Responses to comments

From LID SWM Planning and Design Guide
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Thank you to all of our active community members below, for helping us to make corrections and find additional useful content[edit]

28 October 2019

Could we add some settling velocities here? It's something I've found very useful in other manuals and I think it would be good to have here.

  • Thank you - it has now been added to the Dry ponds page.

17 September 2019

This section should include a link to the City of Toronto Green Streets Technical Guidelines Plant Material Selection tool. This is the most complete and comprehensive tool available for selecting tree, shrubs and herbaceous species for all GI SWM installations, by GI type.

  • Thank you this resource has now been referenced on the Plant lists page.

12 September 2019

Overview section - You may want to add to the list of bullet points: Composite plastic/recycled rubber permeable unit pavers Under the 'fundamental' heading - 3rd Bullet 'cast in place' should be changed to 'cast-in-place" Under the 'Uses' section- Add to the list of additional components ' Impervious liner for installations where infiltration is not desirable including well-head, protection areas, high water table sites and sites where installations are proximate to building faces/foundations'. Pretreatment section - Last sentence - Change the word 'element' to 'method' Risk of Groundwater Contamination section - 2nd bullet - Add a comma after 'such as' This section would benefit from some discussion related to the use of an impervious liner and an underdrain to provide a barrier to protect groundwater. The system functions as a 'filtration/attenuation' installation. Private Systems section - Last sentence - Change 'existing practices' to 'existing permeable pavement installations'. Design section - Finish course - 1st sentence - chage 'of' to 'for and add 'specific' ('for their specific product'). Performance section - This section would benefit from some discussion related to attenuation/filtration (non-infiltration type installations). On urban sites where underground parking garages are lot-line to lot-line, we commonly use permeable pavement with a liner and a stone reservoir as a tool to achieve SWM targets. This technique is one of the few means available to assist on very tight sites or within projects that are located on Brownfield sites that have been remediated through capping to encapsulate contaminated subsoils.

4 September 2019

In the second line 'n' should be changed to 'in' Overview section - 1st line, add a hyphen between 'well' and 'recognized' Additional Components section - Add Impervious liner to the list of components with the explanation that an impervious liner can be used where the bioretention installation is proposed in close proximity to buildings, in areas where the water table is high and over contaminated soils Space section - 3rd bullet, second line - add hyphen between 'trade' and 'off' 4th bullet should be changed to read '...from having very curvilinear, soft edges and variable depth...'. Add a hyphen between 'hard' and 'sided' 6th bullet - add 'with' before 'regards'. Change text to read, '...check to ensure that the future canopy height...' Overflow routing section - sidebar sketches should include labels 'Off-line' and 'On-line' in order to correspond with the text in the 'Routing' section Overflow Elevation section - 2nd line - 'timeltime' should be changed to 'timeline' Freeboard section - 3rd bullet - 'above grade' is repeated. Delete second 'above grade' and add hyphen between 'above' and 'grade' in the remaining reference. Gallery - 2nd image from the left. Correct the location of the photo credit and change capital 'B' in subsequent word to lower-case. Plant Selection section - Add text that discourages the use of non-native, invasive species and promotes use of native species that are indigenous to the region

  • Thank you for all of your edits, changes have been made on the Bioretention page.

15 August 2019

C.Davidson, Golder Associates - The Wiki says "Void Ratio of 0.4", but the Stormtech reference cited says "Porosity of 40%". These are not the same number. -Porosity = Volume of Voids / Total Volume of Material -Void Ratio = Volume of Voids / Volume of Solids For clearstone layer with 40% porosity, should not void ratio be 40% / 60%, or 0.67? SWMM5 also gives "Typical values range from 0.5 to 0.75 for gravel beds"

  • Thank you Chris, this has been changed to proper "Porosity value of 0.4" instead of "void ratio" on the Infiltration trenches.

12 August 2019

Hello. Please include an external link to Thanks - Brent

  • Thanks Brent - it has now been added to the Rain barrels page.

12 August 2019

Hello. Please include an external link to Thanks. - Brent

  • Thanks Brent - it has now been added to the Rain Gardens page.

25 July 2019

Please add the STEP video about the LID tool to this page.

24 July 2019

Clarify porosity vs storage capacity. there is no provided definition for storage capacity, though it might infer media porosity. Please specify.

15 July 2019

ASCE standard for permeable pavers should be referenced. Base depths and layering specifications are provided in this document. Consider referencing these depths here for easy reference.

3 July 2019

Armtec link is broken.

3 July 2019

The first photo is owned by Bill Trenouth, taken in 2009.You are welcome to use it though!

  • Thank you, we provided acknowledgement of ownership now - much appreciated!

