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==Groundwater== | ==Groundwater== | ||
− | + | Primary sources of information for this section on groundwater, unless otherwise indicated, are the following papers. | |
+ | *[http://www.metrocouncil.org/Wastewater-Water/Publications-And-Resources/WATER-SUPPLY-PLANNING/Impact-of-Stormwater.aspx Nieber et al.] (2014). The authors provide an extensive literature review and provide results of an 18 month study of water quality beneath three infiltration systems. | ||
+ | *[http://www.pca.state.mn.us/index.php/view-document.html?gid=7732 Weiss et al.], (2008). The authors provide an extensive literature review of studies on groundwater impacts associated with stormwater infiltration. | ||
+ | *[http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.404.9299&rep=rep1&type=pdf Pitt et al.] (2002). The authors discuss the potential for groundwater contamination resulting from stormwater infiltration based on the chemical properties of the pollutant and the characteristics of the stormwater treatment system. The paper includes additional references and work done by the same authors in the 1990's. | ||
===Potential risk of different chemicals to groundwater=== | ===Potential risk of different chemicals to groundwater=== | ||
The risk of groundwater contamination from different chemicals is summarized below. Specific information for each chemcial can be found at the links below. | The risk of groundwater contamination from different chemicals is summarized below. Specific information for each chemcial can be found at the links below. | ||
− | *[http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Metals_in_stormwater '''Heavy metals''']. Heavy metals are typically present at low levels in urban stormwater and are generally retained in the upper soil layers via adsorption to solid particles. They therefore represent a low risk to groundwater except in certain specific areas, such as vehicle operations and outdoor storage areas. Eventual breakthrough can occur in filter media due to the finite sorption capacities of the media. Periodic replacement of the upper soil layer within infiltration systems will maintain low soil concentrations and decrease the potential for contaminating groundwater. | + | *[http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Metals_in_stormwater '''Heavy metals''']. Heavy metals are typically present at low levels in urban stormwater and are generally retained in the upper soil layers via adsorption to solid particles. They therefore represent a low risk to groundwater except in certain specific areas, such as vehicle operations and outdoor storage areas. Eventual breakthrough can occur in filter media due to the finite sorption capacities of the media, but this is not expected for decades in most media. [[Glossary#K|Kakuturu and Clark]] (2015) observed displacement and downward migration of metals from bioretention media by sodium at salt concentrations of 150 and 1200 milligrams per liter. Periodic replacement of the upper soil layer within infiltration systems will maintain low soil concentrations and decrease the potential for contaminating groundwater. Runoff water containing high concentrations of sodium from road salt application should not be introduced into infiltration practices when concentrations of metals in the runoff are elevated. |
*'''Organic compounds''' ([http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Pesticides_in_stormwater Pesticides]; [http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Polycyclic_Aromatic_Hydrocarbons_.28PAHs.29_in_stormwater PAHs]; [http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Volatile_Organic_Compounds_.28VOCs.29_in_stormwater VOCs]). Because of the diversity of organic compounds, it is difficult to generalize, but typically these are at low concentration in stormwater runoff. Many compounds are attenuated within the infiltration media, where they may be degraded or immobilized. Risk to groundwater from organic chemicals is typically low. BMPs with little or no organic material, particularly underground practices, may present some risk if concentrations of organic chemicals are elevated in stormwater runoff. | *'''Organic compounds''' ([http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Pesticides_in_stormwater Pesticides]; [http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Polycyclic_Aromatic_Hydrocarbons_.28PAHs.29_in_stormwater PAHs]; [http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Volatile_Organic_Compounds_.28VOCs.29_in_stormwater VOCs]). Because of the diversity of organic compounds, it is difficult to generalize, but typically these are at low concentration in stormwater runoff. Many compounds are attenuated within the infiltration media, where they may be degraded or immobilized. Risk to groundwater from organic chemicals is typically low. BMPs with little or no organic material, particularly underground practices, may present some risk if concentrations of organic chemicals are elevated in stormwater runoff. | ||
*[http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Nitrogen_in_stormwater '''Nitrate''']. Although nitrate is poorly attenuated in most infiltration BMPs, concentrations in stormwater are generally low, resulting in low risk to groundwater. | *[http://stormwater.pca.state.mn.us/index.php/Pollutant_fate_and_transport_in_stormwater_infiltration_systems#Nitrogen_in_stormwater '''Nitrate''']. Although nitrate is poorly attenuated in most infiltration BMPs, concentrations in stormwater are generally low, resulting in low risk to groundwater. |
This page provides information on surface water and groundwater impacts associated with infiltration of stormwater runoff.
Primary sources of information for this section on groundwater, unless otherwise indicated, are the following papers.
The risk of groundwater contamination from different chemicals is summarized below. Specific information for each chemcial can be found at the links below.
Pitt et al. (2002) evaluate groundwater risk based on three factors: chemical mobility, abundance of the chemical in stormwater runoff, and the likelihood of the chemical being attenuated through sedimentation practices, with the most limiting of these factors determining the risk. Table 1 in the paper provides a summary of the risk to groundwater for several chemicals that may potentially impact groundwater.