B01 Attachment 3 Technical Provisions.pdf

TABLE OF CONTENTS

PAGE

1. EXCAVATION, TRENCHING, AND BACKFILLING………………………………1

2. SEWER SERVICE LINES……………………………………………………………..4

3. INDIVIDUAL SEPTIC TANK…………………….…………………………………..6

4. INDIVIDUAL LIFT STATION………………………………………………………..8

5. LOW PRESSURE-DOSED MOUND SYSTEM……………………………………..12

1/06 Technical Provisions- TP 3.0 Excavation, Trenching, and Backfilling Page 1

TECHNICAL PROVISION 3.0

EXCAVATION, TRENCHING, AND BACKFILLING

3.01 Scope of Work

The work covered by this section includes the furnishing of all plant, labor, tools, equipment, and material, and performing all operations in connection with the excavation, trenching, and backfilling for the installation of all pipelines, structures, and accessories, all in accordance with these technical provisions and applicable drawings.

3.02 Protection of Excavation

In conformance with applicable safety regulations, the Contractor shall provide suitable shoring and sheeting to protect all excavations and provide safe working conditions for workers.

3.03 Excavation

3.03.01 General

All excavation required for the performance of this contract shall be made by open cut methods unless otherwise shown on the drawings, required by applicable encroachment permits, or approved in writing by the Project Manager.

3.03.02 Trench Excavation

The sides of all trenches for the installation of utility piping systems shall be as nearly vertical as soil conditions permit below the level of the top of the pipe. The width of the trench shall not be less than 12-inches or more than 24-inches wider than the outside diameter of the pipe barrel. Trench excavation shall be centered on pipe alignment such that a minimum clear space of 6-inches is provided on each side of the pipe. Trench width above the level of the top of the pipe may be as wide as necessary for shoring and sheeting, and for proper installation of the work.

The depth of all trenches shall be as indicated on the drawings. If not otherwise specified, the depth of all trenches shall be sufficient to provide a minimum cover of 24-inches at all locations after final backfilling.

Unless otherwise required by applicable permits to be less, the maximum length of trench that may be left open at any one time shall not exceed 500-feet. No trenches shall be left open unless otherwise permitted in writing by the Project Manager.

All trench excavation shall comply with Federal and local OSHA regulations for trench safety.

1/06 Technical Provisions- TP 3.0 Excavation, Trenching, and Backfilling Page 2

3.04 Placement and Compaction of Pipe Embedment and Backfill Material

3.04.01 Pipe Embedment

Pipe embedment is defined as that material required to bring the trench bottom up to grade and that material placed alongside and above pipe to a level of at least 6 inches over the top of the pipe. The pipe embedment area is divided into three zones as defined below.

Bedding: Bedding is that portion of pipe embedment zone beneath the pipe. If the native soil is suitable for bedding the pipe without over- excavation, the bottom of the trench shall be accurately shaped such that one fourth of the pipe circumference is provided with uniform bearing and support for each section of the entire length of the pipe. Imported bedding material shall likewise be placed to provide uniform and adequate longitudinal support under the pipe. Bedding material shall be placed and compacted in lifts not to exceed 6-inches in loose measure.

Haunching: Haunching is that portion of the pipe embedment zone from the bottom of the pipe to the springline of pipe. Haunching material shall be placed and consolidated to provide adequate side support to the pipe while avoiding both vertical and lateral displacement of the pipe from proper alignment.

Initial Backfill: Initial backfill is that portion of the pipe embedment zone from the springline of the pipe to a minimum level of 6-inches over the top of the pipe. Initial backfill material shall be placed and compacted in lifts not to exceed 6 inches in loose measure. Compaction shall be performed in a manner to avoid damage and disturbance of the embedded pipe.

3.04.02 Compaction

Unless otherwise specified by applicable permits or roadway authority, bedding, haunching, initial backfill, final backfill, and gravel resurfacing shall be compacted to the following percent of the maximum density as determined by ASTM D1557. In-place densities of materials shall be determined by the sand-cone method, ASTM D1556 or by nuclear methods, ASTM D2922.

