At the turn of the 19th century, though, even the tea water pump wells were becoming polluted, especially those closest to Collect Pond, now a stinking cesspool polluted by industry.The contaminated wastewater of the businesses surrounding the pond flowed back into the pond, creating a severe pollution problem and environmental health hazard. Pierre Charles L'Enfant proposed cleaning the pond and making it a centerpiece of a recreational park, around which the residential areas of the city could grow. His proposal was rejected, and it was decided to drain and fill in the pond. This was accomplished with soil partially obtained from leveling the nearby hills of Bayard's Mount and Kalck Hoek, and by digging a canal to the north to encourage the water to drain into the river. The landfill was completed in 1811, and middle class homes were soon built on the reclaimed land.The landfill was poorly engineered. The buried vegetation began to release methane gas (a byproduct of decomposition) and the area, still in a natural depression, lacked adequate storm sewers. As a result, the ground gradually subsided. Houses shifted on their foundations, the unpaved streets were often buried in a foot of mud and mixed with human and animal excrement, and mosquitoes bred in the stagnant pools created by the poor drainage.
