On Site: Halftime Update

We're half way through the site assessment, and there is much more work to do. We've conducted some interviews with village elders, a couple of families, an oxcart driver passing through the site, and an older man living directly behind the northern end of the embankment.

You'll get a different story on the dam, depending on who tells it. We're surprised to hear the dam was likely constructed with forced labor as part of a major irrigation project by the Khmer Rouge. The dam failed three or four times since then, always by overtopping, rebuilt by voluntary teams from the community. This failure mode (overtopping) is consistent with our site observations (we're finding a lot of strong, low-porosity clay material in our borings), and constructing the water gate is the best way to prevent a future failure.

Thursday we went with Mr. Yin Sovann (Ministry of Hydrology & Meteorology -- the guy who made the conceptual design for the watergate at Balang) to visit another watergate he designed and constructed recently. It was smaller than our structure, but helpful to visualize potential construction and design issues (eg. settlement and erosion) and to stimulate our conversation with him.

We've spent the past week making nearly daily technical visits

Last week's accomplishments:
- staked out a project baseline (with wil's cool homemade surveying equipment)
- surveyed the embankment north of washout
- GPS coordinates of the larger basin limits, outstanding topo features, canals
- water quality testing in the stream
- bore holes
- surveyed locations of bore holes and old test pits
- in situ porosity testing (bore hole permeameter method)
- soil lab work (liquid limit, plastic limit, shrinkage, moisture content and dry density of undisturbed samples, resistivity (as a measure of corrosivity), siev test and soil classification

Work to be completed this week:
- detailed site map
- detailed survey data adjacent to washout
- survey embankment north of washout
- locate potential sources of borrow material (eg termite hills are a great source of clay)
- GPS large scale area within the entire irrigated zone
- ongoing soil lab work
- embankment inspection
- additional soil borings at locations of severe erosion

Also, we'll have an auger fabricated by our new buddy at the machine shop down the street.

Wil has some cool photos of the badass improvised engineering we've been doing, and I'm sure you'll get a kick out of seeing it.

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