Percent of Maximum Density

Location Bedding Haunching Initial Backfill

Final Backfill

Roadways and Driveways 95% 95% 95% 95%

Unimproved Surfaces, Fields, Etc. 90% 90% 70% 70%

1/06 Technical Provisions- TP 3.0 Excavation, Trenching, and Backfilling Page 3

3.05 Surface Restoration and Resurfacing

3.05.01 General

The inclusion of a bid item and estimated quantity for asphaltic, concrete, or gravel resurfacing in the Bid Schedule indicates that these items are probable. However, the exclusion of these items from the Bid Schedule does not preclude the possibility that they will be required, merely that they are not anticipated. If unanticipated resurfacing is required, unit prices will be negotiated between the Contractor and the Contracting Officer.

3.05.02 Surface Restoration

After the piping and structures have been installed and all backfilling has been completed, areas which were disturbed shall be brought to true grades. All slopes shall be trimmed and dressed, and all surfaces graded to maintain existing drainage. All streets, alleys, driveways, sidewalks, curbs, or other surfaces which have been disturbed or damaged shall be resurfaced with like materials to a condition equal to or better than the original condition. All excess excavated material shall be properly disposed of by the Contractor.

3.05.03 Gravel Resurfacing

All gravel resurfacing shall be done on a properly compacted subgrade. The gravel shall be spread uniformly and compacted to a minimum thickness of 3-inches. The gravel shall conform to the following gradation requirement.

Sieve Size Percent Passing Square Opening By Weight

3/4 inch 100

0.250 inch (No. 3 sieve) 50-65

0.0029 inch (No. 200 sieve) 5 max.

1/06 Technical Provisions TP 10.0 Sewer Service Lines Page 1

TECHNICAL PROVISION 10.0

SEWER SERVICE LINES

10.01 Scope of Work

material, and performing all operations in connection with the construction of sewer service lines, including connection to sewer mains or side sewer stubouts, connection to building (house) drains, cleanouts, abandonment of existing septic tanks, fittings, and appurtenances in accordance with these technical provisions and applicable drawings.

10.02 General

All work shall be done in accordance with the National Plumbing Code, except as otherwise specifically mentioned in this specification. During the installation of the sewer service line facilities to existing houses or buildings, the Contractor must provide for temporary sewage disposal if sewer service is to be interrupted for more than 24 hours.

10.03 Location of Facilities

The location of the facilities specified herein shall be as shown on the drawings and/or as staked in the field by the Project Manager. The Contractor shall not change the designated location of these facilities without the prior approval of the Project Manager.

10.04 Elevation Control

In order to install the facilities specified herein at the optimum grade and elevation, the Contractor is required to utilize an accurate builder's level and rod, or approved equal, during construction. The level shall be mounted on a tripod and shall be on site at all times during installation.

10.05 Connection to Stubout or Main

Sewer service lines shall be connected to the existing side sewer stubout using the existing tee, wye, or riser if available, utilizing approved fittings. Where no tee, wye, or riser is provided or available, the connection shall be made with a saddle utilizing a machine-made tap in the main.

The sewer pipe saddle shall have a cast iron body with a stainless steel strap and a rubber O- ring gasket seal where the saddle connects to the main. The saddle shall be equal to Sealtite sewer pipe saddle. The saddle shall be aligned on the sewer main such that it is at about a 45 degree angle with vertical, and in no case shall it deviate by more than 15 degrees from either side of 45 degrees without prior approval. During the installation of the sewer saddle, the Contractor shall not allow the pipe cutout or other foreign objects to enter the collection system. Ground and surface water shall be prevented from entering the collection system. If necessary the contractor

1/06 Technical Provisions TP 10.0 Sewer Service Lines Page 2 shall provide pumps and equipment, at no additional cost to the government, to prevent water from entering the collection system.

