Section V – Sanitary Sewer System
PART 1 – GENERAL
1.01 WORK INCLUDED
A. The work included under this section consists of furnishing all Labor, equipment and materials necessary for the construction of sanitary sewers, sewer connections and appurtenances as shown on the Drawings or specified herein.
1.02 RELATED WORK
A. Section I – Trenching, Backfill and Compacting for Utility Systems
B. Section III – Concrete
1.03 QUALITY ASSURANCE
A. Design Requirements: Sewer mains and laterals shall have a minimum cover of thirty-six (36) inches below finished grade. Sewer lateral ends shall have a maximum cover of forty-eight (48) inches below finished grade, unless otherwise indicated.
B. Storage: Polyvinyl chloride pipe shall be stored on level ground, preferably turf or sand, free of sharp objects which could damage the pipe. Stacking of the polyvinyl chloride pipe shall be limited to a height that will not cause excessive deformation of the bottom layers of pipes under anticipated temperatures conditions. Where necessary due to ground conditions the pipe shall be stored on wooden sleepers, spaced suitably and of such width as not to allow deformation of the pipe at the point of contact with the sleeper or between supports.
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A. Shop Drawings:
1. In general, six (6) copies of the following data or shop drawings shall be submitted to the Engi neer for approval prior to construction:
a. Precast manholes
b. Manhole frames, covers and other castings
c. Manufacturer’s Certified Test Report on castings
d. Certified test records for polyvinyl chloride pipe
e. Pipe adapters
2. A copy of the approved shop drawings shall be submitted to the Owner prior to delivery of materials.
B. Record Information:
Record drawings shall be prepared and submitted to Gulf Shores Utilities. These record drawings shall specifically locate via discrete, manual measurements each and every component of the installed system, including: Manholes, main line service fittings, main line pipe material transitions, end of service laterals, depth of service lateral end, flow line of each line connected to each manhole, elevation of each manhole cover, and any other such items or project elements as may be required. Main line service fittings, main line pipe material transitions, and lateral information shall be stationed from the nearest downstream manhole. Lateral ends shall have left/right offsets measured from the centerline of the main sewer line. Manhole cover elevations shall be at the center of the cover.
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A. APPROVED PRODUCT
PVC PIPE: SDR-35 PVC PIPE(LATERALS):SCHEDULE 40 DUCTILE IRON PIPE: CLASS 52-CEMENT LINED PIPE ADAPTER: PVC OR POLYURETHANE FERNCO OR EQUAL PRECAST MANHOLE: CEMENT TYPE II WITH 100% CALCAREOUS AGGREGATE, BASE 8″ MINIMUM THICKNESS WITH 6″ ANTI-FLOTATION COLLAR, WALL THICKNESS 5″ MINIMUM, JOINT SEAL AND RAM-NEK OR EQUAL, GROUT TYPE II CEMENT OR NON-SHRINK HYDRAULIC CEMENT, PIPE SLEEVES SYNTHETIC RUBBER WITH STAINLESS STEEL BAND & amp; SCREWS, FRAME AND CAST IRON W/TYPE 2 PICK VULCAN FOUNDRY COVERHOLES AND APPROVED V-1418-1B CASTING PATERN
SEWER LATERAL MARKERS: STAMPED OR LABELED SEWER LATERAL CURB STAMPING: SEWER LATERALS SHALL BE IDENTIFIED WITH AN “S” PLACED IN THE CONCRETE CURBING IDENTIFYING THE SEWER SERVICE
PIPE BEDDING MATERIAL: WET TRENCHES ANGULAR STONE NOT GREATER THAN 3/4″ DRY TRENCHES ANGULAR STONE OR CLEAN SAND
B. Pipe and Fittings:
1. Polyvinyl Chloride Pipe For Gravity Sewers:
a. Plastic gravity sewer pipe and fittings shall be unplasticized polyvinylchloride(PVC), meeting or exceeding ASTM Specification D-3034, latest edition, Classification SDR 35.
b. Pipe lengths shall not exceed thirteen (13) feet and provisions shall be made at each joint to accommodate expansion and contraction.
