Reviving the Glory of Dravyavati

Known to be one of the first-of-its-kind river rejuvenation activities in India, the Dravyavati River Rejuvenation Project was recently inaugurated in Jaipur by Rajasthan Chief Minister Vasundhara Raje. Originating from the western slopes of the Nahargarh-Amer Hills, Dravyavati River—also known as Amanishah Nallah—flows through the west side of the Pink City. On account of rapid urbanisation along with dumping of sewage, industrial waste water and solid waste, the once historically important river had been reduced to a nallah. A consortium of Tata Projects, a Tata Group company, and SUCG International Engineering Company, a company of Shanghai Urban Construction Group (SUCG), bagged the contract to bring the river back to life. Developed at Rs 14.71 billion, the project was inaugurated on schedule after 30 months. However, an extension of six months had been granted to complete additional and finishing items.The benefitsThe Dravyavati River project is an example for all states in India that face open drainage and sewage problems. Satyanarayana Kasinadhuni, COO-Industrial Systems, Tata Projects, elaborates on the benefits of the project:Public health: Several public health benefits after the rejuvenation of the river include groundwater recharge, improved irrigation, better farm products, reduced open defecation, improved sanitation, cleaner air, mitigation of vector and water-borne diseases, creation of walkways and cycle tracks, and mitigation of foul smell owing to open sewage. Flood control: Removing encroachments, clearing the flow of the river and constructing the river channel throughout have prepared the city for floods that might occur in the next 100 years. Major benefits include river channelisation, river flow control, and revival and restoration of dams. Fillip to the economy: Notable changes include attraction of investment and tourism, land for development and better public amenities. Land prices adjoining the riverfront have doubled or tripled. Urban infrastructure: Residents now have access to open green spaces, new roads and linkages, museums and an experience centre, a river promenade, sit-outs and public toilets, walkways, cycle tracks, better security, nodes and plazas, sewage treatment plants (STPs), sewer lines and service roads. A major part of the area lighting uses solar lights and LED fixtures.Construction methodologyThe river channel is broadly categorised into three segments. As Kasinadhuni explains, “The initial 6 km lies in the forest area with a comparatively steep gradient. Except for defining the channel and placing gabions, which work as speed-breakers for the flowing surface run-off during the monsoon, no construction was supposed to happen there.” He adds that from 6 km to 36 km, the section is concrete lined on the bed and slopes off the lower channel. The stretch passes through the city amid densely populated localities; hence, there was a restriction on the width on this stretch. As per design calculations, the velocity of water would be such that the concrete surface was needed to avoid erosion. The thickness of the lining is 200 mm. The last 12 km is in the scarcely populated and industrial area on the outskirts of the city. The stretch is stone pitched with an average size of 230 mm—the stones were procured from nearby mines.Construction commenced with the cleaning of 20 lakh cu m of garbage and weeds, deposited for decades. A detailed survey was conducted to design the hydraulics of the river. As Kasinadhuni shares, the primary stages of the construction included defining the centre line; formation of the embankment and channel bed; laying the sewer lines within the embankment; concrete lining and stone pitching; and peripheral developments like walkways, turfing, boundary wall, etc. The construction of the STPs were parallel and independent activities.Sewage treatment and controlFive STPs have been developed along the length of the river that aim to collectively treat 170 mld of sewage per day and ensure the continuous flow of clean water. Physical, chemical and biological processes have been used to remove contaminants and produce treated wastewater that is safe for agricultural purposes and aqua life. “A by-product of sewage treatment is a semi-solid waste called sewage sludge that has to undergo further treatment before being suitable for disposal or application to land,” adds Kasinadhuni. “This will help prevent diseases.”The numbers, locations and sizes of the STPs were decided after studying the sewage entering the Amanishah Nallah. C-Tech, a cyclic activated sludge treatment process, was used to provide the highest treatment efficiency possible in a single step. Also, SBR (sequential batch reactor) design was used as it uses less land than a conventional activated sludge process. The five STPs are Bassi Sitarampura (20 mld); Devri (15 mld); Sanganer (100 mld); Bambala (25 mld); and Goner (10 mld).Technological excellenceSewage interception and transportation are primarily based on gravity flow except at one location, where the sewage is being pumped upstream to the treatment plant. The sewage interception chambers were designed based on a detailed survey of the location and discharge of the incoming drains. Discharge from several drains is diverted to one interception chamber, which then connects to the main sewer trunk passing under the embankments. The sewer trunk carries the sewage to the nearest STP at the downstream.Once the sewage is received at the STP, it is pumped to the primary treatment unit; after that, the treatment process is initiated. The advantage of SBR over conventional activated sludge technology is that biological treatment aeration is done by air diffusers placed at the base of the tanks. In the traditional method, aeration is done by surface aerators, which create the nuisance of odour and aerosol. Moreover, a much larger area is required in the activated sludge process, which is less in the case of SBR. Sustainable practices and equipmentThe project used nearly 5 lakh cu m of concrete. Manufactured sand (M-Sand), a waste from stone crushers, was largely used. Stone dust is washed to meet the parameters of construction sand. Thus, M-Sand is a sustainable material as it replaces river sand. Fly ash was used in the concrete mix, thus reducing the carbon footprint by cutting back on the usage of cement.Earth was excavated from the channel bed and used to form the embankment. “No additional earth was brought from outside,” informs Kasinadhuni. “Also, the concrete was cured chemically rather than with water.”Vital to the project was the semi-automatic concrete paver, which was used in the concrete lining of the channel, both in the bed and slopes. At the peak of construction, 24 pavers were deployed at various locations.Combating challengesThe need for water for curing was mitigated by using a curing compound. Temporary embankments were created to divide the channel width into two halves; the existing flow was diverted to one half while the other half was constructed. “Although encroachment removal was not in our jurisdiction, we had to support the client in enforcement works,” reveals Kasinadhuni. “Also, several technical alterations had to be done wherever hindrances were unavoidable, such as altering the section depth and increasing wall height.” All necessary safety measures were followed during construction: every worker underwent an induction for safety procedures upon joining and safety training and tool box meetings took place every day at the construction sites. The result: The project, which involved around 8,000 workers at its peak, has completed over 22 million safe man hours to date. DIKSHA JAWLEProject detailsSize: 47.5 kmLandscape: 1 lakh sq m parks; 5 lakh sq m green belt along the riverThree major gardens in area: 10 hectare; Walkway/cycle track: 30 km; plantation: 22,000; exhibition centre: 1,000 sq m; storage yard: 9,200 sq m.Number of check dams: 104.Quantity of stone pitching: 6 lakh tonne.Total capacity of sewage treatment plants: 170 mld.Year of completion: 2019.Cost: About Rs 14.71 billion (approximately 50 per cent is the cost of construction; the rest comprises engineering, procurement and project management)Development agency: Jaipur Development Authority. Tel: 0141-256 9795. Website: www.jda.urban.rajasthan.gov.inContractor: Tata Projects-SUCG Consortium.Tata Projects. Tel: 040-6725 8800. Website: www.tataprojects.com;SUCG. Tel: 011-4600 1203. Website: www.sucgi.inCivil engineer: Tata Projects.Project management consultant: PDCOR. Tel: 141-409 6666. Website: www.pdcor.comArchitect/planner: Phoenix Planning Studioz. Tel: 0141-402 8515; Anagram Architects. Tel: 011-2652 2137. Website: anagramarchitects.com; Abha Narain Lambah. Tel: 022-2605 6367. Website: www.anlassociates.comContracting agencies: Over 200 subcontractors deployed.