10.06 Sewer Service Lines

The Contractor shall install a solid smooth sewer service line from the sewer main or side sewer stubout to the building (house) drain. Sewer service line and fittings shall be PVC plastic of the size indicated, conforming to ASTM D3034, SDR 35. The pipe shall have integral wall, bell and spigot joints equal to Johns-Manville or Certain-Teed gravity sewer pipe. Standard lengths shall be at least 20-feet to minimize the number of joints required. All joints and connections in the pipe shall be watertight.

All sewer service lines and appurtenance shall be installed in accordance with Technical Provision 3.0, Excavation, Trenching, and Backfilling. Sewer service lines shall be installed in a practical alignment and at a uniform minimum slope of ¼-inch per foot, or 2%. A minimum of 18 inches of cover is required over the top of the pipe unless otherwise approved by the Project Manager.

Sewer service lines and connections shall be constructed with maximum joint deflection not to exceed the manufacturer's printed recommendations and in no case shall exceed 1 inch per foot in any joint. Larger changes in direction shall be made by use of standard 1/16 or greater bends.

Sewer service lines shall not be installed as vertical risers, but shall be laid on a slope not to exceed 2 feet vertical to 1 foot horizontal unless otherwise approved by the Project Manager.

The Contractor shall connect the sewer service line to the existing sewer service line stubout or building (house) plumbing if available, utilizing approved fittings or adapters. If not available, this line shall be extended to within 5 feet of the proposed building (house) and the end plugged with a water tight compression plug or equal and the location marked with a 2x4 board extending at least 18 inches above ground level and the sewer service line marked with a plastic and metal foil locator tape. In addition, the contractor shall give the Project Manager a clearly labeled sketch or drawing including the distance between the end of the sewer service and two permanent objects. Connections to existing building (house) drains which result in a change of direction of the line by more than 45 degrees requires the installation of an underground cleanout at that location.

10.07 Underground Cleanout

Where required and as shown on the plans, the Contractor shall install an underground cleanout on the sewer service line. The cleanout shall have a threaded brass plug and be of the same size and material as the sewer service line and constructed as detailed in the drawings. The cleanout shall be extended so that the square nut on the threaded plug is ½-inch below finished ground level. A concrete pad 18 inches square and 4 inches deep shall be poured around each cleanout at the ground surface. This pad shall be reinforced with welded wire mesh with a minimum 1 1/2-inch concrete cover over mesh. The wire mesh shall be ASTM approved W1.4 (1/8-inch) wire mesh on 6 inch centers.

1/06 Technical Provisions TP 11.0 Individual Septic Tank Page 1

TECHNICAL PROVISION 11.0

INDIVIDUAL SEPTIC TANK

11.01 Scope of Work

material, and performing all operations in connection with the construction of individual septic tanks, including connection to building (house) drains, solid sewer pipe, cleanouts, abandonment of existing septic tanks, fittings, effluent filters, and appurtenances in accordance with these technical provisions and applicable drawings.

11.02 Permits and Approvals

The Government shall secure the applicable site approvals and sewage disposal permits for the work specified herein.

11.03 Location of Facilities

The location of the facilities specified herein shall be as shown on the drawings and/or as staked in the field by the Project Manager. The Contractor shall not change the designated location of these facilities without the prior approval of the Project Manager.

11.04 Inspection of Installation

In addition to the applicable inspection requirements of the Tribe and/or County, the Contractor shall notify the Project Manager at least 2 working days prior to placing final backfill over the septic tank so that the Project Manager may inspect the installation.

11.05 Solid Sewer Pipe

The Contractor shall install a solid smooth pipe from the septic tank to the building (house) drain. Solid sewer pipe and fittings shall be 4-inch PVC plastic, ASTM 3034, SDR 35, Sewer Service Lines. Installation shall be in accordance with all state and local standards.

