For a typical 2-inch monitoring well, what material is best for the filter pack?

For a typical 2-inch monitoring well, what material is best for the filter pack?

• A. Fine sand
• B. Gravel
• C. Coarse clean silica sand
• D. Silt

Answer: (C)

The key idea is choosing a filter pack that protects the screen from sediments while letting groundwater flow freely. For a typical 2-inch monitoring well, coarse clean silica sand is the best choice because it is clean, has a uniform grain size, and provides high permeability without supplying excess fines. This combination helps trap any fine silt or clay from the surrounding formation around the screen, prevents fine particles from entering the well, and keeps the pack from compacting too much or forming channels. Fine sand brings many fines that can clog the screen and pack, reducing yield. Silt is so fine it clogs almost immediately. Gravel is too large to fill the space properly around the screen and can create voids or channels, compromising the seal and allowing unwanted particles to move. Coarse clean silica sand strikes the right balance, making it the standard material for filter packs in 2-inch monitoring wells.

The key idea is choosing a filter pack that protects the screen from sediments while letting groundwater flow freely. For a typical 2-inch monitoring well, coarse clean silica sand is the best choice because it is clean, has a uniform grain size, and provides high permeability without supplying excess fines. This combination helps trap any fine silt or clay from the surrounding formation around the screen, prevents fine particles from entering the well, and keeps the pack from compacting too much or forming channels.

Fine sand brings many fines that can clog the screen and pack, reducing yield. Silt is so fine it clogs almost immediately. Gravel is too large to fill the space properly around the screen and can create voids or channels, compromising the seal and allowing unwanted particles to move. Coarse clean silica sand strikes the right balance, making it the standard material for filter packs in 2-inch monitoring wells.