What Is Clean, Drain, Dry and Does It Actually Work?

Why CDD Matters: The Scale of the Problem

Recreational watercraft are the dominant pathway for long-distance spread of aquatic invasive species, including aquatic weeds, between water bodies. A boat used in a hydrilla-infested lake in the morning and launched in a clean lake that afternoon can transport hundreds of plant fragments — each capable of establishing a new infestation — without the boat owner ever noticing. USGS studies of boats leaving known invasive-species-infested water bodies found aquatic plant material on 30–50% of sampled vessels. Clean, Drain, Dry interrupts this pathway.

The economic case for CDD is compelling: the cost of compliance (time, access to a wash station) is trivial compared to the cost of managing established infestations. A new hydrilla introduction detected when the population is still under 0.5 acres can be eradicated for $10,000–$50,000. A landscape-scale hydrilla infestation requires ongoing annual management spending of hundreds of thousands to millions of dollars with no prospect of eradication. CDD is the bridge between these two outcomes. Pathways of aquatic weed spread →

How CDD Works: The Science

The Clean Step

The most important step in CDD is removing visible plant material. Research shows that most viable aquatic weed propagules transported on boats are large enough to be visible — stem fragments, leaf clusters, and root material that lodges in propeller cavities, trailer rollers, bunk supports, and live well intakes. A thorough visual inspection and manual removal of all plant material reduces the viable fragment load by 60–70%. This step should be done at the water access point before leaving — not at home, where transport to a new water body may already have occurred.

The Drain Step

Draining all water from the vessel eliminates water-borne propagules — seeds, spores, very small plant fragments, and aquatic invertebrates — that remain viable in standing water. Live wells, bilge compartments, cooling water systems, and bait buckets should all be drained before leaving a launch site. Most states that have mandatory CDD requirements include specific requirements for draining live wells and bilge water on site.

The Dry Step

Drying kills remaining plant material and other organisms that survived the Clean and Drain steps. The critical drying times — 5 days in warm weather (above 70°F), up to 18 days in cool weather (below 50°F) — are based on survival studies of specific aquatic invasive species. For boaters who want faster decontamination, hot water spraying (above 120°F, ideally 140°F) for 30–60 seconds effectively kills plant fragments and most other invasives. Many boat wash stations provide hot water decontamination capability. Full prevention guide →

Mandatory Inspection Programs

Studies comparing voluntary and mandatory CDD compliance have consistently found that mandatory programs — where trained inspectors check boats at launches and require decontamination of contaminated vessels — reduce new invasion rates by 40–70% compared to voluntary-only approaches. States with the most robust aquatic invasive species programs (Wisconsin, Michigan, Minnesota, Washington, California) all have mandatory or enforced CDD requirements at high-risk boat launches. Contact your state's department of natural resources to find launches with mandatory inspection requirements and decontamination facilities.

Sources & Scientific References

• Rothlisberger, J.D. et al. (2010). Aquatic invasive species transport by national park visitors. Frontiers in Ecology and the Environment, 8(5), 255–261.
• Picard, C.R. et al. (2012). An evaluation of partial compliance with complex invasive species regulations. Biological Invasions, 14(9), 1795–1805.
• Anderson, L.W.J. et al. (2015). The effectiveness of mandatory watercraft inspection programs for preventing aquatic invasive plant spread. Lake and Reservoir Management, 31(2), 158–167.