Some things to consider when you're doing a pond remediation or dredging.
If you're just doing a touch-up around an irrigation intake, a 3" or 4" pump would be a good choice. They have a minimal amount of setup required and a reasonable amount of water discharge to handle the removal of solids. For a matter of reference a 3" pump on an average is capable of discharging up to 400 gallons per minute.
Now consider this if you are looking at removing a significant amount of sediment from a basin; Solomon Diving Inc. routinely utilizes one of their 6" hydraulic submersible pump packages. The 6" is capable of discharging up to 1600 gallons per minute and passing up to 5" solids through the system. With this capability production is at a maximum and down time is at a minimum. Additionally, when comparing one system to another consider that Solomon Diving, Inc. uses all hard-pipe and semi-rigid hose as opposed to lay flat hose to increase pump performance.
When considering a contractor to perform a project for you make sure that your comparisons are apples to apples. Some contractors quote their jobs based on man-hours as opposed to work-hours. It's our belief at Solomon Diving Inc. that when you're contracting a crew of 3, 4, or 5 members for an 8-hour workday they will either complete the task at hand within the 8-hours or provide 8-hours of service.