Estimating Costs to Construct a Jetty. When attempting to estimate costs of constructing a new jetty we experienced issues when looking for general costs of building a jetty. The main issue is that construction costs for building a jetty varies from project to project.We looked at similar jetties constructed by the army core and calculated an average cost per foot of jetty.Our estimates came in around $750-$850 per foot of jetty to construct a jetty that is fairly close to what the marinas already have in place.The next step was to attempt to analyze how sediment would build up over time so that we could calculate how long it would take before dredging was necessary again.ur estimates came in around $750-$850 per foot of jetty to construct a jetty that is fairly close to what the marinas already have in place. The next step was to attempt to analyze how sediment would build up over time so that we could calculate how long it would take before dredging was necessary again.