Dry Swales

11/12/2025

“How do we categorize water quality swales that are dry for most of the time?”

Water quality swales treat stormwater runoff using vegetated open channels. Not all of these interventions are designed the same. Some are dry for most of the time, giving them the name Dry Swales. Dry swales have specifically selected, highly permeable soil, an underdrain system, and surrounding check dams. Dry swales provide strong performance for metals and nitrate removal, but have higher costs from using highly permeable soils and underdrain systems.

Image credit: https://aqualisco.com/

Water Quality Swales

11/11/25

“How can we treat stormwater runoff using vegetated open channels?”

Stormwater runoff can carry pollution into nearby water bodies. Government bodies may require building and construction operators to slow down and treat stormwater pollution loads coming from their properties. So what’s one way people can accomplish this without using a complicated system? Well, we know that vegetation naturally slows down water and absorbs pollutants while providing infiltration potential. We also know that directing water through a channel allows people to manage the direction of flow. So what if we were to create landscaped vegetation channels that can slow down water, allowing for sediments to settle, infiltration to occur, and pollutants/nutrients to get trapped? Well, this is the basis for Water Quality Swales. Water quality swale slopes are typically at a gentle 3 feet horizontal by 1 foot vertical slope to avoid quick channel flow and maximize surface area for filtration. Land-use managers should install water quality swales before impervious surfaces to enable proper infiltration.

Image credit: https://megamanual.geosyntec.com/

No Net Increase

11/08/25

“How do we ensure new developments don’t increase the amount of hazardous substances in a body of water?”

People generally don’t want a water body to become more polluted, especially if it already has many hazards. Consequently, environmental regulators work to prevent more toxins from entering sewer systems using No Net Increase rules. No net increase regulations state that any development must not increase the amount of pollutants entering the water body of release. Infrastructure and construction operators must undertake best management practices to satisfy no net increase rules. One approach is to remove as much pollution as you discharge.

Why New York City’s Gowanus Canal is So Polluted

11/05/25

“Why is the Gowanus Canal so polluted?”

The Gowanus Canal has been a fixture of Brooklyn for the past 150 years. Built as a major industrial transportation route, the body of water was subject to decades of pollution from surrounding coal yards, tanneries, machine shops, and many other types of industrial activity. The canal’s design prevented regular movement between the more oxygenated water in New York Harbor and the deoxygenated water in the canal, leading to a filthy, pathogen-infested environment. People also used the Gowanus Canal to carry out illegal dumping activities. Combined sewer overflow events dump raw sewage into the canal during heavy rainstorms. When we look at these reasons together, it’s easy to see Why New York City’s Gowanus Canal is So Polluted.

Image credit: https://cdn.vox-cdn.com/

Soil Compression Index

09/07/25

“How can we measure the compressibility of fine-grained soils to effective stress?”

When soil is drained of water and air, the particles will close together and consolidate, increasing effective stress. The Soil Compressive Index measures the ratio of the change in void ratio to the change in effective vertical stress. The equation solid compression index = change in void ratio/log_10(final effective vertical stress/initial effective vertical stress), or C_c = delta_e/(log_10(sigma_2’/sigma_1’)), governs the solid compression index.