Page 137 - Villas at Savona Close-out Manual
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The typical MaxWell Plus provides over 2,500 gallons of chamber capacity to process incoming water for
            the removal of suspended solids and floating organic compounds. These chambers are constructed of
            4000 PSI pre-cast concrete liner segments that are 48-inches I.D., 54-inches O.D. with a 3-inch wall
            thickness. In constructing the chambers, these sections are carefully aligned, centered, and stacked in the
            borehole to maximize bearing surfaces.

            A filter sleeve made of non-woven geotextile fabric is placed inside the drilled shaft to encapsulate the
            aggregate backfill, and inhibit the migration of fines from the surrounding soils into the gravelpack. Next, a
            corrugated HDPE drainage pipe with a slotted Schedule 40 PVC drainage screen attached to the lower end
            is inserted into the pilot-hole excavation. This component is then capped and suspended slightly off the
            bottom of the borehole. Clean, washed aggregate sized between 3/8” to 1 ½” to best complement site soil
            conditions is utilized for the backfill material surrounding the drainage pipe in the lower excavation of the
            main well. The pre-cast concrete chambers are then erected in the 72-inch diameter reamed portions of the
            upper excavation.

            An overflow pipe constructed of Schedule 40 PVC is installed in the main chamber, and is mated to the
            drainage pipe with a coupling under the chamber bottom. This vertical pipe is supported by a fusion-
            bonded epoxy-coated galvanized steel bracket attached to the liner wall. Our PureFlo Debris Shield
                                                                                               ®
            equipped with an internal screen is then fitted onto the top of the overflow inlet. This cylindrical shield is
            approximately 24-inches in length, and is fabricated from rolled 16-gauge galvanized steel. The component
            is coated with fusion-bonded epoxy, and fitted with an anti-siphon vent. In operation, the shield forces
            water to be drawn into the system from several inches beneath the surface, effectively isolating and
            containing floating trash, paper, debris and pavement oils within the chambers. The internal screen
            effectively filters out suspended material, and the vent prevents floating debris from being sucked into the
            overflow pipe as the water level inside the chamber subsides.

            The primary settling chamber is interconnected to the main well with a 4-inch diameter Schedule 40 PVC
            pipe installed with a two percent slope between chambers. This connecting pipe is feed through a vented,
            shielded and screened inlet that is fitted with a reduction orifice. This component narrows the opening of
            the 4-inch pipe to 2-inches to manage excessive inflow velocity, and provide a manageable metered flow to
            the main well. The restriction also increases the residence time of the water in the inlet structure, thereby
            further enhancing the gravity settlement of suspended solids.

            Each chamber of this design is equipped with two hydrophobic floating absorbent pillows, which will
            remove a wide range of hydrocarbons and organic liquids. The sponges are 100% water repellant, and
            literally “wick” floating petrochemical compounds from the surface of the water. Each pillow has a removal
            capacity of at least 128 ounces to accommodate effective, long-term treatment.

            At the surface of the ground, the inlet structure will be equipped with a 24” or 30” diameter cast-iron grate
            and ring assembly, while the main well will be fitted with a 30-inch diameter cast-iron ring and solid cover.
            See Appendix 1-A for MaxWell detail.

        Installation


            Once the locations of any utilities have been identified, the exact locations of the drywell chambers on the
            jobsite are laid out and identified by the Civil Designer’s survey team. When installed with standard inverts,
            the layout requires center stakes for each chamber, with (2) 10-foot offsets, 90 degrees apart.

            The installation begins with the excavation of a pilot-hole boring, which will be accomplished using either a
            bucket-auger drill rig, or a SoilMec machine. When a bucket-auger is utilized, the initial borehole is drilled
            using a 48-inch diameter bucket. The upper part of this excavation where the chamber will be built must be
            enlarged to 72-inches,  in order to  provide sufficient access to stack the liner segments, and place the
            aggregate backfill around the outside of the chamber. In order to expand the upper portion of the drilled
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