Robert M. Roseen

Maintenance of Low Impact Development (LID) systems represents a significant barrier to the acceptance of LID technologies. Despite the increasing use of LID over the past four decades, stormwater managers still have minimal documentation in regards to the frequency, intensity, and costs associated with LID operations and maintenance. Due to increasing requirements for more effective treatment of runoff and the proliferation of total maximum daily load (TMDL) requirements, there is greater need for more documented maintenance information for planning and implementation of stormwater management strategies. This study examined 7 different types of stormwater treatment systems for the first 2-4 years of operations and studied maintenance demands in the context of personnel hours, costs, and system pollutant removal. The systems were located at a field facility designed to distribute stormwater in parallel, with normalized watershed characteristics including pollutant loading, sizing, and rainfall. System maintenance demand was tracked for all systems and included labor, activities, maintenance type, and complexity. Annualized maintenance costs ranged from $2000/ha/yr for a vegetated swale to $7600/ha/yr for a retention pond. In terms of mass pollutant load reductions, marginal maintenance costs ranged from $4-$8 per kg/yr TSS removed for porous asphalt, a vegetated swale, bioretention, and a gravel wetland, to $11-$20 per kg/yr TSS removed for a retention pond, a detention pond, and a sand filter system. When nutrients such as nitrogen and phosphorus were considered, maintenance costs per kg/yr removed ranged from reasonable to cost prohibitive especially for systems with no nutrient removal mechanisms. As such, best management practices (BMPs) designed for targeting these pollutants should be selected carefully. The results of this study indicate that generally, LID systems, as compared to conventional systems, have lower marginal maintenance burdens (as measured by cost and personnel hours) and higher water quality treatment capabilities as a function of pollutant removal performance. Annual system maintenance expenditures equal total upfront capital costs after 4.5 years for retention ponds and after 20 years for the porous asphalt system. In general BMPs with higher percentages of periodic and predictive, or proactive maintenance activities have lower maintenance burdens than BMPs with incidences of reactive maintenance.

This study examined the functionality of a porous pavement storm-water management system in coastal New Hampshire where 6 months of subfreezing temperatures typically occur. The usage of porous pavements for storm-water management in northern climates has many challenges, most of which relate to the extreme cold and significant frost penetration into the porous media. The porous pavement system was monitored for hydraulic and water-quality performance from 2004 to 2008. The use of porous pavements for parking lots for new and redevelopment projects are one watershed-based strategy that can both mitigate impacts for new development and reverse impacts in areas with redevelopment. Surface infiltration capacity and frost penetration were measured monthly to assess winter performance. Because of the well-drained nature of the porous pavement and reservoir base, issues related to frozen media were minimized. Significant frost penetration was observed up to depths of 71 cm without declines in hydrologic perform...

A Bayesian statistical approach for determining the parameter uncertainty of a storm-water treatment model is reported. The storm-water treatment technologies included a sand filter and a subsurface gravel wetland. The two field systems were loaded and monitored in a side-by-side fashion over a two-year period. The loading to each system was storm-water runoff generated by ambient rainfall on a commuter parking lot. Contaminant transport is simulated by using a one-dimensional advection-dispersion model. The unknown parameters of the model are the contaminant deposition rate and the hydrodynamic dispersion. The following contaminants are considered in the study: total suspended solids, total petroleum hydrocarbons–diesel range hydrocarbons, and zinc. Parameter uncertainties are addressed by estimating the posterior probability distributions through a conventional Metropolis-Hastings algorithm. Results indicate that the posterior distributions are unimodal and, in some instances, exhibit some level of skewness. The Bayesian approach allowed the estimation of the 10th, 25th, 50th, 75th, and 95th percentiles of the posterior probability distributions. The prediction capabilities of the model were explored by performing a Monte Carlo simulation using the calculated posterior distributions and two rainfall-runoff events not considered during the calibration phase. The objective is to estimate effluent concentrations from the treatment systems under different scenarios of flow and contaminant loads. In general, estimated effluent concentrations and the total estimated mass fell within the defined uncertainty limits.

