CSLB C-27 Landscaping ContractorSite Preparation and DrainageHard
A C-27 contractor is planning to install a drywell as part of a stormwater management system for a residential property. Which of the following conditions would render a drywell installation ineffective or problematic?
- AA site requiring additional landscape irrigation.
- BA site with a gentle slope towards the drywell location.
- CA site with highly permeable sandy soil.
- DA site with a high seasonal water table.
Show answer & explanationAnswer & explanation
Correct answer: D. A site with a high seasonal water table.
Drywells rely on the surrounding soil's ability to absorb water. A high seasonal water table means the ground is already saturated or close to it for significant periods, preventing the drywell from effectively draining and potentially causing it to overflow or become a standing water hazard.
Why the other options are wrong
- A. A drywell's function is to manage excess stormwater, which is unrelated to the property's irrigation needs; this condition does not impact drywell effectiveness.
- B. A gentle slope towards the drywell location is beneficial, as it directs surface water efficiently to the collection point.
- C. Highly permeable sandy soil is ideal for drywells, as it allows for rapid infiltration and effective drainage.
Drywell Suitability
The conditions under which a drywell (an underground structure that disposes of unwanted water by dissipating it into the ground) is an effective and appropriate stormwater management solution.
- Requires permeable soil for effective drainage.
- Ineffective in high water table areas.
- Must be sized for anticipated water volume.
Memory trick: Drywell's thirst, quenched by earth's first; but if water's high, its purpose will die.