Testing

Section 8.2 - 8.9 content text (only) Appendix C as A SCROLLING DOCUMENT!!!

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Soil Characterization Testing

The soil component of an LID BMP contributes substantially to its stormwater treatment performance and overall function. If the soil is overly compacted or very finely textured, it may drain too slowly. If the soil is highly organic or contains excessive amounts of chemical fertilizer it may contribute to nutrient loads to receiving waters rather than reduce them. If the soil is too shallow it may not provide adequate treatment of contaminated stormwater or may not support healthy vegetation. Whether it be the engineered filter media of bioretention cells, the growing media of green roofs or the topsoil of enhanced swales, vegetated filter strips and soil amendment areas, it is important that the soil provide a healthy growing environment for plantings while being within design specifications for key parameters specific to the type of BMP.

It is most important to sample and test soil characteristics as a part of Construction and Assumption inspections, to confirm the BMP has been constructed with materials that meet design specifications and that installation of the soil component is acceptable. Testing to confirm that the material meets quality specifications (i.e., particle-size distribution, organic matter, pH, cationic exchange capacity, nutrients and soluble salts) needs to be completed prior to it being delivered to the construction site. Testing to confirm that installation of the soil component is acceptable (i.e., depth and compaction) should be performed after the installed material has been allowed to settle for at least two (2) weeks, and prior to planting.

Sampling and testing is also recommended as a part of Verification inspections, to determine if the BMP is being adequately maintained and if soil characteristics are still within acceptable ranges. It may also be done as part of Forensic inspection and Testing (FIT) work to help diagnose the cause of poor vegetation cover, drainage or treatment performance and decide on corrective actions.

Maximum allowable bulk density values by soil texture class (Sustainable Sites Initiative, 2009). Click to enlarge.

