A view of a manhole cover near the Kwun Yam Temple in Hong Kong's Hung Hom district, leading to a network of sewers connected to the Hong Kong Polytechnic University (PolyU) in Hong Kong, China, September 29, 2020. Hundreds of protesters trapped during the siege of PolyU last November used this network of sewers to escape, which volunteers like Dave, a diver, helped scout out. Picture taken September 29, 2020. REUTERS/James Pomfret To match Special Report HONGKONG-DEMOCRACY/ACTIVISTS

A passerby stands next to an illuminated manhole cover with designs of popular animation character from 'The Melancholy of Haruhi Suzumiya', on the street in Tokorozawa, near Tokyo, Japan August 19, 2020. REUTERS/Hideto Sakai

A passerby using a smartphone takes a photo of an illuminated manhole cover with designs of popular animation character Gundam, on the street in Tokorozawa, near Tokyo, Japan August 19, 2020. REUTERS/Hideto Sakai

A municipal worker stands next to an uncovered manhole on a flooded street during heavy rains in New Delhi, India, August 19, 2020. REUTERS/Adnan Abidi

Municipal workers wearing protective masks stand next to an open manhole on a waterlogged street during heavy rains in Mumbai, India, July 5, 2020 REUTERS/Francis Mascarenhas

Chevy Larocque is lowered into a manhole for some repair work during a phased reopening from the coronavirus disease (COVID-19) restrictions in Toronto, Ontario, Canada May 19, 2020. REUTERS/Carlos Osorio

A worker climbs into a manhole to install a cable in the drains in the Central Business District in Beijing as the spread of the novel coronavirus disease (COVID-19) continues, China April 22, 2020. REUTERS/Thomas Peter

A worker leans into a manhole to talk to his colleague who is installing a cable in the drains in the Central Business District in Beijing as the spread of the novel coronavirus disease (COVID-19) continues, China April 22, 2020. REUTERS/Thomas Peter

Pedestrians walk past a manhole fire in the Brooklyn borough of New York, U.S., July 1, 2019. REUTERS/Lucas Jackson

Pedestrians walk past a manhole fire in the Brooklyn borough of New York, U.S., July 1, 2019. REUTERS/Lucas Jackson

Pedestrians walk past a manhole fire in the Brooklyn borough of New York, U.S., July 1, 2019. REUTERS/Lucas Jackson TPX IMAGES OF THE DAY

A woman walks past a manhole fire in the Brooklyn borough of New York, U.S., July 1, 2019. REUTERS/Lucas Jackson

Members of the New York Fire Department monitor a manhole fire in the Brooklyn borough of New York, U.S., July 1, 2019. REUTERS/Lucas Jackson

Members of the New York Fire Department monitor a manhole fire in the Brooklyn borough of New York, U.S., July 1, 2019. REUTERS/Lucas Jackson

A manhole cover depicting the Osaka castle is seen on the sidewalk at Shinsekai neighbourhood in Osaka, Japan, June 26, 2019. REUTERS/Jorge Silva

A manhole cover depicting the Osaka castle is seen on the sidewalk at Shinsekai neighbourhood in Osaka, Japan, June 26, 2019. REUTERS/Jorge Silva

Kenyan 'froggers' slum dwellers Godfrey Ndalo and Patrick Osunda are assisted as they empty a metallic barrel of excrement from a pit latrine into a manhole in Kibera slum within Nairobi, Kenya February 24, 2019. Picture taken February 24, 2019. REUTERS/Njeri Mwangi

German police officers seal a manhole cover after searching for explosives outside the Cologne Central Mosque before this weekend's official inauguration of the grand mosque by Turkish President Recep Tayyip Erdogan during his official visit to Germany, in Cologne, Germany, September 28, 2018. REUTERS/Wolfgang Rattay

German police officers seal a manhole cover after searching for explosives outside the Cologne Central Mosque before this weekend's official inauguration of the grand mosque by Turkish President Recep Tayyip Erdogan during his official visit to Germany, in Cologne, Germany, September 28, 2018. REUTERS/Wolfgang Rattay

A worker builds a manhole near a construction site of residential apartment blocks in Beijing, China, September 27, 2018. REUTERS/Thomas Peter

A man crosses the street in the business district past a manhole cover marked by engineers in Toronto, Ontario, Canada August 31, 2018. REUTERS/Chris Helgren

