Location, size and invert elevation of any existing or proposed retention or detention basins, culverts, and drainpipes, the location of manholes, catch basins, hydrants, electric power, and telephone poles, and the location and size of any existing gas mains within the exterior boundaries of the plat or immediately adjacent thereto. If no storm sewer mains are located on or immediately adjacent to the lands being platted, the nearest such mains which might feasibly be extended to serve such lands shall be indicated by their direction and distance from the nearest exterior boundary of the plat and their size, and invert elevations;