Critical soil characteristics, acceptance criteria and tests by LID BMP type

LID BMP Type	Soil Characteristic	Acceptance Criteriai	Test
Bioretention / Bioswales / Dry swale
	Textureii	Loamy Sand or Sandy Loam; 70 to 88% sand-sized particles; 12 to 30% silt- and clay-sized particles; <20% clay-sized particles.	Particle-Size Distribution (PSD), or % Sand/Silt/Clay (i.e., Soil Texture) plus Sand Fraction
	Organic Matter (OM)	3 to 10% by dry weightii	Walkley-Black method when OM <7.5% or Loss On Ignition (LOI) method when OM ≥7.5%iii
	Soil pH	6.0 to 7.8	pH of a Saturated Pasteiii
	Cationic Exchange Capacity (CEC)	>10 meq/100 g	Cationic Exchange Capacity Test
	Phosphorusiv	12 to 40 ppm	Extractable Phosphorus
	Soluble Saltsv	≤2.0 mS/cm (0.2 S/m)	Electrical Conductivity of a Soil-Water Slurry (2:1 water to soil ratio by volume)iii
	Depth	+/- 10% of design specification	Soil Cores, Test Pits or Cone Penetration Tests
	Compactionvi	Surface Resistance: ≤110 PSI; Sub-surface Resistance: ≤260 PSI Bulk Density: ≤1.60 g/cm3	Cone Penetration Tests or Bulk Density Tests
	Permeability	i ≥25 mm/h (KS ≥ 1 x 10-5 cm/s); and i ≤203 mm/h (KS ≤ 0.02 cm/s).	Surface Infiltration Rate Tests
Enhanced swale (topsoil)
	Texture	Same soil texture classification as specified in the final design or recorded on the as-built drawing	Particle-Size Distribution (PSD), or % Sand/Silt/Clay (i.e., Soil Texture) plus Sand Fraction
	Organic Matter (OM)ii	5 to 10% by dry weight	Walkley-Black method when OM <7.5% or Loss On Ignition (LOI) method when OM ≥7.5%iii
	Soil pH	6.0 to 7.8	pH of a Saturated Pasteiii
	Phosphorusiv	12 to 40 ppm	Extractable Phosphorus
	Soluble Saltsv	≤2.0 mS/cm (0.2 S/m)	Electrical Conductivity of a Soil-Water Slurry (2:1 water to soil ratio by volume)iii
	Depth	+/- 10% of design specification	Soil Cores, Test Pits
	Compaction	Surface Resistance: ≤110 PSI; Sub-surface Resistance: Use soil texture class and "Soil & Texture Class Table" (below) to determine maximum acceptable value; Bulk Density: Use PSD to interpolate maximum bulk density value from bulk density figure beside this table.	Cone Penetration Tests or Bulk Density Tests
	Permeability	i ≥15 mm/h (KS ≥ 1 x 10-6 cm/s)	Surface Infiltration Rate Tests
Vegetated filter strips and Soil Amendment Areas (topsoil)
	Texture	Same soil texture classification as specified in the final design or recorded on the as-built drawing	Particle-Size Distribution (PSD), or % Sand/Silt/Clay (i.e., Soil Texture) plus Sand Fraction
	Organic Matter (OM)ii	5 to 10% by dry weight	Walkley-Black method when OM <7.5% or Loss On Ignition (LOI) method when OM ≥7.5%iii
	Soil pH	6.0 to 7.8	pH of a Saturated Pasteiii
	Phosphorusiv	12 to 40 ppm	Extractable Phosphorus
	Soluble Saltsv	≤2.0 mS/cm (0.2 S/m)	Electrical Conductivity of a Soil-Water Slurry (2:1 water to soil ratio by volume)iii
	Compaction	Surface Resistance: ≤110 PSI; Sub-surface Resistance: Use soil texture class and "Soil & Texture Class Table" (below) to determine maximum acceptable value; Bulk Density: Use PSD to interpolate maximum bulk density value from bulk density figure beside this table.	Cone Penetration Tests or Bulk Density Tests
	Permeability	i ≥15 mm/h (KS ≥ 1 x 10-6 cm/s)	Surface Infiltration Rate Tests
Green roof (growing media)
	Texture	See product vendor or BMP designer for specifications	Particle-Size Distribution (PSD), or % Sand/Silt/Clay (i.e., Soil Texture) plus Sand Fraction
	Maximum Media Density	See product vendor or BMP designer for specification	Maximum Media Density Test (ASTM E2399/E2399M-15)
	Water Storage Capacityvii	Extensive: ≥35% by volume / Intensive: ≥45% by volume	Both part of Maximum Media Density Test (ASTM E2399/E2399M-15)
	Air-Filled Porosityvii	≥10% by volume	Part of Maximum Media Density Test (ASTM E2399/E2399M-15)
	Permeability, Saturated Media	See product vendor or BMP designer for specification	Part of Maximum Media Density Test (ASTM E2399/E2399M-15)
	Organic Matter	See product vendor or BMP designer for specification	Walkley-Black method when OM <7.5% or Loss On Ignition (LOI) method when OM ≥7.5%iii
	Soil pHviii	6.5 to 7.8	pH of a Saturated Paste
	Soluble Saltsviii	≤0.85 mS/cm (0.085 S/m)	Electrical Conductivity of a Saturated Media Extract (SME)solution
	Phosphorusix	2.2 to 40 ppm	Electrical Conductivity of a Saturated Media Extract (SME)solution

Notes
i Values represent acceptable ranges for established BMPs (i.e., in operation for 3 years or more). For Construction and Assumption inspections, final design and soil or media product specifications and permissible tolerance ranges should be used as the acceptance criteria, which may be smaller ranges than the values in this table.
ii Suggested range for diagnosing suspected problems with drainage function, vegetation cover or vegetation condition for established BMPs constructed with filter media that meets recommended guidelines (CVC & TRCA, 2010). For proprietary filter media products, different ranges may be acceptable. Product specifications should be provided by the media supplier. Test results should be compared to the media supplier’s specifications and permissible tolerance ranges
iii Based on Ontario Ministry of Food and Rural Affairs’ Soil Fertility Handbook guidance on soil fertility testing for crop production (OMAFRA, 2006).
iv Based on Minnesota Pollution Control Agency (MPCA, 2015) for minimum to sustain plant growth and Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA, 2014) for a maximum to avoid unnecessary fertilization that would have low or no effect on plant health.
v Based on the threshold for non-saline soils (Whitney, 2012).
vi Interpolated value from bulk density figure beside this table. based on a sandy loam soil containing at least 70% sand-sized particles.
vii Based on German green roof standards (FLL 2008). Specifications will vary depending on the green roof growing media product. Product specifications should be provided by the media supplier. Test results should be compared to the media supplier’s specifications and permissible tolerance ranges.
viii Based on Penn State University Center for Green Roof Research (Berghage et al. 2008).
ix Based on Penn State University Center for Green Roof Research (Berghage et al. 2008) for the minimum to sustain plant growth and Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA, 2014) for the maximum to avoid unnecessary fertilization that would have low or no effect on plant health.

