by Gregory Field
At a meeting of the Citizen Advisory Group on the Waimanalo Wastewater Facilities Plan, Roy Abe of Hawaii Pacific Engineers revealed in general terms the results of the survey. He said in response to a question if residents would choose to be on sewers if onsite systems were found to be harmful to the environment, 45% said "yes." If onsite systems were not causing a problem, 23% said they would still prefer to be on the sewer line. He did not reveal the full results of the survey but said the information would be available soon.
It was pointed out by residents that there is no evidence to indicate that the onsite systems are causing any environmental problems in the groundwater or Waimanalo Bay, and therefor no basis on environmental reasons for a decision. If the decision to sewer or not to sewer were based on economic reasons, sewering the Beach Lots and Bell Street area would be very costly for both the City and the homeowner. In the words of one resident "If it ain't broke, don't fix it."
Mr. Abe presented a diagram illustrating a geological cross section of
Waimanalo. In the area near the beach, the uppermost layer is sand. Underlying
the sand is an impervious layer. Below that is a porous calcareous
layer--originally coral deposits. He related that liquid effluent from the
Wastewater Treatment Plant is discharged via injection wells into this porous
calcareous layer. This porous layer provides no filtering. Onsite systems, on
the otherhand, leach liquid effluent into the sand which is an excellent
filter.
Mr. Abe described the monitoring with the test wells drilled in the Beach lot area. Two 4 inch diameter wells were installed on Laumilo Street near Alaihi and Huli Streets; two similar wells were installed upgradient at the mauka end of Alaihi and Huli Streets. The wells will be sampled and tested for nitrogen, phosphorous, silica, pH, turbidity, salinity and microbiological contaminants. Six samples over three months will be taken from each well and analyzed by Dr. Aly El-Kady of the Department of Geology and Geophysics, and Dr. Roger Fujioka of the Water Resources Research Center of UH.
Also discussed at the meeting was the possibility of water reuse as part of the up-grade at the Waimanalo Wastewater Treatment Plant. Mr. Abe stated that the State Department of Agriculture was interested in using the liquid effluent for irrigation of certain crops. If this were to come about, a separate reservoir and water transmission line would be required as some farmers, depending on their crops, would not be able to use re-use water. Also discussed were pond systems to bring the effluent to a higher level of treatment. A low tech system to treat current effluent levels would require 76 acres; a high tech system with aeration, would require 37 acres. Either pond system would require lining the pond and extensive pipe work.
For more information about the Waimanalo Wastewater Facilities Plan contact Roy Abe at 524-3771. For information about the Citizen Advisory Group contact Nancy Glover at 259-8946.