Members of the defense forces check a manhole in front of city hall in Helsinki, Finland July 14, 2018. REUTERS/Leonhard Foeger

A police officer and his dog check a manhole in a street Helsinki, Finland July 14, 2018. REUTERS/Leonhard Foeger

A police officer and his dog check a manhole in a street Helsinki, Finland July 14, 2018. REUTERS/Leonhard Foeger

Members of the defense forces check a manhole in front of city hall in Helsinki, Finland July 14, 2018. REUTERS/Leonhard Foeger

A police officer and members of the defense forces check a manhole in front of the Presidential Palace in Helsinki, Finland July 14, 2018. REUTERS/Leonhard Foeger

A police officer and members of the defense forces check a manhole next to the Presidential Palace in Helsinki, Finland July 14, 2018. REUTERS/Leonhard Foeger

Municipal workers stand next to a choked manhole on a water logged street during heavy rains in Mumbai, India July 9, 2018. REUTERS/Danish Siddiqui

Municipal workers attempt to unclog a choked manhole on a water-logged street after heavy rains in Mumbai, India, June 9, 2018. REUTERS/Francis Mascarenhas

A municipal worker fumigates a manhole in a street to prevent the spread of dengue fever and other mosquito-borne diseases in Mumbai, India, May 24, 2018. REUTERS/Francis Mascarenhas

Sewage flows from a manhole as water bowsers queue to collect fresh water for distribution to their clients in Dagoretti neighbourhood of Nairobi, Kenya April 17, 2018. Picture taken April 17, 2018. REUTERS/Njeri Mwangi

The shadows of workers are seen in the City of London financial district, London, Britain, January 25, 2018. Picture taken January 25, 2018. REUTERS/Toby Melville

A man stands near steaming manhole covers on a cold day in Beijing, China, December 1, 2017. REUTERS/Thomas Peter

A man rides an elecric scooter past steaming manhole covers on a cold day in Beijing, China, December 1, 2017. REUTERS/Thomas Peter

Officers of Catalonia's regional police force, Mossos D'esquadra, search unded a manhole cover outside the regional assembly in Barcelona, Spain October 10, 2017. REUTERS/Gonzalo Fuentes

Officers of Catalonia's regional police force, Mossos D'esquadra, search unded a manhole cover outside the regional assembly in Barcelona, Spain October 10, 2017. REUTERS/Gonzalo Fuentes

A Enel Group manhole cover is seen in the street in Perugia, Italy, June 23, 2017. Picture taken June 23, 2017. REUTERS/Alessandro Bianchi

A municipal worker sits on the cover of a manhole after uncovering it on a flooded street after heavy rains in Kolkata, India, June 20, 2017. REUTERS/Rupak De Chowdhuri

German policemen seal a manhole cover in front of the Brandenburg Gate ahead of the visit of U.S. President Barack Obama in Berlin, Germany, November 15, 2016. REUTERS/Fabrizio Bensch

German policemen seal a manhole cover in front of the Brandenburg Gate ahead of the visit of U.S. President Barack Obama in Berlin, Germany, November 15, 2016. REUTERS/Fabrizio Bensch

German policemen seal a manhole cover in front of the Brandenburg Gate ahead of the visit of U.S. President Barack Obama in Berlin, Germany, November 15, 2016. REUTERS/Fabrizio Bensch

A municipal worker uncovers a manhole on a flooded street during heavy rains in New Delhi, India, August 29, 2016. REUTERS/Adnan Abidi

The emblem of the western German city of Koblenz, a young boy with the nickname "Schaengel" is seen on a manhole cover in the city centre of Koblenz, March 1, 2016. REUTERS/Wolfgang Rattay

A manhole cover is pictured in Dresden, Germany, February 19, 2016. REUTERS/Pawel Kopczynski

A manhole cover commemorates the 25th anniversary of the Schengen Agreement in the small village of Schengen, Luxembourg January 27, 2016. The Schengen Agreement with the goal to eliminate internal border controls was signed on June 14, 1985 in the small village at the river Moselle and the tripoint of France, Germany and Luxembourg between the five countries of Belgium, France, Germany, Luxembourg and the Netherlands. European Union interior ministers are to discuss extending temporary border controls in the passport-free Schengen zone to control migration flows, as well as identity document fraud following France's request to improve the detection of fake Syrian passports used by people trying to get into Europe. REUTERS/Wolfgang Rattay

