The typical Grand Blanc area well penetrates thick clay with thin sand/gravel interbeds, terminating in sandstone bedrock at depths of 160-280 feet.
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A geological estimate for the Grand Blanc area.
Typical Well Depth
Static Water Level
Recommended Method
Based on an aggregate of representative well logs, the common geologic sequence in Grand Blanc consists of an upper clay unit (sometimes with boulders, stones, and thin sand/sand & gravel layers) from surface to about 100-120 ft, underlain by sand or sand & gravel lenses (20-60 ft thick), with additional clay or mixed lenses. Bedrock (sandstone, sometimes with shale) is encountered at 120-190 ft, and most wells are completed in the sandstone to total depths of ~160-280 ft. The static water level typically ranges from 20-65 ft. Typical household wells targeting 10+ GPM are completed at depths of 160-200 ft, while higher capacity wells may range up to 280 ft or more.
| Depth (Feet) | Formation Type | Description | Characteristics |
|---|---|---|---|
| 0 – 12 ft | Clay (variable color: yellow/brown/gray) | Surface clay, sometimes mottled; may include topsoil/silt. | Color: Brown/Yellow/Gray Hardness: Soft |
| 12 – 90 ft | Clay (w/ occasional sand, gravel or stones) | Thick lacustrine or glacial clay, with intervals of blue/gray color and occasional stones/boulders or thin sand/sand & gravel interbeds. | Color: Gray/Blue/Brown Hardness: Soft to Medium |
| 90 – 130 ft | Sand & Gravel (sometimes mixed with clay) | Predominantly sand and gravel with some clay layers, providing secondary aquifers. | Color: Gray/Brown Hardness: Medium |
| 130 – 160 ft | Clay or Sandy Clay, w/ occasional stones | Intermediate clay with rare sand or stones, often blue or gray. | Color: Gray/Blue Hardness: Medium |
| 160 – 280 ft | Sandstone (bedrock, sometimes with shale) | Consolidated sandstone forming principal bedrock aquifer, sometimes with shale or broken zones at top. | Color: White/Gray/Light Brown Hardness: Hard |