This page provides a discussion of how tree trench/tree box practices can achieve stormwater credits. Tree systems with and without underdrains are both discussed, with separate sections for each type of system as appropriate.
Credit refers to the quantity of stormwater or pollutant reduction achieved either by an individual best management practice (BMP) or cumulatively with multiple BMPs. Stormwater credits are a tool for local stormwater authorities who are interested in
- providing incentives to site developers to encourage the preservation of natural areas and the reduction of the volume of stormwater runoff being conveyed to a best management practice (BMP);
- complying with permit requirements, including antidegradation (see Construction permit; Municipal (MS4) permit);
- meeting the MIDS performance goal; or
- meeting or complying with water quality objectives, including total maximum daily load (TMDL) wasteload allocations (WLAs).
Green Infrastructure: Trees can be an important tool for retention and detention of stormwater runoff. Trees provide additional benefits, including cleaner air, reduction of heat island effects, carbon sequestration, reduced noise pollution, reduced pavement maintenance needs, and cooler cars in shaded parking lots.
| TSS | TP | PP | DP | TN | Metals | Bacteria | Hydrocarbons |
|---|---|---|---|---|---|---|---|
| 80 | link to table | link to table | link to table | 50 | 35 | 95 | 80 |
| NOTE: removal efficiencies are 100 percent for water that is infiltrated. TSS=total suspended solids; TP=total phosphorus; PP=particulate phosphorus; DP=dissolved phosphorus; TN=total nitrogen Sources. |
|||||||
Warning: Models are often selected to calculate credits. The model selected depends on your objectives. For compliance with the Construction Stormwater permit, the model must be based on the assumption that an instantaneous volume is captured by the BMP. For more information on using models to calculate credits see Methods and resources for calculating credits.
Contents
Overview
Tree trenches and tree boxes are specialized bioretention practices practices. They are therefore terrestrial-based (up-land as opposed to wetland) water quality and water quantity control process. Tree systems consist of an engineered soil media designed to treat stormwater runoff via filtration through plant and soil media, evapotranspiration from trees, or through infiltration into underlying soil. * Pretreatment is REQUIRED for all bioretention facilities, including tree-based systems, to settle particulates before entering the BMP. Tree practices may be built with or without an underdrain. Other common components may include a stone aggregate layer to allow for increased retention storage and an impermeable liner on the bottom or sides of the facility if located near buildings, subgrade utilities, or in Karst formations.
Pollutant removal mechanisms
Like other bioretention practices, tree trenches and tree boxes have high nutrient and pollutant removal efficiencies (Mid-America Regional Council and American Public Works Association Manual of Best Management Practice BMPs for Stormwater Quality, 2012). Tree practices provide pollutant removal and volume reduction through filtration, evaporation, infiltration, transpiration, biological and microbiological uptake, and soil adsorption; the extent of these benefits is highly dependent on site specific conditions and design. In addition to phosphorus and total suspended solids (TSS), which are discussed in greater detail below, tree practices treat a wide variety of other pollutants.
Removal of phosphorus is dependent on the engineered media. Media mixes with high organic matter content typically leach phosphorus and can therefore contribute to water quality degradation. The Manual provides a detailed discussion of media mixes, including information on phosphorus retention.
Location in the treatment train
Stormwater treatment trains are multiple best management practices (BMPs) that work together to minimize the volume of stormwater runoff, remove pollutants, and reduce the rate of stormwater runoff being discharged to Minnesota wetlands, lakes and streams. Tree trenches and tree boxes can be incorporated anywhere in the stormwater treatment train but are most often located in upland areas of the treatment train. The strategic distribution of tree BMPs help control runoff close to the source where it is generated.
Methodology for calculating credits
This section describes the basic concepts and equations used to calculate credits for volume, Total Suspended Solids (TSS) and Total Phosphorus (TP). For specific tools and methods that can be used to calculate credits see Methods and resources for calculating credits.
Tree practices generate credits for volume, TSS, and TP. Practices with underdrains do not substantially reduce the volume of runoff but may qualify for a partial volume credit as a result of evapotranspiration, infiltration occurring through the sidewalls above the underdrain, and infiltration below the underdrain piping. Tree practices are effective at reducing concentrations of other pollutants including nitrogen, metals, bacteria, and hydrocarbons. This article does not provide information on calculating credits for pollutants other than TSS and TP, but references are provided that may be useful for calculating credits for other pollutants.
