Related to nominal surface

Pervious surface means an area that releases as runoff a small portion of the precipitation that falls on it. Lawns, gardens, parks, forests or other similar vegetated areas are examples of surfaces that typically are pervious.
Water surface elevation means the height, in relation to the National Geodetic Vertical Datum (NGVD) of 1929, the North American Vertical Datum (NAVD) of 1988, or other datum, where specified, of floods of various magnitudes and frequencies in the floodplains of riverine areas.
Mine drainage means any drainage, and any water pumped or siphoned, from an active mining area or a post-mining area. The abbreviation “ml/l” means milliliters per liter.
Impervious surface means a surface that has been covered with a layer of material so that it is highly resistant to infiltration by water.
Built-Up Area and/or “Covered Area” in relation to a Flat shall mean the floor area of that Flat including the area of balconies and terraces, if any attached thereto, and also the thickness of the walls (external or internal) and the columns and pillars therein Provided That if any wall, column or pillar be common between two Flats, then one-half of the area under such wall column or pillar shall be included in the built-up area of each such Flat.

nominal surface definition