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c. All pipe and fittings shall be joined by means of an integral wall bell and spigot and sealed with a rubber gasket. This joint shall be capable of withstanding an internal hydrostatic pressure of 25 psi for one hour with no leakage.
d. Pipe shall be retained in shipping cradles when stored along the right-of-way until pipe is ready to be laid. In no case will removal of pipe from cradles be permitted more than 24 hours in advance of placing in trench.
e. PVC pipe shall be installed in accordance with ASTM D2321, latest edition and as modified herein. If there is a conflict between the provisions of ASTM D2321 and the Project Specifications, the Project Specifications shall govern.
2. Polyvinyl Chloride Pipe For Sewer Laterals:
a. Plastic sewer lateral pipe and fittings shall unplasticized polyvinylchloride (PVC) meeting or exceeding ASTM Specification D-2665 Schedule 40.
b. All pipe and fittings for PVC lateral pipe shall be joined by means of solvent-cement joints in conformance with ASTM D-2855. Joints shall be capable of withstanding an internal hydrostatic pressure of 25 psi for one hour without leakage.
3. Ductile Iron Pipe For Gravity Sewers And Laterals:
a. Ductile iron pipe and fittings shall be as specified in ASTM A746 for thickness Class 52.
b. Ductile iron pipe for gravity sewers shall be mechanical joint or push-on joint, unless specified otherwise, conforming to ANSI/AWWA C151/A21.51. Ductile iron pipe shall have a cement-mortar lining conforming to ANSI/AWWA C104/A21/4. A standard bituminous coating shall be applied to the exterior of all ductile iron pipe and fittings.
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c. Ductile iron lock joint pipe shall meet the requirements of ANSI/AWWA C151/A21.51 for ductile iron pipe and may be of the bolted or boltless type suitable for 150 psi working pressure. If bolted type pipe is used, all bolts shall be Corten Steel.
d. Ductile iron fittings shall be designed for pressure rating of 350 psi and shall be in accordance with ANSI/AWWA C110/A21.10. Fittings shall be mechanical joint. Fittings shall be cement-mortar lined in accordance with ANSI/AWWA C151/A21.51.
e. Cutting of ductile iron pipe shall be by saw, cutter, abrasive wheel or other approved means. In no case shall ductile iron pipe be cut by burning.
f. Marking of ductile iron pipe shall include the pressure rating, metal thickness, net weight of pipe without lining, length of pipe, name of manufacturer, and letters “DI” which shall be clearly marked on each length of pipe.
g. Transitions from ductile iron pipe to other pipe material shall be made using approved adapters specifically designed for this purpose.
h. Polyethylene sheath shall be on ductile iron pipe where indicated on the Plans and where directed in the field. The exterior of ductile iron pipe shall be covered with a sealed polyethylene sheath in accordance with AWWA Specification C105. Polyethylene sheath shall be “Polyetube” as manufactured by Polyetube Corporation, or an approved equal. Backfill shall be as specified elsewhere in these Specifications. Care shall be taken not to damage the polyethylene sheath during the backfill operation. Any polyethylene sheath which is damaged shall be replaced or repaired by the Contractor at no additional expense to the Owner.
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B. Concrete and Reinforcing Steel: Concrete and reenforcing steel shall conform to the requirements of Section III. Concrete classes for the various purposes shall be as follows:
1. Manhole bottoms, Class A
2. Precast manholes, Class A
3. Pipe and riser encasement, Class B
4. Protective slabs, Class B
C. Castings: Gray iron castings for manhole frames, covers and other items shall conform to the ASTM Designation A 48, Class 30. Castings shall be true to pattern in form and dimensions and free of pouring faults and other defects in positions which would impair their strength, or otherwise make them unfit for the service intended. The seating surfaces between frames and covers shall be machined to fit true. No plugging or filling will be allowed. Lifting or “pick” holes shall be provided, but shall not penetrate the cover. Casting patterns shall conform to those shown or indicated on the drawings. The words “GULF SHORES SANITARY SEWER” shall be cast in all manhole covers. All manhole frames and covers shall be traffic bearing – Vulcan Foundry V-1418-1B, Type 2 Pick Hole or approved equal. A “Sailboat” pattern will be cast in lid.
