Project Purity Project Purity is a water purification project in the Capital Wasteland in 2277 and 2278 . History . Project Purity was created prior to the beginning of the " Fallout 3 " storyline . It was the ambition and dream of both the Lone Wanderer ' s parents , Catherine and James , and other scientists , including Madison Li . The project ' s goal was to turn the polluted and irradiated waters of the Potomac River into clean , potable water , thus increasing the quality of life in Capital Wasteland . The technology used was similar to Vault - Tec water filtration systems used in the vaults , but at a much more massive scale . It was originally supported by the Brotherhood of Steel when they first came to the Capital Wasteland , who would send knights and paladins to defend the project from super mutant s and other threats in the ruins . Although the support eroded over time due to the project ' s lack of results and need for Brotherhood troops elsewhere , e . g . guarding the Citadel or purging the super mutants from the D . C . ruins . Later , more soldiers would be taken from the project in an attempt to make up for soldiers lost to the Brotherhood Outcasts . This support ended indefinitely after the newborn Lone Wanderer ' s father James left , thus ending almost all promising research and possibility of future success . After James ' abandonment and no support from the Brotherhood , the other scientists abandoned the project , Doctor Li and presumably what was left of the team left to the nearby Rivet City . In Rivet City , Doctor Li will tell the Lone Wanderer that James left Vault 101 to seek her out and restart Project Purity . Doctor Li refused and James moved on . Project Purity is what motivated him to eventually leave the Vault in search of a G . E . C . K . in the hope of completing the project . After finding James , it is revealed Project Purity was briefly rekindled at the Jefferson Memorial , but the location was captured by Vault 87 super mutant s . After enlisting the assistance of Doctor Li and her staff from Rivet City , the location is cleared before the project finally resumes progress . However , the Enclave seizes the Jefferson Memorial and Colonel Autumn attempts to persuade James to cede control to them . James refuses , and kills both himself and the Enclave soldiers with lethal doses of radiation , although Autumn survives . The player is forced to escort the remaining staff to the relative safety of the Citadel , contending with feral ghoul s and even more Enclave soldiers . Though the Enclave managed to capture the Jefferson Memorial , a crucial component , the G . E . C . K . , is still required to bring the project to fruition . Once the Lone Wanderer does obtain the G . E . C . K . , they are incapacitated by the Enclave and taken to Raven Rock . President John Henry Eden asks that the Lone Wanderer install the modified FEV when they reach the Project Purity control room , which will purge the Capital Wasteland of any beings " tainted " with radiation , regardless of severity . The Lone Wanderer battles his or her way to the control room and , after finally stopping Colonel Autumn , a final decision is posed . The Lone Wanderer will either choose to insert the modified FEV , fulfill the original intent of Project Purity , or allow Sentinel Lyons to execute the latter . In the original game , as a result of James ' actions , the Lone Wanderer ultimately dies if they choose to enter the control room . However , in the downloadable content pack " Broken Steel " the Lone Wanderer will survive and the decision made at the purifier will have repercussions across the wasteland . Activation . After the decision is made , the water of the Capital Wasteland is purified at last , and life begins anew in the Capital Wasteland . The Lone Wanderer can also , if he / she chooses , simply not do anything , allowing the purifier to self destruct , thus sacrificing the lives of everyone in the facility for no reason . The ending that follows is shorter than the normal ending . In " Broken Steel " the purifier is activated , and the Brotherhood of Steel ( along with the security team from Rivet City ) begins distributing Aqua Pura ( purified water ) to the various regions of the Capital Wasteland . In addition , the small body of water directly in front of the Jefferson Memorial ( the area before the bridge ) known as the Tidal Basin is free of radiation . Any water beyond the bridge is still irradiated as Project Purity will take some time to purify all the water in the Potomac River . If the Modified FEV was inserted into the purifier , then the Aqua Pura will be infected with it . Related quests . The project is tied to Following in His Footsteps , The Waters of Life , Holy Water , Protecting the Water Way and The Amazing Aqua Cura ! , as well as the Jefferson Memorial location . Appearances . Project Purity appears in " Fallout 3 " , " Broken Steel " , and is briefly mentioned by Deacon in " Fallout 4 " as well as a raider in " Fallout Shelter " during the quest Game Show Gauntlet .