Approved by the Energy, Environment, and Water Policy Committee on February 25, 2021
Approved by Public Policy and Practice Committee on May 4, 2021
Adopted by the Board of Direction on July 16, 2021


The American Society of Civil Engineers (ASCE) supports efforts to reduce harmful algal blooms and hypoxia through:

  • Continued federal support for the Harmful Algal Bloom (HAB) and Hypoxia Research and Control Acts and their amendments. 
  • Continued funding for research, development, education, and monitoring of HABs and hypoxic events, including the development of a comprehensive database by which to more accurately monitor and assess HABs and hypoxia occurrences and to improve data access by government agencies and the public. 
  • Public outreach and education regarding effluent guidelines for industrial and municipal discharges that may contain nutrient-related limits. 
  • Continued funding for state-implemented operational nonpoint source management programs and other efforts to reduce, control, and prevent HABs and hypoxic events. 
  • Timely development of action plans to reduce, mitigate, monitor, and control hypoxia and HABs.
  • The Environmental Protection Agency (EPA) establishing human health advisories for microcystins, and standard analytical procedures for measuring toxin concentrations in drinking water and recommending feasible drinking water treatment techniques to remove microcystin toxins from drinking water supplies. 


Harmful algal blooms (HABs) are episodes of excessive growth of poisonous algae that upon ingestion can cause illness or death in humans, pets, wildlife, or food sources such as fish and shellfish. HABs occur in fresh and marine waters and upon death result in the depletion of oxygen (hypoxia) in the water. HABs and hypoxic events are known to affect all U.S. Waters. The frequency and geographic distribution of HABs and hypoxia occurrences have increased. 

HABs generate toxins that pose human health risks. Blooms can cause taste and odor problems and are associated with the death of wildlife and livestock. HABs have been responsible for contamination of drinking water supplies. In August 2014, the City of Toledo, Ohio issued a "Do not drink" order for almost a half million people when a drinking water treatment plant measured high levels of cyanoHAB in Lake Erie.

Hypoxic areas, also called “dead zones,” frequently occur in coastal and estuarine areas where rivers introduce nutrient-rich freshwater. There are over 405 hypoxic zones around the world (Science, 2008). In recent decades, large areas of hypoxia have occurred in the Gulf of Mexico, along the Oregon coast, and in the Chesapeake Bay. The most notable dead zone in U.S. waters is located in the Gulf of Mexico. This dead zone has been detected annually since the 1970s and is reported by EPA to be the second largest in the world. Since 2000, a concerted federal/state multi-interagency Hypoxia Task Force effort has been underway to reduce this hypoxic zone.  


HABs and hypoxia can be caused by natural processes; however, the predominant reason for growth is associated with human activities that have increased nutrient and organic loadings to marine and fresh waters. Sources of nutrients include discharges from point and non-point sources. Other causes can be attributed to man-made alterations to waterways and land development. 

Congress recognized the severity of the impacts caused by HABs and hypoxia in 1998 through the passage of the HAB and Hypoxia Research and Control Act of 1998 (P.L. 108-456) and its amendments in 2004 (P.L. 108-456) and 2014 (P.L. 113-124).  Congress has also appropriated over $250 million dollars (1999 through 2018) to support the work required through the Acts. The 2014 amendment established a national program and Federal interagency task force, the Interagency Working Group on Harmful Algal Bloom and Hypoxia Research and Control Act (IWG-HABHRCA) to advance the understanding of HABs and hypoxia events and to develop assessments, mitigation plans, and action plans for controlling hypoxic events.

ASCE Policy Statement 482
First Approved in 2000