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Checks that need to be carried at different stages of urban stormwater system construction includes checklist for excavation, trenching, pipes before application, pipe installation, gravel envelope, manholes, outlets, jacket crossing and backfilling. In this article, inspection checklist required during the urban storm water construction process are provided.
Fig.1: Stormwater System
Inspection Checklists for Construction of Urban Storm Water System
1. Excavation Checklist
Necessary checks required to be conducted during excavation include:- Alignment and grade of the excavation need to be continuously monitored.
- It should be guaranteed that the excavated material be placed at a minimum distance of 1m from the edge of the excavation.
- It should be ensured that the guidelines of applicable codes or specifications are followed regarding dust abatement
- Over excavate and stabilize in areas of unstable sub-grade should be notified and reported in the daily project report.
- In the case of classified excavation, representative of contractor should be informed and the quantity of excavated rock should be recorded. Classified excavation means that there are different prices for common excavation and for rock excavation.
- It should be checked whether the plan of classified excavation is submitted by contractor and accepted by contracting officer.
2. Trenching Checklist
- The engineer should watch for underground utilities which are not illustrated on the plan or marked by utility company on the field.
- If workers are required to step into a minimum 1.5m trench, then it will be required to take necessary precautions unless the soil is adequately stable.
- This is required to prevent undesired events due to failure of the trench wall. Examples of the necessary precautions include the provision of sloped trench wall or placement of shoring to avoid trench wall failure.
- Check whether safeguards such as fences are placed in required places to avoid falling or individuals and equipment into the trench.
- The placement of escape ladder in the trench at a space of 7.5m should be checked.
- If shields are required in the trench, then proper sizes and strength of the shields shall be checked.
- Types of soil, which are not recorded in the specifications, need to be recorded.
3. Checklist for Pipes before Application
- Check the pipe size to make sure that the correct size is being installed.
- In the case of corrugated pipe utilization, check for integrity of the coating, proper coupler, and inspect seam rupture visually.
- If gasket joints are used, the seating of the gasket should be checked.
- Seals need to be checked provided that sealed pipe are applied
- If corrugate plastic tubing is used, perform stretch test at least one time for each shift and record both stationing of the test and stretch percentage.
4. Pipe Installation Checklist
- Insure that instrument of surveyor is installed whenever the pipe is placed and the grade of the pipe should be checked frequently.
- The grade should be checked after the trencher left its position
- Check for pulled joints when shield is utilized on an open joint pipe
5. Gravel Envelope
- Gravel envelope should be checked to ensure that it meets the grading specifications.
- The dimension of gravel envelope should be checked.
- The gravel envelope should be checked for any contamination such as soil or organic material prior to its placement into the hopper.
- Check gravel feed in the trenching machine hopper and gravel thickness over the pipe to make sure that the required thickness is placed as per applicable specifications.
6. Checklist for Manholes
- Installation of surveyor instrument shall be insured wherever manholes are placed and observe the grade regularly during construction.
- Grade, alignment, and plumb of the manhole should be checked.
- Check the size and location of pipe inlet holes.
- Check the filter gravel under the inlet and outlet
- Check the connection between manhole and drainpipe. Grade, length of the pipe into the manhole, and length of the pipe of the first joint should be checked.
- Check the gravel around lower part of the manhole to make sure that no discontinuity is left.
- The manhole should be checked to ensure that it is free from silt.
- After backfilling is completed, the grade of manhole shall be rechecked.
7. Checklist for Outlets
- Outlet pipe should be checked to make sure that it is coated, selected in accordance with applicable specifications, and has a suitable riprap for protection.
- Grade and location of outlet pipe end shall be checked to ensure that it is executed according to applicable code.
- The compaction of backfill around the pipe shall be checked. In addition to the backfill thickness which shall be not less than 300mm.
8. Jacket Crossing Checklist
Before the start of jacking operation,- Required safety fencing and signs placed by contractor should be checked.
- If the plan recommends specific pipe, the available pipe should be checked to find out whether it meets the requirements of the special pipe or not.
- All equipment need to be checked
- Check the safety of jacking pets and make sure that adequate spaces are provided for the escape of labors
- Check the joints of the pipes
- Check the alignment and grade of jacking equipment
- Determine the grade of the pipe
- Check the proper placement of any special backfill
- Check pipe grade at both ends and write it down
- Backfilling and compaction of jacking pit should be checked.
- Check the restoration of the ground surface to its original position
9. Backfilling Checklist
- Measure considered to prevent pipe movement need to be checked
- It should be guaranteed that compaction is applied for required location only.
- Backfilling shall be carried out shortly after trenching operation
- Check that compaction will not be applied apart from specified locations.
- Make sure that the surface restoration is performed on time
- Report any damage and the degree of the damage caused by the construction work.
