Arika, Caleb N.

Human activities including agricultural cultivation, forest harvesting, land development for residential housing, and development for manufacturing and industrial activities can impair the quality of water entering the wetland, thereby detrimentally affecting the natural ecological functions of the wetlands. This can lead to degradation of biota health and biodiversity within the wetland, reduced water quality in the wetland, and increased release of water quality degrading chemicals to receiving waters. Under natural conditions wetlands develop buffer areas that provide some protection from the natural processes occurring on adjacent areas of the landscape. Buffers serve the function of enhancing infiltration of surface runoff generated on adjacent areas, thereby promoting the retention of nutrients in the soil, and retention of sediment suspended in the runoff water, while still allowing runoff water to reach the wetland through subsurface flow routes. To protect wetlands and receiving waters downstream from the wetlands it is important that wetlands in areas disturbed by human activities be provided with sufficient buffer to prevent degradation of wetland biotic integrity as well as degradation of wetland water quality. The question arises, "How much buffer is sufficient?" The objective of this study was to investigate the sufficiency of buffers to protect wetland biotic integrity and water quality, and to evaluate the benefits extended to wildlife by the habit available in wetland buffers. The study was conducted by using a wetland data base available for 64 wetlands in the Twin Cities metro area.

In 2008 a Phase II implementation project was conducted to test whether presence/absence surveys could provide accurate and cost effective estimates of invasive weed species infestation in roadway rights-of-way within Mn/DOT District 4. A 225-ft survey, in which infested areas were mapped, was used as the standard for comparison to the presence/absence surveys which were conducted using 14-ft 'stick walks'. A 2007 Phase I project had shown the presence/absence surveys to be more cost effective, but the infestation estimates were consistently lower than the standard. The 2008 study provided additional data to test the efficacy of the presence/absence surveys. The results of the 2008 study showed that the presence/absence surveys were significantly less costly than the standard, but the estimates of infestation themselves were not satisfactory relative to the standard scheme. From this study it is concluded that surveys should be conducted using the 225-ft sampling scheme for invasive species that form contiguous patches. The lower cost of the presence/absence surveying scheme might make it a good option for sampling of invasive weed species infestations for the case of rare species such as poison ivy which do not typically form contiguous patches.

A guide for evaluation of highway subsurface drainage needs and design of subsurface drainage systems for highways has been developed for application to Minnesota highways. The guide provides background information on the benefits of subsurface drainage, methods for evaluating the need for subsurface drainage at a given location, selection of the type of drainage system to use, design of the drainage system, guidelines on how to construct/install the subsurface drainage systems for roads, and guidance on the value of maintenance and how to maintain such drainage systems.

A study initiated in 2004/2005 in District 4 of Mn/DOT compared the use of 100 1/4-mi long segments against seven 3-mi segments on sampling precision for the estimation of weed infestations in highway rights-of-way for Canada thistle (Cirsium arvense (L.)(Scop.), leafy spurge (Euphorbia esula L.), and poison ivy (Toxicodendron radicans). The comparison showed that the 3-mi and 1/4-mi plans yielded equivalent estimates of mean weed population density, although the results indicated that at the district level precision was greater with the 1/4-mi plan. Further investigations suggested that additional improvements in precision and efficiency would likely occur if segment lengths were shortened to 125' or less. The project implementation phase reported here aimed to investigate efficiencies of two sampling plans, one with weed density measured over 100, 225-ft segments, and one with presence/absence of weeds measured over 150, 14-ft segments. Results showed that the presence-absence surveys almost consistently underestimated the area infestation derived from the 225-ft surveys. The 14-ft survey required substantially less time to conduct, but at this time they appear to be less precise than the 225-ft surveys with regard to quantifying infestation density. It is recommended that an additional season of survey data be analyzed to better quantify the precision of the 14-ft survey results.

By law, Departments of Transportation are required to control noxious weeds along highway rights-of-way (ROWs). Since 2000, District 4 (D4) of Minnesota Department of Transportation (Mn/DOT) adopted a survey design consisting of n= 7, 3-mi segments to quantify infestations of Canada thistle (Cirsium arvense (L.)(Scop.), leafy spurge (Euphorbia esula L.), and poison ivy (Toxicodendron radicans) in chosen regions of the district. In 2004 and 2005, a second survey design was added to see if stratification by ecozone in D4, and greater numbers of 1/4-mi segments could improve precision. Comparison of matching sample statistics from the 3-mi and 1/4-mi plans in each year indicated the two plans yielded equivalent estimates of mean acres per roadway mile of each weed (α = 0.05). However, precision at the district level was much greater in all cases with the 1/4-mi plan. In addition, weed abundances varied substantially among ecozones (α < 0.05); this knowledge will allow managers to direct control efforts to problem areas. Finally, a combination of computer based mapping and resampling of the 1/4-mi segments observed in the two years suggests that additional improvements in precision and efficiency are likely to occur if segment lengths are shortened to 125' or less. Shorter segments would reduce inspection costs, increase sample sizes, improve precision, and possibly allow conversion from an area-measurement approach to one based on presence or absence of chosen weeds in selected segments. Plans are underway to compare the latter two approaches in 2007.

Highway infrastructure represents a substantial portion of the total impervious areas that generate runoff water. Because of long winters in congested areas that require frequent applications of de-icing materials, much of the runoff has the potential for affecting downstream water quality. However, storm water management techniques themselves have the potential for compromising the integrity of adjacent highways when they result in significant increases of water content in the soil beneath the roadway. Because of impacts and the costs associated with construction and maintenance, any storm water management system needs to be assessed before any decisions are made regarding new highway development or redevelopment. The authors consider Best Management Practices (BMPs) as they relate to the most commonly used storm water management approaches including dry ponds, wet ponds, infiltration trenches, infiltration basins, constructed wetlands, grassed swales, bioretention cells, sand filters and porous pavements. They provide a framework for considering cost of practices, negative impact on infrastructure, results from a BMP-related survey of highway design and maintenance professionals and cost-estimation formulas for each of the most commonly used storm water management approaches in urban Minnesota.

Highway infrastructure represents a substantial portion of the total impervious areas that generate runoff water. Because of long winters in congested areas that require frequent applications of de-icing materials, much of the runoff has the potential for affecting downstream water quality. However, storm water management techniques themselves have the potential for compromising the integrity of adjacent highways when they result in significant increases of water content in the soil beneath the roadway. Because of impacts and the costs associated with construction and maintenance, any storm water management system needs to be assessed before any decisions are made regarding new highway development or redevelopment. The authors consider Best Management Practices (BMPs) as they relate to the most commonly used storm water management approaches including dry ponds, wet ponds, infiltration trenches, infiltration basins, constructed wetlands, grassed swales, bioretention cells, sand filters and porous pavements. They provide a framework for considering cost of practices, negative impact on infrastructure, results from a BMP-related survey of highway design and maintenance professionals and cost-estimation formulas for each of the most commonly used storm water management approaches in urban Minnesota.