SECTION 5.00

PIPE TRENCHES

5.01 EXCAVATION AND PREPARATION

The minimum trench width at the top of the pipe shall be at least 18 inches greater than the outside diameter of the pipe. Rock shall be removed to a depth of at least 6 inches below the bottom of the pipe and the trench backfilled with suitable material. Wet trenches shall be stabilized with a base layer of #78 M or #57 stone. The bottom of the trench shall be shaped to provide uniform support along the length of the pipe, and a space shall be excavated at each bell.

5.02 PIPE LAYING AND BACKFILLING

Open ends of pipe shall be plugged when pipe laying is not in progress to prevent trench water, soil, and debris from entering. Backfill material shall be free from construction material, frozen material, organic material, or unstable material, and shall be placed and compacted in accordance with Section 2.05 Earthwork. All trenches along roadways, and otherwise as directed by the Inspector, shall be properly backfilled at the end of each working day.

5.03 PAVEMENT REPAIR

All pavement cuts shall be repaired within a maximum of three (3) days from the date the cut is made. If conditions do not permit a permanent repair within the given time limit, permission to make a temporary repair must be obtained from the Inspector. Pavement repairs shall be in accordance with the Details.

5.04 BORING AND JACKING

All utility crossings within Town streets shall be by boring and jacking. Bores larger than 6" must use casing pipe. The Town also recommends that all utility crossings of State maintained streets within the Town ETJ be by boring and jacking . In cases where utility conflicts, rock, or other obstructions prevent crossing by boring and jacking , the Town may consider approving other methods.

Encasement pipe shall be manufactured of grade 'B' steel with a minimum yield strength of 35,000 psi in accordance with ASTM A139 and A283. When used within NCDOT right of way, the encasement pipe shall meet NCDOT requirements.

If voids are encountered while installing encasement pipe thirty (30) inches and larger, grout holes shall be installed as necessary and filled with 1:3 Portland cement grout at sufficient pressure to prevent settlement of the roadway, unless NCDOT approval stipulates otherwise. Other grout mixtures may be submitted for approval.

In the event that an obstruction is encountered during boring and jacking, the pipe is to be cut off, capped, and filled with 1:3 portland cement grout at a sufficient pressure to fill all voids before moving to another boring site.

Size and wall thickness of smooth wall or spiral welded encasement pipe shall be as follows:

Casing pipe shall be installed with a minimum cover of 3 feet under pavement.

All carrier pipe shall be slip joint ductile iron pipe resting on steel spiders, treated timber skids or other approved spacer to prevent damage to the pipe bells, which shall not contact the interior of the casing pipe. The spacing interval of the aforementioned spacers shall be the minimum number needed to assure necessary grade, clearance, and support. No blocks or spacers shall be wedged between the pipe and the top of the casing. Casing pipe shall have the following minimum sizes: