Ash Pond Seepage Control, Containment & Water Recovery

Stop water leaving the pond where it should not, and start recovering the water that should stay in the plant.

Ind-Barath JSW Energy (Utkal) Limited engaged Geotech Design Consultants to carry out a detailed site assessment and feasibility study of the existing ash pond at Jharsuguda and its surrounding water management system.

The facility carried several engineering and environmental problems at once: seepage through the bund towards the village side, deterioration of the existing HDPE lining, inadequate water-slope management, no effective decantation system, and no dedicated water recovery pumping arrangement. Stormwater from outside the pond catchment was also entering the system uncontrolled.

The objective was a technically sound, buildable solution covering seepage prevention, hydraulic containment, liner protection, controlled decantation, water recovery and external stormwater management — suited to the site as it actually stood and aligned with applicable engineering and environmental requirements.

Six conditions were identified during the assessment, each undermining a different part of the containment and water management system.

The problems were connected, so the solution had to be. Seepage through a bund, a damaged liner, a flat water slope and missing recovery infrastructure are not four independent defects — each one increases the load the others have to carry.

Geotech Design Consultants therefore approached the work as a single containment, seepage-control and water-management scheme: improve the containment barrier, protect the geomembrane from mechanical damage, restore controlled hydraulic gradients, provide decantation and recovery facilities, and keep external stormwater out of the pond altogether.

A multilayer containment and protection arrangement was developed for the areas identified as needing improvement. HDPE geomembrane provides the primary low-permeability barrier; a 300 GSM non-woven geotextile sits beneath it as a protection layer, giving separation and cushioning between the prepared subgrade and the membrane, subject to site-specific subgrade conditions and design requirements.

The geotextile layer reduces the risk of puncture or mechanical damage to the HDPE during installation and subsequent covering activities — the stage at which geomembrane containment systems are most often compromised.

Fig. 1 — Typical liner build-up. Layer thicknesses indicative; final specification subject to site-specific design.

Where the existing HDPE was deteriorated or inadequate, the rehabilitation approach was developed from the actual site condition, with preparation, overlap and welding requirements, anchoring and transition detailing carried into the engineering drawings.

Seepage towards the village was treated as the project's critical issue, not one item on a defect list.

The engineering response was to establish a reliable barrier between ash pond water and the surrounding ground environment: improvement of the relevant bund sections, preparation of the surface and subgrade, and installation of a geosynthetic containment system of HDPE geomembrane with geotextile protection wherever the detailed assessment showed it was required.

Particular attention went to liner continuity, termination, anchoring, joints, penetrations and interface details. These are the locations where geomembrane systems fail in practice — a barrier is only as good as its edges and connections. The design philosophy was to eliminate preferential seepage paths and create a continuous containment barrier while maintaining the stability and constructability of the existing bund.

Available levels were evaluated and a hydraulic slope and collection arrangement developed so that pond water moves towards a designated decantation and collection zone instead of standing where it falls.

A proper decantation arrangement allows controlled withdrawal of water while minimising carryover of suspended ash particles, integrated with the settling and collection arrangement and with the recovery facilities downstream. Recovered water from the decantation and settling arrangement is collected and transferred by a dedicated water recovery pumping system for reuse within the plant, subject to the client's process requirements. The pump house and associated civil works — pump foundations, access, pipe routing and interface requirements — were carried in the same engineering package.

Together this replaces uncontrolled surface withdrawal with a defined hydraulic path, and gives the plant a systematic route to water recovery, recycling and reduced fresh-water demand.

1. 01Contained Ash PondDESIGNED SLOPES
2. 02DecantationCONTROLLED DRAW-OFF
3. 03Settling & CollectionSOLIDS SETTLE
4. 04Recovery Pump HouseRECOVERY PUMPING
5. 05PlantPLANT REUSE

Fig. 2 — Water management circuit, with external stormwater kept separate from pond water throughout.

A dedicated peripheral stormwater drainage system was proposed to intercept clean runoff generated outside the ash pond area and convey it safely around the containment.

The intent is a clear separation between clean external runoff and ash pond process water. Diverting external stormwater away from the pond removes avoidable inflow and reduces hydraulic loading on the containment system — a preventive measure that protects every other element of the scheme. The arrangement was developed against site levels, drainage paths, available right-of-way and safe discharge requirements.

The engineering assessment was carried out through site visits, physical observation, review of available information and feasibility evaluation of the existing infrastructure. It focused on locating the seepage and its likely causes, evaluating the condition of the existing HDPE lining, assessing bund conditions, understanding existing water movement and levels, and identifying suitable locations for decantation, water recovery and stormwater drainage infrastructure.

Those findings were converted into a design and drawing package covering the geomembrane lining system, geotextile protection, bund treatment, anchoring and termination details, water-slope arrangement, decantation, settling and collection, the recovery pump house, piping interfaces and the external stormwater drainage system. Typical construction details and sections were developed to guide site execution and to hold continuity between the civil and geosynthetic components.

Documentation and technical recommendations were prepared to support implementation, inspection, quality control and compliance — with specific attention to geomembrane installation quality, welding and joint integrity, subgrade preparation and protection of the liner system.

The intervention gave the client an integrated framework addressing the key shortcomings of the existing ash pond system rather than a sequence of isolated repairs.

Containment rehabilitation using HDPE geomembrane with geotextile protection, combined with bund treatment and appropriate detailing, provides a substantially more reliable basis for controlling seepage and improving containment integrity. Controlled decantation and water recovery improve the plant's ability to manage pond water, while peripheral stormwater drainage keeps external runoff out of the system in the first place.

The Jharsuguda project is a comprehensive application of geotechnical, civil, hydraulic and geosynthetic engineering to the rehabilitation of an existing ash pond facility — technically appropriate, constructible and environmentally responsible engineering for power plant ash management and water containment infrastructure.

• 01

  Ash pond seepage investigation and containment assessment

• 02

  HDPE geomembrane and geotextile containment design

• 03

  Bund treatment and liner detailing

• 04

  Decantation, settling and water recovery systems

• 05

  Stormwater drainage and diversion design

• 06

  Design, drawings and compliance support