D. Brick: Brick for manhole construction shall be dense, hard burned, shale or clay brick conforming to ASTM Designation C 32, Grade MM or C 62, Grade MW, except that brick absorption shall be between five and twenty-five grams of water absorbed in one minute by dried brick, set flat face down, in 1/8-inch of water. Brick used to construct manholes or adjust manhole rings to final grade must be laid in acceptable cementitious mortar – No dry stacking allowed.
E. Cement Mortar: Cement mortar for manhole construction shall be one part cement and three parts clean sharp sand to which may be added lime in the amount of not over ten percent volume of cement. It shall be mixed dry and then wetted to proper consistency for use. No mortars that have stood for more than one hour shall be used.
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F. Pipe Adapter:
1. Donut pipe adapter shall be manufactured from virgin polyvinyl chloride (PVC) or polyurethane adaptable to similar or dissimilar pipes of the same or different sizes. Donuts shall be as manufactured by Fernco Joint Sealer Company or approved equal.
2. Flexible couplings shall be manufactured from virgin polyvinyl chloride (PVC) or polyurethane adaptable to dissimilar pipes of the same or different sizes. The flexible coupling shall be as manufactured by Fernco Joint Sealer Company or approved equal and supplied with #300 stainless steel bands and screws.
3. Flexible manhole sleeves for connecting sewer pipe to precast manholes shall be of a synthetic rubber compound resistant to ozone, weather, acid and water. The sleeve shall either be cast-in-place with a water stop or shall be firmly affixed to the inner face of a smooth opening in the manhole wall by means of a stainless steel retainer band. The sleeve shall have a cast-in-place water stop and accommodate settlement up to 15 degrees. The binding of the sleeve to the pipe shall be a non-corrosive, non-magnetic type stainless steel strap and screws.
1. Pipe Cradle: Upon satisfactory installation of the pipe bedding, as specified in Section I, a continuous trough for the pipe barrel and recesses for the pipe bells or couplings shall be excavated hand digging. When the pipe is laid in the prepared trench, true to line and grade, the pipe barrel shall receive continuous uniform support and no pressure shall be exerted on the pipe joints from the trench bottom.
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2. Cleanliness: The interior of all pipe shall be thoroughly cleaned of all foreign material before being lowered in the trench and shall be kept clean during laying operations by means of plugs, or other approved methods. During suspension of work for any reason at any time, a suitable stopper shall be placed in the end of the pipe laid to prevent mud or other foreign material from entering the pipe.
1.Gravity sewer mains shall be installed upgrade with the spigot ends pointing in the direction of flow. All pipe will be installed straight and true to the specified grade using a laser or other devise specifically designed for pipeline installation. Pipe shall be bedded as trench conditions indicate. A GSU representative will determine if trench conditions allow the use of clean sand in lieu of angular stone. Contractor shall provide sufficient well points or pumps to control any water that may be present. No laying of pipe in water filled trenches or on unstable bedding will be allowed. A minimum of 6 inches of compacted bedding material shall be required below the pipe. Overcuts shall be filled with compacted bedding material. Pipe cradle shall be constructed in a manner that provides continuous, uniform support to the barrel of the pipe with no pressure exerted on the pipe joints from the trench bottom. Pipe cradle shall be constructed of compacted bedding material to the spring line of the pipe. From the spring line to 12 inches above the pipe, the trench shall be filled with compacted select material from excavation. In paved areas, backfilling of the trench above the pipe envelope shall be as required by the City of Gulf Shores. Whenever pipeline construction is stopped for the night or any other reason, the end of the pipe shall be plugged to prevent any trench water, mud, or foreign material from entering the pipe.
