CC-1000_2018

Soil Gas Control Systems ANSI/AARST CC-1000 2018 in New Construction of Buildings 8 5.5.4 Other gravel or crushed stone options 5.5.4.1 A uniform layer of gravel or crushed stone not less than 4 inches (10 cm) in depth with size numbers 1, 2, 3, 4 and 367 as classified by ASTM C33 shall be permitted as an alternative to Sectio n 5.5.2a if confirmed to be acceptable for: a) structural support requirements of the building or slab; and b) sustainable integrity of adjoining soil gas retarders. Informative note— These aggregates contain a high percentage of 3-inch (75 mm) stone; 2-inch (50 mm) stone; 1.5-inch (37.5 mm) stone; or 1-inch (25 mm) stones, respectively. 5.5.4.2 Gravel or crushed stone size #67 as classified by ASTM C33 shall be permitted as an alternative to Section 5.5.2a when applied as a uniform layer not less than 8 inches [20 cm] in depth and inlet size is doubled or augmented to achieve compliance with Section 5.7.1 . Informative note — This aggregate contains a high percentage of nominally 3/8-inch (10mm) stone with less than 5% fines. 5.5.5 Depth of gas permeable aggregates 5.5.5.1 Exceeding required 4-inch depth (encouraged) Uniform layers of gas permeable aggregates shall be permitted to exceed 4 inches (10 cm) in depth, as sometimes desired to enhance pressure field extension (PFE) or needed to prevent potential damage to concrete if supported inconsistently as a result of soil adjoining fixed height surfaces (e.g., blocks or rigid piping). 5.5.5.2 Limits on less than 4-inch depths Portions of gas permeable layers that are less than 4 inches (10 cm) in depth that can result from limited maneuverability of grading machinery are permitted only to the extent that the hydraulic conductivity for air movement across the nominal breadth of gas permeable layer is not reduced. 5.6 Duct sizes 5.6.1 Primary and main trunk sizing Duct piping for exhaust vent pipes or within soil gas collection plenums that route the entire system air volume from the soil gas collection plenum(s) to the system exhaust location shall not be smaller than required in Table 4.3 . 5.6.2 Secondary trunks and branches Smaller duct piping that routes only a portion of the system air v olume shall be sized in accordance with Table 4.3 as applicable for each individual plenum and comply with Section 5.7 for inlet capacity. 5.6.3 All air duct sizing All duct inner dimensions, including secondary trunk and branches that route only a portion of the system air volume, shall not be less in size than the nominal cross-sectional inside diameter of 3-inch (7.6 cm) pipe. Informative —Table 5.6 Cross-sectional area dimensions Pipe Inner Diameter (ID) Cross-sectional Area 2-inch (50 mm) 3.1 sq. in. (20 cm 2 ) 3-inch (75 mm) 7.1 sq. in. (46 cm 2 ) 4-inch (100 mm) 12.6 sq. in. (81 cm 2 ) 6-inch (150 mm) 28.3 sq. in. (182 cm 2 ) Exceptions: When provided for condensate control or when it is known that a fan-driven air volume less than 40 cfm (1.1 m 3 /min) is adequate to establish a vacuum within a soil gas collection plenum. For these situations, branch piping or secondary trunks that are not less than 2-inch (50 mm) ID are permitted in lengths to individually not exceed the equivalent length of 25 feet (7.6 m). Such pipes shall not be used for soil gas control with plenums that are more than 800 square feet (74 m 2 ) in size. 5.6.4 Size changes The size of exhaust vent piping between the connection to inlets or inlet ducting below the top of the plenum and the point of discharge or termination at the roof shall not be reduced in the direction of airflow toward the exhaust location. Exception: It shall be permitted to reduce pipe size in the direction of airflow toward the exhaust location when pipes larger than the minimum size for the main trunk or secondary trunks are employed along the pipe route for a particular purpose, such as to join larger sized inlets ; minimize pressure loss; facilitate condensate control or to slow airflow velocity in an effort to reduce noise. 5.6.5 Transitions Transition connections between different materials or shapes shall maintain cross-sectional dimensions of the connected main trunk, secondary trunk or branch ducting. 5.6.6 Airflow resistance within Inlet trunk networks The design and construction of Inlet trunk networks below a slab or membrane shall consider concerns of excessive airflow resistance at the furthest distances away from the location of the network transition to exhaust piping . Informative note— Examples of concern include piping with equivalent lengths that exceed: a) 75 feet (23 m) for 3-inch (7.6 cm) pipe; b) 150 feet (46 m) for 4-inch (10.2 cm) pipe; and c) 440 feet (134 m) for 6-inch (15.2 cm) pipe.