11.06 Effluent Filter

The Contractor shall install in the outlet tee of the septic tank a 1/16th-inch effluent filter cartridge equivalent to Orenco Biotube Residential Septic Tank Effluent Filter. The outlet tee in the septic tank shall be of sufficient length to extend one (1) inch below the bottom of the filter cartridge (See detail drawings).

1/06 Technical Provisions TP 11.0 Individual Septic Tank Page 2

11.07 Septic Tank

11.07.01 Tank

The tank shall be precast, reinforced, watertight concrete as manufactured by an established firm specializing in concrete products conforming to ASTM 6913. Minimum liquid capacity below the outlet level shall be as specified on the drawing(s) and each tank shall have 2 compartments. The walls, floor & top shall have a minimum thickness of 2 ½-inches. Adequate steel reinforcement shall be provided. Each compartment shall be provided with adequate tees, elbows and baffles. The tank shall meet all state and local standards.

11.07.02 Access Riser

Each compartment of the septic tank shall be provided with a watertight access riser with a minimum dimension of 24-inches for inspection and sludge removal. The access riser on the second chamber shall be centered so as to provide access to the effluent filter.

Access risers shall meet all state and local standards. Additional access ports, if required by local health codes, shall be installed by the Contractor at no additional expense to the Government. Risers shall be equal to Orenco systems lids and risers.

11.07.03 Septic Tank Installation

The septic tank shall be set in a hole excavated by the Contractor in accordance with all state and local standards.

11.08 Underground Cleanout

Where required and as shown on the plans, the Contractor shall install a two-way underground cleanout on the solid sewer line. The cleanout shall have a threaded plug and be constructed as detailed in the drawings. The cleanout shall be extended so that the square nut on the threaded plug is ½-inch below finished ground level. A concrete pad 18-inches square and 4-inches deep shall be poured around each cleanout at the ground surface. This pad shall be reinforced with welded wire mesh with a minimum 1 1/2-inch concrete cover over mesh. The wire mesh shall be ASTM approved W1.4 (1/8-inch) wire mesh on 6-inch centers.

1/06 Technical Provisions TP 12.0 Individual Lift Station Page 1

TECHNICAL PROVISION 12.0

INDIVIDUAL LIFT STATION

12.01 Scope of Work

materials, and performing all operations in connection with the construction of an individual lift station, including lift station basin, effluent pump, piping, force main, fittings, control panel, electrical controls and alarms, and appurtenances in accordance with these technical provisions and applicable drawings.

12.02 Lift Station

The lift station basin shall be either the second chamber of a septic tank, as shown in the drawings, or a precast, reinforced, watertight concrete basin as manufactured by an established firm specializing in concrete products, and shall conform to ASTM C. The basin shall have a minimum wall thickness of 2½-inches and the concrete shall obtain a minimum 28-day compressive strength of 3,000 psi.

The basin shall be as specified on the drawing(s), including the required minimum volume. The lift station basin shall be provided with a watertight access riser with a minimum dimension of 24-inches for inspection and maintenance. The Access riser shall meet all state and local standards.

An 18-inch square pedestal 4-inches high shall be provided as a base for the pump. The pedestal shall be located as shown on the drawing.

The installation of the lift station basin shall conform to the provisions of TP 11.0 for the installation of the septic tank and meet all state and local standards.

12.03 Effluent Pump

The sewage pump shall be as specified on the drawing(s), 230/240 volt, single phase submersible effluent pump. The pump shall be capable of passing 3/8-inch solids and running at the flow rate and total dynamic head as specified in the design. Differing site conditions may require a similar pump with minor differences in flow/head characteristics to be provided by the Project Manager.

The pump power cord shall be easily detachable from motor housing. Connector shall be sealed to motor housing with rubber O-ring. The pump details shall be as shown on the drawings or equal. If specified in the design, the effluent pump shall be installed within an Orenco Systems or equivalent effluent filter vault. If installed in the septic tank, the vault shall be installed with the inlet holes of the vault not less than 31-inches from the floor of the septic tank.

