CONCRETE PIPE Manhole Anatomy The definitions/descriptions below and depictions to the right demonstrate the typical anatomy of a manhole likely to be encountered in any North American jurisdictions, though it is important to note that appearance, terminology, and dimensions may vary by region. Frame and Cover, Frame and Grate – A manhole frame refers to a steel frame the sits atop the manhole structure and holds either a manhole cover or grate. A manhole cover is a solid piece of steel that does not allow water to infiltrate the manhole, while a manhole grate is a slotted piece of steel that does allow water to infiltrate the manhole. Manhole Collars – Sometimes called “grade adjusters” or “adjuster rings”, a manhole collar sits directly beneath the manhole frame and directly above the concrete top slab. The collars range in height and are used to make the manhole frame sit as close to the final grade as possible. In the center of the manhole collar is an opening to allow access to the manhole. Manhole Top Slab – A manhole top is essentially a transition slab that brings the 1200 mm diameter manhole barrels down to a 710 mm opening for access (size of opening varies according to jurisdiction). Risers/Barrels – Manhole barrels, sometimes called “risers” make up the majority of manhole structures, acting as the intermediate pieces between the manhole base and top. Spigot Up, Spigot Down – Each manhole barrel has a bell end and a spigot end. Spigot up or down refers to the orientation of the barrels within the manhole structure. Spigot up manholes are currently the standard at Lafarge. Manhole Adapter Barrels – Manhole adapter barrels are sometimes required to connect manhole barrels to one another if their orientations do not match (i.e. spigot up versus spigot down). Perforated Barrel – A perforated barrel is a concrete barrel with perforated openings located throughout the barrel. These openings allow any stormwater collecting in the barrel to infiltrate into the surrounding groundwater, or conversely, allow the groundwater to collect inside the barrel where it can be conveyed elsewhere. PAGE 4 LAFARGE PIPE eMANUAL