3trenchless ayanangshu.pdf

No-Dig Madrid 2014 Ref 3B-2

International No-‐Dig 2014 32nd International Conference and Exhibition

______________________________________________________

Madrid 13-‐15 October 2014

Ref: 3B-‐2

LESSONS LEARNED IN TRENCHLESS SEWER RENOVATION AND

REPLACEMENT IN INDIA AND THE GROWING INITIATIVE TOWARDS SUSTAINABLE ASSET MANAGEMENT

Dec Downey1, Ayanangshu Dey2, Raman Kumar3, Deepika4 1 Principal, Trenchless Opportunities Ltd., Peterborough, UK 2 Partner, AND Engineers & Associates, Kolkata, India 3 Associate Director / Project Manager, AECOM (India) 4 Planning & Design Engineer, AECOM (India) ABSTRACT: Substantial advancement has been made in the past two decades in trenchless sewer renewal and construction in the Indian Metro Cities. The paper represents the case study of Delhi and Kolkata. During the refurbishment of century-old sewers using an array of trenchless techniques including, pipe bursting, CIPP, GRP slip-lining, spiral-wound, and ferro-cement spray lining, and also for new construction using micro-tunnelling and HDD in congested un-sewered areas in the Metros and smaller cities, several situations like extremely congested conditions, acute space constraints, huge logistical, social, and environmental challenges were resolved. Not only the executing municipalities, but their consultants and contractors have also earned valuable lessons. This knowledge, in turn, is expected to encourage initiatives towards more effective sanitation asset management for the Indian Metros and their sanitation master planning as a tool for augmentation of facilities to un-sewered areas both in Metros and in smaller cities. Implementation experiences of these Metro cities are pooled to help define a recommended method of approach to the challenges of sewer construction in smaller cities. This paper reflects a collaborative work to draw together the lessons learned in condition assessment analysis, method selection, specification, project execution and contract administration in some very difficult environments. 1. Introduction

Rehabilitation may be defined as repair, renewal, or replacement of pipeline components to return the system to near-original condition and performance. Until the 1970s, rehabilitation of sewers was generally limited to man-entry pipes (Diameter >36” or 0.9 m), and the works were comprised mainly of slip-lining or local in-situ repair of damaged sections such as re-pointing of mortar in brick sewers. Smaller sewers or man-entry sewers with more extensive problems were simply replaced in open trench works. However, more recent developments have considered economic, social, logistical, and contractual drivers for sewer rehabilitation programs using trenchless technology to avoid any environmental impacts in or around built up area. Most rehabilitation methods have been developed as proprietary systems; the standards for their design and use have been developed on a technique-by-technique basis, even though the design principles have many common elements. In recent years India has gained experience in the application of various technologies for the rehabilitation of sewers. The paper presents the case study of Delhi and Kolkata. The objectives of this paper are first to reflect the lessons learnt in implementing a sewer rehabilitation program in densely congested urban conditions and later to present the need for sewerage asset management for other cities involving rehabilitation and installation of sewers by trenchless technology as key agenda for sustainable development.


2. Case Study: Kolkata

Present Condition of the Kolkata Sewerage System: Need for rehabilitation

Trenchless rehabilitation of underground sewerage and drainage assets in Kolkata picked up momentum in the middle of the past decade, most-likely triggered by the success stories in Mumbai and Delhi. Since then, both man-entry and non man-entry types of Victorian-age brick sewers in the central city area have been refurbished by adopting trenchless technology for several projects initiated by the Kolkata Municipal Corporation (KMC) (Basu and Dey, 2012). The layout of the very first brick sewers and some others which form the basic sanitation and drainage infrastructure of the historic centre of Kolkata is shown in Figure 1. Such undertaking by KMC, at first proved to be immensely challenging not only for the engineers of Kolkata Municipal Corporation with limited knowledge about these new techniques, but also for the contractors who executed the works. Local factors gave rise to conditions which the engineers involved found quite daunting, conditions that posed huge logistical challenges and extreme space constraints. Once these renewal projects got underway, some very difficult situations had to be sorted out quickly to progress the works. A brief account of these challenges and lessons learnt is given in the following.

