Ecosol Tree Pits are mini rain gardens (also known as Tree Filter Boxes or Street Tree Wells) that comprise of a tree planted within an underground pre-cast concrete pit that generally consists of a combination of media layers that allows stormwater to slowly infiltrate from the surface down to underdrain pipes where the treated stormwater is then conveyed to a traditional stormwater drainage system.

Today Tree Pits are an integral part of a total treatment train approach and are incorporated into most street scape designs. As they are applied at a street scale to capture and treat stormwater runoff close to its source, they not only provide us with a compact, efficient stormwater treatment solution they also help to enhance streetscape aesthetics.

The Ecosol Tree Pit is a modern, fully self-contained stormwater treatment system that provides tertiary treatment of stormwater flows in one compact device at a street scape level.

The system has been designed to provide a robust and durable cost effective, aesthetically attractive kerb-side treatment system. The system is filled with porous filter media and planted with vegetation to remove pollutants from stormwater runoff using natural and physical processes.

In developing this innovative stormwater treatment system careful consideration has been given to durability, longevity, cost, and maintainability.  Key commercial technical features include:

  • low visual impact and energy footprint
  • designed hydraulics with proven performance and longevity
  • scalable, adaptable design and
  • cost effective maintenance regime.

At Urban Asset Solutions we can site measure, fabricate, install and maintain your Tree Pit making the whole process seamless.

The Ecosol Tree Pit is designed as a fully self-contained stormwater treatment system for roadside applications.  It is supplied to site complete with all internal drainage components factory installed and with the engineered soil media and grated access covers supplied loose.

Ecosol Product CodeInternal Pit Dimensions
L x W x D (mm)
External Pit Dimensions
L x W x D (mm)
Loading ClassificationWeight (t)
Ecosol Tree1200 x 1200 x 12001650 x 1650 x 1650B4.0
Ecosol Tree Pit Typical Dimensions - 2018

The components and accessories supplied with the Ecosol Tree Pit, providing a complete system thereby reducing on site installation times.

Item No.
1Kerb inlet penetration (typically standard BBC Tye E) 150 x 100 WSUD inlet
2Roof water inlet penetration (typically 100mm PVC)
3Drain clean-out riser pipe (100mm PVC screc cap) factory fitted
4Underdrain layer pipes (slotted 100mm PVC) factory fitted
5Drainage layer (150mm washed fine gravel) suplied in bag to site
6Transition layer (100mm FAWB approved coarse washed sand) supplied in bag to site
7Bio filtration layer (750mm FAWB approved sandy loam) supplied in bag to site
8Gravel screening layer (50mm coarse 18m gravel) supplied in bag to site
9Pedestrian access grate (loading class light duty)
10Pre-cast concrete steel reinforced Tree Pit (ecternal dimensions 1.65L x 1.65W x 1.65D m) 40Mpa
Ecosol Tree Pit Components Specification - 2018

General Notes:

  • The products engineered media for the range of Ecosol Tree is supplied and installed separately.
  • Installation and operation of the Ecosol Tree Pit is recommended once site conditions have stabilised.
  • The under drain collection pipes, geo-fabric and ductile iron access covers are supplied factory fitted with the Ecosol Tree Pit.
  • For optimal performance a temporary ponding depth of 300mm above the infiltration layer is recommended.
  • Careful selection of the most appropriate vegetation is necessary to ensure optimal performance of your Tree Pit. Urban Asset Solutions can supply the system complete with appropriate plants ready for installation.  Alternatively you can select your own, however we recommend you consult with your local council to determined preferred species or refer to the Adoption Guidelines for Stormwater Biofiltration Systems Table 15 List of known species” released July 2015 as part of the CRC for Water Sensitive Cities.


The typical infiltration rate of a biofilter is 150mm/hour (0.04L/s/m2) for established vegetated zones. Urban Asset Solutions can assist with the most appropriate design and sizing of your biofilter specific to your site requirements.

Treatable Flow Rate

Careful selection of the soil media and vegetation is necessary along with appropriate ponding depths and detention to ensure optimal performance of your Ecosol Tree Pit.  As the system has a surface footprint of 1.44m2 an estimated infiltration rate of approximately 0.056L/s is likely with a 100mm ponding depth.

By-Pass Capacity & Headloss

The systems is designed to have a ponding depth of approximately 100mm and will by-pass flows exceeding the estimated infiltration rate downstream to the next available kerb inlet.

Suggested removal efficiencies for the Ecosol Biofilter are in accordance with the CRC for Water Sensitive Cities Adoption Guidelines for Stormwater Biofiltration System (July 2015).

PollutantRemoval efficiencyDetails
Gross Pollutants (GP)98%Particulate >200 micron
Suspended Solids (SS)95%Particulate
Phosphorous (P)65%Particulate
Nitrogen (N)50%Particulate
Heavy Metals90%Particulate
Total Petroleum Hydrocarbons (TPH)99%In dry and wet weather flows
Ecosol Tree Pit Removal Efficiencies - 2018

Water Sensitive Urban Design (WSUD) assets require regular scheduled maintenance to ensure they remain healthy and perform as intended. It is important to regularly inspect the filter media to monitor sediment, gross pollutant and leaf litter accumulation.  Additionally any weeds should be removed, plant health and detention zones monitored and periodic flushing out of the underdrain system is necessary to ensure the system continues to perform to its designed specification. The Ecosol Tree Pits simple design makes access for cleaning and maintenance easy using standard equipment.

The below table provides a general guide of key activities necessary to maintain your Tree pit system.

ItemActivityRecommended Frequency
MulchEnsure you have adequate mulch cover to prevent scouringEvery 3 months or immediately after a storm event
Filter MediaRemove leaf litter and gross pollutantsEvery 3 months or immediately after a storm event
Monitor ponding depths to ensure soil media is providing adequate infiltration ratesEvery 3 months or immediately after a storm event
If necessary remove excess sediment or replace the top layer of soild media and remulchEvery 3 months or immediately after a storm event
VegetationEnsure plant life is healthyEvery 3 months or immediately after a storm event
Remove all weedsEvery 3 months or immediately after a storm event
Water as necessarySeasonal Activity
Structural ComponentsInspect all structural elements to ensure structural integrityAnnually
Flush underdrain pipe systemsAnnually
Ensure all inlets and outlets from the system are free of any debrisAnnually
Ecosol Tree Pit Functions of each Chamber and Cleaning Frequency - 2018
lvenessEcosol Tree Pit