Acceptable Soil Cone Penetrometer Readings (Soil & Texture Class)

Surface Resistancei	'Sub-surface Resistancei
All Soil Textures	Sandy (includes loamy sand, sandy loam, sandy clay loam and sandy clay)	Silty (includes loam, silty loam, silty clay loam, and silty clay)	Clayey (includes clay loam and clay)
≤ 110 PSIii	≤ 260 PSI	≤ 260 PSI	≤ 225 PSI
≤ 7.7 kg/cm2	≤ 18.3 kg/cm2 iii	≤ 18.3 kg/cm2	≤ 15.8 kg/cm2
≤ 758 kPaiv	≤ 1793 kPa	≤ 1793 kPa	≤ 1551 kPa

Notes
i Adapted from Gugino et al. (2009)
ii PSI = pounds per square inch (lb/in2)
iii kg/cm2 = kilogram per square centimetre.
iv kPa = kilopascals

For further information regarding soil characteristics, acceptance criteria per LID BMP type and associated testing tools and protocols scroll down to the embedded 2016 guide below.

Sediment Accumulation Testing

A primary function of LID BMPs is to capture and retain sediment, trash and debris that are suspended in stormwater runoff. Over time, sediment and natural debris accumulates in certain portions of a BMP, particularly in pretreatment devices (e.g., forebays, gravel diaphragms, hydrodynamic separators, vegetated filter strips, grass swales, catchbasin/manhole sumps) and at inlets, where inflowing runoff is slowed down and spread out, which promotes sedimentation of suspended materials by design.

Without adequate inspection and maintenance (at least annually), accumulated sediment and debris in pretreatment devices and inlets can inhibit the flow of stormwater into the BMP or be transported onto the filter bed . Extensive sediment accumulation on the surface of a filter bed will eventually lead to drainage problems due to clogging of the filter media with fine-textured sediment. When sediment accumulation on the surface of a filter strip or swales becomes excessive the BMPs begin to export sediment and associated pollutants into receiving waters rather than retain them.

Key Components, Test Methods and Equipment

Key components of LID BMPs that should be the subject of sediment accumulation testing (i.e., depth measurements) are described in the table below along with recommended test methods. Depth measurements should be recorded on inspection field data forms provided on each associated BMP's I&M page on the wiki, used to determine if sediment removal maintenance is needed.

Picture of a typical Secchi disk to help measure sediment depth in underground holding structures. (Photo Source: Wildco, 2018