10 June 2019

Often asked to provide a specification for deeper monitoring wells. This is a good start. More specifications please. Minimum diameter 100 mm, as smaller pipes tend to bend when soil is backfilled into the trench. Rigid material such as PVC preferred. Perforations only along the bottom where it intersects with the stone drainage layer. Lockable cap preferred. Top elevation above surface overflow elevation (you have that one, but hoping they don't forget about the overflow pipe at surface if there is one). Sock to keep sediment out of the well. Perforation spacing similar to typical perforated drainage pipe. Bottom should penetrate below the drainage pipe and into the native soil by at least 150 mm as the sensor is not at the very bottom of the instrument. This allows calculation of drain down time of water between the invert of the drainage pipe and the native soil. If the drainage pipe is installed in a small v-notch trench, the well should extend min 150 mm below the invert of this pipe. Deeper wells may also be installed to monitor groundwater table fluctuations below the facility, in which case the well must extend below the lowest annual elevation of the groundwater table. Simple schematic would be helpful. See Lakeshore pilot drawings as example. Normally we are using the monitoring well to measure water level fluctuations in response to rain events - you mention that it is used to measure water retention in the well, which may be confusing.

28 May 2019

The document should also provide links for plastic chambers by Prinsco and StormChamber.

  • In our effort to make this guide as functional as possible, we have decided to include proprietary systems and links to manufacturers websites. Inclusion of such links does not constitute endorsement by the Sustainable Technologies Evaluation Program. We have updated the page and link updates are welcomed using the form at the bottom of the chambers page.

9 May 2019

well should penetrate into the native soil by 10 cm or more to accomplish the objective of determining drainage to native soils. Currently depth of well spec suggests it penetrates below underdrain only. Typical diameter of monitoring well and the option of a lockable cap for continuous water level sensor monitoring should be provided. A schematic would be helpful.

  • Fixed and added schematic on the wells page

18 April 2019

Snout link is broken

12 April 2019

It looks like there is a unit conversion error in the equation: ST=RVCT×Ac×C×0.1. When I do a unit conversion from mm.ha to m3, I find that the conversion factor should be 10, not 0.1.

7 Feb 2019

There is no "L" in the equation. Perhaps a second equation for a pipe orifice would help clarify that.

  • There were a few typos in the orifice equation, it has been reviewed and we believe that they have all been corrected. That page also has a link to the adapted variation for perforated pipe flow.

20 November 2018

What if different calculation pages were part of the table of contents? So the section could be titled "Calculations" and within that link could be different pages of calculations instructions from area and volume calculations to gradient slope calculations. Also I think the table of contents should be available on the left margin especially when a user is browsing through the wiki site and would like to read another section of the wiki.

  • Thanks Hilary, a category tag of Calculations has been created to help screen for these types of resources. The table of contents is now available on the left menu bar.

20 November 2018

What a great site and resource you have created. It’s a pleasure to be part of it.

  • Thanks Jeff

4 November 2018

While navigating the wiki, I have come across a number of references to using excess water for irrigation on green roofs or rain barrels. However, it may be useful to include information on 'Keyline Design,' first developed by P. A. Yeomans in the 1950's. While geared towards agricultural and pastoral improvement, it has applications in most water management systems.

  • Excellent reference, thank you Alex. I shall create a page explaining these Keyline design principles, some of which I believe are similar to 'micro-grading'.

31 August 2018

Take a look a this address : There's plenty interesting plans with notes to see how to make important changes to the plans following the field reality!

  • GreenGirl subscribes to the same share-and-share alike Creative Commons licensing as we do. We have her website and a few similar resources linked on our Drawings page.

25 July 2018

Do the units check out for calculating the total depth of the stone reservoir? (i.e. should f' be in units of m/hr instead of m/day?)

  • The notation used in the equations on Permeable pavements: Sizing is being brought into line with the other sections of the site. Units have also been checked and brought into line to millimeters and hours as used for the other BMPs.

16 July 2018

I think Table 1 in this article ( would be good for the wiki guide - it explains the traits of vegetation and how they impact hydrology or water quality.

  • Thanks Sylvie, the information from within that article has been used to produce a similar table on the Plants page.

11 June 2018

The term "forebay" has a strong industry connection to SWM ponds, should this page have a different/more specific name?

  • Thanks Alana and Steve, "Forebay" now redirects to the newly named Pretreatment features page as you suggest.

24 April 2018

A general feedback from a french user - I do not know the meaning of the acronym LID, used profusely in this article, making it hard to understand. I think it would be very helpful to have a definition for all the acronyms by hovering the mouse cursor over them, just like you did in the sixth paragraph of "Targeting hard surfaces" with the definition of "Rainwater harvesting". This type of definition should be available for all the acronyms used in every other pages of this wiki, at least once per acronym per page.

  • 'LID' has been added to the terms using the same definition for 'Low Impact Development'. We will continue to look for missing information of this type.

10 April 2018

Do you have any specs for designing berms around a bioretention pond?

23 March 2018

Is it possible to get the the planting list updated to include native species?

  • Certainly! This information will be added as we review the plant tables in summer 2018.

21 March 2018

Is there a reliable set of estimated design infiltration rates for sites where only soil type is currently known? Additional tests will be conducted, but for now we are looking for numbers to begin an estimate, and a reasonable basis for those numbers.

  • The curators of Minnesota's stormwater wiki have conducted a very thorough literature review to establish their suggested values for design infiltration rates[1]. The lowest value on their table for clayey soils is 15 mm/hr, we believe that this is a reasonable estimate for clay soils. Designers may wish to add a safety correction to this number before undertaking their design calculations.

  1. Minnesota Stormwater Manual contributors, "Design infiltration rates," Minnesota Stormwater Manual, , (accessed May 11, 2018).