A Bayesian statistical approach for determining parameter uncertainty of a stormwater treatment model is reported. The stormwater treatment technologies included a sand filter and a subsurface gravel wetland. The two field systems were loaded and monitored in a side by side fashion over a two year period. Stormwater runoff was generated by ambient rainfall on a commuter parking lot, which was the loading to each system. Contaminant transport is simulated by using a one-dimensional advection-dispersion model. The unknown parameters of the model are the contaminant deposition rate and the hydrodynamic dispersion. The following contaminants are considered for the study: total suspended solids, total petroleum hydrocarbons-diesel range hydrocarbons, and zinc. Parameter uncertainties are addressed by estimating the posterior probability distributions via a conventional Metropolis—Hastings algorithm. Results indicate that the posterior distributions are unimodal and, in some instances, exhibit some level of skewness. The Bayesian approach allowed the estimation of the 10th, 25th, 50th, 75th, and 95th percentiles of the posterior probability distributions. The prediction capabilities of the model are explored by performing a Monte Carlo simulation using the calculated posterior distributions and two rainfall-runoff events not considered during the calibration phase. The objective is to estimate effluent concentrations from the treatment systems under different scenarios of flow and contaminant loads. In general, estimated effluent concentrations and the total estimated mass fell within the defined uncertainty limits.

A field study was conducted to assess biases of suspended sediment concentration (SSC) analyses (ASTM Standard D3977-97) performed on discrete samples obtained by automatic sampler in comparison with actual sediment concentrations from large volume sampling. Research results indicate that the biases attributed to the monitoring of sediment event mean concentration (EMC) and median particle size in parking lot runoff by automated samplers (nonisokinetic) were minimal. Large volume samples (∼15,000 L) of the first-flush event runoff were taken from a storm-water sewer system for eighteen storm events over two years. The intent was to obtain a complete portion of a storm to accurately determine EMCs and particle size distributions (PSDs). Concurrently, flow-weighted discrete samples were obtained by automatic samplers for the same portion of the events. Thus, characteristics of sediments from a whole-storm sample were compared with those of subsamples obtained by an automatic sampler using nonisokinetic sam...

The preliminary results to examine the 4 years of monitoring of runoff temperature for a range of stormwater management BMPs and the affects on stormwater runoff temperatures in relation to established environmental indicators are presented for a study in Durham, NH. Research indicates that thermal impacts are not limited to summer months but include other times important for life-cycle considerations. Stormwater BMPs examined include conventional, Low Impact Development, and manufactured treatment designs. Surface systems that are exposed to direct sunlight have been shown to increase already elevated runoff temperatures, while other systems that provide treatment by infiltration and filtration can reduce runoff temperatures by thermal exchange with cool subsurface materials. Results indicate there is an increase in the thermal mass of runoff from a storm sewer system draining an area of asphalt pavement with a 97% impervious cover. For the storm sewer system, the mean EMT value of 53.5°F (± 12.7°F), which is greater than the mean groundwater temperature, which resembles the mean daily average annual air temperature, of 47°F that feed coldwater streams (NCDC 2005). The examination of stormwater BMPs indicates that the larger surface systems will see greater thermal variations and the larger subsurface systems will see greater thermal buffering. One large surface system, the Retention Pond, with a mean value of 61.8°F (± 11.8°F) is susceptible to greater thermal variations. One large subsurface system, the Gravel Wetland, whose mean value of 48.7°F (± 12.0°F), indicates a greater thermal buffering. The Runoff, the Retention Pond, and the Gravel Wetland calculated maximum and minimum values of event mean temperatures of 75.4°F and 33.3°F, 81.3°F and 32.7°F, 70.0°F and 33.0°F respectively. These temperatures are important to note when considering lethality indices of aquatic species. Another indicator of the health of a system that has been utilized by environmental monitoring programs is the mean July temperature of the stream under investigation

