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

Sieve size (mm)	A		B type I		B type II		B type III		M		O		(SSM) Select Subgrade Materials		(OGDL) Open Graded Drainage Layer
	High	Low	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			100	100
26.5	100	100	50	100	50	100	50	100			95	100	50	100	100	95
19	85	100							100	100	80	95			100	90
13.2	65	90							75	95	60	80			86	40
9.5	50	73					32	100	55	80	50	70			55	20
4.75	35	55	20	100	20	55	20	90	35	55	20	45	20	100	10	0
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	2	0
d60	13	6	35	0.25	25	6	40	1.2	10	5	15	7	35	0.15	2	NaN
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	0.658	0.466
Content Uniformity	19	60	35	3	21	80	33	14	17	56	6	23	29		3	NaN
Porosity (Vukovic)	0.26	0.26	0.40	0.26	0.26	0.26	0.27	0.26	0.27	0.26	0.34	0.26	0.26		0.40	0.25
Mean porosity (Vukovic)	0.26		0.33		0.26		0.26		0.26		0.3		0.26		0.38
K(Hazen)(mm/hr)	1764	36	3600	23	5184	20	5184	26	1296	29	22500	324	5184	NaN	62500
Mean K(hazen)(mm/hr)	900		1812		2602		2605		663		11412		NaN		62500

Porosity values were calculated based on the coefficient of uniformity (C_U): $n=0.255\left(1+0.83^{C_{U}}\right)$ 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.

References

1. OPSS. (2020). Construction Specification for Open Grades Drainage Layer. OPSS.PROV 320. Retrieved from: https://www.roadauthority.com/Standards/Home/FileDownload?standardFileId=b159a440-9c86-4086-a9d1-4906c1ecb258

Soil particles with a diameter less than 0.050 mm.

A broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.

Gravel, or crushed stone of various size gradations (i.e., diameter), used in construction; void forming material used as bedding and runoff storage reservoirs and underdrains in stormwater infiltration practices.

Gravel, or crushed stone of various size gradations (i.e., diameter), used in construction; void forming material used as bedding and runoff storage reservoirs and underdrains in stormwater infiltration practices.

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

The porosity (n) of a mixture is the ratio of the volume of void-space to the total or bulk volume of the mixture. It is closely related to the concept of void ratio (e) where void ratio is the ratio of the volume of void-space to the volume of solids. n = Volume of voids/Total volume of mixture = e/(1+e)

The porosity (n) of a mixture is the ratio of the volume of void-space to the total or bulk volume of the mixture. It is closely related to the concept of void ratio (e) where void ratio is the ratio of the volume of void-space to the volume of solids. n = Volume of voids/Total volume of mixture = e/(1+e)

A broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.

A parameter that describes the capability of a medium to transmit water.