Vehicles engaged in the delivery or pick-up of supplies and materials to or from construction projects shall be loaded or unloaded on the construction site whenever possible. Vehicles are not to arrive at the construction site before the hour of eight a.m. and must depart the construction site no later than five p.m. The engines of delivery and pick-up vehicles shall be shut off upon arriving at the site and shall remain shut off during the time supplies, materials, or equipment are being loaded onto or unloaded from the vehicle unless the operation of the engine is required to load or unload the vehicle. (Ord. 535 § 2, 2002; Ord. 526 § 4, 2001; Ord. 514 § 1 (part), 2000)