Recommended for

Areas having basement seepage (flowing shallow springs) either near the surface or oozing out in the form of boils near the surface or in the basements or parkings etc (up to 18 meters) which are exposed to the atmosphere.

Potable quality seepage water.

Channelised Basement Seepage Water into the surface drainages (Wastage of seepage water).

Drilling of a new single Injection borewell with assured yield > 2000 lits/hour indicating presence of productive shallow/ deep aquifer/s.

Prefer the dug well or good yielding borewell if present nearby.

Methodology

Delineate the exact aerial extent of the shallow seepage.

Based on its location, construct a shallow trench all along the open basement walls with slope between 2 to 5%. The trench will start from the seepage and end near the borewell. Accordingly, maintain the slope within the trench so that the seepage water will flow by gravity towards the borewell.

A trench of 600 mm thickness is sufficient. However, if the seepage discharge is more or if rainwater is also getting collected into it, then increase the width based on the flow of water. The length and depth will vary from site to site.

At the end of the trench and near the recharge shaft chamber make a provision to drain excess seepage water.

Near the seepage discharge point, construct a chamber at least of 1.5 m x 2 m x 3 m (Lx W x D) size. The depth of the trench will depend upon the depth of the seepage below the ground.

Near the recharge shaft, construct a chamber at least of 1.5 m x 2 m x 5 m (Lx W x D) size. Considering the slope provided for trench the depth of this chamber should be decided. Practically its depth should be more by at least 1 m than the depth of the seepage discharge chamber.

In the recharge shaft chamber entry wall, make channels to put temporary wooden gates to arrest the muddy water especially during the rainy season.

Allow the seepage water to get collected into the shallow trench.

Presence of a deeper aquifer is essential. Hence, drill a borewell of at least 6” diameter and 50 to 60 m depth within the project premises at geohydrologically appropriate location. This borewell should yield at least 2820 lits/hour, then only it will accept the seepage discharged water. Usually, this borewell is not used for pumping purposes. Hence, it is treated as a Recharge Shaft.

Preferably use perforated (slit type) M.S. casing pipe of at least 6 meters depth for the borewell during drilling. After drilling grout only lower the 2 m part of the casing using cement slurry. Wrap silicon mesh of < 70 micron in upper 4 m part of the casing. Cover the borewell with the cap.

Create a filter bed using pebbles (600 mm thickness), gravels (750 mm thickness) and sand (600 mm thickness) layers around the recharge shaft. As seepage water is passing through the open to sky shallow trench, there are chances of bacterial contaminations. Hence, it is necessary to add a 150 mm thick layer of activated charcoal in between sand and gravel layers. This filter material is readily available in the market.

For safety purposes and to trap the leaves/ litter, cover the complete trench with MS bars or grill.

Process

Seepage water will automatically get collected into the collection chamber.

As soon as the seepage chamber gets filled up to the trench level, slowly the collected water will start flowing towards the recharge shaft under gravity.

Precautions

Cover the seepage collection chamber and the filter chamber from the top. Keep proper air vents while covering it.

Protect the shallow trench from any activity like parking of vehicles, dumping of waste etc.

During the rainy season if muddy water enters the trench, then immediately insert the wooden gate into the recharge trench chamber. This will stop the muddy water there itself and drain through the given outlet directly into the stormwater drainage line.

If the borewell starts overflowing, then also the wooden gate should be inserted.

Maintenance

If muddy water comes during monsoon, then the trench should be cleaned immediately.

Every year check the water quality parameters (chemical and bacteriological) of the collection well water at least during pre- and post-monsoon seasons.

If there is bacterial contamination, then immediately stop the recharge process.

Regularly clean the shallow trench, collection chamber and the recharge shaft chamber along with the filter bed.