CSLB C-27 Landscaping ContractorSite Preparation and DrainageMedium
A landscape contractor is planning to install a dry well as part of a stormwater management system for a portion of a residential property. Which of the following soil characteristics is most critical for the effective functioning of a dry well?
- AHigh clay content
- BHigh organic matter content
- CHigh sand or gravel content
- DLow permeability
Show answer & explanationAnswer & explanation
Correct answer: C. High sand or gravel content
Dry wells rely on the soil's ability to quickly absorb and infiltrate water. High sand or gravel content indicates a highly permeable soil, which is ideal for a dry well to function effectively by allowing stormwater to dissipate into the ground.
Why the other options are wrong
- A. High clay content indicates low permeability, which would prevent a dry well from effectively infiltrating water.
- B. High organic matter content can improve water retention but doesn't guarantee the high permeability needed for rapid dry well infiltration.
- D. Low permeability means water cannot pass through the soil easily, rendering a dry well ineffective.
Dry Well Soil Permeability
Dry wells require highly permeable soil, such as those with high sand or gravel content, to effectively infiltrate stormwater into the ground.
- Permeability is the rate at which water moves through soil.
- Low permeability soils (e.g., clay) will cause dry wells to fail.
- A percolation test is used to determine soil suitability.
- High permeability ensures rapid drainage of the well.
Memory trick: For a dry well to drink, the soil must be quick!