A major project to increase wastewater holding capacity which bosses say will reduce releases into the sea by almost a third has been completed.

The improvements by Southern Water - a £750,000 upgrade to Swalecliffe Works near Whitstable – has led the utility company to claim it will cut storm water overflows by 30% as a result.

The announcement, part of a wider £25 million investment at the facility, follows criticism of the firm for presiding over a series of sewage spills.

Residents say these have been impacting both business and recreation in Whitstable and along the coast in Herne Bay.

In August alone there have been 18 overflow releases in the Whitstable area.

Meanwhile in Herne Bay, there were 19 incidents in the space of a month between July 4 and August 2 with residents seething about Southern Water saying “there’s always an excuse” by the company when it comes to dumping sewage in the sea.

Traders are furious that visitor numbers to the town this summer have dropped and feel the ongoing saga involving the water company has contributed to the lack of business.

Speaking about the upgrade, Southern Water’s project manager Jon Yates said: “We are under no illusions that our environmental performance in the Whitstable area must improve.

“This is just the latest milestone in the programme of work we’re doing to address storm overflows here.

“It is really positive that the redesign of the Swalecliffe site is set to cut storm overflows by up to 30%.

“But we are keen to press ahead and continue our work to increase this number with other measures we’re taking in the area.”

Southern Water has faced a volley of scrutiny over its releases in recent years and was named among the country’s worst-performing companies by Ofwat in 2022.

In 2021, it was fined a record £90m for dumping billions of litres of raw sewage into the sea at 17 sites, with various spillages around the east Kent coast.

The overflows are designed to legally discharge excess sewage and rainwater when under strain to prevent sewers becoming overloaded and backing up into homes.

Southern claims the releases are made up of 95% rainwater and are permitted by the Environment Agency.

The redesign of the Swalecliffe site which will significantly improve the capacity of its pipes and tanks meaning wet weather is less likely to overload the system.

The Environment Agency has worked with the private water treatment firm to design a complex engineering solution to the issue which sees the release of wastewater off the coastline.

Once complete the site will have an additional 1,800 cubic metres of storage capacity, allowing space for 450 litres of stormwater per second to be contained.

Over the course of two hours, this is the equivalent of more than an Olympic-size swimming pool, which Southern Water assures customers will then be fully treated once levels drop.

The company is also investing in infrastructure to reduce and slow the amount of surface water entering the system.

This includes installing 2,000 slow-draining water butts at homes near Tankerton Beach in collaboration with community groups including SOS Whitstable and introducing sustainable drainage schemes and efforts to ‘green’ community spaces like Cornwallis Circle.

A spokesman for SOS Whitstable added: “We support all of the efforts made by Southern Water but cannot make any comments on the actions taken until we see they are really creating improvements and reducing combined sewer overflow releases.”