Item #: SCP-2717
Object Class: Euclid
Special Containment Procedures: A pair of inline, two-ton, one-way pumps constitutes the upstream containment boundary in each of the three known feeder pipes (roughly 2m in diameter) on the intake side of the designated containment zone. These pumps permit ordinary city waste to flow inward, but prevent backflow even under severe flood conditions. Each day at 6AM, 10L of propofol shall be introduced into each feeder pipe via the injection ports.
The outlet pipe (roughly 4m in diameter) on the downstream side of the designated containment zone empties about 20 Ml of yellow-green effluent daily into an underground reservoir lined with acetal resin. Each day at 6PM, this effluent shall be tested for levels of creatinine, ketone bodies, hemoproteins, and bioactivity. Statistically significant deviations from baseline shall be reported to the site supervisor immediately. Rarely, solids larger than two cubic centimeters may be detected in the effluent. These must be extracted, identified, catalogued, and incinerated.
After processing, effluent shall be sterilized via cobalt-60 irradiation, and then reintroduced to city infrastructure for treatment as ordinary sewage at the downstream boundary of the containment zone.
Monthly, as many biopsies as is practically possible shall be obtained by robotic tool, at 100m intervals starting from the extent of SCP-2717 closest to the outlet pipe. Currently, about 10-12 samples can be reliably obtained each session, without risking damage to the tool.
Quarterly, the pumps will be stopped for up to 48 hours for inspection and maintenance while SCP-2717 is “pruned”. Three crews shall be assembled and introduced to the intake piping through the positive pressure airlocks located just downstream from the pumps.
Each crew shall consist of two D-class personnel who have been rated for high physical exertion, low susceptibility to claustrophobia, and who possess at least some close-quarters combat experience.
Each member of the crew shall be issued the following:

One 60cm machete, with a UGPS emitter1 concealed in the handle
One 1m spade
One pair of waterproof hip-waders
Two pairs of elbow-length gloves
One activated carbon respirator for nose and mouth, containing a miniature two-way radio
One soldering torch with piezo ignition
One liter tank of propane
Four liters water
Four high-carbohydrate snack bars
6 two-hour fusees

All metal tools and fasteners shall be of wrought iron, low carbon steel, or similar easily-corroded metal. To the extent practical, all other equipment shall be made of strongly biodegradable materials, e.g. rubber, latex, or leather. Per the Ethics Committee, video recording or transmitting equipment shall not be issued to crews.
The following briefing has been constructed by memetic specialists for maximum comprehension and motivation when used with typical D-class. One Level-2 researcher shall memorize and deliver this briefing verbatim to each crew immediately prior to them entering the airlock:

Have you ever heard of a fatberg? Imagine an iceberg - only it's made out of sewage debris that gets stuck together when too many people flush things they aren't supposed to. There is a fatberg lodged in this pipe, and until we remove it, the D-class dormitories have no plumbing. It's too big to remove it all in one go, so your task is to clear away at least 25 meters of it on this shift – that's about a quarter of a football pitch. Use your bladed tools to cut or pry chunks from the piping, and your propane torches to burn away bits that are too small or too difficult to remove with your tools. About every 5 meters, where each pipe section joins the next, there is a four-character manufacturing code embossed in the concrete. You will read each code to us as you uncover it so that we can monitor your progress. You will have to clear the blockage thoroughly, or you will miss the codes. You will not be extracted, nor will further rations will be issued to you, until we are satisfied that you have completed your task. In return for your effort, you will be granted improved rations and special conjugal privileges for the next two weeks.

Crews have historically reported their progress to be easier than expected at first - at its exploratory boundary, SCP-2717 tends to form rings of dull, warty masses, at most about 8cm thick. The use of fusees effectively conceals the color of the fluid that erupts from damaged tissue.
Simple radio communication with the crew is to be maintained until Foundation monitors are reasonably assured the crew has completed their true task, namely, pruning about 100m of SCP-2717. Experience has consistently demonstrated that crews underestimate their progress under these conditions, which extends the effectiveness of the ruse.
In fact, there are no "embossed manufacturing codes" to be found. As work progresses, and in particular once SCP-2717 eventually reacts by the secretion of gastric acid, additional communications may be adapted from the current version of the METH.2 In the event the crew fails to survive long enough to prune the prescribed 100m, additional crews may be introduced as necessary until the task is accomplished.
Per the Ethics Committee, no detailed records shall be kept of crew reports, except to denote progress (in meters), success, or failure.
Under no circumstances are any crews to be recovered from the sewers. Once maintenance is complete, or in any event, after 48 hours, the pumps shall be restarted.
Description: SCP-2717 is a complex of living animal tissues that have grown to line roughly 4 linear kilometers of sewer pipes centered beneath ███████ Pumping Station, Amsterdam, NL. Historical data places the construction of this section of the sewers to 1887, and current estimates based on extant maps place the total biomass at approximately 350 metric tons.
The organic complex is estimated to be at least six years old. Initial analysis indicated that the growth consisted of 88% muscle, 5% connective, and 1% adipose tissues of porcine origin. Current lines of investigation support the theory of unintentional human introduction of SCP-2717 to its current environment.3
Since discovery in 2010, SCP-2717 has consistently and steadily grown upstream (presumably towards nutrient sources) with almost no increase in mass in the downstream direction.
In the lab, samples have been stabilized and/or grown in a wide range of nutrient-rich liquid environments. The cells display quorum sensing and self-regulation that is not fully understood. Cell division is unusually rapid at low concentrations; however, above a certain density threshold, the rate of mitosis appears to adjust in order to avoid exceeding the rate of nutrient replenishment.
Recently, the monthly biopsies have revealed unexplained differentiation of tissues, which currently include primitive osseous structures, neural fibers, and trace photoreceptor cells.
Although the Foundation's ability to take tissue samples is limited to roughly the first kilometer from the effluent outlet, it is clear that the degree of differentiation markedly increases in the upstream direction.

Footnotes
1. Underground GPS utilizes a set of surface receivers to triangulate the position of the emitter.
2. Motivation, Encouragement, and Threat Handbook, 33rd Edition
3. See also: Vlees Vellen: Metastabiele Proliferatie van Sus scrofa Spiercellen in vitro, Van Koot et al, Utrecht University Press, 2008.

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