Paid tier only. Calling this without an authenticated CivilQuants account returns TIER_INSUFFICIENT — sign up at https://civilquants.com/pricing or use the free-tier alternative compute_manhole. Fully monolithic precast concrete circular manhole comprising factory-cast base + bottom ring + integral benching + pre-formed channel as a single delivered unit (BS 5911-3), with stacked precast chamber rings, optional reducing slab and access shaft, precast cover slab, ductile-iron frame and cover (BS EN 124 loading classes), step irons cast into rings, granular or concrete bedding, granular surround, geotextile separator, and excavation. Catalogue-driven sizing from PMC_1200 (1200mm ID) to PMC_2400 (2400mm ID). Routes via manhole_type=precast_monolithic attribute discrimination through CESMM4 Class K.1.2.x, NRM2 33.7.5, MMHW 500.5.5-.8 (SHW Cl. 507), and SMM7 R12.3.1.x. Example params: invert_depth=3.5 m (0.5–12), bedding_thickness_mm=150 mm (100–300), bedding_overhang_m=0.15 m (0.1–0.3). Example call: {"params": {"invert_depth": 3.5, "bedding_thickness_mm": 150, "bedding_overhang_m": 0.15}, "standard": "MMHW"}. Omitted parameters use sensible engineering defaults. Pass deliverables=["xlsx","dxf","pdf"] (any subset) to also receive one-shot download URLs in the same call: Excel BoQ (both tiers, watermarked free) plus the dimensioned DXF (CAD) and PDF drawing sheets (paid tier).