2. Any pipe which is disturbed or found to be defective after laying shall be taken up and relaid or replaced.
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3. Polyvinyl Chloride Pipe:
a. Transportation: Care shall be taken during transportation of the pipe that is not cut, kinked or otherwise damaged.
b. Handling Pipe Lengths: Ropes, fabric or rubber protected slings and straps shall be used when handling pipes. Chains, cables or hooks inserted into the pipe ends shall not be used. Pipe or fittings shall not be dropped onto rocky or unprepared ground.
c. Handling Pipeline: The handling of the joined pipe line shall be in such a manner that the pipe is not damaged by dragging it over sharp and cutting objects. Sections of the pipes with deep cuts and gouges shall be removed.
d. Lowering Pipe Into Trench: Care shall be exercised when lowering pipe into the trench to prevent damage to or twisting of the pipe.
e. Special Precautions: Polyvinyl chloride pipe connected to heavy fittings, manholes and rigid structures shall be supported in such a manner that no subsequent relative movement between the pipe and the joint with the rigid structures is possible.
B. Service Connections:
1. Service connections, of the type called for on the Drawings, shall be provided in accordance with the details therefore as shown or indicated on the Drawings.
2. Where called for on the Drawings, sewer pipe of the size and type noted shall be extended to the street right-of-way line with an approved cap. All connections and changes of direction shall be made using standard fittings designed for the purpose.
3. Where deep house connections or shallow connections are called for, but no service line is to be installed under this contract, all unused branches of such fittings shall be plugged watertight with a specified plug.
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4. Without special approval all lateral ends shall have a minimum depth of thirty-six (36) inches and a maximum depth of forty-eight (48) inches.
5. Markers shall be installed on lateral ends. Markers shall be 66″ long fiberglass/plastic; Green)Curv-Flex Anchor (attached) with Decal (Caution: Sewer Pipeline)bearing the inscription “Gulf Shores Utilities Board 968-6323”.
C. Precast Concrete Manholes:
1. Precast concrete manholes may be used when the following conditions are satisfied:
a. Details and shop drawings of the manholes, proposed to be furnished for this work, are submitted to and approved by the Engineer. prior to the manufacture of the units. Manholes which are not manufactured in strict compliance with the approved shop drawings and these specifications will be rejected.
b. The design and manufacture of the manholes and special pipe construction at manholes shall conform to these specifications.
c. Manhole excavation, bedding and pipe trench excavation and bedding at manhole junctions shall be performed in accordance with the provisions of Section I. A minimum of 12 inches of compacted angular stone shall be required below manholes or lift stations.
2. Precast manholes shall conform to the requirements of ASTM Designation C 478 with reinforcement of Grade 40 bars and the following modifications thereto:
a. The minimum shell thickness shall be 5-inches.
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b. Cement to be used in precast manholes shall be Type II. All aggregate to be 100% calcareous rock.
c. Joints, regardless of position in the complete structure, shall be filled with Ram-Nek plastic joint sealing compound. Height of wall sections shall not be less than three feet.
d. Lifting holes through the structures are permitted.
e. The design of the structure shall include a base of not less than 8-inches in thickness and shall incorporate an integral anti-flotation collar.
The base of the precast manhole may be cast monolithically or be cast on the riser section the day following the casting of the riser section in the following manner:
The day following the casting of the riser section, four (4) 18 inch sections of the bell portion of the riser shall be removed leaving the remainder of the bell for support of the riser during the process of casting the base. The portions of the riser which will be cast into or contact the base slab shall be coated with an approved chemical bonding agent. The re-enforcing steel cage of the riser shall be exposed in the 18 inch openings from which the concrete has been removed, and the re-enforcing steel for the bottom slab shall be tied to this exposed riser re-enforcing cage. The bottom slab shall then be cast around the riser section, all in accordance with the approved shop drawings.
f. All grout used for sealing around pipe opening shall be Type II cement and designed for use in water. All openings and joints shall be sealed watertight.
