Site utilities takeoff

Buried pipe is measured along its centre line, the developed length, running straight through every elbow, tee, bend, and offset, never a diagonal and never shortened for the fittings. The International Plumbing Code calls this the developed length, CESMM4 Class I and RICS NRM2 measure along the centre line, and the WSDOT standard specifications include the length through elbows, tees, and fittings. For gravity sewers the line is read along the invert on the profile.

Where a run stops at a structure is the biggest source of divergence, and it changes the number. A gravity sewer through a manhole is measured centre of manhole to centre of manhole, with the barrel inside not deducted, the dominant municipal and highway department convention in the United States. A pipe into a catch basin, inlet, or box stops at the inside face of the structure. A culvert with no structures is measured end of pipe to end of pipe along the centre line, exclusive of aprons and end sections, which are counted each. A pressure main is measured through fittings, valves, and couplings, so the appurtenance lay length is not deducted, while the valves, bends, tees, and hydrants are counted each in a separate item. The error is either deducting that lay length or forgetting to count the appurtenance.

The plan is a horizontal projection and the profile carries the slope. On a typical sewer grade of 0.4 to 2 percent the slope correction is negligible, but a steep storm lateral or a skewed culvert is measured at its true length along the centre line at the actual skew and grade.

Pipe length is split into separate measured lines by nominal size, by material, and by system, and the systems are never combined. Storm, sanitary, water, and gas are distinct trades with distinct permits, and each size and material combination carries its own rate. CESMM4 Class I bands the nominal bore, division specifications measure each type and size separately, and RICS NRM2 measures by diameter.

CESMM4 Class I divides the nominal bore into bands of 200 millimetres or less, 200 to 300, 300 to 600, 600 to 900, 900 to 1200, 1200 to 1500, 1500 to 1800, and over 1800 millimetres. Materials such as reinforced concrete, PVC, high density polyethylene, ductile iron, and polyethylene each form their own line, and joint or pressure class can split them further. Each size, material, and system combination is its own bill item.

The deeper a pipe sits, the more it costs to install, because there is more excavation, shoring, dewatering, and restoration, so the same length is re-priced by depth. The estimator segments each run by depth off the profile, since a flat average depth understates the deep, expensive reaches.

CESMM4 Class I classifies pipes in trenches into fixed depth bands: not exceeding 1.5 metres, 1.5 to 2, 2 to 2.5, 2.5 to 3, 3 to 3.5, 3.5 to 4, and exceeding 4 metres, cross-classified by bore so each combination is its own item. In Australia and New Zealand the equivalent banding follows AS 1181, the civil method of measurement. United States municipal and utility contracts often use depth of cut pay tiers, for example 0 to 6, 6 to 8, 8 to 10, and 10 to 12 feet and deeper as separate length items, though the breakpoints are set by each owner. Highway department specifications more often use one length price and pay trench excavation separately by volume, so depth flows through the earthwork item.

Manholes, catch basins, inlets, junction boxes, valves, hydrants, cleanouts, and vaults are counted each under every method, not folded into the pipe length. CESMM4 Class K enumerates manholes and ancillaries, RICS NRM2 enumerates chambers and manholes, and division specifications measure each per each. Segregate the count by structure type and depth class.

Depth is a price axis on the each item, because a deeper manhole has more barrel sections and more excavation. CESMM4 Class K enumerates each manhole within a depth band, such as not exceeding 1.5 metres or 1.5 to 2 metres. The highway department approach pays a manhole per each up to a base height plus a linear rate beyond it. The WSDOT specifications set that base at 10 feet, measured flow line to top of ring to the nearest foot, with manholes over 10 feet measured per linear foot for each additional foot. Other agencies use different base heights, commonly 6 to 8 feet. Depth is read from the rim and invert on the profile.

Connections and tie-ins to existing structures are counted each, separately from new structures: the WSDOT specifications measure connections to existing drainage structures per each. Service connections and laterals are also counted each by size, and measured by length where the run matters, segregated by service type and size.