Flow conditions and their drastic seasonal variations, intrusion of utilities inside sewers, and illegal body connections make Kolkata’s sewers quite unique from the perspective of performing comprehensive rehabilitation works. The city sewers carry both storm water runoff and sewage. Renewal works were carried out during the small time-window from 11 pm to 5 am at lean flow hours (Basu et al., 2013a) so that minimum flow conditions could limit over-pumping. Stanking arrangement for flow control and isolation of particular sections of sewer were set up so that the sewers could operate normally during the daytime. However, Kolkata often receives extreme weather, locally known as “Nor’westers” during early summer months with little or no notice at all. During these occasions, additional protection for stanking and securing them against the incoming sudden storm runoff was required. This proved to be quite challenging in cases where such contingencies were not adequately planned. Numerous un-documented sewer connections were found during the de-silting process of stretches of sewer. These connections were located , mostly on the sides or crown of the sewer (e.g. Hazra Road sewer). Each of these connections had to be blocked with pneumatic plugs before start of the night’s work and reinstated each morning before putting the sewer back into service again. Such plugging and unplugging of incoming sewers had to be done systematically to ensure that no connections were left plugged after the night’s work was done. Sewers in central and north Kolkata were constructed in the1860s and are generally shallower than the trunk sewer of the southern side of the city. Lower cover, more illegal connections, drastic changes in over ground land use pattern over the last century and increase in loading conditions on these sewers has inflicted a steady process of structural deterioration and prompted a significant number of sewer collapses in the past decades. The most challenging incidents have happened in sewers along Lenin Sarani, Beadon Street and Nimtola Ghat Street (see Fig 2). These sewers had silted up to 70-80% of their depth and in some cases the silt proved too hard to be removed using water jetting and large vacuum suction machines (super suckers). The de-silting equipment was actually damaged by the hard silt which had to be chiseled and jack hammered prior to removal by mechanical or manual means. On a few occasions, it was necessary to lower a forklift vehicle into the sewer to assist in de-silting work. Locating sewers and manholes had been quite challenging for the Contractors, too. Being a century-old the as built recording was either not undertaken or not available during execution, no GIS mapping for underground utilities in those days. The mapping of underground utilities was an important recommendation of the World Bank Study Report of 2001; however the implementation was not addressed adequately (Basu et al., 2013b) till now. Sometimes the sewers were aligned away from the road creating problem to locate the access pits. Manholes were often aligned eccentrically with respect to the sewer, even under tram lines. This created accessibility problems as the tram lines were rehabilitated a few years back by placing them on solid concrete slab of about 600 mm thick. De-silting such sections manually was seriously troublesome. Inadequate sewer information also affected the time schedule of the project with major time lost in identifying the correct alignment, assessment of the exact sewer size, finding manhole locations and connections. Most importantly, such inadequate information created a number of contractual issues. These contracts were item-rate contracts and dependent on actual measurement of quantities, which went haywire in the event of changes in sewer sizes, silt quantity or liner sizing. Further, as no authentic information on existing water supply lines was made available to the contractors, sometimes additional access pits had to be built as those already constructed had water supply mains running across the excavated pit making them unsuitable for liner installation. One of the most challenging and time consuming affair in execution of the work was the existence of several types of utility lines inside the sewer crown (Figure 3). Such lines included water supply trunk mains, distribution lines, electrical cables, telecom cables and optical fiber data cables. For utility relocation, several agencies had to be contacted, e.g. the Water Supply Department and Sewerage and Drainage Department of KMC, Calcutta Electric Supply Corporation (CESC), Calcutta Tramways Company (CTC), Calcutta Telephones, Irrigation Department (for diversion/ disposal of flow) and Calcutta Traffic Police (mainly for traffic control and road accessibility). Utility lines were isolated and shifted out of sewers in most of these cases


