Un aula con sabor a evangelio

Concrete structures shall be protected both internally and externally where indicated on the Drawings and by the methods detailed.

9.2.2 Protective Coatings/PVC Liners

All protection systems shall be applied strictly in accordance with the manufacturer's instructions, two copies of which shall be included with the Contractor's application for the approval of the material, and when approved will be deemed to be part of this specification unless stated otherwise.

The permissible rate of permeation of all protection systems shall not exceed 0.0027 per inches (ASTM, 1 per inch = 1 gramme of water per hour per square foot (0.0929 m2) per mil (0.0254 mm) of thickness for a 1 inch (25.4 mm) difference in Hg vapour pressure on each side of a membrane.

Coatings shall not be applied at expansion, contraction or construction joints which incorporate a sealant.

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9/8

The external surfaces of concrete substructures shall be protected or "tanked" by one of the following methods which will be indicated on the Drawings. a) An approved impervious bituminous waterproof membrane:

The membrane shall be tropical grade, cross laminated to have high tear strength; and puncture and impact resistance and shall be chemically resistant for protection against aggressive soils and contaminated groundwater.

The membrane shall comply with the following :-

Property Test Method Typical Results Tape Strength ASTM D638 Long 4.2 N/mm22

Trans 4.8 N/mm2

Tensile Strength ASTM D638 Long 42 N/mm2 Trans 48 N/mm2 Elongation Film ASTM D638 Long 210 %

Trans 160 % Tear Resistance ASTM D1004 Long 340 N/mm22

Trans 310 N/mm22 Adhesion to Self Concrete ASTM D1000 1.8 N/mm2 Puncture Resistance ASTM E154 220 N 65 mm22 Water Resistance : After 24 hours After 35 days ASTM D570 0.14 % 0.95 % Environmental Resistance ASTM D543 Conforms Moisture Vapour

Transmission Rate ASTM E96 0.3 g/m

22_{/24 hrs.}

The membrane shall be laid on to smooth concrete blinding surface free from sharp edges and projections and on to walls primed with an approved primer and applying the performed membrane, sticky side downwards, laid strictly in accordance with the manufacturer's instructions. The minimum over laps shall be 50 mm side and end.

During the backfilling operation around all tanked structures, the waterproof membrane shall be protected from damage by the use of an

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approved protection board. The board shall be manufactured from graded and selected kork granules bound with modified bitumen and encased between two layers of tough asphalt paper. The board shall be light weight and capable of providing protection against abrasive backfilling. The board may be stored outside, but shall be kept flat on original pallets.

b) A brush applied bituminous emulsion:

The surface shall first be wire brushed and all dust and loose scale removed. Three coats of bituminous rubber emulsion paint shall then be applied. The second coat shall not be the same colour as either the 1st or 3rd.

Both methods of protection shall totally enclose the substructure within a waterproof membrane to the limits shown on the Drawings.

(2) Internal and External Exposed Surfaces

Where exposed surfaces of concrete structures are not protected by reinforced plastic liners one of the following systems will be indicated on the Drawings where required.

a) An epoxy resin, acrylic, polyester or latex paint system:

The surface shall first be wire brushed and all dust and loose scale removed (refer to Clause 19.4 for schedule of surface preparations). An epoxy resin or other primer/sealer (for concrete and allied substrates) shall then be applied followed by coats of high build epoxy airless spray or other coatings to give a minimum dry film thickness (dft) of 300 microns. Freedom from pinholes shall be established by use of a spark tester. The approved paint system must have adequate flexibility to suit the thermal movements of the concrete without cracking whilst maintaining an effective bond.

b) A PVC sheet lining system :

The PVC sheet lining shall be fixed such that the keys or ribs are cast into the concrete surface. The lining shall be capable of taking up the same profile as the concrete substrate as indicated on the Drawings. Site operatives for employment on this work shall be certified by the manufacturer as trained to a satisfactory standard in fixing and welding techniques.

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After completion of either of the linings or systems as described in sub- clauses (a) and (b) above they shall be offered for inspection and testing. Two sets of testing equipment, e.g. feeler probes and spark testing, shall be provided and be maintained and available at all times for the sole use of the Engineer's Representatives.

Only linings or systems completely free from pinholes will be accepted. 9.2.3 Reinforced Plastic Liners

The construction methods employed shall be so as to ensure that a completely water and gastight seal is made preventing any exposure of the concrete surround to the corrosive liquids and gases present as detailed below and in Clauses 15.5.4 and 15.5.5.

In particular:-

Reinforced plastic liners shall be handled in the same manner as reinforced plastic pipes. In addition, extra care shall be taken to avoid damage to the liners which are not designed to carry loads.

The manufacturer shall visit the site to demonstrate to the Contractor in the presence of the Engineer's Representative the methods of handling and lifting, including formation of the joints between the chamber liner.

The Contractor is reminded that these liners are not designed to withstand pressure exerted by the concrete during construction.