Whether the earthwork is a separate quantity or included in the pipe length price is a contract decision, not geometry. Under the PennDOT specifications the length price includes the pipe, the bedding, and the backfill, so the earthwork is priced inside the pipe length. Under the WSDOT specifications, trench digging is paid as structure excavation by the cubic yard, and gravel backfill and pipe zone bedding by the volume placed within the neatline limits, as distinct volume items. The takeoff must know which, or it double-counts or omits the earthwork.

When the earthwork is its own quantity, the trench volume is the neatline prism of width times depth times length. Trench width is keyed to the pipe outside diameter and set by the standard detail, with a common minimum working clearance of roughly 12 inches each side. Depth is read from the profile as cover plus pipe outside diameter plus bedding. Owners pay only to the neatline.

Pipe zone bedding is a distinct volume from the trench backfill: a granular bed below the pipe, haunch material to the springline, and surround to a stated height above the crown set by the bedding class, for example a Class B granular surround of roughly 100 millimetres of bed with cover to 150 millimetres above the crown. The pipe's own displaced volume is not deducted in a rough takeoff but is deducted in a rigorous net backfill calculation.

Excavated and imported volumes change as they are loosened and compacted, the most missed civil factor. Excavated material bulks loose, so the disposal volume exceeds the neat trench volume, by roughly 14 percent for clean sand and gravel, 20 percent for loam or common soil, 35 percent for dense clay, and more for rock. Imported backfill shrinks on compaction, so the order volume of select fill exceeds the compacted void, by roughly 5 to 10 percent for soils and more for rock. These are engineering reference ranges that vary with the material, best calibrated to the contractor's own history. Apply swell to disposal and haul, shrinkage to the import order, and never either to the neat in place pay quantity.

The same traced run resolves three ways: the bid quantity is the net installed centre line length, the material order rounds each run up to whole pipe joints plus a small cut allowance, and the progress quantity follows the contract method, almost always centre of manhole to centre of manhole. Pipe is supplied in nominal lengths, such as the 18 or 20 foot ductile iron laying length under AWWA C151, so joint rounding is the real overage rather than a flat percentage. A scrap or cut allowance of roughly 2 to 5 percent is a shop convention rather than a published figure. Quantities are reported in linear feet in the United States and in linear metres in the United Kingdom, Europe, Australia, New Zealand, and most international work, rounded to the whole foot or 0.1 metre.

Adverse conditions are measured as extra over items on top of the base excavation, applied only to the affected reaches. RICS NRM2 and CESMM4 measure excavating below the groundwater level, breaking out rock, working next to existing services, and earthwork support or shoring as separate items. United States highway department specifications mirror this, with rock excavation measured by the cubic yard in original position. The estimator reads the profile and boring logs to flag the affected reaches. Dewatering and bypass pumping are contract sensitive: some owners make dewatering incidental to the excavation, while others pay it, and the bypass pumping at tie-ins, as a separate item.

Trenchless reaches are measured differently from open cut. For directional drilling, jack and bore, and auger bore there is no separate trench volume, because the jacked or bored pipe length price includes the excavation under the PennDOT specifications. Casing pipe is measured by length by size, carrier pipe inside the casing by length as a separate item, bore and jacking pits are counted each, and directional drill pull back is measured at the installed developed length.

Several smaller quantities round out the scope. Pipe testing, by air, exfiltration, infiltration, or pressure, and closed circuit television inspection are measured per length, since the WSDOT specifications carry testing storm sewer pipe as a per foot item. On pressure mains, thrust restraint at bends, tees, valves, and dead ends is captured as concrete thrust blocks counted each or by volume, or as restrained joint length measured back from the fitting. Non-metallic mains require tracer wire and often warning tape, quantified per length of pipe run, and surface restoration over the trench, including pavement saw cut, patch, and topsoil, seed, or sod, is a separate quantity measured by length or area. Exayard reads the plan and profile drawings and applies these rules, resolving the quantity for the region and purpose in use.