Search Content

Man-made floatable litter (MMFL) appears commonly in area rivers. The litter consists of plastic containers, Styrofoam, and other materials. It has been found along river banks, at hydroelectric power plant intakes, and at other locations on the river. It is expected that this litter is derived from recreational and commercial uses of the river and from street litter which is transported to the river by storm sewers and creeks. The goals of this project were to: estimate the volume of man-made floatable litter which enters the Mississippi River from the Twin Cities Metropolitan Area, estimate the portion of litter which is contributed by storm sewers, and evaluate possible techniques for reducing the litter problem. The project included three main work tasks, which were: a literature search, a telephone survey of regulatory agencies in other parts of the country, and a field investigation.

In order to improve the performance of standard sumps as a best management practice (BMP) in treating stormwater runoff, a baffle was designed to be installed as a retrofit in standard sumps. The retrofit is a porous baffle called "SAFL Baffle." The effect of the SAFL Baffle on the performance of standard sumps was assessed by conducting laboratory tests on small scale as well as full scale straight flow-through standard sumps equipped with the baffle. In addition, a number of tests were conducted to determine the performance of standard sumps with the SAFL Baffle when the baffle is clogged with debris like trash and vegetation. Furthermore, the performance of two other configurations of the baffle was studied: (1) the SAFL Baffle in a sump with an outlet pipe 90 degrees to the inlet pipe, and (2) the SAFL Baffle in a sump with some water entering the sump through an overhead inlet grate. Standard sumps equipped with the SAFL Baffle were evaluated using two metrics: (1) How well the system captures sediment during low flow conditions (Removal Efficiency Testing), and (2) how well the system retains the previously captured sediment during high flow conditions (Washout Testing). The results of the tests showed that the SAFL Baffle dissipates the energy of water entering the sump and as a result, at low flow rates, it captures sediment better than a standard sump with no baffle. More importantly, at high flow rates, the washout of the previously captured sediment reduces to near zero. Vol 1 is 2011-08.

Volume I: Standard sumps are installed in many urban and suburban storm sewer systems. They may qualify as a best management practice (BMP) to pre-treat stormwater runoff by removing suspended sediment from the water. However, no data exist on the effectiveness of sediment removal by and maintenance requirements for sumps. Such data could justify giving pollution prevention credits to transportation departments, municipalities, counties and other local governments for the use of standard sumps. To determine whether the standard sumps remove suspended sediments from stormwater runoff, two standard sumps with different sizes were tested in a laboratory setting to determine their removal efficiencies under lowflow conditions as well as the effluent concentrations under high-flow conditions. The removal efficiency tests included feeding a specific sediment size and concentration into the influent pipe and then collecting, drying and weighing the sediments removed by the sump at the test conclusion. The high-flow condition tests involved placing a commercial sediment mix inside the sump and assessing the amount of sediment remaining after the sump was subjected to high flows for a period of time. At the conclusion of testing, removal efficiency functions as well as washout functions were developed for the sumps, which can be used to predict the performance of all standard sumps. In addition, an uncertainty analysis was conducted to aid with data interpretation.

Storm-water runoff from the Woodbridge neighborhood of the City of Shoreview had previously been managed through culverts and other hydraulic structures. In adherence to the Clean Water Act, many watersheds instituted limits to the percentage of storm water that may be allowed into certain lakes and rivers. To minimize this run-off and the associated impacts and in accordance with the City’s sustainable design policy, the City of Shoreview built the Woodbridge neighborhood local roads using pervious concrete pavements in 2008. Pervious concrete pavements exhibit high hydraulic conductivity and high sound absorption coefficient in local or low volume roads. They also provide cost savings through the minimization of hydraulic structures.

This Implementation Summary relations to Report 2023RIC08, published April 2023.

The use of stormwater treatment strategies, often referred to as best management practices (BMPs), has increased significantly due to new stormwater regulations. The goal of this project was to create a scoping-level tool that could assist City and County public works staff in the selection of BMPs appropriate for specific projects.

Technical Summary of Decision Tree for Stormwater BMPs.

This presentation pertains to report 2011RIC01, Decision Tree for Stormwater BMPs.

This Technical Summary pertains to Reports 2011-08 and 2012-13, “Assessment and Recommendations for the Operation of Standard Sumps as Best Management Practices for Stormwater Treatment, Volumes 1 and 2,” published February 2011 and May 2012, respectively

The time individual engineers, administrators and their staff invest in researching drainage law and defining the best approach to solving drainage issues can be considerable. This document provides quick access to information needed to solve those problems and discover legal solutions to recurring drainage issues and the time saved could be invested in other pressing public responsibilities. This study also contains information which might be useful to local elected officials, private property owners and other interested parties as it offers concise educational materials that simplify and inform them on drainage issues and laws related to regional watershed protection, county road/highway ditches, city street/storm sewers and related drainage infrastructure.