Considered holy and used by millions of pilgrims, the baoli (step-well) at Nizamuddin was built in 1321-22. It is the only step-well in Delhi still fed by underwater springs, albeit heavily polluted by sewerage and garbage. A portion of the baoli wall collapsed in July 2008, endangering both residents and pilgrims, and necessitating urgent remedial measures. Pre-conservation assessment of the baoli was based on ground penetrating radar survey, high definition 3D laser scans, geotechnical and structural assessments. The Ground Penetrating Radar Survey (GPRS) allowed structural engineers to evaluate the underlying soil condition and plan conservation accordingly. The baoli was partially drained and cleared of rubbish to its foundation (80 ft below ground level) and a 3-5cm thick epoxy coating (applied by the Delhi Jal Nigam in 2002) chiselled off manually. The entire wall surface was grouted and re-pointed with lime mortar to fill the underlying voids identified in the GPRS report.
The conservation work provided an opportunity to de-silt the baoli of debris accumulated over hundreds of years. The de-silting work was done manually with a few inches of water retained in respect of community sentiments. Water quality test of the baoli revealed high levels of E-coli indicative of sewage contamination. Happily, after the re-laying of over 100m of sewer lines as part of the conservation initiative, the water quality was found to be greatly improved with drastic reduction in E-coli levels. Waste water from the wuzu area which earlier drained into the baoli has since been re-routed.
Collapsed portions of the baoli were rebuilt as per original construction techniques while severely buckled wall surfaces were partially dismantled before being rebuilt. Ashlar facing stones which had fallen into the baoli were retrieved and reused after being manually lifted from the sludge.
The discovery of a blocked passage connecting the baoli to the mosque believed to have been used by the Hazrat Nizamuddin was the cause of much celebration. At present, conservation works at the baoli is ongoing with specific attention paid to the structural stability of the surrounding structures and to the safety of the 14th c. vaulted passage used by pilgrims.