1/06 Technical Provisions TP 12.0 Individual Lift Station Page 2

12.04 Electrical Controls and Alarm

The Contractor shall furnish and install a control system compatible with the supplied pump.

The controls shall include; circuit breakers for the pump and alarm system, magnetic contactor, mercury level control floats, a high liquid level alarm, running and alarm lights, and a Hand-Off- Automatic selector switch. All wiring shall be in accordance with the National Electrical Code and applicable state and local electrical codes. The installation shall be inspected and approved by the State Electrical Inspector.

Electrical service to the lift station shall be either from a new properly sized circuit breaker in the existing circuit breaker panel servicing the home, if space permits, or through a separate subpanel. Separate circuit breakers are required for both the pump magnetic contactor and for the alarm system. In any case a fused disconnect is required if service entrance panel or sub-panel is greater than 50 feet from the lift station and/or not in clear sight of the lift station and shall be located as shown on the drawings or as directed by the Project Manager.

The control panel shall be a NEMA 4X enclosure and shall house the "Hand-Off- Automatic" switch, green "pump on" indicator light, a terminal block for connecting the mercury float level controls, and the alarm system. The green "pump on" light, red alarm light and silence button shall be mounted through the enclosure door.

The magnetic contactor, alarm system, and control panel shall be mounted on outside wall of the home at a location acceptable to the homeowner. As an alternative, and with the approval of the Project Manager, the control panel or alarm panel may be located on a post near the lift station as long as the components are housed in NEMA 4X enclosure.

The pump electrical cable shall be Type UF single conductor cable sized to limit the overall voltage drop from the service entrance to the pump motor to less than 2 percent. In no case, shall wires smaller than 12 gauge be used. The electrical cable and control wires shall be buried at least 18 inches deep. House interior wiring shall be 12 gauge minimum and shall be Type NM or UF cable, while required conduit shall be EMT, PVC, or liquid tight flexible metal. All supports, nails, bolts, straps and screws shall be galvanized. The submersible power cable from the pump and the float cables shall be secured to a hook and secured such that the cables are not allowed to slip from their adjusted height.

The mercury level control switches shall be completely encapsulated in polyurethane foam and equipped with cord weights. The float switch shall be installed at the elevations indicated or as otherwise directed by the Project Manager. The electrical cable housing from the switches to the control panel shall be Type UF 14 gauge copper single conductor cable. Splices shall be made by using mechanical connectors and covering with heat-shrink tubing.

1/06 Technical Provisions TP 12.0 Individual Lift Station Page 3

12.05 Control System Functional Requirements

12.05.01 Demand Dosing

The liquid level in the individual lift station is sensed by three mercury level control switches suspended at different elevations from the top of the lift station. The first (lowest) mercury level control switch shall be a redundant off switch and shall de-energize the pump should the middle dual action on-off float fail. The middle float shall be dual action and energizes and de-energizes the lift station pump. The third (highest) mercury level control switch energizes the red light and alarm bell indicating a high water level condition.

During the normal mode of operation, the HAND-OFF-AUTOMATIC switch shall be in the "Automatic" position. As the liquid level in the individual lift station reaches energize level of the middle dual action mercury level control switch, an electrical signal shall be transmitted through the buried electrical cable to the control panel. The controls shall energize the lift station pump and green running light. As the liquid level in the individual lift station drops to the middle de-energize level, an electrical signal shall be transmitted to the control panel which shall de-energize the lift station pump and green running light. This cycle shall continue to repeat itself. Should the middle dual action on-off float fail, the redundant lowest level float shall de-energize the pump and activate the alarm bell and red alarm light indicating a low level float failure.

If the liquid level in the individual lift station rises to the top mercury level control switch, the red light and alarm bell shall be energized indicating a high liquid level condition. The alarm shall be silenced by manually pushing the "Alarm Silence" button, however, the red pilot light shall remain energized until the liquid level has fallen below the third mercury level control switch. This high liquid level light and alarm shall operate independently of the position of the pump selector switch.

