SAND particle size distribution recommendation – for the LAST time
I know what I know, did what I did, documented it … and this is what (ALL) I can speak to from authority/experience (recommend).
The sand that I used performed spectacularly well in every aspect/way – IMO – I can’t image a greater efficacy. I’m not saying that some other fractionation will not ‘work’ … however defined/determined/felt … but how well is good enough for you is for you the decide?
I used sharp (crushed) quartz (SiO2), which was chemically inert (does not effect pH) in the following grain size distribution (summarized):
- 30% by volume in the size range between 1 to 2 mm (+/- 2%)
- 40% by volume in the size range of 0.5 to 1 mm (+/- 2%)
- 25% by volume in the size range of 0.25 to 0.5 mm (+/- 2%)
- less than 0.25 mm (combined, including silt) at a maximum of 8% by volume (less is better).
FYI, with this particle size distribution I experienced lateral water movement in pristine furrows (very first irrigation) of approximately 4 to 5 meters in length – no problem. For furrows of 8 to 10 meters in length I laid a 4-6″ wide strip of 5 mil clear polyethylene film in the furrow and cut closely spaced slits/holes in that film to help the water/wastes reach the end, but only for approximately the first week. After that, the biofilms and detritus layer had developed to the point where I removed the temporary perforated film (leaving any detritus on the actual film in the furrow). With or without an initial ‘film assist’, I observed virtually no erosion of sloughing of the ridges from day one or at any other point in time in any ‘system’. Believe it or not. Everything I say is intended for YOUR benefit, not mine.
For further discussion on sand, please use the search function (upper right) to access previous discussions – including as it compares to gravel.
And while on the sand topic (AGAIN) … I keep hearing complaints about it being so hard to find (in the US that’s BS) and also that is so damn expensive (also BS). In the US virtually anywhere, sand, pea gravel and 3/4″ gravel are basically the same price by volume and/or by weight, whether from a quarry or in bags at your local big-box store. Price varies by location and volume ordered, typically from $20 to $40 per ton (as low as $11yd3 in upper Midwest States).
In fact, for our US friends, it’s as close as your nearest Home Depot or Lowe’s. A company called Quikrete supplies both retailers with a diverse range of aggregates…including graded sands in many types and sizes…and for all manner of purposes.
For example, in the Quikrete product line: product # 1961 is 30-70 mesh or 0.2 to 0.6mm), #1962 (20-50 mesh or 0.3 to 0.8 mm) and #1963 (12-30 mesh, or 0.6 to 1.7 mm). With these particle size distributions, one might get away with using all as #1963, but personally, for every 10 bags, I’d make 3 of them #1962 to increase SSA, improve moisture retention and also improve lateral water flow along the furrows until such time as a detritus layer is established.
Bag prices (50 lbs or 22.7 kg) range from $4 to $8 per bag at retail outlets everywhere – varies by location – but bags are the most expensive route possible. One cubic yard = 52 bags of 50# at 2,600 lb/yd3 for dry sand
1 cubic yard of dry sand weights from 1.3 to 1.35 ton, so per cubic yard quarry tonnage rates range from $26 to $54/ yd3, or $34 to $71/ m3. Bulk bags in the midwest states (e.g. Oklahoma): 3000# bulk-bag of 20-40 US sieve #24 filter sand = $206 delivered to OKC (from Wisconsin, March ’17)). At 2600#/yd3 = 1.15 yd3 or 0.88 m3. for $179/yd3 or $234/m3.
Here in Montana, bags (sand, pea gravel, etc) at Lowe’s (et al) are $4.25 /50#. (in bags you’re paying 3 to 4 times as much by volume than in bulk) Local quarry prices range $35 to $45/cubic yard for single units of washed graded sand or $30 to $35/cubic yard in 10-yard truck loads (plus $0.25 to $0.30 per mile) I have a choice of at least 3 quarries, 2 concrete batch plants and a cinder-block plant just within 60 miles in one direction – each with multiple grades (size distributions) to choose from or mix and match). In other words I can have 10 yards delivered (enough for 30 square yard of biofilter for under $500 – all day long from multiple sources. (<$1.85 ft2, <$20/m2). Yes, it cost much more in bags … but still damn CHEAP compare to clay ball crap.
Compare sand prices to Hydroton at Walmart (today) for $86 / 50 liter = $1,720 m3 ($1,338/yd3) – you order and go pick it up. – or compare with Gyco branded Hydro-Clay, at $27 per 50 liter bag (online) plus shipping (one bag at $59.72 UPS ground to me) which for 8 bags (most they would calculate shipping on) = $659.36/ 400 liter = $1,650 m3
To summarize Basically, (in the US) gravel, pea gravel and sand are nearly the same price whether by the cubic yard, ton, or in bags, Varies by location and volume purchased. Cost ranges from $20 to $40/ton (bulk) or $4 to $8 /50# bag (as low as $11 cu yd in Michigan or Wisconsin)
Delivered quarry sand at $50/yd3 is 25 times LESS (+/- 4%) than expanded clay pebbles (which is a vastly inferior media relative to sand in several aspects and it also degrades (breaks down) over time (sand does not degrade).
In iAVS, the sand does it all = 1) mechanical filtration (99+% particulate removal) , 2) exponentially superior Nitrification substrate than ‘alternatives’, 3) Oxygen rich ‘home’ for biofilms and soil microbial community including robust rhizosphere, and 4) excellent, aerated anchor for vascular plant roots. That’s 4 critical (key) functions all in one package, at 4% of the cost of a significantly inferior ‘alternative’. What’s not to love (complain about)?
I can’t speak for Gary but I am DONE with the entire sand subject. If sand is felt to be too difficult to source and/or deemed to be too expensive for what it can do for you, then you would probably not be successful in maintaining a functional iAVs or any other AP so-called ‘system’ – IMO.