Department of Civil & Environmental Engineering, Northern Arizona University, Flagstaff, AZ 86011
The final design will consist of a STEG (Septic Tank Effluent Gravity) system with constructed wetlands.  The design incorporates five public use facilities located within the community.  Each facility will include restrooms, sinks, and showers and will be located near community and residential centers.  With each facility, a septic tank (or interceptor tank) will be added for primary treatment purposes.  The clarified effluent will be piped to constructed wetlands at lower elevations near the community.  After treatment in the wetlands, the effluent is dispersed into the soil for further filtration and eventually into the ocean.
Septic tanks located directly next to each facility will remove 75% of suspended solids in the system, as well as initially lowering the BOD from 300 mg/L to 130 mg/L.  The wetlands reduce the BOD an additional 85% down to 20 mg/L.  The facilities will feed clarified effluent through a 2” sewer pipe to the 4” main line.  The wastewater is then transported by gravity down to the wetlands.
Three cells of 70 ft x 25 ft will provide sufficient hydraulic control.  The first two cells will be lined with a clay or synthetic liner to prevent seepage of contaminants.  The third cell will not have a liner and allow for effluent dispersal into the ground for further treatment as well as groundwater recharge.  Filter media in the wetlands will consist of rounded stone at the inlets and outlets with the remainder being course sand. Local vegetation such as bulrush, reeds, cattails, and mangroves will help transport oxygen deep into the media.  This final effluent is compliant with EPA standards for discharge into the environment.
The community of Policárpo is located on the Honduran island of Roatán. Most houses are currently without electricity or bathroom facilities, which is the leading cause of poor sanitary conditions in the community.  The Roatán Design Group will develop a wastewater management system design, with the aid of the EPA Design Guide, to improve the existing sanitary conditions of the community.  In January 2009, a site visit was conducted by our team to collect data on the soil and surface water characteristics, topography, local culture, and design alternatives.  The design incorporates a septic system to settle out solids, with a constructed wetland for treating the effluent.  However, due to lack of space and the high cost of land on the island, the client is provided with an alternate system design, which implements a self-contained treatment system.
Current housing conditions in Policárpo are subject to available materials people can find on the island.  Many houses use bags of cement as foundations, and keep their houses wrapped in tarps until they can find enough wood to cover the outside.  Most houses now have piped drinking water available which they can store in case of  power outages.  Rainwater collection is common during the wet seasons and is stored in collection barrels.  Few homes have bathroom facilities adequate for the amount of people using the facilities, and consist of an outhouse in the back attached to a large cesspit.  The lack of regulated facilities diminishes the water and soil quality of the entire area.
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Water-borne illnesses and deaths have been reported throughout the community.  Surface water samples came back positive for E-coli, fecal coliform, and several other contaminants.  After installation of a wastewater treatment system, we project these contaminants will diminish along with water related illnesses.
The constituents in the runoff are currently damaging the 2nd largest barrier reef in the world.  If the reef continues to be harmed, the amount of tourism on the island will drop and the economy will be greatly impacted.  With the proposed wastewater treatment system in place, the pollutant level will be reduced and effects on the oceanic ecosystem will be minimized.
EGR Design
Sponsors: Ron & Jamie McDonald, Henry & Frances Zittrower, Mike Hayes, Living Water 4 Roatán.
Faculty/Advisors:  Dr. Paul Trotta, P.E., Dr. Joshua Hewes, P.E., Dr. Wilbert Odem, P.E., Dr. Bob Shinham, P.E.
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"Septic Field Size Determination Methods - Septic Systems Design, Inspection, Testing, & Maintenance - detailed how to information - an online textbook - Chapter on Septic Absorption Field Size - drain fields, leach fields, etc." InspectAPedia Building & Environmental Problem Diagnostic & Repair Encyclopedia. 9 Mar. 2009 <http://www.inspect-ny.com/septic/fieldsize.htm>.
 
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Due to the difficulty of obtaining land on the island, the group designed a second option.   Community facilities will still be installed, but aerobic digesters will be utilized in place of septic tanks and constructed wetlands.  Aerobic digesters will be able to remove the high BOD concentrations before discharging the effluent into the soil without requiring a large footprint.  These systems are more expensive and require more maintenance than the constructed wetland, but are effective in the overall treatment process.
Future involvement in Policárpo will bring a better quality of life to the community.  Upkeep with trash collection, roadway repair, and erosion control are all substantial projects which need to be addressed.  One of the biggest factors is community education.  Currently a community center is underway, which will help provide general community education and strengthen responsibility for the system.
The Roatán Design Group completed an efficient and convenient system design for the community of Policárpo.  This system is easily maintained and can be expanded to accommod-ate additional communities.  Local vegetation in the wetlands will provide an aesthetically pleasing and environmentally integrated system.  The public facilities will be easily accessed from several locations within the community and will improve the overall sanitary
conditions.  Education is a key factor in the project’s success.  The residents of Policárpo should be involved in the system installation so they develop a sense ownership and responsibility.
Laura Langdon, Stephanie Lindstrom, Michael Martuscello, & David McDonald