for which constant persuasion and coordination were required both from KMC and Contractors’ sides. On one particular occasion, the existing “jelly-filled” power cable of CESC could not be replaced as such types of cable were laid way back in the 1800s and use of such cable had been discontinued long back (P&D, KMC, 2014). Almost in all the cases, these sewers did not have any convenient bypass sewer where the huge quantity of flow could be diverted. Hence, temporary HDPE lines for over-pumping of incoming flow in most sewer sections had to be laid over ground. Because of existence of road crossings, such lines had to be buried locally to make way for traffic. These lines conflicted with existing local utilities at numerous locations, information about which was not made available by the concerned agencies. At the crossings of tram lines, such HDPE lines had to be maneuvered sharply to negotiate the concrete bed under the tram tracks. All the trunk sewers drained into terminal pumping stations and to reduce the water level to a manageable level was vital for contractor’s work. Despite best possible efforts, a few times coordination between sewer rehabilitation team and pump operators at these terminal pumping stations was not adequate. Crucial time was lost in negotiations incurring delays in working. Some sewers passed through areas inhabited by minority groups. During the Holy month of Ramadhan, the peak flow in sewers used to occur before sunrise and this shortened the effective working hours. During prominent Hindu festivals like Durga Puja and Holi, large numbers of pilgrims were expected to visit prominent places in Kolkata. Access pits in these areas would have to be closed off completely to ensure public safety and avoid any untoward incident. Once the sewers had been relined, removal of stanking proved to be quite exhausting. As per the tender, such stankings could not be built by sand bags but only with adequately strong brick masonry walls and steel plates to resist the volume of flow. Dismantling such robust walls and taking them out from the sewers proved to be a challenging task before re-commissioning of the sewers. At times additional pumping to avoid flooding of branch sewers, that outfall into the trunk sewers was necessary. Blocking of these branch lines during work by pneumatic plugging created some local water stagnation, specially after a short but intense downpour. The agencies executing the project had to make separate provision to remove such water by additional pumping to pacify the local residents, whose cooperation at times became very critical for the execution of the project and its success. Lastly, coordination with local resident population proved to be crucial and keep the work going at odd hours. Objections from residences during the work was prompted by operation of heavy machinery, super suckers, blowers for sewer ventilation, carrying off the silt in large trucks and infestation of disease carriers like rats and cockroaches.


Figure 1 Layout of Major Brick Sewers in Kolkata

Calcutta Map Courtesy: Imperial Gazetteer of India, New Edition, University of Chicago Library, USA

Figure 2: Collapsed and Silted Sewer

Figure 3: Major Utility Lines inside Sewer

Photos Courtesy: Planning and Development Department, Kolkata Municipal Corporation, Kolkata, India


