Construction - Back to Dirt Work - Insulation/Watershed Umbrella (Cont'd some more)

This is the third post on the insulation/watershed umbrella.  The first post covered some tasks that had to be done before starting the umbrella then it described the installation of the first three layers of the umbrella.  The second post detailed the installation of the next six layers.  This post covers the last layer -- the topsoil backfill.  

Reminder:  click on any photo to enlarge it to full screen.

Vacillation on Methods
For months, I have dreaded the time when the umbrella had to be backfilled because I assumed that it would have to be done with wheelbarrows and shovels instead of the trackloader in order to avoid damaging the underlying sheet plastic and foam board insulation. The excavation contractor who had done work for us earlier described a method for using the loader safely.  Not only was it rather complicated but I felt that my track loader skills were not up to the task.  Ultimately I did use the loader somewhat like he recommended but only after some trial and error.

By the time we had installed the two layers of carpet and the four layers of sand over the foam insulation, I became convinced that the umbrella might be resilient enough to withstand the weight of the loader.  But I still bought three sheets of 3/4" plywood to lay down in front of the loader on which to drive thinking that the weight would be more evenly distributed and less likely to damage the umbrella.  But this method took three of us -- I drove the loader while two guys moved the plywood.  

Trackloader Saves the Day

First few tentative trips onto the umbrella with the
trackloader before deciding that it could be used for
backfilling without damaging the umbrella

After the first trip onto the umbrella using the plywood, we realized that the soft loamy topsoil, close to 2' deep, would suffice as a cushion as long as I avoided two maneuvers that the contractor warned about -- spin turns or raising the bucket too high.   So I began bringing in the topsoil in straight line pathways and, in so doing, not only distributed the soil but also began slowly to compact the soil over which I passed. Eventually, the compaction was enough that I felt comfortable making looping turns to fill in the gaps in the corners that were left by the straight line pathways.  And, as much as possible, I used straight pathways when smoothing and leveling the grade.

I would estimate the amount of backfill we used over the umbrella at 3 - 4 tandem truck loads or 40 or 50 loader bucket loads.  To

The backfilling about half done; notice that it is easily deep
enough to support vegetation; we plan to use shallow-
rooted native plants eventually even though turf grass
 is going in first to stabilize the soil against erosion in 
the short term

have moved this much fill with wheelbarrows would have been unbelievably arduous and time-consuming.

Perfecting the Grade for Seeding

Final grading with hand tools; ready for seeding

I thought I had done a pretty good job with the loader with regard to sloping the grade over the umbrella for proper drainage and leaving a smooth surface almost ready to seed.  But, on close inspection, it left a lot to be desired.  So I rented a self-propelled tiller and asked friend Pat to help run it for the several hours it took to loosen the soil enough to be able to shape and smooth it with hand tools, which, in itself, took 1 1/2 man-days between my wife's Uncle Archie and I.

Seeding and Stabilizing

Coffee bag burlap over grass seed to prevent erosion

Our long-term goal is to landscape with native plants instead of turf grass but the immediate goal was to establish a cover crop that would prevent erosion of the soil during the heavy rains next spring. Consequently, we planted conventional grass seed with the intention of replacing it over time with ground-hugging shallow-rooted natives (if there is such a thing as shallow-rooted native plants).

Wheat straw over grass seed to prevent erosion

Our soil is wind-blown loess left by the glaciers.  In order for it to have been transported by the wind, the particle size had to have been minute -- a fine-grained silt -- which is highly erodible.  In order to hold it in place on the steep slopes, I cut open recycled coarse burlap coffee bean sacks and fastened them together with hog rings.  After the seed was broadcast, we positioned the burlap over the slopes.  The burlap was stable in the wind so we only needed to anchor it by stapling it to boards laid under the critical edges of it, as opposed to anchoring it also in the middle with landscaping fabric staples.   All but a small section of the remainder of the seeded area was covered with wheat straw for erosion control.

The French drain can be seen in the
shadows to the left

Finally, we used a sprinkler to compact the burlap and straw, to stick the seed to the soil and to jump-start germination.  And luckily, it rain a few days later. 

Tweaking the Solar Collector Before Surrounding It With Topsoil 
Before adding the topsoil to the slope immediately south of the solar collector, I needed to dump six loader buckets of sand into the collector for use later when it goes into service as part of the AGS system. However, as described in a previous post, water collected in the collector numerous times and deposited about a foot of soil that had to be removed. The main reason for its removal was to uncover a French drain that passed under the collector (one of seven placed early on) so that it would be available to drain any water falling into the collector after it is finished.  As step-son, Keith, and I pitched the excess soil over the wall of the collector, we shaped the dirt floor so it will direct water to the French drain after it soaks through a thick layer of sand.  The sand overlaying the soil will support the corrugated steel that will adsorb the sun's rays for the AGS system -- the topic of a future post.

Collector after the sand has been added and
spread enough to cover all of the soil

As for the time being, we merely made sure that all of the dirt floor was covered with sand until the collector can be finished then left the rest of the sand piled up.

Insulating the Porch Footing
Another task to be done before finishing the topsoiling was to insulate the screened porch footing.  Since the foundation of the porch is a frost-protected shallow foundation, the footing needed to be insulated on its exterior where not already insulated by the umbrella, i.e., on the three sides not facing west towards the umbrella.  

Future Plans for the Insulation/Watershed Umbrella
Now the only area within 20' of the front of the house not covered by the umbrella is the section in front of the main entrance and the garage.  The umbrella here will be installed next year in conjunction with pouring the sidewalk and driveway.  The umbrella next to the retaining wall west of the house and the umbrella behind the concrete north wall of the house will also be installed next year.

Insulation at the level of the porch footing before backfilling

Landscaping Beyond the Umbrella
The catch basin lies in the rough ground south of the umbrella and the solar collector.  Because the basin is critical for keeping runoff onsite, it and the area around it will be the last portion of the building site to be landscaped.  The basin will give way to a series of rain gardens planted with natives so that rainwater will leave the property underground and purified instead from the surface and contaminated.

Rough area containing the catch basin (click on photo to enlarge it)

I guess we were pretty fortunate considering that it took almost three weeks to install the umbrella without having to deal with any serious rain. The final photo shows the site in mid-October as we return our attention to the carpentry phase in hopes of getting the house under cover before the rainy season in spring and early summer.

Status of the building site after the latest round of dirt work