Subsoil Drainage

• Description of flooding: Water is pooling in several areas along driveway, overflowing to neighbouring property causing nuisance and damage to landscaped areas.
• Investigation results: Existing concrete formed incorrectly resulting in pooling even causing collapse of several driveway areas.
• Solution: Cut and remove existing concrete, new fill and compact, install side subsoil drainage and new cesspit, pour new concrete to correct levels, flood test.

• Description of flooding: House built early 70’s, constructed into elevated section positioning outside ground level 1.2 meters above inside finished floor levels.Water penetrating building envelope causing flooding in semi basement living areas. Mould and damaged timer frame visible.
• Investigation results: Existing subsoil drainage in field tile format (earthenware), degraded due to age and possibly collapsed in several locations.
• Solution: Excavate a total of 1.5 meters (below existing finished floor levels) and remove existing field tiles. Install new subsoil drainage at correct level and backfill with approved fill. Connect as per NZBC at lower levels.

• Description of flooding: Many homes in Auckland are built in areas where soakage is limited due to dense ground percolation (slow soakage), Homes built in and around clay sections are usually prone to severe flooding where homes built in volcanic areas are less prone as water can drain to lower levels much quicker preventing excessive higher level ground and surface flooding.
• Investigation results: Percolation tests show minimal soakage, in heavy rain water levels raise quickly causing sever ground and surface water, flooding lower levels, basement flooding and garage.
• Solution: Excavate and install subsoil drainage below finished floor levels of liveable areas and install new subsoil drainage to manage ground and surface water to lower levels preventing ingression.

• The basement area affected with water flooding is deeper than 2 meters from the outside ground levels and excavation of this area(along outside) to install subsoil drainage is too difficult and expensive due to depth. Creating a catchment area within the basement area (inside the building envelope) diverting all ground water to an internal chamber which in return will pump all ground water to upper levels in an existing stormwater system.
• A Commercial parking area floods in heavy rain, new channels are installed which discharge into a bubble-up chamber which in return overflows into a pumped chamber.

Pump chambers are also commonly used in sanitary sewer applications if site falls are not available.

BASEMENT / GARDEN FLOODING SUBSOIL SOUTIONS