We have some pipes and 200 feet longer near large mature crepe myrtles on a mound in full sun. The mound is actually an island (median) 20 feet wide. Also on this mound are some woody shrubs (Holly), about 40 years old. Deep beneath the mound (six feet?) are old house laterals (sewers) made of terra cotta pipes. The pipes have become impacted by the roots of the woody shrubs. Can roots of crepe myrtles also go this deep so as to impact pipes? The median is not irrigated and surrounded by pavement, so the only water source is from the leaking house laterals.