Water Quality Assessment of the Lewis Ginter Botanical Garden Irrigation Pond

Abstract

Stormwater reuse for irrigation purposes on public and private land is a way to overcome the increasing pressure on finite water resources. Unfortunately, stormwater runoff can contain common pollutants such as nutrients, bacteria and petroleum products. Lewis Ginter Botanical Garden is an 82-acre public garden in Richmond, Virginia that uses stormwater runoff to irrigate garden displays. The objective of this study was to determine levels of Escherichia coli (E. coli), nitrogen, phosphorous, and total petroleum hydrocarbons in the irrigation water that contains stormwater runoff. Results of the study showed that the irrigation water E. coli level of 91mpn/100ml was below both United States Environmental Protection Agency (U.S. EPA) and Virginia Department of Environmental Quality (VA DEQ) recreational freshwater system standards. Total nitrogen of 0.3 mg/L, Total Kjeldahl Nitrogen of 0.28 mg/L, and nitrate + nitrite of <0.1 mg/L indicate that the irrigation water quality is very near U.S. EPA reference conditions. Total ammonia nitrogen of 0.19 mg N/L was well below VA DEQ surface freshwater criteria. Results from two separate testing methods show total phosphorus levels at 0.05 mg/L and 0.16 mg/L which indicates the irrigation water level is above both U.S. EPA reference conditions and VA DEQ water quality criteria levels. Total Petroleum Hydrocarbons-Volatiles (Gas Range Organics) and Total Petroleum Hydrocarbons-Semi-Volatiles (Oil Range Organics) levels of < 0.5 mg/L and 1 mg/L were below Lab Quantitation Limits indicating that results are below applicable limits as established by the U.S. EPA.