Assumptions and approach
In developing the credit calculations, it is assumed the tree practice is properly designed, constructed, and maintained in accordance with the Minnesota Stormwater Manual. If any of these assumptions is not valid, the BMP may not qualify for credits or credits should be reduced based on reduced ability of the BMP to achieve volume or pollutant reductions. For guidance on design, construction, and maintenance, see the appropriate article within the tree section of the Manual.
Warning: Pretreatment is required for all filtration and infiltration practices
In the following discussion, the Water Quality Volume (VWQ) is delivered as an instantaneous volume to the BMP. The VWQ is stored within the filter media. The VWQ can vary depending on the stormwater management objective(s). For construction stormwater, VWQ is 1-inch times the new impervious surface area. For MIDS, VWQ is 1.1 inches times the impervious surface area.
Volume credit calculations
No underdrain
Volume credits are calculated based on the capacity of the BMP and its ability to permanently remove stormwater runoff via infiltration into the underlying soil, evapotranspiration (ET) from trees, and interception of rainfall by the tree canopy. The total volume credit, V in cubic feet, is given by
$^V = V_{inf_b}\ + V_{ET}\ + V_I^$
Where
Vinf is the volume of captured water that is infiltrated, in cubic feet;
VET is the volume of captured water that is lost to evapotranspiration, in cubic feet; and
VI is the volume of precipitation intercepted by the tree canopy, in cubic feet.
Interception credit
Water intercepted by a tree canopy may evaporate or be slowly released such that it does not contribute to stormwater runoff. An interception credit is given by a simplified value of the interception capacity (Ic) for deciduous and coniferous tree species [1].
Values of Ic for coniferous and deciduous trees:
Ic coniferous = 0.40 inches (2.2 millimeters)
Ic deciduous = 0.14 inches (1.1 millimeters)
These values intercept approximately 30% and 57% of annual rainfall over the canopy area.
This credit is per storm event.
Infiltration and ET credits
Information: In calculating the credit for evapotranspiration, use the rooting depth as the depth of media. This would equal the thickness of engineered media and the depth of soil below the engineered media into which tree roots can extend.
The infiltration and evapotranspiration (ET) credits are assumed to be instantaneous values entirely based on the capacity of the BMP to capture, store, and transmit water in any storm event. Because the volume is calculated as an instantaneous volume, the water quality volume (VWQ) is assumed to be instantly stored in the bioretention media. The volume of water between saturation and field capacity is assumed to infiltrate through the bottom of the BMP. The volume credit (Vinfb) for infiltration through the bottom of the BMP into the underlying soil, in cubic feet, is given by
$^V_{inf_b} = (n-FC)\ D_M\ (A_M + A_B)^$
Where
n is the porosity (f) of the media in cubic feet per cubic foot;
FC is the field capacity of the media in cubic feet per cubic foot;
AM is the area at the surface of the media, in square feet;
AB is the area at the bottom of the media, in square feet; and
DM is the media depth within the BMP, in feet. In calculating the credit for evapotranspiration, use the rooting depth as the depth of media. This would equal the thickness of engineered media and the depth of soil below the engineered media into which tree roots can extend.
Vinfb should be calculated to infiltrate within a specific drawdown time. The construction stormwater permit has a 48-hour drawdown requirement (24 hours is recommended for discharges to trout streams).
ET is calculated as the volume of water between field capacity and the permanent wilting point. Two calculations are needed to determine the evapotranspiration (ET) credit. The smaller of the two calculated values will be used as the ET credit.
The first calculation is the volume of water available for ET. This equals the water stored between field capacity and the wilting point. Note this calculation is made for the entire thickness of the media.
The second calculation is the theoretical ET. The theoretical volume of ET lost (Lindsey and Bassuk, 1991) per day per tree is given by
$^ET = (CP) (LAI) (E_{rate}) (E_{ratio})*3^$
Where:
CP is the canopy projection area (square feet);
LAI is the Leaf Area Index;
Erate is the evaporation rate per unit time (feet per day);
Eratio is the evaporation ratio; and
3 accounts for the number of days over which ET occurs (the average number of days between rain events in Minnesota).
Caution: The theoretical ET must be adjusted if the actual soil volume is less than the recommended volume. See the adjustment calculation below.
The canopy projection area (CP) is the perceived tree canopy area at maturity and is given by
$^CP = Π (d/2)^2^$
Where
d is the diameter of the canopy as measured at the dripline (feet).
