Building "In the Dry"
Handling High Groundwater: 3 Effective Strategies
Groundwater considerations are a critical part of any construction project, including everything from a building structure with a basement or crawlspace to the installation of underground utilities. Groundwater depths will vary with time, season, lake levels, and natural climate variations. For the past couple of years, groundwater levels have risen significantly, along with lake levels.
1. Dewatering Considerations
During design, soil borings are used to gather subsurface soil and groundwater information. Based upon the groundwater levels encountered in the soil borings, a dewatering system may be required during construction. In addition, the contractor must provide proper control of all groundwater and precipitation runoff during construction, and water must not be allowed to collect in excavations. Proper preparation of the subgrade, including compaction, must be completed “in the dry.”
2. Perimeter and Under Slab Drains
To provide long-term groundwater control, perimeter drains should be placed in the bottom of foundation areas to control groundwater collecting outside any below-grade walls. Often, a system of drains is also recommended under the lower floor slab. The walls should be backfilled with well-graded granular (sand) material and compacted as recommended by a licensed geotechnical engineer. All drains should be connected to a positive gravity outlet at multiple locations to remove water from the building area.
3. Plan Ahead
The best time to fix a water problem is during the design phase of a project. Sometimes, unexpected subsurface conditions are encountered during construction, or the groundwater levels rise, but a thorough geotechnical exploration before construction can many times eliminate or minimize potential problems before they arise.
When challenges occur, Gosling Czubak has the personnel, tools, and experience to diagnose the problem and provide the right recommendations to get any project back on track. Please contact Geotechnical Engineer Doug Hula, P.E. for further information.