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g. Precast manhole tops, if used, shall terminate at such elevations as will permit laying up brick courses (maximum of 4 courses) under the manhole frame to make allowance for future street grade adjustments.
h. Drop connections, where required on precast manholes, shall be manufactured with the manhole elements at the casting yard. The manufacturer shall submit for approval the method of drop manhole construction. (Utilize 100% DI drop connection assemblies.)
3. Shallow manholes may substitute an eight-inch precast reinforced slab on the top in lieu of the cone section. slabs shall be laid in a full bed of mortar and pointed to form a dense joint.
4. Precast manholes shall utilize flexible wall sleeves for connection of sewer pipe. All openings and joints shall be watertight. The flexible wall sleeves shall be as specified in Paragraph 2.01.F.3. of this Section.
6. The invert channels shall be smooth and accurately shaped to a semicircular bottom conforming to the inside of the adjacent sewer section. Steep slopes outside the invert channels shall be avoided. Changes in size and grade shall be made gradually and evenly. Changes in the direction of the sewer or entering branch shall be a smooth curve with radius as long as practicable. Invert channels shall also be formed for pipe stub-outs.
D. Connections To Existing Structures And Sewers:
1. Various sewer lines shall be connected to existing manholes and structures. Provisions have been made in some of the existing structures for future connections and may require only the removal of a plug and the connection of the proposed line, while other connections will require cutting into the existing structure. Openings in existing manholes shall be created by core drilling the manhole at the proper grade. The use of jackhammers is prohibited. Any damage to existing manholes shall be repaired by the contractor in accordance with GSU requirements. In precast manholes, a properly sized flexible rubber connector with stainless steel bands shall be installed in the drilled hole. Connection to existing brick manholes requires a 3-foot ductile iron nipple through the manhole wall. The nipple shall be connected to the main line using an approved flexible connector(Fernco or equal). The ductile iron nipple shall be sealed to the opening in the manhole using approved non-shrink grout for a watertight seal. Invert of existing manhole shall be re-formed to accommodate flow from the new connection. The Contractor shall exercise care in cutting into the existing structure and any damage done to the structure shall be repaired as required by GSU and the Engineer, at the Contractor’s expense. The contractor shall be responsible for the cleaning of any effected portion of the existing system if flow from new lines is not properly contained. Drop connections to existing manholes shall be installed as detailed on the Drawings for new construction.
2. New sewer lines connected to existing manholes must have Ductile Iron nipple (3′+) thru manhole wall then connect to main line via approved flexible connector. (Fernco).
3. The drop connection for existing Manhole shall be constructed of Class 51, Ductile Iron pipe. Anchor straps shall be not less than 3/16-inches by 1-1/2-inches and constructed of A1S1 304 stainless steel. Wall anchor bolts shall not be less than 5/8-inch and constructed of corrosion resistant metal. The Contractor shall provide an approved adapter for the connection between the DIP fitting and PVC pipe.
E. Additional Work: Additional items of construction such as cleanouts, terminal lamp holes, special manholes and other items necessary for the complete installation of the system shall conform to specific details on the Drawings and shall be constructed of first-class materials conforming to the applicable portions of these specifications.
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F. Where an existing manhole is not available for connection to the existing gravity sewer system, the contractor shall construct a “doghouse” manhole over the existing main. All requirements governing bedding and construction of standard manholes shall apply. Any damage to the existing main shall be repaired at the contractor’s expense. The section of existing pipe inside the manhole shall be cut only after successful testing and inspection of the new lines are complete.
