Waterdeep/Sewers

The sewers of Waterdeep were a sanitation system of tunnels beneath the city that connected to most locations throughout the city, including its dungeons.

Structure
The depth of these sewers varied around Waterdeep, due to Mount Waterdeep and the plateau the northern portion of the city was built upon. The Field Ward, the harbor islands, and the heart of Mount Waterdeep were the only areas in the city that the sewers did not run beneath.

Partially due to city’s ever changing layout, the tunnels of this sewer system did not match up with the routes of the city's streets by the 14 century DR.

Functionality
Refuse, as well as air, were brought down into the sewers by numerous feeder pipes scattered throughout. These pipes measured less than in diameter.

The sewer network operated on a system of tidal flushing, meaning that its waters were flushed out by the ocean tides that came into Deepwater Harbor. The sewer's tunnels emptied into the harbor at places that were covered by extremely large and strong gratings. These places were purposely difficult to access, as the sewer network's designers sought to hamper the movements of less desirable visitors from the sea and to prevent the sewers from being used by criminals as an underground highway.

The areas in which the sewer network was constructed at, as well as the varied sizes within, were designed to optimally account for the ocean tides. Their layout was also dictated by where springs rose and flowed down to the sea. And finally, to ensure the city's harbor did not become a cesspool, Ahghairon and other mages bound spells into the city's wards that assisted the flows of water in carrying away sewage.

Interior
The ceilings, floors, and walls all throughout the sewer system were made of masonry. There was little to no lighting within the sewers and a terrible stench pervaded the entire network. Gratings in the sewers were all quite thick stout. Some were permanent, while others could swing open. By the 14 century DR many were suffering from rust.

The passages of this sewer network were denoted as two types, primary and secondary. The first were easily navigable, while the other type required human-sized creatures to crawl or swim their way through. Those who worked in the sewers were known to navigate passages by laying down boards as temporary bridges or by vaulting across ledges with catchpoles. The latter of which were carried in order to reach below the water and clear debris from gratings.

Primary passages measured across and had parallel,  wide, walkway ledges that lacked rails. Secondary passages measured and had on one of its sides, usually the more easterly or southerly side, a single  wide ledge. Besides these two types of passages there were many older, smaller passages that had over time been put out of service and walled up by the 14 century DR.

Groups of Interest

 * Cellarers' & Plumbers' Guild: Most members of this learn the general layout of the sewers after two to five years. This is because their primary concerns were keeping the sewers of the city functional and safe, with guild members being engaged in constant small repair jobs in the sewers, such as on plumbing in old buildings.
 * Dungsweepers' Guild: This guild normally did not work on the sewer system, but for security reasons the city reserved the right to contact the guildmaster and hire members to help in such work.
 * Guild of Watermen: Members of this guild knew various spots where the sewer system emptied into the harbor.
 * Merfolk: Living within Deepwater Harbor, these people regularly patrolled the areas where the sewers emptied. They would use pole mounted catch-nets to scoop up and gather any debris they found into large tow-globes, which they then used to transport the debris far out to sea.
 * Xanathar's Thieves' Guild: This guild had safehouses scattered throughout the sewers, hidden by secret doors. Tunnels were often marked with the symbol of the guild in yellow chalk, helping to guide members to the safehouses. Every few days these were erased, either by members of the guild or by the Dungsweepers' Guild.

History
During the days of Ahghairon, a number of Underdark creatures tried to invade the sewers and Waterdeep proper by means of a portal within Undermountain, which he put an end to by means of the gatewarp spell.

In 1358 DR, during the Time of Troubles, the mortal avatar of Myrkul opened a portal between Hades and the Prime Material plane. Hoards of undead came rushing out through the sewers and up into the Dock Ward. The guardsman Ylarell tracked these undead and in the process was slain by Myrkul.

In Eleint, 1367 DR, new creatures began to be encountered in the sewers by members of the Plumbers' Guild, such as the sewerm.

In 1369 DR, during the event known as Halaster's Higharvestide, a number of creatures crawled out from the sewers and terrorized the people of Waterdeep.

That same year the city faced an attack by the forces of Iakhovas and in its wake a number of sea creatures escaped into the sewer system. A trio of aboleths, hailing from the Swordsea Depths, joined in this assault for the sole purpose of gaining access to this sewer system.

In 1492 DR, Jeryth Phaulkon sent awakened rats into the sewers to search for Xanathar's hidden lair, eventually discovering a secret spiral stairwell in the sewers beneath the Castle Ward.

Rumors & Legends

 * There were persistent rumors that Uluryk Malogh made an extensive map of the city's cellars and sewers, detailing all their various barriers, locks, and traps.
 * Around the mid-14 century DR, there were rumors circulating that Xanathar's Thieves' Guild had trained guard rats roaming the sewers and that slavers dwelling within the uppermost rooms of Undermountain creeped out into the sewers at night to kidnap unsuspecting Waterdhavians.

Appearances

 * Adventures
 * Waterdeep • Undermountain: The Lost Level • Waterdeep: Dragon Heist
 * Undermountain: Stardock • Expedition to Undermountain
 * Novels
 * Waterdeep • Escape from Undermountain • The Abduction • The Diamond • Rising Tide • Silverfall, "Lady Cassalanter’s Busy Day" • Daughter of the Drow • City of the Dead • The God Catcher • Circle of Skulls • Timeless
 * Windwalker • The Shadowmask • Elminster Enraged
 * Video Games
 * Eye of the Beholder • Dungeons & Dragons: Eye of the Beholder
 * Video Games
 * Eye of the Beholder • Dungeons & Dragons: Eye of the Beholder