Atch_3_Wastewater_Design_Document.pdf

YAKUTAT RANGER DISTRICT, TONGASS N.F.

YAKUTAT EMPLOYEE HOUSING

WASTEWATER DESIGN DOCUMENT

Contract No. 53-0116-3-00611

June 29, 2004

Prepared for: Prepared by:

USDA Forest Service Tryck Nyman Hayes, Inc.

648 Mission St., Federal Bldg. 911 W. 8th Ave., Suite 300 Ketchikan, AK 99901 Anchorage, AK 99501

NOTE:

PAGE 62 MODIFIED WITH CALCULATION FOR #2 DRAINFIELD SIZED

FOR 2 - THREE BEDROOM HOUSES. (06-15-2012 SMJ)

TABLE OF CONTENTS

INTRODUCTION

SITE NARRATIVE

DESIGN CRITERIA

DRAINFIELD CRITERIA

DESIGN CONCEPT

OPERATIONS & MAINTENANCE CONSIDERATIONS

REFERENCES

APPENDICES

A YAKUTAT WASTEWATER DESIGN REPORT (YWDR)

B WASTEWATER CIVIL SHEETS

C SOIL LOGS & PERCOLATION TEST RESULTS

D NSF/ANSI STANDARD 40 RESIDENTIAL WASTEWATER TREATMENT SYSTEMS

E DESIGN CALCULATIONS

INTRODUCTION

This report presents the design of six septic systems required for the Yakutat Administrative Housing in Yakutat, Alaska. A summary of the appropriate design criteria and an evaluation of different wastewater treatment systems/techniques shall be presented. The most appropriate system is recommended based upon evaluation of site–specific conditions and needs.

There are currently four separate onsite septic systems serving 6 residences, one 12-person barracks, and a warehouse at the Yakutat Administrative Site. The Forest Service is proposing to construct 6 new residences at the site. Six new wastewater systems will be developed at the site to serve these 6 residences.

A Yakutat Administrative Housing Wastewater Design Report (YWDR) was prepared by Gerald Herbrandson, Yakutat Ranger District, Tongass, N.F., on November 5, 2003. A copy of the YWDR is located in Appendix A. It describes the existing site, identifies need, design criteria, discussion of wastewater systems considered, recommendation of a wastewater system, associated costs, and O&M. Since these conditions have been evaluated and a recommendation has been given in the YWDR, this report follows upon the recommendation given in the YWDR. Any summaries addressing these conditions have been referenced from the YWDR. The recommendation stated in the Wastewater Design Report is an extended aeration tank (treatment unit) with a raised mound absorption bed and ultraviolet (UV) treatment.

However, a Value Analysis performed by the Forest Service on February 23 – 26, 2004, has changed the recommendation of mound absorption beds to standard shallow trench drainfields.

Tryck Nyman Hayes, Inc. has been contracted by the Yakutat Ranger District, Tongass N.F. to provide the design for six new septic systems to serve the six new residences. The system has been designed in accordance with State of Alaska, Department of Environmental Conservation (ADEC) regulations, as described 18 AAC 72 Wastewater Disposal, as amended through July 11, 2002. Other references used in preparing this design are listed immediately following this report.

It is the intent of this design to provide the Yakutat Ranger District, Tongass N.F. with the most beneficial wastewater collection, treatment and dispersal system based on long-term use and cost effectiveness.

SITE NARRATIVE

The City and Borough of Yakutat is located at 139° 44’ W and 59° 33’ N. It is approximately 300 miles southeast of Anchorage and 200 miles northwest of Juneau. The Yakutat Administrative site is located in the Yakutat Ranger District, approximately 3 miles SE of the City of Yakutat near the public airport. The Administrative Site is on 20 acres of land. The buildings are served by local electrical and telephone utility, so there is availability of continuous power. There are no local water and wastewater utilities, therefore on-site systems are required. However, the excessive distance to the community utility system results in a lack of local maintenance and service personnel on-site.

The topography is fairly level but heavily wooded so there is not much available space. Soils consist of very well-drained sandy gravels and cobble. There is a high water table and low ground temperature. Soils yield a high percolation rate. A seasonal high ground water table is reported to reach 6-inches above ground surface in several of the lower areas of the compound.

The existing septic system for the Yakutat Administrative Housing currently consists of four separate onsite septic systems serving: 1) the ranger house, 2) a modular home, 3) 12-person barracks, and 4) 3 mobile trailers + 2 modular units. Upon completion of improvements planned for the Yakutat Administrative Housing in 2005, six new on-site wastewater treatment systems and three drainfields will be constructed as shown in Table 1.

Table 1. New Employee Housing Septic Systems, Yakutat, Alaska.

Housing Number1 Test Pit2 Bedrooms1 Septic Tank Drainfield #1/#2 TP-9 2-bdrm/3-bdrm 2 1 #3/#4 TP-5 2-bdrm/3-bdrm 2 1 #5/#6 TP-2 3-bdrm/3-bdrm 2 1

1 As labeled on Wastewater Site Plan. See Appendix B.

2 Performed by Shannon & Wilson on January 2004. See Appendix C.

Each house will have its own treatment unit and UV unit, but will share a common drainfield with another new house within the closest vicinity. One drainfield per two houses will save on costs and space since available cleared land is limited.

Water service for the Housing has in the past been provided by a Class C water well located at least 100 feet horizontally from the new septic drainfields. The water well was installed in 1965.

The water distribution system and pressure tanks were replaced approximately 5 years ago.

The existing water system is unchlorinated and unfiltered. A pump house on top of the well casing produces between 50 to 70 gpm. No water meter readings have been recorded. This Class C water well will be replaced by a Class B water well in the summer of 2004. The new wastewater components have been located at least 200 feet horizontally from the proposed Class B well site.

An Environmental Assessment has been prepared for the proposed development including the wastewater treatment systems. No adverse impacts from the installation of the new system are foreseen.

DESIGN CRITERIA

Site evaluations were conducted by the Forest Service. The YWDR gives a Design Criteria which was referenced from 18 AAC 72 ADEC Wastewater Treatment and Disposal. All new septic systems were designed and located under these conditions. The wastewater systems were also designed in general conformance with the Site Development Plans. The Design includes the preparation of application to ADEC for Plan Review and Approval to Construct.

On January 2004, soil evaluations were conducted at the Yakutat Administrative site by Shannon and Wilson. Eleven test pits were dug at eleven different sites. At each of the three proposed drainfield locations, one test pit was dug and one percolation test was performed. The summary of soil test results for the three new drainfield locations are shown in Table 2. The soil classification of Schoeneberger et al., 1998 was used to design the mound system based on Converse and Tyler, 2000.

Table 2. Test Pit Data for Three New Drainfield Locations for Yakutat Housing, January 2004.

ClassificationTest Pit Soil Composition (%) USCS 1 Schoeneberger et al., 1998 2

Groundwater Depth (feet)3

Percolation Rate (min/in)

TP-2 55% Gravel, 43% Sand, 2% Silt

GW COS 4.0 3.40

TP-5 51% Gravel, 46% Sand, 3% Silt

GW COS 4.0 4.85

TP-9 45% Gravel, 54% Sand, 2% Silt

GW COS 3.0 12.31

1 Wagner, A.A., 1957. The Use of the Unified Soil Classification System by the Bureau of Reclamation.

2 Schoeneberger et al., 1998. Soil Science Abbreviations from the Natural Resource Conservation of the United States Department of Agriculture.

3 Water levels are for January 9, 2004 and may vary.

The Forest Service in conjunction with ADEC requires that all the new septic systems installed for this project be NSF/ANSI STANDARD 40 certified. The NSF (National Sanitation Foundation) provides public health and safety-related information to consumers. Residential Wastewater Treatment Systems are classified as STANDARD 40. Appendix D lists all the latest NSF/ANSI STANDARD 40 systems which were downloaded off the internet. Appendix D-1 includes a summary sheet listing each system and the reason why it was not chosen. The bold-face systems in Appendix D-1 detail the preferred systems. These septic systems were chosen on the basis of:

� Service area � Distribution area � Complete model availability with a rated capacity of 500 gpd � Complete treatment systems tested by NSF

Using the above criteria, five systems fit the category. A steel tank was chosen due to its durable nature in all conditions.

A 5-day Carboneous Biochemical Oxygen Demand (CBOD5) and Total Suspended Solids (TSS) influent and effluent measurements were researched and presented for the five preferred septic systems in Appendix D-2. All five systems meet ADEC requirements, but the first choice was the Advantex AX20 Mode 1A system made by Orenco Systems, Inc. The results show the best CBOD5 and TSS percent reduction. The Advantex AX20 is also able to be used in all conditions, and O&M is low.

The Advantex AX20 systems satisfy ADEC and AWWU requirements and are currently installed in the Municipality of Anchorage and throughout the State of Alaska.

The Processing Tank has been sized at 1500 gallons which meets ADEC’s 18 AAC 72 Wastewater Disposal, as amended through July 11, 2002. The 1500-gallon Processing Tank also meets the size needed for the Treatment Recirculation Tank of 500 gallons.

The wastewater strength intended to be treated by this system is that defined as “medium concentration” in Table 3-16 of Wastewater Engineering, Treatment, Disposal, and Reuse (Metcalf and Eddy, Inc., 3rd Edition, 1991). The assumption is made that for any events that might cause a flow that exceeds the capacity, portable facilities will be brought onsite.

The recommended UV Treatment system is the UV3025K-PTP made by Trojan Technologies Inc. Designed as a generic type of UV disinfection unit, the Trojan Package Treatment Plant (PTP) is very price competitive and offers an "off-the-shelf" solution for operators with limited treatment requirements. The system uses low-pressure, low-output lamps. The advantages and benefits of UV are numerous. For example, UV technology:

· is EPA-endorsed

· destroys bacteria (E. coli), viruses (hepatitis and polio), and virtually all other water-borne pathogens

· destroys Giardia and Cryptosporidium which are resistant to chlorine

· eliminates harmful micropollutants (such as herbicides and pesticides)

· is safe to handle

· works at least 20 times faster than chlorine

· is environmentally friendly -- no toxic chemicals, no chlorine leaks

· produces no known disinfection by-products, unlike chlorine

· is more cost-effective than chlorine systems

DRAINFIELD CRITERIA

Even though there is a seasonal high water table in the project area, a shallow bed drainfield has been chosen for the dispersal system due to the high rate of treatment provided by the Advantex and UV units. This shallow bed system utilizes flow dividers to ensure even distribution of the effluent to each lateral in the system. The drainfields have been sized using an application rate determined as a result of the percolation tests (see Appendix B). The effective area of a shallow bed system is the area of the bottom of the bed (i.e., the sidewalls are not considered to add to the infiltrative surface). Each of the three beds occupies a slightly different area: 780 ft2 for Drainfield #1, 636 ft2 for Drainfield #2, and 756 ft2 for Drainfield #3.

One monitoring points will be installed in each of the three drainfield beds. Cleanouts will be installed such that access to the piping (distribution or laterals) is no greater than 100 feet between cleanouts.

The new drainfield beds will be scarified along the sides and bottoms, below the top of the drain rock, to remove any smearing caused by the excavator bucket. All drain rock will be specified as clean, washed rock. Finished vegetative cover for drainfield beds will be limited to grass only. Trees and bushes are prohibited because their roots can intrude into the drainfield laterals, restricting flow.

The laterals within each bed have been designed so that there is no more than 6 feet on-center between laterals and there is no more than 3 feet between a lateral and the edge of the shallow bed. The actual drainfield portions of the bed will be level, although the distribution lines that transport the effluent to the beds will slope at varying degrees no less than 2% and no more than 10%. The laterals have been designed such that the lengths do not exceed 63 feet;

shorter lengths tend to be more effective in distribution of the effluent along the length of the bed.

During the installation of the new system, the area over the existing drainfield will be cleared, topsoiled and seeded.

DESIGN CONCEPT

The preferred choice of the five NSF/ANSI STANDARD 40 systems was the Advantex Model AX20N by Orenco Systems, Inc. There are four Modes for the Advantex Model AX20N, Mode 1A, 1B, 3A, and 3B. Mode 1 recirculates the filtrate through the second compartment of the Processing Tank. Mode 3 recirculates the filtrate through the primary chamber of the tank to enhance nutrient removal. Mode A includes the Discharge Pump Basin and discharge filtrate exiting on the opposite side of the Processing Tank. The difference between A and B depends on whether the Discharge Pump Basin is included and the direction the discharge filtrate exits the system.