3. CASE STUDY: DELHI rehabilitation program

Over the last 30 years, the population of Delhi has rapidly increased from 4 million (in 1971) to around 18 million people today. The burgeoning population coupled with slow and unorganized development in sewage infrastructure has posed a major threat to the city’s sanitation issues, subsequently affecting river water quality and public health of the inhabitants. The entire National Capital Territory of Delhi (NCT) with an area of 1483 square kilometers has been broadly categorized into two: sewered area and un-sewered areas, as shown in Figure-4. The Delhi Jal Board (DJB) is responsible for water supply & sewerage works in Delhi. Only about 50% of the population in Urban Delhi (UD) has access to the sewerage system. The rest of the untreated sewage overflows to river Yamuna through drains. The existing sewerage system is old and was built progressively since 1930. There are currently more than 7000 Km of sewers of diameter from 150 mm to 2800 mm with the depth of deep sewers up to 12 meters. Most of the sewer network built in the 1950-60’s have not only outlived their intended economic life span but also degraded and exhausted their functionality due to a multitude of problems i.e. poorly made joints, improper bedding, infiltration, exfiltration of water from joints, uneven settlement and heavy siltation. The sewers are heavily silted with opened joints and structurally deterioration as the pipe material is generally reinforced concrete and is prone to H2S induced corrosion. Till now many places in Delhi employ traditional methods of de-silting in which the body of the sewer often gets damaged due to abrasion caused by the silt removal equipment such as bucket and chains. Due to rapid urbanisation and congestion, there is little space available to lay new sewers adjacent to the existing sewers. Furthermore the construction of new sewers by conventional methods will not be technically viable, there will be additional risks to the nearby structures, such as buildings like high rise residential complexes. 3.1 Approach for Sewerage Management in Delhi Looking to the poorly organized set up in sewerage sector, the DJB decided upon a judicious approach to tackle the sewerage problems in Delhi as shown in Figure-5. For un-sewered areas of Delhi, DJB intends to develop a holistic, integrated and sustainable Master Plan for design horizon of 2031. This master plan shall ensure that comprehensive, technically and financially viable plans (CAPEX & OPEX) are in place for the implementation of sewerage works in unsewered areas of Delhi by integrating with existing network and sewerage infrastructure to bring the latter to their optimum utilisation state. The un-sewered areas of Delhi have a complex situation with much congestion and little space left for laying the sewerage utility. In view of this, trenchless technology methods such as microtunnelling and HDD have been proposed for laying new networks. The sewerage master plan for design year 2031 (SMP-2031) has been developed by AECOM for a huge sewerage network of around 10,000 Km. However, as an immediate measures a viable option has also been convened which is to trap the sewage flowing in the drains from un-sewered areas by implementing an interceptor Sewer system, it is intended that this shall cut off untreated sewage contamination in the drains leading towards the River Yamuna. This is a short term immediate relief for the improvement of sanitation condition and hence quality of The River Yamuna. The master planner, AECOM with inputs of DJB has taken up the proposed infrastructure in SMP-2031 by integrating with these proposed interceptor sewers. The proposed sewerage schemes under SMP-2031 shall be implemented in various phases according to the intended priority over next few years. For sewered areas, DJB took a significant initiative to rehabilitate sewer conveyance system in a phased manner. Initially150 Km of sewer was examined for its structural strength and stability. DJB decided to rehabilitate around 50 Km of trunk sewer and 20 km of peripheral sewer based on criticality and need. The rehabilitation of remaining sewerage network will be taken up in subsequent phases which have been described in section below. DJB also took up the initiative for asset management of its catchments namely Okhla, Rithala & Kondli WWTP under JICA assisted Yamuna Action Plan-III and Coronation WWTP, where sub-catchments are being analyzed

Figure 2: Sewered & Unsewered area of NCT of Delhi

Figure 5: Approach towards Sewerage Management in Delhi


in a holistic manner for overall zone representation. Network is being optimized to achieve an energy efficient system. The rehabilitation of the sewerage network is also being analyzed to rejuvenate the existing system. Hence, this identifies the appropriateness of trenchless technology for strengthening and rehabilitating the existing sewer pipe with least disruption by various methods. The lessons learnt and experience gained on rehabilitation projects in Delhi have been represented in this paper. DJB is also planning various other projects and studies to address the sewerage improvement needs of Delhi as a priority. In view of this, a sustainable Asset Management strategy is being devised for the long term to maintain the sewerage system in efficient manner. The approach thus will lead to improve the general sanitation conditions and enhance the water quality in holy River Yamuna. 3.2 Rehabilitation Technologies implemented in Delhi DJB has tried Cured in Place Pipe (CIPP), Glass Fiber Reinforced Pipe (GRP) and Spirally Wound Pipe (Ribloc & Rotaloc) for rehabilitating sewers in Delhi. These have been identified as viable solutions to meet the rehabilitation requirements of Delhi. However, these methods have been adapted according to site requirements to satisfy specific local issues. Details of these works including length rehabilitated and the technologies used are shown in in Table 1 & 2 and Figure 6 & 7: Table 1: Trunk Sewers Rehabilitated by DJB:

Sl. No.

Name of the Trunk Sewer Length in (Km.)

