Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Subdrainage
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## Pre-Installation Conference {toc}
−### A pre-installation conference shall be held before subdrainage work begins, attended by the Contractor, the installing firm, the earthwork subcontractor, and the Engineer of Record or designated representative. {note}
+### A pre-installation conference shall be held before subdrainage work begins, attended by the Contractor, the installing firm, the earthwork subcontractor, and the Engineer of Record or designated representative.
### The pre-installation conference shall review the geotechnical report's groundwater findings, the design slopes and outlet elevations, the filter-fabric and aggregate selections, and the sequencing of subdrainage relative to earthwork and paving operations.
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## Pipe Diameter {toc}
−### Pipe diameter shall be sized by the Engineer of Record at the design flow using Manning's equation, not selected by convention alone. {note}
+### Pipe diameter shall be sized by the Engineer of Record at the design flow using Manning's equation, not selected by convention alone.
### A 4 in. lateral is the standard selection for underslab and pavement edge drains serving tributary areas up to approximately 5,000 to 10,000 sf per run. {note}
### A 6 in. collector main is the standard selection where multiple laterals combine or the tributary area exceeds the capacity of a 4 in. lateral. {note}
−### An 8 in. or larger outlet main shall be provided where the combined tributary area and design flow exceed the capacity of a 6 in. pipe. {note}
+### An 8 in. or larger outlet main shall be provided where the combined tributary area and design flow exceed the capacity of a 6 in. pipe.
```datasheet
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## Aggregate Gradation {toc}
−### Drainage aggregate shall be clean, washed, durable crushed stone or gravel conforming to a defined gradation; "clean gravel" without a gradation reference is not acceptable. {note}
+### Drainage aggregate shall be clean, washed, durable crushed stone or gravel conforming to a defined gradation; "clean gravel" without a gradation reference is not acceptable.
### Drainage aggregate shall conform to ASTM C33 No. 57 gradation (3/4 in. to No. 4) unless the design specifies an alternative gradation.
### The aggregate shall have a wash loss not exceeding 0.5% when tested in accordance with AASHTO T-11.
−### Aggregate gradation shall be selected together with the filter-fabric apparent opening size so that the fabric retains the native soil while the aggregate conducts water freely. {note}
+### Aggregate gradation shall be selected together with the filter-fabric apparent opening size so that the fabric retains the native soil while the aggregate conducts water freely.
```datasheet
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# Filter Fabric {toc}
−## The geotextile filter fabric is the boundary between native soil and the drainage envelope; it must pass water freely while retaining soil particles, or the system either clogs or fills with migrating fines. {note}
+## The geotextile filter fabric is the boundary between native soil and the drainage envelope; it must pass water freely while retaining soil particles, or the system either clogs or fills with migrating fines.
## Fabric Type {toc}
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### A circular-knit pipe sock conforming to ASTM D6707 is an alternative used where a factory sock around the pipe replaces or supplements a full-trench wrap. {note}
−### A woven geotextile shall not be used as a subdrainage filter fabric, because its open structure passes fines and clogs the aggregate. {note}
+### A woven geotextile shall not be used as a subdrainage filter fabric, because its open structure passes fines and clogs the aggregate.
```datasheet
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## The geocomposite drainage core shall discharge into the aggregate envelope or collector pipe at its base, and shall not be terminated against the trench wall. {note}
−## The transition detail between a geocomposite wall panel and a pipe-in-aggregate collector trench shall be shown on the drawings to avoid field improvisation. {note}
+## The transition detail between a geocomposite wall panel and a pipe-in-aggregate collector trench shall be shown on the drawings to avoid field improvisation.
## A geocomposite drainage system shall be installed in accordance with the panel manufacturer's written instructions, including lap, fastening, and termination details.
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## In paved or trafficked areas, cleanout risers shall terminate in a traffic-rated frame and cover.
−## Observation ports shall be provided where the design requires post-construction verification of the water level or flow within the drain. {note}
+## Observation ports shall be provided where the design requires post-construction verification of the water level or flow within the drain.
```datasheet
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## Outlet Elevation {toc}
−### The outlet invert shall be set above the 10-year high-water elevation of the receiving channel or storm structure. {note}
+### The outlet invert shall be set above the 10-year high-water elevation of the receiving channel or storm structure.
−### The outlet shall daylight above the normal water surface of the receiving channel; a submerged outlet creates backpressure and can reverse-flow silt into the aggregate envelope. {note}
+### The outlet shall daylight above the normal water surface of the receiving channel; a submerged outlet creates backpressure and can reverse-flow silt into the aggregate envelope.
### Where site topography does not permit a gravity daylight outlet above the receiving water surface, the system shall discharge to a sump pit with a pump sized for the design flow.
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## Backfill and Compaction {toc}
−### Heavy compaction equipment operating within the aggregate envelope zone can crush corrugated HDPE laterals; compaction near the pipe shall be controlled accordingly. {note}
+### Heavy compaction equipment operating within the aggregate envelope zone can crush corrugated HDPE laterals; compaction near the pipe shall be controlled accordingly.
### Within 2 ft of the pipe, compaction shall be performed only by hand tamping or a light plate compactor.
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## Pipe and fittings shall be stored on level ground, supported to prevent deformation, and protected from puncture and impact damage.
−## Drainage aggregate shall be stored and handled so as to prevent contamination with soil fines that would defeat its wash-loss compliance. {note}
+## Drainage aggregate shall be stored and handled so as to prevent contamination with soil fines that would defeat its wash-loss compliance.
# Warranty {toc}
−## The Contractor shall warrant the subdrainage installation against defects in materials and workmanship for the period required by the Contract Documents, but not less than one year from Substantial Completion. {note}
+## The Contractor shall warrant the subdrainage installation against defects in materials and workmanship for the period required by the Contract Documents, but not less than one year from Substantial Completion.
## The warranty shall cover correction of installed pipe with reverse grade, blocked or crushed outlets, and fabric or aggregate placement defects discovered within the warranty period.
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default: Annual
```