I fly out of a towered airport with a high volume of helicopter operations along with a moderate amount of fixed wing traffic. The helicopters rarely use the runway and instead land to the left and right of the runway, on either the ramp or an open grassy area. Tower will clear airplanes to land/takeoff while helis are using these areas (which are abeam the runway's touchdown zone). According to Google Earth's ruler the heli's end up being only 250-300ft from the runway's edge. These are large turbine powered Bell and Europcopter helicopters, some of which are practicing autorotations. The majority of the time fixed wing operates left traffic while heli's use right traffic. Is this too close? What are the regulations that pertain to this?