Mode 1A was chosen since the system must provide high treatment level and utilize a separate Processing/Recirculation Tank. The Advantex Model AX20 Mode 1A or engineer-approved equal will contain the following components:

� PVC Splice Box � Universal Biotube Pump Vault or engineer-approved equal, 57” typical height � Discharge Assembly � Float Switch Assembly � Orenco Pump, 115 V or engineer-approved equal � VCOM Advatex AXA/UV Panel, 115V � Recirc Splitter Valve Assembly � Advantex Filter or engineer-approved equal w/ Vent Assembly and Antiflotation

Flanges

Components that can be provided by Orenco Systems, Inc. include:

� 1500 gallon steel Processing tank

Components that are not provided by Orenco Systems, Inc. include:

� Sewer pipe from building to processing tank � External piping between tank, filter and final dispersal area � Ventilation piping � Electrical conduit and fittings � Dispersal area materials, such as rock, lateral piping, geotextile fabric, etc.

Insulation on the lid of the Advantex filter or engineer-approved equal, an anticondensation heater in the Control Panel, and a drainback style discharge assembly shall be used for cold weather treatment systems.

Raw sewage will enter the two-compartment Processing Tank through its inlet tee (see Appendix B). In the first compartment, the raw sewage separates into three distinct zones: a scum layer, a sludge layer, and a clear layer. A flow-through port in the Tank’s baffle wall allows effluent from the clear layer to flow into the second compartment of the tank. The Biotube Pump Package or engineer-approved equivalent in the second compartment pumps filtered effluent to a distribution manifold in the Advantex Filter or engineer-approved equivalent. Effluent percolates down through the textile media and is collected in the bottom of the filter pod. The treated effluent flows out of the filter pod through the Filtrate Return Line that returns the treated effluent to the Recirculating Splitter Valve (RSV). The RSV automatically splits or diverts the flow between the Processing Tank and the final discharge. The RSV also controls the liquid level within the Processing Tank. During extended period of no flow, 100% of the treated effluent is returned to the Processing Tank. The residential Advantex Filters or engineer-approved equivalent have a passive vent system and do not require the use of a fan.

Home with flows up to 500gpd require a minimum two-compartment, 1500 gallon tank with flow-through ports equaling a minimum flow-through area of not less than 12 in2 at 60-70% of the lowest normal liquid level.

A 24-inch insulated manhole riser will be installed over the septic tank to allow better access to the tank for operations and maintenance (O&M). The Advantex Treatment System, or engineer-approved equal, fits directly over the Processing Tank and its top lid should be level to the septic manhole accesses. The recessed bolts hold the watertight lid in place and can be removed when the filter needs cleaning. The risers facilitate improved accessibility in pumping the tank.

The preferred choice for an Ultraviolet treatment Unit is the Trojan UV 3025 PTP by Trojan Technologies, Inc, or an engineer approved equal, and will contain the following features:

� Optimized hydraulics within the UV system, with proper inlet and outlet flow conditions

� UV Modules constructed of type 316 stainless steel with excellent corrosion resistance

� Compact lightweight monitoring panel (no forced air cooling) � Triple seal lamp sockets which fully protect against moisture entry � Algae growth inhibition within the channel and transition connections � Compact design for simple installation � Stainless steel channel � Built-in weir

UV Modules are the basic building blocks of the UV Package Treatment System. Disinfection takes place within an array of lamps, with the UV lamps submerged in the liquid and parallel to the flow. The size and number of UV modules required in a particular application is determined by the flowrate, water/wastewater quality and disinfection requirements.

Power supply to the UV modules is provided through standard outdoor ground fault protected receptacles.

UV modules are mounted in a stainless steel channel. An overflow weir maintains correct water depth over the complete range of flowrates to be treated. A built in drain facilitates channel cleaning. The UV channel has been designed to be installed inside an insulated steel box (such as the Advantex filter basin) with an insulated, bolted lid for easy access.

OPERATIONS & MAINTENANCE CONSIDERATIONS

No Operator’s License is required for the recommended system. Both Advantex and Trojan Technologies will supply Operation and Maintenance Manuals for their equipment.

It is recommended that remote telemetry control panels coupled with a web-based monitoring application for communication and alarm management be installed with the Advantex system.

