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of rooftop area.and parking lot area will cause sufficient stormwater runoff to warrant the requirement. Internal drainage is defined to cover all stormwater runoff within the property to be developed. This includes rooftops and parking areas. Only the concrete apron between the pro- perty line and the curb is allowed to fall to the street. Catch basins for the internal drainage shall be provided in all parking areas outside of the street right-of-way and storm drainage pipe shall extend to the nearest drainage facility of sufficient capacity. These are mandatory requirements except: (i) When the developer receives the concurrence of the City Engineer with the certified statement and calculations of the developer's Registered Professional Engineer or Licensed 3(b) Land Suveyor that no hazard or danger would result from the restricted release Of stormwaters into the City street or right-of-way while: a) using, in the cal- culations, a stormwater runoff coefficient for a parking lot paved in its entirety with non-porous bituminous concrete; and b) detaining all stormwaters up to a minimum storm of 5-year frequency with ~ controlled release into the City right-of-way of only those quantities that would result from a storm of a 2-year frequency with the site in its undeveloped state. Criteria for a hazardous condition in- cludes, but is not limited to, th~ exceeding of an eight foot (8') spread of. stormwater in a curbed street for a 2-year storm frequency.at the nearest downstream inlet. (ii) Where alterations are proposed to a building w!th an existing parking lot with inadequate internal drainage, the facility may continue to be used without installation of internal drainage if: a) the City Engineer concurs with the certified statement and calculations of the developer's Registered Professional Engineer or Licensed 3(b) Land Surveyor that no hazard or danger would result from continuing the present method, rate and quantity of stormwater discharge and if paved in its entirety with non-porous bituminous concrete pavement; and b~ if no addition to the parking area and roof area is performed. Where the City Engineer considers a danger or hazard to exist, the developer shall, prior to building occupancy, eliminate or minimize his site's contribution to the problem to the satisfaction of the City Engineer. Where an addition to the parking lot or roof top area will result in additional stormwater runoff, drainage and/or site modifications shall be performed by the developer as approved by the City Engineer. Adopted by the Council of the City of Portsmouth, Virginia, at a meeting held April 28, 1981. Teste: City Clerk