Key components and test methods for sediment accumulation testing by BMP type

LID BMP Type	Key Components	Recommended Test Method
Bioretention / Bioswales / Dry swale / Enhanced grass swales / Vegetated filter strips
	Inlets; Pretreatment devices	Use a tape measure or probe to measure the depth from the bottom elevation of the pretreatment device or surface of the filter bed (adjacent to the inlet structure), below any stone or mulch cover present, to the highest elevation of accumulated sediment present. For catchbasins, manholes and hydrodynamic separator pretreatment devices a sludge sampler (e.g., “sludge judge” sampler) should be used to sample the sediment and estimate depth accumulated in sumps. Record the measurement and remove the sediment if it exceeds trigger values for follow-up action.
	Filter Bed	Use a tape measure or probe to measure sediment depth from the surface of the filter bed, below any stone or mulch cover present, to the elevation of accumulated sediment present in at least five (5) locations evenly distributed over the filter bed surface area. Record the measurements, calculate the mean sediment depth and compare to trigger values to determine if follow-up/corrective actions are needed.
Underground infiltration systems (Soakaways, infiltration trenches, infiltration chambers and perforated pipe storm sewer systems
	Inlets; Pretreatment devices	Use tape measure or probe to measure the depth from the bottom elevation of the inlet pipe or pretreatment device, below any stone or mulch cover present, to the highest elevation of accumulated sediment present. For catchbasins, manholes and hydrodynamic separator pretreatment devices a sludge sampler (e.g., “sludge judge” sampler) should be used to sample the sediment and estimate depth accumulated in sumps. A measuring tape or staff gauge installed in the structure and set to the bottom elevation can provide another means of tracking sediment accumulation. Record the measurement and remove the sediment if it exceeds trigger values.
	Filter Bed	(Applicable to vault-type infiltration chamber systems only) - Use a tape measure or probe to measure sediment depth from the surface of the gravel bed to the elevation of accumulated sediment in at least five (5) locations evenly distributed over the bed surface area. Record the measurements, calculate the mean sediment depth and compare to trigger values to determine if follow-up/corrective actions are needed.
Cisterns (Rainwater Harvesting & Rain barrels)
	Cistern	From outside the cistern use a tape measure or probe to measure the depth from a fixed point (e.g., rim of the access hatch) to the bottom elevation of the cistern and to the highest elevation of accumulated sediment present. Subtract the two values to calculate the sediment depth. A sludge sampler (e.g., “sludge judge” sampler) may also be used to sample the sediment and estimate depth. A staff gauge installed on the cistern wall and set to the bottom elevation provides another means of measuring sediment depth that does not require entry into the confined space. Record the measurement and remove the sediment if it exceeds trigger values for follow-up action.

Measuring sediment depth in a catchbasin utilizing the "two prong method" (Photo Source: King County, 2010)

Standard Equipment Used

Equipment needed for sediment accumulation testing can include the following:

• Safety apparel (hard hat, steel toed boots, gloves and eye protection)
• Safety cones or barriers (for restricting access around open hatches/grates/manhole covers)
• Clipboard, inspection field data forms, pens
• Pick shovel (for opening catchbasin grates or manhole covers)
• Measuring tape
• Probe (rigid)
• Secchi disk
• Sludge sampler
• Rope
• Flashlight or headlamp
• Harness
• Tripod (certified and tested)
• Winch (certified and tested)
• Multi-gas detector (recently calibrated and tested)

Sediment accumulation testing should be conducted frequently during construction (e.g., weekly and after any storm event of 15 mm depth or greater), as part of Assumption inspection work, once construction is fully completed and sediment accumulated on the CDA, in conveyances (e.g., gutters, catchbasins, storm sewers) and pretreatment devices has been removed, and as part of Routine Operation and Verification inspections.

For further information regarding soil characteristics, acceptance criteria per LID BMP type and associated testing tools and protocols scroll down to the embedded 2016 guide below.

Surface Infiltration Rate Testing

For LID BMPs like bioretention and bioswales, enhanced swales, vegetated filter strips and permeable pavements, the rate at which stormwater infiltrates through the BMP surface greatly affects its drainage performance. If the surface infiltration rate (i) is too low, inflowing stormwater will quickly begin to pond on the surface and, once the overflow outlet elevation is reached, will by-pass treatment by the BMP. In extreme cases the BMP may pond water on the surface for longer than 24 hours, creating nuisance conditions (e.g., poor vegetation cover, ice formation, ideal mosquito breeding ground habitat).

Causes of excessively low surface infiltration rates include use of soil during construction that does not meet design specifications, accumulation of fine sediment on the soil surface or in permeable pavement joints or pore spaces, and over-compaction of the soil, that can occur during construction or routine operation. Therefore it is important to test the surface infiltration rate of LID BMPs as part of Assumption and Verification inspections. As part of Assumption inspections it helps determine if the BMP is ready to be assumed by the property owner. As part of Verification inspections it provides an indication of whether or not the surface drainage performance of the BMP is still within an acceptable range, if it is being adequately maintained, and to diagnose the cause of any problems with drainage or vegetation detected through visual inspection or other types of testing. Tests may also be done as part of Forensic Inspection and Testing (FIT) work to diagnose the cause of problems with drainage or vegetation, with the number and locations of test determined by the nature of the problem being investigated.

