The City Council on Tuesday approved a "control gate" at the foot of Aetna Mountain Road in the Cummings Cove development in Lookout Valley.  Alan Solon, a partner in the development of the remainder of Cummings Cove as well as a thousand acres on top of the mountain, said the gate was needed to prevent trespassers and to protect private property.  Steve Leach, city public works administrator, said the old dirt road up the mountain is regularly used by Jeepers and four-wheelers. He said those using the road have destroyed survey markers as well as stolen material at building sites.  He said those using the road have trespassed on private and created extensive erosion problems.   NPDES rules and regulations require the use of erosion control blankets, turf reinforecement mats, hydraulic mulch, silt fence, straw wattles and other erosion control products to eliminate sediment from leaving a jobsite >1 acre in size.  Sedimentation ponds, lined with high-strength geomembrane liners, help control high flow areas from overburdening these erosion control measures during large storm events.