“The waste disposed of in the sea and creeks does not sink and continues to float. During the monsoon, high tidal waves push this floating waste back onto the beaches,” a civic official said.

According to BMC data, Juhu Beach alone accounted for 1,824 MT, nearly 72 per cent of the total waste recovered. It was followed by Versova (277.6 MT), Dadar Mahim Chowpatty (152 MT), Chimbai (127.2 MT), Madh Marve (44.24 MT), Gorai (38.82 MT) and Girgaon Chowpatty (33.66 MT).

Officials attributed the disproportionately high accumulation at Juhu to the presence of multiple stormwater drain outfalls that discharge directly into the sea.

“Normally, floating waste drifts away from the mainland. During the monsoon, however, stronger and more frequent high tides prevent it from dispersing and instead push it back onto the shoreline,” another official said.

Officials also said the western suburbs witness greater accumulation because of their dense residential catchment, with a significant quantity of waste entering drains and canals before eventually reaching the sea.

A view of Juhu beach is seen as garbage has accumulated at the shore during high tide, in Mumbai. (Express photo by Sankhadeep Banerjee/File)

The mounting marine litter comes even as Mumbai’s coastal waters continue to record pollution levels far exceeding prescribed standards.

A study conducted by the BMC’s sewerage department as part of its Sewage Treatment Plant (STP) project found Biochemical Oxygen Demand (BOD) levels of around 100 mg per litre in seawater samples from Bandra and Versova and nearly 50 mg per litre at Juhu, well above the Central Pollution Control Board’s prescribed limit of 10 mg per litre for coastal waters. BOD measures the oxygen required by microorganisms to decompose organic matter in water, with higher levels indicating greater organic pollution.

The scale of marine pollution has also been documented by The Ocean Cleanup, a Netherlands based non profit organisation, which estimates that nearly 5,000 MT of plastic waste enters the Arabian Sea every year through around 50 drains across Mumbai, affecting 220 km of coastline, 152 sq km of mangroves and 107 protected species.

Marine ecologist Shaunak Modi, Director of the Coastal Conservation Foundation, said the problem persists throughout the year but worsens during the monsoon.

“Plastic waste on beaches directly affects marine life. Crabs and other organisms burrow beneath the sand, but when beaches are covered with plastic, they are unable to emerge, disrupting the ecosystem,” Modi said.

He added that the problem extends beyond the coastline.

“Plastic does not decompose. After beach clean ups, much of the waste is transported to landfills near mangroves. During the monsoon, leachate generated from these dumps enters adjoining mangroves and water bodies, causing secondary pollution,” he said.

To reduce the flow of floating waste into rivers and the sea, the BMC has installed trash booms, floating barriers fitted with submerged nets, at 21 stormwater drain outfalls, including along the Dahisar, Poisar and Mithi rivers.

Officials said the civic body plans to expand the network to all 82 stormwater drain outfalls over the next five years.

“The expansion will significantly reduce the amount of floating waste entering the sea,” a civic official said.

Environmental experts, however, cautioned that intercepting waste downstream cannot substitute for fixing the source of the problem.

“Most floating waste entering water bodies originates in areas where solid waste management remains inadequate. Unless waste collection improves and dumping into drains is prevented, marine litter will continue to accumulate despite these interventions,” said Rahul Ahir, professor of wastewater engineering and former adviser to the Maharashtra government.

Mumbai’s water pollution levels at a glance :

• Projected waste entering Mumbai’s sea water :- 5,000 MT
• Average BOD level recorded at Juhu — 100 mg/liter
• Average BOD level recorded at Versova — 50 mg/liter

What is BOD?

BOD is the amount of oxygen required by aerobic microorganisms to decompose organic matter in a water sample. It is the most common indicator of organic water pollution. Higher BOD means more water pollution.

What is the CPCB parameter ?

10 mg/liter