These control panels give water/wastewater system operators and maintenance organizations the ability to monitor and control each individual system’s operation remotely, with real-time efficiency. Vericomm AXA panels allow remote operators to change system parameters, including timer settings, from the web interface.

DRAINFIELD & COMPONENT INSPECTIONS

� Inspect all cleanouts to ensure that they have caps in place.

� Replace any missing caps.

� Inspect cleanouts for obstructions in the risers or effluent piping.

� Remove any obstructions noted.

� Inspect each monitoring point.

� Measure the effluent level in each port and record the level on the log.

� Check that each monitoring point is fitted with a cap. Replace any caps that are not in place.

� Inspect each flow divider riser. Replace any missing caps.

� Check the surface of the drainfield area.

� The surface is intended to be a grass area, which is free of brush and tree growth.

� Check for stored items on the drainfield.

� Moveable storage buildings, building materials, trash, etc. shall not be placed on the drainfield.

REFERENCES

Converse and Tyler, January 2000. Wisconsin Mound Soil Absorption System: Siting, Design, and Construction Manual. University of Wisconsin – Madison.

Herbrandson, Gerald, November 5, 2003. A Yakutat Administrative Housing Wastewater Design Report (YWDR). Yakutat Ranger District, Tongass, N.F.

Metcalf and Eddy, Inc, 1991. Wastewater Engineering, Treatment, Disposal, and Reuse. 3rd

Edition, McGraw-Hill.

National Sanitation Foundation website, February 2004. Listing of NSF/ANSI STANDARD 40 Residential Wastewater Treatment Systems.

http://www.nsf.org/certified/wastewater/Listings.asp?TradeName=&Standard=040

Orenco Systems, Inc., Advantex Treatment Systems Version 4.0. Sutherlin, OR 97479

State of Alaska, Department of Environmental Conservation (ADEC), as amended through July 11, 2002. 18 AAC 72 Wastewater Disposal.

State of Alaska, Department of Environmental Conservation (ADEC), as amended through January 17, 2002. Domestic Wastewater System Plan Review, Guidelines and Procedures

State of Alaska, Department of Environmental Conservation (ADEC), as amended through August 1, 2000. Installer’s Manual for Conventional Onsite Domestic Wastewater Treatment and Disposal Systems.

Schoeneberger et al., 1998. Soil Science Abbreviations from the Natural Resource Conservation of the United States Department of Agriculture.

Tyler, 2001. Hydraulic Wastewater Loading Rates to Soil. University of Wisconsin – Madison

Wagner, A.A., 1957. The Use of the Unified Soil Classification System by the Bureau of Reclamation: Proceedings, 4th International Conference on Soil Mechanics and Foundation Engineering (London), vol. I, p. 125.

APPENDIX A

YAKUTAT WASTEWATER DESIGN REPORT (YWDR)

APPENDIX B

WASTEWATER CIVIL SHEETS

APPENDIX C

SOIL LOGS & PERCOLATION TEST RESULTS

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APPENDIX A

TEST PIT LOGS AND GRAIN

SIZE CLASSIFICATION

LIST OF FIGURES

Figure A-1 Log of Test Pit TP-1 Figure A-2 Log of Test Pit TP-2 Figure A-3 Log of Test Pit TP-3 Figure A-4 Log of Test Pit TP-4 Figure A-5 Log of Test Pit TP-5 Figure A-6 Log of Test Pit TP-6 Figure A-7 Log of Test Pit TP-7 Figure A-8 Log of Test Pit TP-8 Figure A-9 Log of Test Pit TP-9 Figure A-10 Log of Test Pit TP-10 Figure A-11 Log of Test Pit TP-11 Figure A-12 Grain Size Classification

APPENDIX D

NSF/ANSI STANDARD 40

RESIDENTIAL WASTEWATER TREATMENT SYSTEMS

APPENDIX E

DESIGN CALCULATIONS

#2 DRAINFIELD DESIGN FOR THREE BEDROOM HOUSE:

USE 125 S.F. OF DRAINFIELD / BEDROOM

125 S.F. X 3 = 375 S.F.

TWO - THREE BEDROOM HOUSES SHARE DRAINFIELD:

2 X 375 S.F. = 750 S.F. OF DRAINFIELD

DIM = 12 FT. WIDE X 62.5 FT. LONG