An evaluation of the use of the Storm Water Management Model (SWMM) for predicting Storm Water Runoff of Remediated Areas in Newton County, Missouri of the Tri-State Mining District

Abstract

Granby, Missouri is located in the Newton County Mine Tailings Superfund site (Site) within the larger Tri-State Mining District of Missouri, Kansas, and Oklahoma. Ongoing remediation efforts of large mine waste areas centered in and around the city of Granby in Newton County, Missouri have left large swaths of un-vegetated native soil areas. Remediation efforts began in 2015 and addressed over 100 acres of mine waste and contaminated soils. As part of the remedy, the five remediated areas were first cleared of all vegetation to facilitate access to the mine waste and underlying contaminated soils. Many of these areas were heavily vegetated with large trees and tremendous undergrowth. The removal of the mine waste, vegetation, and contaminated soils were hypothesized to contribute to a change in storm water runoff and surrounding surface water resources. This project will examine the effects of the remediation actions at one remediation area, selected as a study area. The United States Environmental Protection Agency (USEPA) Storm Water Management Model (SWMM) was evaluated as a potential tool for modeling environmental impacts in response to excavation. Models were conducted using a range of input parameters, with a goal of identifying the most important parameters for future monitoring. The SWMM model compiled in this research is based on field- and geospatially derived values for study area width, surface area, pervious and impervious land surface, and slope. Where specific model input parameters have not been measured at a site, published values at similar sites were used. Model outcomes provided information on sediment volume, erosion potential, and contaminant concentrations in runoff, which would allow for recommendations regarding future site remediation action. A sensitivity analysis determined the most critical variables required for reliable modeling was the Washoff Coefficient. The outcome demonstrates the importance of site-specific measurements of these parameters, and the need to conduct periodic monitoring of surface water runoff volume and mass contaminant loading from remediated areas in the study area.