An Infiltration Trench System includes an inlet pipe or water source, catch basin sump, perforated DESIGN PRINCIPLES distribution pipe, infiltration trench and overflow to the storm drainage system.

■ Infiltration Trench System: A Soakaway Manhole (Sump, or Dry Well) System includes an inlet pipe, a sedimentation manhole, and one or more infiltration shafts with connecting pipes. Use of Infiltration Shaft will be limited by hydro- a) Locate infiltration trench at least 3m geotechnical conditions in much of GVRD. from any building, 1.5m from Limitations of Infiltration Trench or Soakaway Manholes: property lines, and 6m from adjacent a) To avoid groundwater pollution, do not direct un-treated polluted runoff to Infiltration Trench or Shaft: infiltration facilities (or as recommended by a geotechnical ▪ Direct clean runoff (roof, non-automobile paving) to Infiltration Trench or Shaft. engineer). ▪ For polluted runoff (roads > 1000 vehicles / day, parking areas, other pollution sources), provide upstream source control for pollutant reduction prior to release to Infiltration Trench or Shaft. b) Sump: Provide a lid for periodic b) Use infiltration trench or shaft only in areas with footing drains. inspection and cleanout. Include a 1. Grass or Other Planting T-inlet pipe to trap oils, sediments 2. Finish Grade and debris. 3. Growing Medium Backfill 4. 100mm Dia PVC DR28 Perforated 19 c) Infiltration Trench: installation of Pipe distribution pipe and bottom of 5. Light Non-woven Polyester drainrock to be level. If more than Geotextile c/w Min. 400mm Laps one section of infiltration trench is 9 1 required, design so that underground 6. 50mm Drain Rock or Rock of water is temporarily ‘ponded’ in each Equal Porosity infiltration section. 7. Maximum Groundwater Elevation 10 8. Non-polluted Drainage From 8 Building or Terrace d) Install the Infiltration Trench in native 18 2 12 ground, and avoid over-compaction 9. Alternate Surface Route - With 3 of the trench sides and bottom, which 17 Splash Pad and Vegetated Swale reduces infiltration. 20 4 5 to CB 6 14 16 13 15 10. CB Lid / Access Hatch for e) Observation well for each infiltration Cleanout, Inspection and Inflow / trench (optional): vertical standpipe, Infiltration Trench 7 Overflow from Sump with perforated sides, and locking lid, 11. Solid Pipe c/w Inlet Tee to allow the monitoring of water Notes: depth. All precast sections shall conform to the requirements of ASTM C 478. 12. Observation Well (Optional) Provide a min. of 150mm of 25mm or 19mm clean crushed rock 13. Provide pipe elbows to have outlet ■ Soakaway Manholes System: under all pipes. pipe invert at top of infiltration pipe Invert shall be level and smooth. 14. PVC Solid Pipe a) Provide a report from an engineer Soakaway Manhole barrel shall not be perforated within 1200mm of 15. Discharge to Storm Drainage with experience in geotechnical the cone. System. Ensure Drainage Does engineering including on-site test Not Impact Neighbouring Uses. data of infiltration rates at the depth Direct Discharge to Road of the proposed infiltration. The 21 Right-of-way if Necessary bottom of the shaft shall be at least 1 24 16. Infiltration Trench with Level 600mm above the seasonal high 21 Bottom water table or bedrock, or as 2 22 26 17. Catch Basin recommended by the engineer. 24 3 23 18. Building Footing Drain (Not 21 b) If steep slopes or drinking water 22 26 Connected to Infiltration Facility) wells exist within 200m horizontally 19. Building from the proposed Soakaway 11 20. 50mm Dia Drain Hole Manhole, provide a hydro- 14 26 22 21. Standard Manhole Frame and geotechnical report to analyze 27 Cover 27 14 site-specific risks and determine 5 22. Seal Joints with Cement Grout or setbacks. 28 29 Approved Mastic 23. Street Inlet Connection 5 c) Provide a sedimentation manhole, 6 24. Ladder Rung and a maximum of two Soakaway 28 25. 25mm Crush Gravel or Drain Rock Manholes in series, unless otherwise 6 approved. 25 Base 26. Native Soil Back Fill Sedimentation d) Provide an overflow from the 27 27. Undisturbed Ground Manhole 25 28. 1200mm Perforated Barrel Soakaway Manhole to the storm Soakaway drainage system or major storm flow (Langley Concrete or Equal) path. Manhole 29. Overflow to storm drainage Soakaway system. Manhole Greater Vancouver Infiltration Trench & Soakaways Regional District

Stormwater Source Control Design Guidelines 2005

Goya Ngan Landscape Architect

Detailed design guidelines can be found in the Design Guidelines 2005 report, available at www.gvrd.bc.ca