I am a fourth grade teacher and my class is researching costs for building a jetty in a coastal area. We would like a list of materials that will environmental friendly as well as the cost of building it. We would also like to know the lifespan of a jetty in such an area. Thanks!

You give no specifics so its impossible to start. A jetty can be built from most anything including soil or rock. You would need to pick a material, decide how long the jetty will be and also know the waters depth. Having taugh for many years I would just pick a different project since it not critical to use a jetty to convey the concepts being taught. Lets build a 20 x 30 garage on a slab. You can get plans and a materials list for a project like this just by googling