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LID SWM Planning and Design Guide β

OPSS aggregates

The fines can clearly be seen on these piles of standard OPSS aggregates for road reconstruction

Of the standard granular materials in the standard OPSS.MUNI 1010 only Granular O is recommended as a substitute for clear stone in LID construction.

Where Granular O is substituted for clear stone in underground reservoir structures, the porosity used in design calculations shall be 0.3 unless laboratory testing proves otherwise.

Examples of BMPs with underground reservoirs include Underdrains, infiltration trenches, permeable pavements, infiltration chambers, exfiltration trenches.

All other mixes must be avoided for free drainage or storage as they are permitted to contain a higher enough proportion of fines to reduce permeability below 50 mm/hr.

Justification

Grain size analysis, percent passing[1]
Sieve size (mm) A B type I B type II B type III M O SSM
High Low High Low High Low High Low High Low High Low High Low
150 100 100 100 100 100 100
106 100 100
37.5 100 100
26.5 100 100 50 100 50 100 50 100 95 100 50 100
19 85 100 100 100 80 95
13.2 65 90 75 95 60 80
9.5 50 73 32 100 55 80 50 70
4.75 35 55 20 100 20 55 20 90 35 55 20 45 20 100
1.18 15 40 10 100 10 40 10 60 15 40 0 15 10 100
0.3 5 22 2 65 5 22 2 35 5 22 5 95
0.15 15 2 65
0.075 2 8 0 8 0 10 0 8 2 8 0 5 0 25
d60 13 6 35 0.25 25 6 40 1.2 10 5 15 7 35 0.15
d10 0.7 0.1 1 0.08 1.2 0.075 1.2 0.085 0.6 0.09 2.5 0.3 1.2 NaN
Content Uniformity 19 60 35 3 21 80 33 14 17 56 6 23 29
Porosity (Vukovic) 0.26 0.26 0.26 0.40 0.26 0.26 0.26 0.27 0.27 0.26 0.34 0.26 0.26
Mean porosity (Vukovic) 0.26 0.33 0.26 0.26 0.26 0.3 0.26
K(Hazen)(mm/hr) 1764 36 3600 23 5184 20 5184 26 1296 29 22500 324 5184 NaN
Mean K(hazen)(mm/hr) 900 1812 2602 2605 663 11412 NaN

Porosity values were calculated based on the coefficient of uniformity (CU)[2][3][4]\[n=0.255\left ( 1+0.83^{C_{U}} \right )\] Where coefficient of uniformity is the ratio of the 60th and 10th percentile grain sizes\[C_U=\frac{d_{60}}{d_{10}}\]

Permeability (K) was estimated from the 10th percentile grain size using the Hazen formula.


  1. OPSS. (2013). Material Specficiation for Aggregates - Base, Subbase, Select Subgrade, and Backfill Material. Retrieved from http://www.raqsb.mto.gov.on.ca/techpubs/ops.nsf/0/0b9aa4d966cac4f9852580820062909e/$FILE/OPSS.MUNI%201010%20Nov%2013.pdf
  2. Vuković, Milan and Soro, Andjelko Determination of hydraulic conductivity of porous media from grain-size composition. Water Resources Publications, Littleton, Colo, 1992.
  3. Odong, J. (2007). Evaluation of Empirical Formulae for Determination of Hydraulic Conductivity based on Grain-Size Analysis. Journal of American Science, 3(3). Retrieved from http://www.jofamericanscience.org/journals/am-sci/0303/10-0284-Odong-Evaluation-am.pdf
  4. Zhang, S. (2017). Relationship between Particle Size Distribution and Porosity in Dump Leaching. the University of British Columbia. Retrieved from https://open.library.ubc.ca/collections/ubctheses/24/items/1.0357233