Minnesota Water Resources Conference - Water Resources Center ...

Concurrent Sessions VI 3:00–4:30
Track C: Urban Pollutants: Source, Transport and Treatment
BOOK OF ABSTRACTS
Wednesday, Tuesday, October 24 28 23
Land Cover and Impervious Classifications of the Minneapolis/St. Paul Metropolitan Statistical Area
Marvin Bauer, University of Minnesota, mbauer@umn.edu
Land cover and land use are critical drivers of environmental change and improved information and
understanding of their spatial and temporal dynamics is essential for effective land and water management and
policy. Over large geographic areas satellite remote sensing represents the most effective means to map and
monitor land cover. Impervious surface area is a key component of land cover-use and an important indicator
of environmental quality, affecting stormwater runoff to streams and lakes and water quality of surrounding
lakes and streams.
This presentation will describe the results of classifications of multispectral Landsat data acquired in 2007 of the
Minneapolis−St. Paul Metropolitan Statistical Area and the St. Croix River Basin of Minnesota and Wisconsin.
The data will provide new, current maps and information quantifying the spatial patterns of land cover and
impervious area of this region that can used as inputs to hydrology, stormwater and water quality models.
Inventory and Hydrologic Transport of Road Salt in the Twin Cities Metropolitan Area
Eric Novotny, University of Minnesota, nov00002@umn.edu; Andrew Sander, University of Minnesota; Omid Mohseni,
University of Minnesota; Heinz Stefan, University of Minnesota
Over 330,000 tons of road salts (NaCl) are applied annually for road de-icing in the Twin Cities Metropolitan
Area (TCMA). Observed salinity exceeds standards in a few streams and lakes seasonally. The hydrologic
transport of salt, including road salt and water softener salt, through the TCMA watershed was analyzed.
A hydrologic salt budget for TCMA watersheds was constructed using salinity data from major rivers, salt
application rates, and wastewater treatment plant effluents. A residual of the amount of salt imported and used
in the TCMA but not carried away by the Mississippi River was determined. Potential retention in soils, lakes
and wetlands, and ground water is being investigated. Physical and chemical effects of saline water runoff into
urban lakes were investigated, including (1) formation of a saline layer at the lake bottom, (2) long-term salinity
increases in surface waters (3) seasonal salinity patterns and (4) penetration of salt into lake sediments. Field
measurements and historical data were interpreted. Results will be reported.
Assessing Hydrodynamic Separators under High Water Flow Conditions
David Saddoris, University of Minnesota, saddo002@umn.edu; Omid Mohseni, University of Minnesota; and John Gulliver,
University of Minnesota
Underground hydrodynamic separators are widely used in urban areas for removal of suspended solids and
floatables from stormwater due to limited land availability for the installation of above ground stormwater
BMPs. Hydrodynamic separators are sized for applications based on design stormwater flow rates. However,
during less frequent storm events, design flow rates are exceeded and previously captured sediments can
be scoured and washed out of these devices. A new methodology will be introduced to assess the scouring
potential of these devices under flow rates exceeding their maximum treatment rates. The test method involves
pre-loading the devices with sediments of known particle sizes, flowing water at flow rates above maximum
treatment rates, and measuring the amount of sediments remaining inside the devices. The results of controlled
field testing and laboratory testing on three commercial devices using this methodology will be presented, and
implications of the findings on design and maintenance will be discussed.
Minnesota Water Resources Conference, October 27–28, 2008 80