CP varies by tree species. Refer to the Tree Species List for these values. Default values can be used in place of calculating CP.
And defaults for CP are based on tree size and are:
- 315 for a small tree;
- 490 for a medium sized tree; and
- 707 for a large tree.
The leaf area index (LAI) is a dimensionless measure that quantifies the amount of leaf material in a canopy.
LAI should be stratified by type into either:
- deciduous tree species (LAI = 3.5 for small trees, 4.1 for medium-sized trees, and 4.7 for large trees), or
- coniferous tree species (LAI = 5.47).
These values are based on collected research for global leaf area from 1932-2000 (Scurlock, Asner and Gower, 2002).
The evaporation rate (Erate) per unit time can be calculated using a pan evaporation rate for the given area, as available at NOAA. This should be estimated as a per day value.
The evaporation ratio (Eratio) is the equivalent that accounts for the efficiency of the leaves to transpire the available soil water or, alternately, the stomatal resistance of the canopy to transpiration and water movement. This is set at 0.20, or 20 percent based on research by Lindsey and Bassuk (1991). This means that a 1 square centimeter leaf transpires only about 1/5 as much as 1 square centimeter of pan surface.
If the soil volume is less than the recommended volume, the theoretical ET must be adjusted. Since the recommended soil volume equals 2 times the canopy project area (CP), the adjustment term is given by
$^Adjustment = (S_v)/(2 CP)^$
Where
Sv is the actual soil volume in cubic feet. Multiply the theoretical ET by the adjustment term to arrive at the true value for theoretical ET.
It is recommended that calculations be based over a three-day period. To determine the credit, compare the volume of water available for ET to the theoretical ET over a 3-day period. The credit is the smaller of these two values.
The annual volume captured and infiltrated by the BMP can be determined with appropriate modeling tools, including the MIDS calculator. Example values are shown below for a scenario using the MIDS calculator. For example, a permeable pavement system designed to capture 1 inch of runoff from impervious surfaces will capture 89 percent of annual runoff from a site with B (SM) soils.
Credit calculations - practice with underdrain
Volume credits for a tree system with an underdrain include the ET and interception credits discussed above and an infiltration credit. The main design variables impacting the infiltration volume credit include whether the underdrain is elevated above the native soils and if an impermeable liner on the sides or bottom of the basin is used. Other design variables include media top surface area, underdrain location, basin bottom area, total depth of media, soil water holding capacity and media porosity, and infiltration rate of underlying soils. The total volume credit (Vinf), in cubic feet, is given by
$^\hspace{2em}V_{inf} = V_{inf_b}\ + V_{inf_s}\ + V_U + V_{ET}\ + V_I^$
Where
Vinfb = volume of infiltration through the bottom of the basin (cubic feet);
Vinfs = volume of infiltration through the sides of the basin (cubic feet);
VU = volume of water stored beneath the underdrain that will infiltrate into the underlying soil (cubic feet);
VET = volume of captured water that is lost to evapotranspiration, in cubic feet; and
VI = volume of precipitation intercepted by the tree canopy, in cubic feet.
Volume credits for ET and canopy interception remain the same as shown above under volume credit calculation - no underdrain.
Volume credits for infiltration through the bottom of the basin (Vinfb) are accounted for only if the bottom of the basin is not lined and the BMP permanently removes a portion of the stormwater runoff via infiltration through sidewalls or beneath the underdrain piping. As long as water continues to draw down, some infiltration will occur through the bottom of the BMP. However, it is assumed that when an underdrain is included in the installation, the majority of water will be filtered through the media and exit through the underdrain. Because of this, the drawdown time is likely to be short. Volume credit for infiltration through the bottom of the basin is given by
$^V_{inf_B} = A_B\ DDT\ I_R/12^$
Where
IR = design infiltration rate of underlying soil (inches per hour);
AB = surface area at the bottom of the basin (square feet); and
DDT = drawdown time for ponded water (hours).
Information: The MIDS calculator assigns a default value of 0.06 inches per hour, equivalent to a D soil, to IR. This is based on the assumption that most water will drain to the underdrain, but that some loss to underlying soil will occur. A conservative approach assuming a D soil was thus chosen.
The Construction Stormwater permit requires drawdown within 48 hours and recommends 24 hours when discharges are to a trout stream. With a properly functioning underdrain, the drawdown time is likely to be considerably less than 48 hours.