Surface infiltration rate testing involves estimating the saturated hydraulic conductivity (K_S) of the BMP surface through measurement at several locations and calculation of an average value. A single measurement can take anywhere from 15 minutes to several hours (Erickson et al., 2013) depending on soil or surface characteristics.

Embedded Reference Guide

To gain further insight into various testing requirements/methods, acceptance requirements, associated tools, equipment and components from STEP on the inspection and maintenance of different BMP LID practices, please see our complete guide here or embedded below:

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.

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.

Watercourses and Lake Ontario, to which Stormwater and Combined Sewer Overflows discharge.

The engineered soil component of bioretention cell or dry swale designs, typically with a high rate of infiltration and designed to retain contaminants through filtration and adsorption to particles.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

The practice of adding organic material, such as mulch or compost to topsoil to improve fertility, and tilling of the native soils to reverse compaction and restore its water retaining capacity.

Refers to the conditions in which an organism lives and survives or the conditions in which an organism resides. These conditions can be described as aspects of a “physical”, “social” or an “economic” environment, depending on the perspective perceived by the observer.

FIT work involves the application of a similar set of inspection and testing indicators as those used in Performance Verification inspections, but focuses on diagnosing suspected problems with the following objectives in mind: (1) Confirm whether or not problems with BMP function exist; (2) Identify the causes of confirmed problems; (3) Determine corrective actions needed.

Mineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm.

Mineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm.

Soil or media particles smaller than sand and larger than clay (3 to 60 m)

1. A mineral soil separate consisting of particles less than 0.002 millimeter in equivalent diameter. 2. A soil texture class. 3. (Engineering) A fine-grained soil (more than 50 percent passing the No. 200 Sieve) that has a high plasticity index in relation to the liquid limit. (Unified Soil Classification System).

Soil or media particles smaller than sand and larger than clay (3 to 60 m)

1. A mineral soil separate consisting of particles less than 0.002 millimeter in equivalent diameter. 2. A soil texture class. 3. (Engineering) A fine-grained soil (more than 50 percent passing the No. 200 Sieve) that has a high plasticity index in relation to the liquid limit. (Unified Soil Classification System).

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 thin layer of vegetation and growing medium installed on top of a conventional flat or sloped roof, also referred to as living roofs or rooftop gardens.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

Box like underground concrete structure with openings in curb and gutter designed to collect runoff from streets and pavement.

Deposition of material of varying size, both mineral and organic away from its site of origin by the action of water, wind, gravity or ice.

Settling-out or deposition of particulate matter suspended in runoff.

Initial capturing and removal of unwanted contaminants, such as debris, sediment, leaves and pollutants, from stormwater before reaching a best management practice; Examples include, settling forebays, vegetated filter strips and gravel diaphragms.

a gently sloping, densely vegetated areas that treat runoff as sheet flow from adjacent impervious areas. They function by slowing runoff velocity and filtering out suspended sediment and associated pollutants, and by providing some infiltration into underlying soils.

a top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales.

Tank used to store rainwater (typically roof runoff) for later use.

Tank used to store rainwater (typically roof runoff) for later use.

The rate at which stormwater percolates into the subsoil measured in inches per hour.

A body of water smaller than a lake, often artificially formed.

An alternative practice to traditional impervious pavement, prevents the generation of runoff by allowing precipitation falling on the surface to infiltrate through the surface course into an underlying stone reservoir and, where suitable conditions exist, into the native soil.

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

Human application of water to agricultural or recreational land for watering purposes. City of Toronto Wet Weather Flow Management November 2006 47

Tank used to store rainwater (typically roof runoff) for later use.

Sustainable Technologies Evaluation Program

Credit Valley Conservation

Toronto and Region Conservation Authority

Low impact development is a stormwater management and land development strategy applied at the parcel and subdivision scale that emphasizes conservation and use of on-site natural features integrated with engineered, small scale hydrologic controls to more closely mimic pre-development hydrologic functions.

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.