale coneflower. Indigenous plants are especially beneficial as their root structures assist with water infiltration and the cooling of ground water. Developing the landscaping to provide a natural flow of rainwater was essential to our landscaping. As a result, rainwater will be guided through a bio-swale into the site’s rain garden to nourish the native plants.
Permeable Pavers
Paver bed for the parking lot.
Permeable pavers were placed over the geothermal well field at the end of the week of October 10. After the individual wells were connected below grade, the arduous task of filling a ten -foot deep basin with clean clay and layering the compaction to ensure a sound base for the pavers took place. Silent Rivers’ staff, along with Ron Gomis, worked through a long weekend to build the complex framework necessary to allow variables in grade for parking, as well as allowing easy access to the building. Hardscape Solutions of Iowa finalized these efforts by bringing its crew to construct the layers of gravel that will control water drainage from the Borgert Granite Paver system, the permeable parking system used in order to meet our stormwater management objectives.
Installation of pavers.
Rain Harvesting
While waiting for the completion of roofs over the carport and entry walkway, the H20 Rainwater Harvesting System was initiated on the concrete wall constructed between the parking area and the landscaping. The H20 HOG water tanks were installed and quietly await the future installation of the gutter system to highlight the ability to contain and reuse stormwater as a positive strategy for water conservation.
H2OG water tanks installed.
Many Thanks are Offered
During the final days of the installation as these various disciplines and projects merged together, many people visited the site to watch our progress. Key staff from Polk County Soil and Water Conservation and Iowa Department of Agriculture visited the site and helped hone installation details to ensure the project design and implementation were effectively produced, providing a model opportunity for urban non-point stormwater management systems. We are very grateful for their encouragement of the process.
Along with the many businesses and people who contributed labor, goods and services, the site was supported by Heartland RC&D, REAP, HRDP, IDALS, DNR, Metro Waste Authority, Iowa Waste Exchange, NRCS, USDA, City of Des Moines, NRBBOG, Polk County Soil and Water Conservation, Iowa State University CBER, IAMU and Growing Green Communities.
-Ann Wilde is a Des Moines marketing strategist and writer who also has a special interest in preserving and creating sustainable communities.
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