Coastal Water Quality
Land-based sources of pollutants, such as sediment, nutrients, and contaminants, are one of several factors threatening water quality and coral reef ecosystems in Hawai‘i. These pollutants are transported in surface water runoff and by groundwater seepage into coastal waters. While the complex interrelationship between land-based sources of pollution, water quality, and the health and integrity of coral reef ecosystems is not well understood, enough is known to require management policies that minimize polluted surface water runoff. Tools, such as the Nonpoint Source Pollution and Erosion Comparison tool, are also available to help understand this relationship and potential impacts of polluted runoff (see the Spatial Information: Coastal Water Quality Tool section for more information).
Coastal Waters
All Hawai‘i State waters are classified as Class A or Class AA. Class A waters have strict pollution discharge regulations to protect them for recreational and aesthetic enjoyment. Class AA waters have regulations against discharge to protect the waters in a natural pristine state. The Wai‘anae coast is designated Class A waters from Barbers Point at the southern end to Mākua Beach. The waters from Mākua Beach to Ka‘ena Point are designated Class AA.
Water quality studies along the Wai‘anae coast describe a "pristine, unperturbed coastal region." Temperature and salinity values indicate that the region is well flushed and minimally affected by surface runoff of terrestrial sediments (Bienfang and Brock 1980, Koch and others 2004, Natural Resources Defense Council [NRDC] 2004). Although these studies described excellent water quality, two concerns regarding pollution have been cited. First, the water quality appears more compromised in the southernmost part of the coast. This appears to be related to runoff associated with development at Barbers Point and even pollution from Pearl and Honolulu Harbors during strong storm events (Bienfang and Brock 1980). These more turbid waters have been seen moving northward along the coast during falling tide conditions. Second, there is some indication that groundwater percolation may be occurring along the shoreline. Groundwater in Wai‘anae has approximately 1,000 fold more dissolved nitrate than does the adjacent marine waters due to leaching from fertilization of agricultural lands. This problem has led to devastating algal blooms in other coastal waters around Hawai‘i , although no intense or persistent algal blooms have been documented in Wai‘anae.
Department of Health Activities
The State Department of Health, Clean Water Branch monitors coastal water quality through the federal Beaches Environmental Assessment and Coastal Health (BEACH) Act and sponsors polluted runoff control projects through the Polluted Runoff Control Program of the U.S. Environmental Protection Agency (EPA).
In 2004, the state received $324,000 of federal grant money through the BEACH Act. The latest available data set is from 2002 (State of Hawaii Department of Health 2002). The following is the status of the beaches in Wai‘anae:
- Mākaha Beach and Pōka‘ī Bay were listed for increased levels of total nitrogen, chlorophyll a, and turbidity. These results were assigned a low priority, indicating either that the levels were only slightly elevated or were due to a temporal event, such as a heavy rain (Koch and others 2004).
- Mā‘ili Beach Park, Maipaloa Beach and Nānākuli Beach were monitored weekly in 2002 and exhibited no elevated levels of nutrients, chlorophyll a, or excess turbidity.
- Mā‘ili Beach Park has no known stormwater or pollution source, although Maipalaoa Beach and Nānākuli Beach do.
- There were no beach closings in 2003 due to pollution (NRDC 2004).
The Wai‘anae Coast Community-Based Watershed Management Project is a product of the Polluted Runoff Control Program. The project's goal was to increase Wai‘anae coast residents' sense of watershed stewardship and prevent further degradation of water quality due to human impacts. This was accomplished through water quality monitoring by Wai‘anae High School students, the removal of 1600 pounds of trash by volunteers from streams and beaches, and the production of public outreach materials (State of Hawaii Department of Health 2002).
Stream Discharge
Many of the streams of the Wai‘anae moku have been channelized through the urban areas. This causes water to reach the ocean much quicker, potentially increasing levels of trash, nutrients and other pollutants entering the coastal water. In spite of this, only one stream, Kaupuni Stream, was on the 2004 list of impaired waters in Hawai‘i (Koch and others 2004). Of the 70 streams in the report, Kaupuni Stream is considered a medium priority listing with nutrients, turbidity and trash as the primary pollutants. Ulehawa Stream was the focus of a community-based trash monitoring and clean up in 2001-2002. Three debris boom barriers were installed in 2001, which trapped 600 bags of trash entering the ocean over an 18-month period.
Wai‘anae Wastewater Treatment Plant
The Wai‘anae Wastewater Treatment Plant earned a national award for achieving perfect compliance with the terms of its federal pollutant discharge permit for five consecutive years.
Source: CZM Hawai‘iThe Wai‘anae Wastewater Treatment Plant (WWTP) outfall pipeline was installed in 1986 and extends 1.8 kilometers (1.1 miles) offshore into 33 meters (108 feet) of water. In 1996, the WWTP was converted from a primary to a secondary WWTP, reducing the concentration of the effluent entering the ocean. The long-term monitoring program at the diffuser reported an immediate drop in levels of suspended particles and nutrients. The plant received a national award in 2001 based on its effectiveness in removing suspended solids, pathogenic bacteria, and toxic heavy metals from its wastewater from 1995 through 2000, in accordance with the terms of its National Pollutant Discharge Elimination System (NPDES) permits (City and County of Honolulu 2001).
References Cited
Bienfang, P.K., and R.E. Brock. 1980. Predevelopment Reconnaissance of the Water Quality and Macrobiota Conditions Affronting the West Beach Coastline, Oahu, Hawaii. Technical Report Submitted to Environmental Communications, Inc.
City and County of Honolulu. 2001. Waianae Wastewater Plant Wins National Award [News Release]. http://www.co.honolulu.hi.us/csd/publiccom/honnews01/amsa.htm
Koch, L., J. Harrigan-Lum, and K. Henderson. 2004. Final 2004 List of Impaired Waters in Hawaii Prepared under Clean Water Act §303(d). Hawaii State Department of Health, Environmental Planning Office. http://www.hawaii.gov/health/environmental/env-planning/wqm/wqm.html#303pcd
Natural Resources Defense Council (NRDC). 2004. Testing the Waters: A Guide to Water Quality at Vacation Beaches. http://www2.nrdc.org/water/oceans/ttw/sumhaw.pdf
State of Hawaii Department of Health. 2002. Hawaii's Polluted Runoff Control Program [End of Year Report - Fiscal Year 2002]. Clean Water Branch: Polluted Runoff Control Program. http://www.hawaii.gov/health/environmental/water/cleanwater/prc/2002rpt-index.html