When the pump selector switch is in the "Hand" position, the mercury level float switches shall be overridden and the lift station pump and green running light shall be energized independently of the liquid level in the lift station. When the pump selector switch is in the "Off" position, there shall be no power provided to the lift station pump and green running light.

12.05.02 Timed Dosing

Timed dosing may control the liquid level in the individual lift station, if specified by the Project Manager and shown on the drawings, with three mercury level control switches.

The third (highest) mercury level control switch serves as a high water level alarm and energizes the red light and alarm bell indicating a pump failure condition. When the pump is operational and dosing overload occurs, the liquid level will reach the second (mid-level) mercury level control switch and the timer shall be overridden, energizing the lift station pump and the green pump running light on the control panel. As the liquid

1/06 Technical Provisions TP 12.0 Individual Lift Station Page 4 level drops, reaching the first (lowest) mercury level, the control switch overrides the timer and de-energizes the lift station pump and the green running light.

When the liquid level in the individual lift station does rise to the third (highest) mercury level control switch, the alarm shall be silenced by manually pushing the “Alarm Silence” button. However, the red pilot light shall remain energized until the liquid level has fallen below the second mercury level control switch. This high liquid level light and alarm shall operate independently of the position of the pump selector switch.

When the pump selector switch is in the “Hand” position, the timer and mercury level float switches shall be overridden and the lift station pump and green running light shall be energized independently of the liquid level in the lift station. When the pump selector switch is in the “Off” position, there shall be no power provided to the lift station pump and green light running.

12.06 Piping

12.06.01 Lift Station Influent

The piping from the septic tank outlet to the lift station inlet shall conform to TP 11.0, solid sewer pipe. The inlet shall include a tee or baffle, as specified. The outlet discharge from the pump shall be Schedule 40 PVC 1120 pipe installed as shown in the drawings and to the approval of the Project Manager. Fittings shall be Schedule 40, ASTM 2466, except for the union, which shall be Schedule 80. The union shall be installed within easy reach from the manhole cover, hand-tight only. The male adapter that screws into the discharge port of the pump shall not be glued in place; standard plumbers’ pipe joint compound shall be used.

12.07 Force Main

The effluent force main pipe from the lift station to the shallow drainfield shall be the size shown on the drawings, PVC 1120, Schedule 40, conforming to ASTM 2241. All fittings for the pipe shall be 160 psi PVC with rubber compression ring joints or schedule 40 PVC with solvent welded joints.

The force main pipe shall be laid on grade in a trench at least 12-inches wide. Care shall be taken to bed the pipe in a material that is free of rocks or otherwise unsuitable material. Backfill shall be compacted by hand from the bottom of the trench to a minimum of 6-inches over the top of the pipe for the full width of the trench. A minimum of 18-inches of cover is required over the top of the pipe.

12.08 Submittals

The Contractor shall submit for approval prior to construction product/material information on the sewage lift station pump and controls.

1/06 Technical Provisions TP 15.0 Low-Pressure-Dosed Mound System Page 1

TECHNICAL PROVISION 15.0

LOW PRESSURE-DOSED MOUND SYSTEM

15.01 Scope of Work

The work covered by this section consists of furnishing all labor, tools, equipment, and materials in connection with the construction and installation of a mound soil absorption system in accordance with applicable technical provisions and drawings.

15.02 Permits and Approvals

The Government shall secure the applicable site approvals and sewage disposal permits for the work specified herein.

15.03 Piping

15.03.01 Transport and Manifold Pipe

The transport and manifold pipes shall be Schedule 40 PVC pipe, PVC 1120, conforming to ASTM 1785, at the diameter specified in the design. Fittings shall be Schedule 40, conforming to ASTM 2466.

15.03.02 Distribution Laterals

The distribution laterals shall be Schedule 40 ASTM 1785 pipe, PVC 1120, at the diameter specified in the design. Field perforations shall be at the diameter, spacing, and orientation as shown in the drawings. Fittings shall be Schedule 40, ASTM 2466. Any laterals that do not end in cleanouts shall be fitted on the end with a male adapter and cap, screwed on hand-tight. Teflon tape shall be used.

