AID; Washington, D.C.; 1982
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Introduction |
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Materials Needed |
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Construction Steps |
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Preparing the Site |
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Staking Pond and Pipe Locations |
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Excavating the Pond |
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Building Embankments |
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Laying Pipes |
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Finishing Embankments |
Before construction can begindetains , the project designer must provide:
1. Location map, or master sewer map, similar to Figure 1;
2. Design drawing of the pond, similar to Figure 2;
3. Design drawing of the inlet, outlet, and embankment, similar to Figure 3;
4. Materials list similar to Table 1
If more than one pond based is being constructed, the project designer must also provide:
5. Design drawing of the pond system layout, similar to Figure 4 or Figure 5;
6. Design drawings of all interpond piping, similar to Figure 6.
7. Materials list attachment similar to Table 2.
You will also need:
8. All labor, materials, and tools described in the materials list and materials list attachment.
Depending on local conditions, availability of materials, skills of workers, and so on, some construction steps will require only a few hours, while others may take a day or more. Read the construction steps and make a rough estimate of the time required for each step based on local conditions. You will then have an idea of when during the construction process specific workers, materials, and tools must be available. Draw up a work schedule similar to Table 3 showing construction steps.
1. Locate the site and temporarily mark it on the ground.
2. Assemble alí labor, materials, and tools needed to begin construction.
1. Set reference stakes 5 -10m apart indicating the boundaries of the bottom of the pond. Find the elevation of each stake using a surveyor's level and rod from the base point used in constructing the sewer. See "Constructing Sewer Systems," SAN.2.C.4.
2. Measuring the distance and elevation from the reference stakes, set slope stakes indicating the points at which to begin building the embankment and excavating the pond. See Figure 7.
3. Set stakes to indicate pipe locations. This will eliminate reexcavating portions of the embankment.
1. Begin excavating at the inside slope stakes. Dig at the slope specified by the project designer until the bottom elevation is reached. Check this elevation with a surveyor's level and rod. See Figure 8.
2. Continue excavating along the bottom elevation of the pond. Use excavated soil to build up the embankments (see "Building Embankments").
3. Make the bottom of the pond as level and as uniformly compacted as possible. If there are soft spots or tree roots, dig them out, fill with moist soil, and compact.
4. Make the corners of the pond rounded.
5. Leave some excavated soil on the pond bottom if small dikes are to be built for the start of pond operation. See "Operating and Maintaining Stabilization Ponds," SAN.2.O.5.
2. Leave gaps in the embankment at pipe locations as shown in Figure 9. It may also be convenient to leave one or more wide gaps for removal of excavated soil.
3. The top of the embankment must be level, well-tamped, and at least 1.0m wide. The horizontal distance from the top of the embankment to the bottom of the pond must equal the design depth of the pond plus 1.0m.
2. Build bases about 0.5m high for the inlet pipes from concrete or stone. The purpose of the bases is to raise the inlet pipe above the bottom of the pond. See Figure 3.
3. Build slabs for the outlet pipes from concrete or stone. The purpose of the slab is to support the outlet pipe and . to prevent erosion due to the discharge of treated sewage. Build support slabs under all valve locations.
4. Lay sewer pipe and mortar together sections; Install valves.
5. Build the vertical outlet from sleeved sections of pipe. The height of the vertical outlet determines the depth of the pond. It must be equal to the design depth calculated by the project designer. The sleeved sections will allow the pond to be drained when necessary. See Figure 3.
6. Build a protective screen around the vertical outlet . with creosote-treated wood posts and rust-proof wire screen. The screen should extend at least 0.3m above and 0.3m below the vertical outlet. It will prevent floating debris from entering the outlet pipe after the pond is put into operation.
7. Carefully fill in pipe trenches with moist soil and tamp.
1. Fill in any gaps in the embankment that were used for laying pipe or removing excavated soil. Thoroughly tamp the top and slopes and make them uniform with the existing embankment. See Figure l0.
2. Line the entire inner race of the embankment slope with rocks and flat stones. This will prevent erosion due to wave action during pond operation. Rocks and stones should be smoothly graded to conform to the design slope of the embankment. Avoid using gravel and pebbles because this material tends to move downslope.
3. If topsoil or sod was initially removed from the site, use it now to cover the outside slope and top of the embankment. If no sod is available, plant grass seed. This will help prevent erosion of the embankment from wind and rain. See Figure l0.
4. Excess soil excavated from the pond can be used to build small dams to divert surface water away from the pond. If not, it should be graded level or hauled away from the pond site.