Volume credit for infiltration through the sides of the basin is accounted for only if the sides of the basin are not lined with an impermeable liner. Volume credit for infiltration through the sides of the basin is given by
$^V_{infs} = (A_M - A_U)\ DDT\ I_R/12^$
Where
AM = the area at the media surface (square feet); and
AU = the surface area at the underdrain (square feet).
Information: The MIDS calculator assigns a default value of 0.06 inches per hour, equivalent to a D soil, to IR. This is based on the assumption that most water will drain to the underdrain, but that some loss to underlying soil will occur. A conservative approach assuming a D soil was thus chosen.
This equation assumes water will infiltrate through the entire side slope area during the period when water is being drawn down. This is not the case, however, since the water level will decline in the BMP. The MIDS calculator assumes a linear drop in water level and thus divides the right hand term in the above equation by 2.
Volume credit for media storage capacity below the underdrain (VU) is accounted for only if the underdrain is elevated above the native soils. Volume credit for media storage capacity below the underdrain is given by
$^\hspace{2em}V_U = (n-FC)\ D_U\ (A_U + A_B)/2^$
Where
AB = surface area at the bottom of the media (square feet);
n = media porosity (cubic feet per cubic foot);
FC is the field capacity of the soil, in cubic feet per cubic foot; and
DU = the depth of media below the underdrain (feet).
This equation assumes water between the soil porosity and field capacity will infiltrate into the underlying soil. Water stored below the underdrain should infiltrate within a specified drawdown time. The construction stormwater permit has a 48 hour requirement for drawdown (24 hours is recommended when discharges are to trout streams).
The ET and infiltration credits are assumed to be instantaneous values based on the design capacity of the BMP for a specific storm event. Instantaneous volume reduction, also termed event-based volume reduction, can be converted to annual volume reduction percentages using the MIDS calculator or other appropriate modeling tools. Assuming an instantaneous volume will somewhat overestimate actual storage when the majority of water is being captured by the underdrains.
The volume of water passing through underdrains can be determined by subtracting the volume loss (V) from the volume of water instantaneously captured by the BMP. No volume reduction credit is given for filtered stormwater that exits through the underdrain, but the volume of filtered water can be used in the calculation of pollutant removal credits through filtration.
Example calculation
A parking lot is developed and will contain tree trenches containing red maple (Acer rubrum). The tree trench has 1000 cubic feet of sandy loam per tree. Note that the following calculations are on a per tree basis. Total volume credit for the BMP will equal the per tree value times the number of trees, assuming all trees are of the same relative size (large in this case). Soil information is from the Soil water storage properties table.
Infiltration credit
The infiltration credit is given by
(soil volume) x (porosity - field capacity) = 1000 * 0.31 = 310 cubic feet
Evapotranspiration credit
Using the tree morphology table, red maple is a large tree with a mature canopy of 30 feet.
The available storage volume is given by:
Soil volume x (field capacity - wilting point) = 1000 * 0.09 = 90 cubic feet
The theoretical ET volume is given by:
$^(CP)(LAI)(E_{rate}) (E_{ratio}) (adjustment) (3 days) = 707 * 4.7 * 0.02 * 0.2 * (1000/(2 * 707)) * 3 = 28.2 cubic feet^$
The smaller value is the theoretical ET (28.2 cubic feet), so that is the volume credit. Note that if the recommended soil volume of 1414 cubic feet had been used the credit would be 39.9 cubic feet.
To make this calculation we used the default value of 707 for CP and the soil volume information from the table above. The evaporation rate (Erate) of 0.24 inches per day (0.02 feet per day) was from data collected at the Southwest Research and Outreach Center in Lamberton, Minnesota.
Interception credit
The interception credit is given by:
$^\hspace{2em}707 x (0.14/12) = 8.14 cubic feet^$
Where the division by 12 converts the calculation to feet.
Total credit
The total credit is the sum of the infiltration, ET and interception credits and equals (310 + 28.2 + 8.1) or 346.3 cubic feet.
Total suspended solids credit calculations
TSS reduction credits correspond with volume reduction through infiltration/ET and filtration of water captured by the tree BMP and are given by
$^\hspace{2em}M_{TSS} = M_{TSS_{i+ET}} + M_{TSS_f}^$
Where
MTSS = TSS removal (pounds);
MTSSi+ET = TSS removal from infiltrated and evapotranspired water (pounds); and
MTSSf = TSS removal from filtered water (pounds).