15.03.03 Observation Pipe

Observation pipes shall be installed at locations shown in the drawings. Observation pipes shall be 4-inch diameter perforated PVC drainfield pipe fitted with a secure screw cap. All but the bottom 1-foot of the pipe shall be wrapped with filter fabric. The downslope observation pipe shall be placed with its bottom on the original ground surface. The upslope observation pipe shall have its bottom placed at the bottom of the gravel bed. Both pipes shall extend at least 6-inches above the mound surface.

1/06 Technical Provisions TP 15.0 Low-Pressure-Dosed Mound System Page 2

15.03.04 Solvent Cement

All fittings, except as specified shall be solvent-welded in place. Solvent cement shall meet ASTM D2564. Laterals shall not be solved welded to the manifold until after the pressure test. Pipe shall be cut square and deburred inside and out. All joints shall be primed before solvent welding.

15.04 Mound Construction

15.04.01 Materials

15.04.01.1 Medium Sand Fill

The medium sand fill shall be placed as shown in the drawings. The fill material shall meet the following particle size gradation: (Source: ASTM C-33, Specification for Fine Aggregate)

Effective % Passing Sieve Particle Size by Weight

3/8 inch 9.50mm 100% No. 4 4.75mm 95-100% No. 8 2.36mm 80-100% No. 16 1.18mm 50-80% No. 30 0.60mm 25-60% No. 50 0.30mm 10-30% No. 100 0.15mm 2-10%

The sand shall be not more than 45% passing any one sieve and retained on the next consecutive sieve of those shown above.

The fineness modulus shall not be less than 2.3 nor more than 3.1. The fineness modulus is defined as the sum of the cumulative percentages retained in the sieve analysis, divided by 100, for the sieve sizes shown above. Each load of fill sand shall be approved by the Project Manager.

15.04.01.2 Gravel Bed

A gravel bed with shall be provided at the height, width, and minimum overall depth as specified in the design. Gravel shall be placed below and above the distribution laterals to the minimum depths as specified in the design. The gravel shall be clean, hard, strong, non-deteriorating stone, free from coal, clay, soft fragments, or other deleterious materials, and may vary in size from ½- inch to

1/06 Technical Provisions TP 15.0 Low-Pressure-Dosed Mound System Page 3

1½-inches, with not more than ten (10) percent fines below the ½-inch size.

Gravel shall be considered clean if water poured through it remains clear. Gravel to be used must be approved by Project Manager. The gravel bed must be laid level in the bed cut into the top of the sand fill. The bottom of the bed shall be level within ± ½-inch. The top of the gravel bed shall be covered with filter fabric equal to Typar 3401.

15.04.01.3 Backfill Material

Backfill material over the gravel bed may be a finer texture soil than the medium sand material. Acceptable backfill materials are medium sand, silt, loam or topsoil. (Contractor will not be paid extra for use of high quality topsoil as backfill).

15.04.01.4 Topsoil and Seeding

The entire mound shall be covered with a layer of topsoil at the minimum depth specified in the design. Seed and fertilizer shall be uniformly applied over the mound area with approved equipment. Following the sowing and covering, all seeded areas shall be compacted by rolling. The soil shall be compacted to the extent that the seed is firmly embedded. The rolling shall be done along the contour at right angles to slopes.

Seed and fertilizer mixtures shall conform to the latest guidelines of the local offices of the Soil Conservation Services or Cooperative Extension Services.

Seeding shall be permitted only when soil and weather conditions permit.

The final depth of backfill and topsoil combined shall be 18 inches at the center of the bed and 12-inches at the edges of the bed.

15.04.02 Construction

Construction shall only take place when the soil moisture content is sufficiently low to avoid smearing, compacting, and puddling.

15.04.02.1 Equipment

Wheeled tractors shall not be used in the construction of the mound. Only track mounted equipment will be allowed, in order to prevent rutting, localized overloading, and compaction.

