{"id":24962,"date":"2023-06-30t09:53:13","date_gmt":"2023-06-30t14:53:13","guid":{"rendered":"\/\/www.dicovercards.com\/?post_type=snyder-projects&p=24962"},"modified":"2024-03-13t17:05:55","modified_gmt":"2024-03-13t22:05:55","slug":"sediment-buildup-necessitates-lake-dredging-project-at-south-dakota-capitol-complex","status":"publish","type":"snyder-projects","link":"\/\/www.dicovercards.com\/projects\/sediment-buildup-necessitates-lake-dredging-project-at-south-dakota-capitol-complex\/","title":{"rendered":"sediment buildup necessitates lake dredging project at south dakota capitol complex"},"content":{"rendered":"
one of the prominent features complementing the architectural beauty of the capitol complex in pierre, south dakota<\/a>, is the 9.5-acre capitol lake. fed by a naturally occurring artesian well, this expansive lake was built in 1913 on the southeast side of the capitol building. it is surrounded by tranquil park space<\/a> and walking trails<\/a> adorned with historic monuments celebrating south dakota’s heritage and culture, making the area a prime attraction for community members and visitors.<\/p>\n however, as the pierre community grew, additional stormwater<\/a> was routed through the lake due to its location near the bottom of a tributary discharging into the missouri river. thousands of canadian geese and other waterfowl also inhabited the year-round open water. these issues have created poor water quality<\/a> and reduced the lake’s original average depth of 16 to 20 feet to less than 6 feet.<\/p>\n the south dakota department of agriculture & natural resources<\/a>, acting through the office of the state engineer, selected the snyder & associates and morris, inc. design-build team to dredge the lake and restore<\/a> it to its original depth.<\/p>\n before dredging began, preliminary testing indicated that lake sediment included high levels of phosphorous, ammonia<\/a>, and total suspended solids (tss). due to their soluble nature and potential to harm wildlife, containment measures were needed to prevent sediment entry into capitol creek \u2014 the lake’s natural path for overflows. this was achieved by drawing down the lake elevation using silt curtains, screens, and siphons.<\/p>\n by lowering the water level, our team ensured the disturbed sediment would remain in the basin and not flow over the weir during dredging operations. this process allowed the amphibious and barge excavators to maneuver and dredge safely without uncontrolled discharge.<\/p>\n dredging is also a disruptive process for wildlife. while migratory birds tend to avoid the site during construction, aquatic creatures do not have that luxury. the south dakota game, fish, and parks team performed a humane fish removal operation called electroshocking before active dredging operations began. electroshocking fish is a common and effective method used in fishery management. this process directs a small electrical current through the water, stunning the fish so they can be quickly scooped up and removed. electroshocking is a humane method to remove fish from a waterway and has little to no impact on the long-term health of the fish population. once captured, the fish were relocated to several local waterways.<\/p>\n dredging is generally performed using a mechanical method, such as an excavator with a bucket to dig up sediment, or a hydraulic method using a cutting head and suction pump to remove materials. through numerous discussions, it was determined that hydraulic dredging should be ruled out due to the planned winter operations and sediment size and types, which prevent effective settling. a mechanical method using excavators, barges, and dump trucks was selected.<\/p>\n initially, an amphibious excavator was selected for sediment removal. this machine can perform dredging operations while supported on soft terrains such as swamps, wetlands<\/a>, and shallow water. however, it quickly became apparent that as the excavator moved deeper into the lake, it was no longer performing satisfactorily and needed to be replaced. a barge was located rapidly, and a long-reach excavator was positioned on the floating structure to continue the process.<\/p>\n once removed, the lakebed material was loaded into a hopper barge and transferred to dump trucks stationed in a specially designed loading area that had been set up with erosion controls<\/a>. the sediment was taken to a locally permitted landfill, where it was contained for dewatering.<\/p>\ncontrolling sediment flow & protecting wildlife during dredging operations<\/strong><\/span><\/h2>\n
dredging process options & recycling dredged material<\/strong><\/span><\/h2>\n