Costs associated with mitigating the impacts on water quality of future development within the Reedy River watershed using various best management practices

• Pattern of development is particularly indicative as to the level of impact to water quality on a receiving water body.
• Mass loading entering Lake Greenwood for TP and TN increase by 86% and 39%, respectively, for a 5:1 growth scenario.
• Mass loading entering Lake Greenwood for TP and TN increase by 39% and 17%, respectively, for a 1:1 growth scenario.
• At Boyd Millpond, costs to treat TP and TN could range from $8 to 1000 million.
• At Lake Greenwood, costs to treat TP could range from $10 to 263 million.

This study was initiated to gain a better understanding of how patterns of development within Greenville, SC and its surrounding metro area would affect the Reedy River's water quality and thus costs associated any degradation that may occur. A previously prepared watershed-scale model was modified to yield quantity and quality data that would result from projected growth in Greenville through the year 2030 at three different growth scenarios.The major finding of the study was that water quality and quantity impacts are consistently higher for the 5:1 growth scenario as compared to the 1:1 scenario. As more land is developed in the 5:1 scenario, the amount of stormwater increases while water quality decreases. At Boyd Millpond by 2030, total costs for treatment of total phosphorus and total nitrogen loads resulting from newly developed lands’ stormwater contributions could range from $8 to 1000 million. Results are similar by 2030 for the flow entering Lake Greenwood from the Reedy River Arm. Costs for potential treatment of total phosphorus at this location could range from $10 to 263 million.The cost implications of dealing with water quantity and quality impacts of varying growth scenarios suggest an obvious need for proactive planning and action when it comes to management of nutrients associated with stormwater from future developments within an area.