In northern climates, runoff from standard pavements has varying seasonal effects on the surrounding environment. Year-round runoff carries transportation associated contaminants into surface waters. During the winter and spring, deicing practices for pavements result in high levels of chloride-laden runoff that is both toxic to aquatic biota and degrades drinking water supplies. The use of pervious pavements for parking lots for new and redevelopment projects are one watershed-based strategy that can both mitigate impacts for new development and reverse impacts in areas with redevelopment. This study presents the findings from 2 pervious pavements, a pervious concrete and a porous asphalt parking lot, studied at the University of New Hampshire Stormwater Center. Winter in particular places great demands on pavements however it was observed that due to the well-drained nature of the reservoir base that freeze thaw was limited. Surface infiltration rates, frost penetration, degree of snow and ice cover, and surface friction were measured on a monthly basis to assess winter performance. Frost penetration was observed to reach depths of eighteen inches however, surface infiltration capacities remained in excess of 200-in/hr. Analysis of snow and ice cover and pavement skid resistance demonstrated that up to 75% less salt was needed for porous asphalt to maintain equivalent or better surface conditions as the reference dense mix asphalt lot. The annual median snow and ice surface cover for the porous asphalt lot was not significantly different than the reference lot with salt applications four times greater (p=0.749 @95% CI). The annual median weighted skid resistance for the porous asphalt lot was 12% greater than the reference lot with greater salt application (p=0.061 @95%CI). Pervious concrete did not demonstrate substantial salt reduction capabilities during storm events; however, `black-ice' formation did not occur during freeze-thaw conditions indicating possible annual reductions. Pavement color and shading were found to be major factors influencing the amount and duration of snow and ice cover on the pervious concrete lot.

A mathematical and statistical model for simulating contaminant removal from a surface sand filter is reported. The model was based on a mass balance equation and an advection-dispersion transport model. The unknown parameters of the model were the deposition rate and the hydrodynamic dispersion. Changes in space were allowed within the filter media depth and time variability of flow and influent contaminant concentration were taken into account. System field monitoring was performed between 2004 and 2006. A total of 17 storms were selected for the study. Runoff constituent analyses included: total suspended solids, total petroleum hydrocarbons-diesel range hydrocarbons, and zinc. The objective was to explore the capabilities of a two parameter model for predicting effluent contaminant concentrations. Optimized model parameter values were calculated on a storm by storm basis. Thereafter, a gamma distribution was fitted to the optimized values. A Monte Carlo simulation was performed to explore the predicti...

In northern climates, runoff from standard pavements has varying seasonal effects on the surrounding environment. Year-round runoff carries transportation associated contaminants into surface waters. During the winter and spring, deicing practices for pavements result in high levels of chloride-laden runoff that is both toxic to aquatic biota and degrades drinking water supplies. The use of pervious pavements for parking lots for new and redevelopment projects are one watershed-based strategy that can both mitigate impacts for new development and reverse impacts in areas with redevelopment. This study presents the findings from 2 pervious pavements, a pervious concrete and a porous asphalt parking lot, studied at the University of New Hampshire Stormwater Center. Winter in particular places great demands on pavements however it was observed that due to the well-drained nature of the reservoir base that freeze thaw was limited. Surface infiltration rates, frost penetration, degree of snow and ice cover, and surface friction were measured on a monthly basis to assess winter performance. Frost penetration was observed to reach depths of eighteen inches however, surface infiltration capacities remained in excess of 200-in/hr. Analysis of snow and ice cover and pavement skid resistance demonstrated that up to 75% less salt was needed for porous asphalt to maintain equivalent or better surface conditions as the reference dense mix asphalt lot. The annual median snow and ice surface cover for the porous asphalt lot was not significantly different than the reference lot with salt applications four times greater (p=0.749 @95% CI). The annual median weighted skid resistance for the porous asphalt lot was 12% greater than the reference lot with greater salt application (p=0.061 @95%CI). Pervious concrete did not demonstrate substantial salt reduction capabilities during storm events; however, `black-ice' formation did not occur during freeze-thaw conditions indicating possible annual reductions. Pavement color and shading were found to be major factors influencing the amount and duration of snow and ice cover on the pervious concrete lot.

An existing accumulation and wash-off model was applied and calibrated on a standard asphalt parking lot located in the northeastern United States. The field measured data consisted of rainfall, flow, and runoff samples taken from over 26 storm events monitored from 2004 to 2006. The contaminants under consideration include: total suspended solids, total petroleum hydrocarbons-diesel range hydrocarbons (TPH-D), dissolved inorganic nitrogen (DIN) (comprised of nitrate, nitrite, and ammonia), and zinc (Zn). The objective of the study was to provide probability distributions of model parameters for contaminants that have not been documented much (TPH-D, DIN, and Zn). The best fitting parameter values were found on a storm by storm basis. Subsequently, the range and variability of these parameters are provided for modeling purposes and other urban storm-water quality applications. A normal distribution was fitted to the optimized model parameter values to describe their distributions. A simulated annealing al...