How to Install Posts in a High Water Table Area

A high water table makes installing posts for fencing, decks, mailboxes and other applications more challenging but not insurmountable. If, after digging a post hole, standing water appears in the bottom of the hole, this is a strong indication of a high water table. A few extra steps and added supplies can easily resolve the problem.

High water tables create challenges for installing fence posts.

Step 1

Dig a hole at least 42 inches deep and 12 inches wide. Taller fence posts, deck supports and similar posts will require deeper holes. Most experts recommend a depth equal to one-third the length of the post.

Step 2

Pour in large pea gravel to an approximate depth of 3 inches or more. Tamp down with the end of one post.

Step 3

Pour in an equal amount of small-grade pea gravel. Five to 6 inches will suffice, depending on local codes. Tamp down with the end of a post.

Step 4

Insert a post into a post hole and position it until level. Backfill with dry concrete mix, leaving the last six inches for dirt. Tamp around the post with a wide stick or tamping tool.

Step 5

Backfill the remaining space with dirt. Tamp firmly with a tamping tool or boot heel. Let stand 48 hours or more, depending on local conditions.