15.04.02.2 Construction Procedures

The following procedures shall be followed in the construction of the mound.

Alternate proposed methods must be approved by the Project Manager. The Contractor will be responsible for staking the corners of the fill area, together with

1/06 Technical Provisions TP 15.0 Low-Pressure-Dosed Mound System Page 4 offset stakes in case the corner stakes are lost. The Government will provide a benchmark for elevation reference. The construction steps to be followed are listed below.

1. Determine where the pipe from the pumping chamber connects to the distribution system in the fill.

2. Trench and lay the transport pipe from the pumping chamber to the fill.

Cut and cap the pipe one foot beneath the ground surface. Lay the pipe below the frost line or sloping back to the pumping chamber so that it drains after dosing. The line shall be installed at a uniform slope without sags or rises.

Backfill and compact the soil around the pipe to prevent back seepage of effluent along the pipe from the mound area to the lift station. This step must be done before plowing to avoid compaction and disturbance of the surface.

3. Cut trees to ground level, remove excess vegetation by mowing. Prepare the site using a moldboard plow and plowing perpendicular to the slope.

The site should be plowed in a direction so that the plow throws the soil upslope. Use as large a plow as possible to reduce the number of driven-in furrows, which result in the compaction of the subsoil. Chisel plowing may be done if a moldboard plow is not available. Rototilling must not be done. The important point is that a rough, unsmeared surface should be left in fine textured soils. The fill material will intermingle between the clods of soil, which should improve the infiltration rate into the natural soil by minimizing the layering which occurs.

Immediate construction after plowing is desirable. Avoid rutting the compaction of the plowed area by traffic. If its rains after the plowing is completed, wait until the soil dries out before continuing construction.

4. Reset the corner stakes, if necessary, using the offset reference stakes and locate the bed or trench areas by staking their boundaries.

5. Extend the transport pipe from the pump chamber, previously cut off below ground, to several feet above the ground surface.

6. Place the fill material which has been properly selected around the edge of the plowed area. Keep the wheels of trucks off plowed areas. Minimize traffic on the downslope side of the fill system. Work from the end and upslope sides. This will avoid compacting the soils on the downslope side, which, if compacted, would affect lateral movement of water away from the fill and possibly cause surface seepage at the toe of the fill.

1/06 Technical Provisions TP 15.0 Low-Pressure-Dosed Mound System Page 5

7. Move the fill material into place using a small track type tractor with a blade. Do no use a tractor/backhoe having tires. Always keep a minimum of 6 inches of fill material beneath tracks to prevent compacting of the natural soil.

8. Place the fill material to the required depth, i.e., to the top of the bed.

Shape sides to the desired slope.

9. With the blade of the tractor, form the bed. Hand level the bottom of the bed within ± ½-inch.

10. Place the gravel in the bed to the required depth. Level the gravel.

11. Place the distribution laterals on the gravel. Connect the manifold to the transport lines from the pump chamber. Lay the laterals fairly level, removing large rises and dips.

12. Pressure test the distribution system for uniformity of flow. All clogged orifices shall be cleared; all soil and other obstructions shall be removed from the laterals.

13. Solvent-weld the laterals to the manifold. Orifices shall be oriented at the position specified in the design.

14. Place gravel over the laterals to fill the bed to the required depth.

15. Install the two observation pipes (monitoring ports).* One shall be in the downslope portion of the fill with the bottom at the original surface and the top extending above final grade where it can be capped. The other shall be located in the bed extending only from the bottom of the bed to above the final grade.

*This can be done at this point in the installation by digging the hole with an auger, or the observation pipes can be anchored in place after the original surface has been plowed, before the fill material is placed.

16. Place filter fabric over the bed, overlapping the edge of the bed by at lest 6 inches.

17. Place the backfill material over the mount and then the topsoil.

18. Seed the topsoil per 15.10.01.4. Alternatively, the Contractor may sod the mound.