Status Liner Technology Used

1. Punjabi Bagh 7.100 Completed CIPP 2. Jail Road 6.800 Completed CIPP 3. West Delhi 7.000 Completed CIPP 4. University Trunk Sewer (U.T.S.) 5.150 Completed CIPP 5. Ring Road 10.100 Completed Spiral Wound & GRP 6. Bela Road 4.370 Completed GRP 7. Relieving Sewer 5.130 Completed GRP 8. North Trunk Sewer 5.330 Completed CIPP 9. Sewer from Q point to Kilikari PS 2.500 Completed CIPP

10. Sewer from Delhi Gate to College Lane 3.000 Completed CIPP 11. Harsh Vihar Sewer 3.000 Completed CIPP 12. Kalka Ji Trunk Sewer 4.300 Completed CIPP 13. Sita Ram Bajar Trunk Sewer 3.100 Completed CIPP 14. Indian Express Trunk Sewer 3.600 Completed CIPP

Table 2: Peripheral Sewers Rehabilitated by DJB

Sl. No.

Name of Sewer Length in (Km.)

Status Liner Technology Used

1. Cross Connection No. 1 0.315 Completed GRP 2. Cross Connection No. 3 2.00 Completed GRP 3. Cross Connection No. 5 0.80 Completed CIPP 4. PiliKothi Sewer 4.60 80% GRP 5. Subhash Marg Sewer 2.15 Completed GRP 6. Peripheral Sewer from Naraina to Raja

Garden 2.25 Completed CIPP

7. Peripheral of Patel Road 2.50 Completed CIPP 8. Aurbindo Marg 2.35 Completed CIPP

Based on the benefits recognized by DJB in these rehabilitation projects for trunk sewers, DJB is currently implementing sewer rehabilitation project to tackle the next most vulnerable group, the peripheral sewers. The first sets of sewers have been chosen in Rithala and Kondli zones under JICA funded YAP-III project as shown in Table-3. Another set of sewers have been taken up by DJBs own efforts. DJB intends to rehabilitate 110


peripheral sewers, around 161 Km in length to strengthen the existing sewerage system by eliminating sewage overflows to drains and hence reducing pollution in River Yamuna. The details of these sewers are shown in Table 4. Table 3: Sewers Proposed under YAP-III

1 Kondli: Rehabilitation of Sewer Lines: Trunk Sewer No. 4, Narwana Road, Anand Vihar, Hargovind Enclave and Vikas Marg by CIPP

2 Kondli: Rehabilitation of Sewer Lines: Trunk Sewer No. 5 and Jhilmil Colony Sewer by GRP 3 Rehabilitation of Sewers of sizes varying from 600mm to 1400mm Dia in Ashok Vihar and

Jahangirpuri Area by CIPP Structural Lining Method under YAP(III) Table 4: Sewers Proposed under “Rehabilitation of Peripheral Sewers”

S. No. Sewer Diameter (mm)

Length (m)

S. No.

Sewer Diameter (mm) Length (m)

1. 450 84272 6. 900 16781 2. 500 3791 7. 1000 165 3. 600 33957 8. 1100 5177 4. 700 7855 9. 1200 5300 5. 800 3338 10. 1400 550

TOTAL 161186 m Figure 6: Status of utilities in Delhi before renovation


Figure 7: Present Status : Completed / Ongoing works in Delhi


The overall project deliver approach elected by DJB is to first carry out typical condition assessment and analysis of the system. Subsequent phases then include design and tendering works to mobilize the executing agencies with specified rehabilitation technologies. The latter phase shall include project management and construction supervision along with development of an information system for a sustainable asset management approach. The following technology selection matrix shown in Figure 8, has been developed and shall be applied for each project area and on case to case basis. Figure 8: Proposed Technology Selection Matrix

