This is the next step in the preparation of a building site after the installation of the wet utilities as described in Part 2 of this informational series.
Consisting of electrical, telecom, and gas lines, it’s the final underground installation done before site preparation work is completed so that above-ground improvements can commence.
The Joint Trench
Dry utilities are installed away from wet utilities to ensure safety and good connectivity, usually along the side of the street but not under the roadway where contractors bury dry utility lines in a trench that’s a minimum of 5 feet deep and 24 inches wide.
Within the trench, electrical lines are run at the bottom on top of a 12” bed of sand; telecom lines like cable, phone, and internet lines are run on top of those, and then the gas line on top of telecom lines.
Each layer of service lines is separated by another 12” of sand to protect the lines and keep them from contacting each other, even after the ground has settled.
Once the gas line has been padded with more sand on top, contractors backfill the trench with regular soil, then grade the soil as needed.
External Access to Underground Dry Utility Lines
An essential element of the installation of dry utilities with site preparation work is planning spots where access can be made to reach the lines once the trench has been backfilled, which is done by installing pullboxes and handholes in the trench.
Utility lines are run through the pullboxes and into the handholes, where site work contractors and utility personnel can have access to them anytime in the future.
Backfilling is done so the tops of the handholes remain at ground level, leaving the lids accessible.
Mapping Out Mainlines and Crossings
A critical part of the contractors dry utility installation is to map out mainlines and crossings.
- Mainlines are the main trenches where the utilities pass underground just inside the location of the street curb or the edge of the road.
- Crossings are areas where utilities cross over from one side of the street to the other.
Crossings are set in with conduits as opposed to trenches to be certain that there is stability when the road is paved afterward.
Above Ground Improvements Begin Once Dry Utilities Are Installed
By this point, all major grading has been done and all underground utilities, including storm drains, have been installed to produce a building site or pad that’s ready for use.
Though each project is different depending on the makeup of the raw land and the type of buildings being built, these are important preliminaries that site contractors must complete for any small or large project for the building site to be stable and the resulting building to be connected to public utilities.
Don't miss the next installment of this series: Land Development – Part Five – Fencing.
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Land Development Series:
Land Development – Part One – Overview
Land Development – Part Two – Rough Grading
Land Development – Part Three – Web Utilities
Land Development – Part Four – Dry Utilities
Land Development – Part Five – Fencing
Land Development – Part Six – Finish Grading
Land Development – Part Seven – Flatwork
Land Development – Part Eight – Landscaping