We will be repurposing the trees felled from the infill lot. This lumber will be used both inside and outside, on the Burnside Boardwalk project.
There was initially 21 large trees on the Burnside Boardwalk infill site. We were able to save 8 of them. The trees varied in sizes from a large of 44 inches in diameter to the smallest of 12 inches. We have taken the trees to a saw mill that will make our fence boards 5/4 x 8 inches and our second and third floor hallway heavy timber floors. We believe that when all done we will get over 6 thousand board feet of usable lumber.
We originally wanted to save the existing trees, but were forced to bring our buildings up to the road by the planning commission. In retrospect this has made for a much nicer and more urban project. It also puts eyes on the street that is a safety feature for both the Trimet station and our residents.
These photos show Vern processing our trees. Vern has been working in saw mills his entire life starting at the age of 17. He is still going strong at 68 years old. Tough old bird.
Our drywell allows the rainwater runoff to recharge the local aquifer, rather than adding to the city’s stormwater overflow. This is one of the features that help make Burnside Boardwalk so green.
In a normal urban environment rainwater is channeled into the city drainage system that pushes the water directly to streams bypassing the traditional means that recharge the ground water system.
The hole that was dug into the ground was 20 feet deep to make sure that the bottom ring was well into the sandy and rock layer of dirt that was deposited at the last ice age. This is a very porous medium that will transfer the water into the aquifer system very nicely.
These photos show the installation of our concrete rings that line the dry well. These will fill with rain water runoff from the property, which will gradually percolate out the perforations in the sides.
When pouring the footing and retaining walls in a small infill lot there are several obstacles to overcome.
We would prefer to use a boom truck so that the filler hose does not need to be dragged across the forms. But when the lot is torn up there is not always room for the boom truck. Even though the pump truck is only 60% the cost of the boom truck sometimes the labor that is saved offsets the additional cost of the boom truck.
Where there is a conflict is when you get a labor only bid for the foundation and retaining wall. Then it is the job of labor to make their job the simplest regardless of the extra cost of the boom truck.
The pouring went well. The surprising thing is that instead of using a vibrator to make sure all of the concrete was smooth, they just had everyone hit the forms with hammers. It did a nice job and the concrete came out smooth.
In digging the foundation, our high retaining walls need a thicker and bigger footing to be able to resist the overturning pressure of the ground at street level. Additionally the amount of rebar in the footing has to be considerably more to add the extra strength that the high wall needs. This created a little challenge for us in the foundation drainage on the exterior wall, since the footing for the high walls were dug 6 inches deeper than the shallow walls. This difference had to be made up before the foundation drainage was put in.
It is amazing how much concrete and steel is needed to retain a wall where the ground is able to maintain a slope of 1 to 1 without any wall. The wall also needs to resist the added pressure of vehicle traffic when the wall is on the roadway. After the foundation is poured the retaining wall needs to be formed and then poured. Again the retaining wall needs a lot of rebar to resist the overturning pressure of the ground that pushes against it.
We’ve started to excavate the foundation for our new Burnside Boardwalk 31unit net zero affordable housing development on E. Burnside.
The site sits in a hole that is approximately 5 feet below the existing sidewalk 271.5 ft elevation we decided to utilize this existing void to install a daylight basement. This required the removal of approximately 2 thousand cubic yards of dirt. The site plans include a driveway on the west side that required the grade to be built up to street level and sloped down to where the parking lot in back is situated. The filling of the driveway and parking lot would have used around 2500 yards of material, requiring approximately 500 additional cubic yards. We are considering lowering the parking lot approximately 2 feet, which would eliminate the need for the additional fill.
This is a very tight infill lot of a little over ½ acre or 21,000 sq.ft. The small lot has created a dirt storage challenge while we shape and form the lot to be useful. Because of this 2 back hoes were used to move the dirt around and a bull dozer to level out the dirt.
Here are some photos.
We’ve laid the ground loops for the geothermal heat exchange pipes at Burnside Boardwalk, our 31unit net zero affordable housing development on E. Burnside. A ground loop is a series of pipes buried underground at a depth where temperatures stay consistent year-round. It serves as the critical link allowing geothermal heat pumps to use the earth as a heat source or heat sink, to assist in both heating and cooling the entire building.
How does a ground loop work?
Just a few feet below the ground’s surface, the earth maintains a steady temperature of 50 to 55 degrees, no matter what the outside air temperature is. This difference allows the earth to act as a heat source in winter and a heat sink in summer.
A geothermal heat pump (located inside the Building) captures this energy by circulating thermally conductive regular water through the buried pipes in the ground loop. In winter, the water absorbs heat from the warmer earth and the heat pump carries it into building, where it enters a heat exchanging system and is used to warm your home. In summer, the same process is used to capture heat from the building and released it into the cooler ground, leaving every unit comfortably cooler.
Horizontal Ground Loop
A horizontal ground loop is installed over a wide area of ground and requires enough space to dig trenches hundreds of feet long and 6-10 feet deep. Horizontal ground loops can only be used when adequate yard space is available and trenches are easy to dig. We have installed 500 feet of pipe in 16 loops, 8 loops buried at 14 feet deep and 8 loops buried at 7 feet deep. When we start to back fill around the foundation we will bury an additional 6 loops at an average of 6 feet deep. This will give us a total of 11,000 feet or a little more than 900 feet of pipe per ton.
To install a horizontal system, workers utilize trenchers or backhoes to dig trenches 5-10 feet below ground and then install a series of plastic pipes that comprise the geothermal heat exchanger. They will then backfill the trench, taking care not to allow sharp rocks or debris to damage the pipes. A common practice is to coil the pipe into a slinky shape to fit the loop field in a smaller area. While doing this reduces the amount of land area needed, it will require installation of more pipe. We have used a combination of straight pipe and a modified slinky approach.
We’ve cleared the land for our new Burnside Boardwalk 31unit net zero affordable housing development on E. Burnside. Aside from a grove of old trees in the SE corner, the land was pretty vacant. Although, we did find a lot of concrete and rocks left over from when they built the light rail.
Most trees that are cut down in the city are used as firewood, we had to look hard to find a mill that would actually cut the logs into usable lumber. We have had our arborist out to the job several times to observe the cutting of the trees and the leaving of the trees that are near the building. Andrew Craig from Springwater has been very helpful. The way the trees were that had to be cut down shielded the roots of the trees that we left. It is a shame to cut down big beautiful trees but it is comforting to know we left as many as possible and will use what we did cut to be part of our building.
Here are some photos.