3.3 Performance Characteristics of the Liners Among the three lining methods used for rehabilitating man entry size sewer and adopted by DJB, CIPP and GRP liners have been extensively used while the Spiral Wound Systems (Rib Loc & Rota Loc) have been selectively used. Over the period, technical knowhow on the application of these technologies has been acquired by local contractors. All the three liner systems are able to meet most of the performance requirements of DJB and are listed below in Table 4 with anticipated difficulties as shown in Table 5. Table 4: Performance requirements achieved Ability to resist chemical and biological attack (with resin rich layer)

Ability to be watertight for life

Ability to enhance hydraulic performance Ability to enhance life span to 50 years Ability to enhance structural capacity Ability to function as standalone liner

Applicability for sewers of all diameter 150 to 2000mm Availability of local expertise Table 5: Difficulties and Challenges Encountered During Sewer Rehabilitation Works Working in congested roads and built-up areas

Substantial delay in obtaining permission from Road authorities

Sometimes religious and political processions lead to change in implementation plan

Diversion of flow & maintenance of laterals

Stanching of sewer manholes for isolation

Rectification of settled Sewer

Structurally Weak Pipes

Lack of appropriate pipe bedding (cause the sewer to sink)

Maintenance of surrounding services Crossing of Major Drains Rectification of Reverse Gradient


4. CONCLUSION The case studies for the two metro cities showcased the experience gained in implementing Trenchless Technology for sewer rehabilitation projects. A number of trenchless techniques for sewer renewal have been successfully implemented despite some substantial problems due to local circumstances. The benefits identified from successful implementation of the projects undertaken to date has encouraged the authorities and stakeholders to take up similar projects to rehabilitate sewerage assets in other cities. Taking cognizance of these issues and bringing the lessons learnt to the planning process of the sewerage rehabilitation programs in these Indian cities is expected to be worthwhile and reasonable from an engineering, social, and logistical standpoint. A need is also recognized for the development of integrated and holistic Sewerage Master Planning taking into account viable Asset Management strategies from experience obtained in more developed urban situations. Progress towards solving the problems of India’s water and wastewater challenge is complicated by population growth and the sheer volume of work that needs to be undertaken. However the achievements in Delhi and Kolkata give confidence that the combined efforts of the sewer undertakers, their contractors and the engineering firms will be up to the task and will evolve and modify proven asset management strategies to improve efficiency and sustainability in the years ahead. 5. REFERENCES

• A Rehabilitation Strategy for Delhi’s Trunk Sewer System, funded by the British Overseas Development Administration, Delhi WS & SD Undertaking, Severn Trent International, 1988

• Detailed Project Report of Yamuna Action Plan, Phase-III, Delhi Jal Board, AECOM, 2010 • Nilangshu Bhusan Basu, Ayanangshu Dey, Duke Ghosh, (2013), Kolkata's Brick Sewer Renewal:

History, Challenges & Benefits, Proceedings of the ICE - Civil Engineering, Volume 166, Issue 2, pp. 74-81

• Nilangshu Bhusan Basu, Ayanangshu Dey, (2012), New Life for Kolkata’s Sewers, American Society of Civil Engineers’ Civil Engineering magazine, July/August 2012, pp. 68-75.

• Nilangshu Bhusan Basu, Somenath Boral, Sushil Kumar Mandal, Ayanangshu Dey, (2013a), Rehabilitation of Kolkata's First Victorian-Age Brick Sewer, Proceedings of the ICE - Municipal Engineer, Volume 166, Issue 4, pp. 230 - 238.

• Planning and Development (P&D) Department, Kolkata Municipal Corporation (KMC), Nilangshu Bhusan Basu, Sushil Kumar Mondal, and Shibnath Das, Personal communications, 2014

• Raman Kumar and Dec Downey (2007), “Trenchless Technology: An integrated approach for sustainable Social and Infrastructure development”. IndSTT

• Raman Kumar, Dec Downey and V.S.Thind (2007), “The New Delhi Experience – upgrade and modernization of sewer networks in the megacity”, National American Society for Trenchless Technology (NASTT).

• Raman Kumar and V.K.Gupta (2013), “Master Planning Sewerage System of NCT of Delhi”, IPHE

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