Cost effective actions to mitigate land-based sources of pollution in West Maui through decision models
Vision: Healthy and resilient coral reefs that support marine life and sustainable human use as a result of active watershed stewardship by businesses and the public, reducing land-based pollution in Kā‘anapali from ma‘uka to makai.
Why reduce nitrogen?
Vision: Healthy and resilient coral reefs that support marine life and sustainable human use as a result of active watershed stewardship by businesses and the public, reducing land-based pollution in Kā‘anapali from ma‘uka to makai.
Every alternative, or management decision, has costs, benefits, and constraints that decisions may be based upon.
Cost, over 30 years, of an OSDS ugrade option varies by system combo (treatment system + disposal system).
Benefit, or the amount of N reduced from wastewater effluent, also varies by system combo.
Different upgrade systems have different site-condition constraints.
Costs, benefits, constraints
Every alternative, or management decision, has costs, benefits, and constraints that decisions may be based upon.
Cost, over 30 years, of an OSDS ugrade option varies by system combo (treatment system + disposal system).
Benefit, or the amount of N reduced from wastewater effluent, also varies by system combo.
Different upgrade systems have different site-condition constraints.
Nutrient reduction with previous conversion to sewer:
Nutrient reduction under different upgrade scenarios:
Cost efficiency of different upgrade scenarios:
Nitrogen reduction and costs
Nutrient reduction with previous conversion to sewer:
Nutrient reduction under different upgrade scenarios:
Cost efficiency of different upgrade scenarios:
Decisions may be based on many factors, and may be weighted by certain priorities.
Decision factors: lowest cost, highest benefit, best cost efficiency ("bang for buck")
Weightings: proximity to reef, visitation value.
Conclusions:
- OSDS is one part of a bigger problem (pollution into the ocean), but it is a manageable piece, and addressing this piece can benefit the health of Hawaii's nearshore ecosystems.
- In West Maui, connecting properties previously on cesspools to sewer systems has reduced nutrient input in the past decade. Nutrient input (and other pollutants) can be further reduced by upgrading the remaining properties to better treatment systems.
- Management decisions are based on a suite of factors, constraints, priorities, and assumptions, and decision science provides a strucutre by which to evaluate those decisions.
Decision-making
Decisions may be based on many factors, and may be weighted by certain priorities.
Decision factors: lowest cost, highest benefit, best cost efficiency ("bang for buck")
Weightings: proximity to reef, visitation value.
Conclusions:
- OSDS is one part of a bigger problem (pollution into the ocean), but it is a manageable piece, and addressing this piece can benefit the health of Hawaii's nearshore ecosystems.
- In West Maui, connecting properties previously on cesspools to sewer systems has reduced nutrient input in the past decade. Nutrient input (and other pollutants) can be further reduced by upgrading the remaining properties to better treatment systems.
- Management decisions are based on a suite of factors, constraints, priorities, and assumptions, and decision science provides a strucutre by which to evaluate those decisions.
