The Congressional Research Service (CRS) issued a report summarizing ballast water management issues. It pointed out that high seas
ballast water exchange is the most commonly used technique. Modification of a large ship so as to utilize onshore ballast water treatment facilities may cost an estimated $400,000. Retrofitting a vessel to treat ballast water may cost between $200,000 and $310,000 per vessel for mechanical treatment and around $300,000 for chemical treatment. (HK Law)