Mumbai potholes: Experts point to drainage, traffic and repeated utility digging

Mumbairsquos roads are not all built to fail The 17yearold BandraWorli Sea Link and newer Coastal Road stretches have largely held up while potholes bumps and crumbling surfaces continue to plague several ordinary city roads So what makes the difference Experts point to everything from pavement design materials and compaction to drainage traffic loads and crucially what happens to a road after it is built mdash including repeated digging for utilitiesThe BandraWorli Sea Link has largely remained free of the potholes and surface damage seen on several city roads PicShadab KhanldquoMinor defects including potholes are attended to through routine maintenance and patchwork A complete renewal of the surface is generally carried out at intervals of around 5 years depending on its conditionrdquo said an MSRDC engineerYou canrsquot just add another layerResurfacing the Sea Link is also different from resurfacing an ordinary road Adding a fresh layer over the existing surface would increase the load on the bridge and change the road level When the surface is completely renewed the existing layer is removed to a depth of 25 mm and replaced with a new layer of the same thicknessA pothole near Mehboob Studio in Bandra PicShadab KhanldquoThis process allows us to maintain the original road level and at the same time prevents any unnecessary additional load from being imposed on the bridge The maintenance work is therefore carried out keeping both the road condition and the structural safety of the Sea Link in mindrdquo the engineer saidWhat makes a road fail earlyGirish Jaysing Arekar council member Indian Road Congress said a road constructed according to IRC norms and properly maintained should not develop potholes within a few months ldquoIf a road is constructed as per Indian Roads Congress IRC norms and specifications potholes should not appear for at least three to five years provided the road is properly maintained On hightraffic roads some wear and tear is expected over time but the surface should gradually wear rather than develop potholes within a few months of constructionrdquo he saidA bumpy stretch near Poisar Metro station in Kandivli PicSatej ShindeArekar pointed to possible reasons for premature potholesMaterial Poorquality bitumen or aggregates can weaken the roadWorkmanship Incorrect laying rolling or compaction can leave weak spots in the pavementDrainage Water can seep into the roadrsquos underlying layers and weaken its foundationCamber The road needs the correct slope to allow rainwater to drain awayTraffic Heavy vehicles such as trucks and trailers put greater stress on the pavementldquoBitumen and water do not work well together and even a goodquality road can develop potholes if water is allowed to remain on or beneath the surfacerdquo Arekar saidDoes heavy traffic cause potholesIt can particularly when roads regularly carry heavily loaded trucks trailers and other heavy vehiclesRepeated heavy loads can cause cracks and other weaknesses in the pavement Once water enters those cracks deterioration can accelerateBut Arekar said there is no single reason why the Sea Link or Coastal Road performs differently from ordinary city roadsldquoThe quality of materials construction technique compaction pavement design drainage camber traffic load and maintenance all play a rolerdquo he saidBy the numbers56 km Length of the BandraWorli Sea Link65 mm Original wearing course laid over the concrete bridge deck40 mm Bituminous carpet25 mm Mastic asphaltAround 5 years Typical interval for complete surface renewal depending on conditionmidday road checkmidday photographers visited roads under BMC jurisdiction and found potholes and uneven surfaces affecting motoristsRoad visited Akurli Road KandivliBMC speaksAbhijit Bangar additional municipal commissioner Projects BMCWhile constructing or resurfacing asphaltbitumen roads in Mumbai does the BMC strictly follow Indian Roads Congress IRC guidelines and standards Is compliance with these guidelines mandatory in BMC tenders If so which IRC standards applyldquoYes we follow the IRC guidelines and their compliance is ensured through mandatory conditions of our road tenders Standard specified requirements listed in our road tenders include technical specifications like required depth levelslayers across the roadrsquos height specific materials with specific thickness for those layers materials like GSB WMM DLC PQC compaction standards testing standards specific material quality concrete mix design fixed aggregates watercement ratiordquoAre there any key differences in the design materials construction methodology drainage and qualitycontrol measures used for asphalt roads on projects such as the Coastal Road compared with conventional BMC roadsldquoThere are no major differences as such with their overall quality standards in their contracts design and drainage is of course requirement based mdash like itrsquos different for say a bridge than a flat road but a flexible pavement asphalt based and rigid pavement concrete based have their own set of quality standards and contractors are mandated to follow the same standards for all roads Notably the same contractors who have made these lsquospecialrsquo projects have also constructed regular city roads with the same set of guidelines and applicable materials Though the quality of these special projects differs most asphalt roads are subjected to the same level of IRCcompliant quality mandates the same is the case with concrete roads although they are more durablerdquoWhy many BMC asphalt roads develop potholes and uneven surfaces particularly during or after the monsoon while roads on major projects such as the Coastal Road appear to have comparatively fewer such problems despite also using asphaltbitumenldquoAlthough the bitumen quality differs for these major bridges one of the key differentiating factors for waterbased damage for asphalt roads is whether one has utilities under it and has gone through trenchingldquoPavement on projects like BWSL and Coastal Road has fared well because their pavement integrity remains unhampered While most regular roads have utilities like electricity lines under them and often experience both unauthorised and authorised digging trenching disrupts the roadrsquos integrity and leaves the pavement more susceptible to damage This is even more so in roads in areas where water does not escape easilyldquoNew asphalt roads which go through trenching also further lose on repairs at the contractorrsquos cost under the Defect Liability Period as opposed to the case of Cement Concrete roads mdash trenching there is precise and doesnrsquot cause larger damage to the road due to rigid concrete one of the reasons why CC roads are preferred by usldquoAnother factor for poorperforming roads that remains is shoddy work from the contractors They donrsquot exercise the required quality standards they agreed to resulting in bad roads for which systematic changes such as harsher penalties are required We are working on these issuesrdquo