How to construct Storm/Rain Water Drainage system

HOW TO CONSTRUCT STORM WATER SYSTEM

                                                

INTRODUCTION

A storm water system is a system to manage runoff from rainfall and maintain the underground water table.

OBJECTIVE:

Main objective of this method statement is to complete the work in a uniform way across all projects with accuracy and efficiency.

 MATERIAL

Bricks, Coarse Sand, Cement, Aggregate, RCC Covers, Reinforcement steel, PVC slotted pipe, Gravels, MS Rungs, MS Grating etc.

 APPARATUS / EQUIPMENT

JCB / Excavator, Tractor with Trolley/Tippers, Plate Compactor, Double Drum Roller, Mixture Machine, Auto Level, Mason Thread, Rope, Measuring tape, Plumb bob, karni, Basuli, Boring machine, Water tanker.

 HEALTH AND SAFETY PROVISION

·         Permission from the engineer in charge shall be taken before any excavation commences, and all persons involved in the task shall be fully briefed.

·         Fencing and safety signage to be put near excavated area and maintained during the progress of construction work.

·         Suitable access to be provided to trenches and pits.

·         Dewatering system is to be implemented wherever required.

PREPARATORY WORK

·         Obtain relevant approved GFC drawings.

·         All required area to be cleared for excavation. 

·         Layout work of the Storm water drainage and location of Recharge well shall be marked.

·         Bench mark should be marked over a column in nearby block.

·         NGL shall be recorded to finalize excavated quantity.

 PROCEDURE OR METHODOLOGY

·         The center line of drain and reference line is marked before start of excavation.

·         Locate the position of the Rain water harvesting well and de-silting chambers on the ground as shown in GFC drawing.

·         Excavation — Trench shall be excavated manually or with the help of JCB to the required dimensions, alignment and gradient. The excavation of trench shall commence from the starting end.

·         The bottom of the trench shall be compacted with the help of plate compactor to achieve plain and well rammed surface.

·         Bedding— 75 mm thick PCC 1:4:8 shall be laid at required level, under the brick walls of drain. The width of PCC would be thickness of brick wall +35 mm projection on both sides.

·         Brick Work —Layout for 230 mm thick or more brick work as specified in drawing is to be done over PCC. Brick work shall be started after minimum 8 hours of PCC with 1: 6 CM over PCC up to required height, keeping allowance for drain cover. Brick work shall be allowed to cure for 7 days, backfilling can be done after 3 days of curing.

·         Backfilling— Backfilling shall be done manually and compacted.

·         Installation of Drain Covers— Perforated precast RCC drain cover shall be fixed in line and level over concrete bed. Concrete bed thickness as per drawing.

·         Cleaning Up—All construction materials, tools and temporary structures shall be removed from the trenches before installation of drain cover.

·         Drain cover – Precast openable perforated drain covers should be placed.

·         Baffle wall – Half brick work baffle wall to be provided @ 15mtr c/c up to 6” below the bottom of drain cover.

·         No plaster shall be done inside the drain.

Installation of Rain Water Harvesting Well:

·         Location of Bore well shall be finalized.

·         Drilling shall be done upto a depth of approx 5 mtr above the water table or as per drawing.

·         Space around slotted pipe in the bore hole is to be filled with 10 mm stone chips. Slot size in the pipe should be 2mm wide & 100 mm in length. Slot has to provide 500mm from filter media and 1m above the last level of bore well.

·         The lower and upper ends of the pipe shall be plugged.

·         Excavation shall be done as per the size and depth of the recharge pit.

·         PCC and Brickwork shall be done as specified in the drawing.

·         Beds of Boulders, Gravels and Coarse Sand shall be laid as specified in the drawing.

·         Rungs shall be provided as per the requirement.

·         Connection to RWH well—Drains shall be connected to collection/sedimentation chamber. MS Grating to be provided at connection point to avoid any foreign material in RWH pit.

·         End plug/Cap to be provided at inlet of RWH for first rain, so that foreign material does not enter into the pit as per drawing attached.

·         Slab shall be casted at the specified height and manhole covers shall be provided as per the drawing.

·         Cleaning Up— All construction materials, tools and other unwanted shall be removed from the pit before commissioning

 INSPECTION

·         Slotted pipe and accessories should be inspected for defects and cleanliness prior to lowering. Any defective, damaged or unsound material should be repaired or replaced.

·         The prepared trench bed shall be inspected with reference to design. Uniform gradient, alignment and proper compaction shall be ensured.

·         The top level of brick work shall be checked for uniform line and level.

·         Drain covers shall not be damaged from the edges.