Pollutant removal for infiltrated and evapotranspired water is assumed to be 100 percent. The event-based mass of pollutant removed through infiltration and ET, in pounds, is given by:
With underdrain:
$^\hspace{2em}M_{TSS_{i+ET}} = 0.0000624\ (V_{inf_b} + V_{inf_s} + V_U + V_{ET})\ EMC_{TSS}^$
No underdrain:
$^\hspace{2em}M_{TSS_{i+ET}} = 0.0000624\ V_{WQ}\ EMC_{TSS}^$
Where:
EMCTSS is the event mean TSS concentration in runoff water entering the BMP (milligrams per liter).
The EMCTSS entering the BMP is a function of the contributing land use and treatment by upstream tributary BMPs. For more information on EMC values for TSS, see the TSS in stormwater page. If there is no underdrain, the water quality volume (VWQ)) is used in this calculation.
Removal for the filtered portion is less than 100 percent. The event-based mass of pollutant removed through filtration, in pounds, is given by
$^\hspace{2em}M_{TSS_f} = 0.0000624\ (V_{total} - (V_{inf_b} + V_{inf_s} + V_U))\ EMC_{TSS}\ R_{TSS}^$
Where
Vtotal is the total volume of water captured by the BMP (cubic feet); and
RTSS is the TSS pollutant removal percentage for filtered runoff.
The Stormwater Manual provides a recommended value for RTSS of 0.80 (80 percent removal) for filtered water. Alternate justified percentages for TSS removal can be used if proven to be applicable to the BMP design.
The above calculations may be applied on an event or annual basis and are given by
$^\hspace{2em}M_{TSS_f} = 2.72\ F\ V_{annual}\ EMC_{TSS}\ R_{TSS}^$
Where
F is the fraction of annual volume filtered through the BMP; and
Vannual is the annual volume treated by the BMP, in acre-feet.
Phosphorus credit calculations
Total phosphorus (TP) reduction credits correspond with volume reduction through infiltration/ET and filtration of water captured by the tree BMP and are given by
$^\hspace{2em}M_{TP} = M_{TP_{i+ET}} + M_{TP_f}^$
Where
MTP = TP removal (pounds);
MTPi+ET = TP removal from infiltrated and evapotranspired water (pounds); and
MTPf = TP removal from filtered water (pounds).
Pollutant removal for infiltrated water is assumed to be 100 percent. The mass of pollutant removed through infiltration and ET, in pounds, is given by
With underdrain:
$^\hspace{2em}M_{TP_{i+ET}} = 0.0000624\ (V_{inf_b} + V_{inf_s} + V_U + V_{ET})\ EMC_{TP}^$
No underdrain:
$^\hspace{2em}M_{TP_{i+ET}} = 0.0000624\ V_{WQ})\ EMC_{TP}^$
Where:
EMCTP is the event mean TP concentration in runoff water entering the BMP (milligrams per liter).
EMCTP entering the BMP is a function of the contributing land use and treatment by upstream tributary BMPs.
The filtration credit for TP in an underdrained system assumes removal rates based on the soil media mix used and the presence or absence of amendments. Soil mixes with more than 30 mg/kg phosphorus (P) content are likely to leach phosphorus and do not qualify for a water quality credit. If the soil phosphorus concentration is less than 30 mg/kg, the mass of phosphorus removed through filtration, in pounds, is given by
$^\hspace{2em}M_{TP_f} = 0.0000624\ (V_{total} - (V_{inf_b} + V_{inf_s} + V_U + V_{ET}))\ EMC_{TP}\ R_{TP}^$
Information: Soil mixes C and D are assumed to contain less than 30 mg/kg of phosphorus and therefore do not require testing
Again, assuming the phosphorus content in the media is less than 30 milligrams per kilogram, the removal efficiency (RTP) provided in the Stormwater Manual is a function of the fraction of phosphorus that is in particulate or dissolved form, the depth of the media, and the presence or absence of soil amendments. For the purpose of calculating credits it can be assumed that TP in storm water runoff consists of 55 percent particulate phosphorus (PP) and 45 percent dissolved phosphorus (DP). The removal efficiency for particulate phosphorus is 80 percent. The removal efficiency for dissolved phosphorus is 20 percent if the media depth is 2 feet or greater. The efficiency decreases by 1 percent for each 0.1 foot decrease in media thickness below 2 feet. If a soil amendment is added to the BMP design, an additional 40 percent credit is applied to dissolved phosphorus. Thus, the overall removal efficiency, (RTP), expressed as a percent removal of total phosphorus, is given by
$^\( R_{TP} = (0.8 * 0.55) + (0.45 * ((0.2 * (D_{MU_{max=2}})/2) + 0.40_{if amendment is used})) * 100 \)^$
Where:
the first term on the right side of the equation represents the removal of particulate phosphorus;
the second term on the right side of the equation represents the removal of dissolved phosphorus; and
DMUmax=2 = the media depth above the underdrain, up to a maximum of 2 feet.