9.2.4 Cutting and Sealing of Reinforced Liners

Where the Contractor is required for any reason to cut reinforced plastic liners, he shall seal the exposed ends with an approved resin before incorporating the cut reinforced plastic in the work. No cut reinforced plastic shall be used until the resin has cured.

The resin shall be as recommended by the manufacturer of the reinforced plastic item and shall be pigmented so that the areas where it has been applied are easily identifiable.

It shall be delivered to site in sealed containers bearing the name of the manufacturer and properly labelled as to its content and shelf life.

SECTION 9 CORROSION PROTECTION AND ODOR CONTROL

9/11 9.3 ODOR CONTROL FACILITIES 9.3.1 General

The Contractor shall provide the labor, materials and equipment necessary to install and test the odor control facilities as shown on the Contract Drawings and as specified herein. The odor control units shall be either of the activated carbon filter types or of the natural soil filter bed types as indicated in the Drawings.

9.3.2 Soil Moisture and pH Probes

Moisture and pH probes shall be able to continuously measure percent moisture and pH in the soil. All components shall be highly resistant to corrosion due to sewage and very high concentration of hydrogen sulfide and other gases. Soil moisture probes shall measure moisture on a percentage basis in the full range of soil moisture (0-100 percent). pH probes shall at a minimum be accurate within the 4-10 standard unit range. All probes shall be designed for maintenance and replacement with minimum soil disturbance. 9.3.3 Activated Carbon Odor Control Filter

The activated carbon odor control filter shall be furnished and installed in accordance with Clause 17.2.48. The air blowers for the odor control unit shall be as specified in Clause 17.2.17.

9.3.4 Natural Soil Odor Control Filter 9.3.4.1 Materials

HDPE (High Density Polyethylene) Liner

The HDPE liner shall be furnished and installed in accordance with Clauses 19.3.4 and 19.2.13 and as shown on the Contract Drawings.

Washed Stone

Stone for the air plenum shall be washed, rounded, uncrushed, well graded in size from 20 mm to 25 mm and consisting of clean, and durable particles free from dirt, vegetation or other objectionable matter and free from an excess of

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soft, thin elongated, laminated or disintegrated pieces. The Contractor shall submit a sample of the stone to the Engineer for approval prior to placement. Wood Chips

Wood chips shall be obtainefrom hardwood and shall be of 10 mm to 50 mm diameter. Not more than 2 percent shall consist of leaves, twigs or shavings. They shall be free of extraneous materials, stone and debris. The Contractor shall submit a wood chip sample to the Engineer for approval prior to placement.

Soil Filter

The soil filter shall be a mixture of approved natural sand or sandy loam and treated compost. The compacted soil/compost mix shall have a 50 percent porosity. The compost shall be a product of thermophilic aerobic stabilization. It shall be adequately stabilized, so as to be completely free of any odors. The compost shall be friable, pass through a 13 mm mesh screen, and be free of stones, stocks and all objectionable debris. Compost shall have a pH of 5.5 to 8.0 and no less than 25 percent volatile solids. The compost source is subject to the review of the Engineer. All compost shall be "cured" to the point that it is no longer self heating.

9.3.4.2 Installation

The Contractor shall place the stone, wood chips, soil and compost in layers of uniform thickness as indicated on the Contract Drawing(s) or as directed by the Engineer. The stone, wood ships, soil and compost shall be placed so as not to damage the aeration piping. Damaged piping is to be replaced by the Contractor at no additional cost to the owner.

9.3.4.3 Monitoring

The Contractor shall perform the following selected soil and atmospheric analyses at the direction of the Engineer, but not more than once per week with the exception of soil moisture and pH, for the length of the natural soil filter maintenance period. The results of the analyses shall be recorded and presented to the Engineer at the end of each month. Soil samples must be taken so as not to disrupt the even distribution of air through the odor control filter.

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Hydrogen sulfide (H₂S) gas concentrations shall be measured in the atmosphere directly over the filter bed with a probe placed immediately above the surface of the natural soil filter. The H₂S levels shall be monitored and recorded continuously.

Soil Moisture and pH

Soil moisture and pH shall be monitored and recorded continuously at a depth of 0.75 meters from the natural soil filter surface using the soil moisture and pH probes as specified in Clause 9.3.2.

Chlorides, Sulfides and Biological Analysis

Chloride and sulfide concentration shall be measured from soil sample collected at a depth of approximately 0.75 meter from the natural soil filter surface. A biological analysis shall be performed on the same soil samples to identify biological organism in the filter media. The samples for these analyses shall be taken once per month unless otherwise directed by the Engineer.

9.3.4.4 Maintenance

Where excessive settling or discontinuities have occurred in the soil filter media, the Contractor shall replace the entire soil/compost media or add additional soil/compost mixture at the direction of the Engineer.

9.3.4.5 Acceptance Test

The Contractor shall test the porosity of the compacted soil/compost mixture before placement and provide the results of the test to the Engineer.

SECTION 10