The Biowell is an Easter egg and a mythical location in Grand Theft Auto: San Andreas, located in the small town of Montgomery, Red County. It is implied that it is used for dumping biohazardous and potentially toxic waste.
The Biowell is a small well in a back lot surrounded by multiple commercial businesses, most notably, the Inside Track betting Shop and the Crippen Memorial Hospital. There is a metal containment fence enclosure surrounding the Biowell with various signs posted on the fence that read "BIO-WASTE." The Biowell is believed to be linked to the nearby Bio Engineering business, and it implies that the business illegally dumps its bio-hazardous waste down the well. The Biowell is a pivotal point of the Water Pollution conspiracy.
The Biowell's presence in the game could be inspired by the 2002 psychological horror film The Ring, and its sequels The Ring 2 and Rings. In the film, a girl by the name of Samara comes out of a well and attempts to kill the protagonist. Rumor has it that if the player approaches the well at midnight, she will come out of the well and kill them. They also say that the well is full of dangerous radiation. Even though the Biowell itself exists, there isn't any credible evidence of the Ring Girl, nor any radiation. The majority of online pictures or videos of the Ring Girl are either faked or are a mod.
The nearby Crippen Memorial Hospital is thought to have illegally dumped bio-hazardous waste in the well to avoid costly disposal fees. If this is true, then it lends credibility to the theory that the hospital may have disposed of dead bodies in the well which led to the myth of the Ring Girl.
At night, a greenish tinge can be seen on upward facing surfaces of the top circular layer of the brickwork of the structure, along with a very bright green coating on one side of a single removed brick that lay at the foot of the surrounding fence on the northeast side. The green tinge is seen again on the inside edges of the two southeastern metal fence corner posts and at the very top edge of a single metal fence corner post in the northern corner.
Interestingly, the green tinge can also be seen outside the metal containment fence. Once on the outside edge of the diagonal support of a metal staircase leading up to the roof of a building to the northeast, and once again on the edge of another diagonal support of a metal staircase to the southeast, but this time on the inside edge of the support nearest the building.
The fact that the green tinge can only be seen at night gives the impression that the contaminated surfaces glow in the dark, leading some players to believe the Biowell is linked with the unlawful disposal of nuclear waste, this, however, is unproven.
This myth is also a part of the Strange Lights mystery.