The assumption of 55 percent particulate phosphorus and 45 percent dissolved phosphorus is likely inaccurate for certain land uses, such as industrial, transportation, and some commercial areas. Studies indicate particulate phosphorus comprises a greater percent of total phosphorus in these land uses. It may therefore be appropriate to modify the above equation with locally derived ratios for particulate and dissolved phosphorus. More information on fractionation of phosphorus in stormwater runoff can be found on the page; Event mean concentrations of total and dissolved phosphorus in stormwater runoff.
The following table can be used to calculate phosphorus credits.
Example calculations
Example 1 Assume the following:
- A tree trench with an underdrain has 1 foot of media above the underdrain
- 50 percent of annual runoff is infiltrated into the underlying soil
- 40 percent of annual runoff is captured by the underdrain
- 10 percent of annual runoff bypasses the BMP
- Media Mix A is used and soil phosphorus is 32 milligrams per kilogram
- Water Treatment Residuals, 7 percent by weight, have been mixed into the top 15 centimeters of the media.
The credits are as follows
- 100 percent credit for infiltrated runoff = 50 percent of annual runoff = 50 percent of annual phosphorus load
- For water that is captured by the underdrain
- The media is Mix A with a P content greater than 30 milligrams per kilogram, resulting in no credit for particulate or dissolved phosphorus
- A P-sorbing amendment has been added to the media and meets the requirements for a credit of 40 percent. The credit applies to the dissolved portion of phosphorus, which is 45 percent of total phosphorus. The credit is therefore 40 percent times 45 percent times the annual runoff volume of 40 percent, resulting in a credit of 7 percent of total annual P (0.4 * 0.45 * 0.4).
- No credit for water that bypasses the BMP
- The total credit is 57 percent of the annual P load.
Example 2 Assume the following:
- A tree trench with an underdrain has 1 foot of media above the underdrain
- 50 percent of annual runoff is infiltrated into the underlying soil
- 40 percent of annual runoff is captured by the underdrain
- 10 percent of annual runoff bypasses the BMP
- Media Mix C is used
The credits are as follows
- 100 percent credit for infiltrated runoff = 50 percent of annual runoff = 50 percent of annual phosphorus load
- For water that is captured by the underdrain
- The media is Mix C resulting in 80 percent credit for particulate phosphorus. Since particulate P is 55 percent of total P, the credit is 0.80 * 0.55 * 0.40 = 18 percent. The value of 0.4 in the equation accounts for 40 percent of the annual runoff volume.
- The media mix is C and there is 1 foot of media above the underdrain. The credit is 0.2 * 1/2 * 0.45 = 5 percent. The 1/2 adjusts for the thickness of media above the underdrain and the 0.45 accounts for 45 percent of total phosphorus being in dissolved form.
- No credit for water that bypasses the BMP
- The total phosphorus credit is 73 percent of the annual P load (50 + 18 +5).
Other pollutants
In addition to TSS and phosphorus, bioretention BMPs can reduce loading of other pollutants. According to the International Stormwater Database, studies have shown that bioretention BMPs are effective at reducing concentrations of pollutants, including metals, and bacteria. A compilation of the pollutant removal capabilities from a review of literature are summarized below.
Related pages
The following pages address incorporation of trees into stormwater management under paved surfaces
- Design guidelines for tree quality and planting - tree trenches and tree boxes
- Design guidelines for soil characteristics - tree trenches and tree boxes
- Construction guidelines for tree trenches and tree boxes
- Protection of existing trees on construction sites
- Operation and maintenance of tree trenches and tree boxes
- Assessing the performance of tree trenches and tree boxes
- Case studies for tree trenches and tree boxes
- Soil amendments to enhance phosphorus sorption
- Fact sheet for tree trenches and tree boxes
- Requirements, recommendations and information for using trees as a BMP in the MIDS calculator
- Requirements, recommendations and information for using trees with an underdrain as a BMP in the MIDS calculator