HAB had a highly productive day and was able to apply about 25,000 gallons of alum of the 100-acre application zone. Effective alum applications require the exact and precise placement of the alum in the lake. HAB’s application equipment is well-suited for the precision required for the Moses Lake restoration project. The exact dose is programed into our software and inline flow sensors measure the flow of alum in the distribution lines in real time. Automated values, which are controlled by a computer, open and close as needed to adjust for barge speed, location and depth to make certain the prescribed dose is applied. Any gaps in coverage would allow for phosphorus from untreated lakebed sediments to leach into the overlying water column and stimulate future algal blooms. An onboard computer system ensures that application is complete and uniform by integrating the location of the barge with GPS, the barge speed, water depth and alum flow rates. Tadd Barrow (HAB’s application specialist) follows a grid and each application path is recored and displayed on the guidance monitor to prevent gaps in the application. At the end of the project, HAB produces a coverage map showing every application path and confirms the complete coverage of the lake.
HAB was also able to quickly respond to a special request from the client to collect some lakebed sediment samples. We collected two cores with our custom coring equipment. The first one was collected in an area of the lake that had been covered with alum earlier in the day. The presence of a 2-3 cm milky white layer of alum floc on top of the sediments confirmed the precision of our application equipment and the calculated settling rate of the floc for the client. The second core was collected in an area of the lake that had not yet been covered with alum. This core was carefully sectioned into eight individual samples that were sent to an analytical lab. The lab will measure the amount of phosphorus in the lakebed that is available internal loading. This information will be used the calculate the remaining required alum dose for Moses Lake and will guide the strategy for future applications.