A labourer works inside the manufacturing unit of manhole cover parts at a factory on the outskirts of Kolkata, India, September 11, 2015. India's annual industrial output growth slowed to 4.2 percent in July compared with an upwardly revised 4.4 percent growth a month ago, government data showed on Friday. REUTERS/Rupak De Chowdhuri

A lifeguard watches over swimming in Waikiki in Honolulu, Hawaii, August 25, 2015 . On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

Waikiki Beach remains closed in Honolulu, Hawaii August 25, 2015. On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

Ala Moana Beach is closed to the public due to a sewage spill, in Honolulu, Hawaii, August 25, 2015. On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

A warning sign is posted on a palm tree at Ala Moana Beach parking warning swimmers to stay out of the water, in Honolulu, Hawaii, August 25, 2015 . On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

Swimmers splash around Waikiki Beach in Honolulu, Hawaii, August 25, 2015. Heavy rain caused a 500,000-gallon sewage spill in Honolulu that sent dirty water streaming into the city's famed Waikiki Beach, and officials warned people to stay out of the water or risk infection. On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

Waikiki Beach is seen in Honolulu, Hawaii, August 25, 2015. Heavy rain caused a 500,000-gallon sewage spill in Honolulu that sent dirty water streaming into the city's famed Waikiki Beach, and officials warned people to stay out of the water or risk infection. On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

A group of beach goers are seen on Waikiki Beach in Honolulu, Hawaii, August 25, 2015. On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

A man sits on the shore of Waikiki Beach in Honolulu, Hawaii, August 25, 2015. On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

A warning sign sits on a palm tree after 500,000 gallons of raw sewage streamed onto the famed Waikiki Beach in Honolulu, Hawaii, August 25, 2015. On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

A warning sign sits on a palm tree after 500,000 gallons of raw sewage streamed onto the famed Waikiki Beach in Honolulu, Hawaii, August 25, 2015. On Monday, Honolulu city officials told people to avoid entering the water, saying in a statement that more than 500,000 gallons of sewage water had overflowed from manholes and streamed into storm drains leading to the ocean. REUTERS/Marco Garcia

Vermont Governor Peter Shumlin (L) and New York Governor Andrew Cuomo take part in a news conference at the Clinton Correctional Facility in Dannemora, New York June 10, 2015. The manhunt for two inmates who escaped from a New York maximum security prison expanded to neighboring Vermont on Wednesday as the pair set a record for the longest jailbreak in New York history, authorities said. Richard Matt, 48, and David Sweat, 34, escaped from Clinton Correctional Facility in Dannemora, New York, five days ago, cutting through steel walls, squeezing through a steam pipe and popping out of a manhole. REUTERS/Chris Wattie

New York Governor Andrew Cuomo speaks during a news conference with Vermont Governor Peter Shumlin (R) at the Clinton Correctional Facility in Dannemora, New York June 10, 2015. The manhunt for two inmates who escaped from a New York maximum security prison expanded to neighboring Vermont on Wednesday as the pair set a record for the longest jailbreak in New York history, authorities said. Richard Matt, 48, and David Sweat, 34, escaped from Clinton Correctional Facility in Dannemora, New York, five days ago, cutting through steel walls, squeezing through a steam pipe and popping out of a manhole. REUTERS/Chris Wattie

Vermont Governor Peter Shumlin (L) and New York Governor Andrew Cuomo arrive at a news conference at the Clinton Correctional Facility in Dannemora, New York June 10, 2015. The manhunt for two inmates who escaped from a New York maximum security prison expanded to neighboring Vermont on Wednesday as the pair set a record for the longest jailbreak in New York history, authorities said. Richard Matt, 48, and David Sweat, 34, escaped from Clinton Correctional Facility in Dannemora, New York, five days ago, cutting through steel walls, squeezing through a steam pipe and popping out of a manhole. REUTERS/Chris Wattie

New York State Correctional Services officers stand near a manhole at the corners of Bouck and Barker streets where two convicted murderers are believed to have emerged after escaping from the nearby Clinton Correctional Facility (in background) in Dannemora, New York June 8, 2015. Two convicted murderers who used power tools to break out of the maximum security New York prison may have had help, and they left a taunting note for their jailors to "Have a nice day," authorities said on Sunday. REUTERS/Chris Wattie