G. Location In Relation To Water Lines: Refer to Section IV, Paragraph 3.02.H.
3.03 FIELD QUALITY CONTROL
A. Tests, Inspections and Acceptance of Materials and Workmanship:
1. Workmanship: It is imperative that all sewers and appurtenances be built practically watertight and that the Contractor adhere rigidly to the specifications for materials and workmanship. All of the sewage must be pumped for disposal and special care and attention must be paid to securing watertight construction. Upon completion, the sewers or sections thereof, will be tested and gauged and if leakage is above the allowable limits specified, the sewer will be rejected.
a. On completion of each block or section of sewer, or such other times as the Engineer may direct, the block or section of sewer shall be cleaned, tested and inspected. Each section of the sewer shall show, on examination from either end, a full circle of light between manholes.
b. Each manhole or other appurtenance to the system shall be of the specified size and form, be watertight, neatly and substantially constructed, with the top set permanently to exact position and grade. All repairs shown necessary by the inspection shall be made; broken or cracked pipe replaced; all deposits removed and the sewer left true to line and grade, entirely clean, and ready for use.
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c. In paved areas, final inspection of manhole construction will be performed after all roadwork is complete.
3. Air Leakage Test of Sewers
a. General: On all sanitary sewer lines, the Contractor shall conduct a line acceptance test using low pressure air. The air test shall be conducted after the pipe has been backfilled and the cost of air testing shall be included in other items of work. Equipment to be used in making the test shall be specifically designed for this purpose and shall be Cherne Air-Loc Equipment or approved equal. The Engineer shall be advised at least 48 hours before tests are conducted.
b. Procedures: All pneumatic plugs shall be seal tested before being used in the actual test installation. One length of pipe shall be laid on the ground and sealed at both ends with the pneumatic plugs to be checked. Air shall be introduced into the plugs to 25 psi. The sealed pipe shall be pressurized to 5 psi. The plugs shall hold against this pressure without bracing and without movement of the plugs out of the pipe.
After a manhole to manhole reach of pipe has been backfilled and cleaned, and the pneumatic plugs are checked by the above procedures, the plugs shall be placed in the line at each manhole and inflated to 25 psig.
Low pressure air shall be introduced into this sealed line until the internal air pressure reaches 4 psig greater than the average back pressure of any groundwater that may be over the pipe. At least two minutes shall be allowed for the air pressure to stabilize. After the stabilization period (3.5 psig minimum pressure in the pipe), the air hose from the control panel to the air supply shall be disconnected.
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The test of that portion of line being tested shall be termed “Acceptable” if the time required in minutes for the pressure to decrease from 3.5 to 2.5 psig (greater than the average back pressure of any groundwater that be over the pipe) shall not be less than the time shown for the given diameters in the following table:
Pipe Dia. In Inc. Minutes ----------------- ------- 4 2.0 6 3.0 8 4.0 10 5.0 12 5.5 15 7.5 18 8.5 21 10.0 24 11.5
In areas where ground water is known to exist, the Contractor shall install a one-half inch diameter capped pipe nipple, approximately 10 inches long, through the manhole wall on top of one the sewer lines entering the manholes. This shall be done atthe time the sewer line is installed. Immediately prior to the performance of the Line Acceptance Test, the groundwater shallbe determined by removing the pipe cap, blowing air through the pipe nipple into the ground so as to clear it, and then connecting a clear plastic tube to the nipple. The hose shall be held vertically and a measurement of the height in feet of water over the invert of the pipe shall be taken after the water has stopped rising in this plastic tube. The height in feet shall be divided by 2.3 to establish the pounds of pressure that will be added to all readings. (For example, if the height of water is 11-1/2 feet, then the added pressure will be 5 psig. This increases the 3.5 psig to 8.5 psig, and the 2.5 psig to 7.5 psig. The allowable drop of one pound and thetiming remain the same.) Other methods for determining groundwater level may be used if approved in advance and if results are expected to be accurate in determining the groundwater level.
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Should the line fail the pressure test, the Contractor shall, at his expense, determine the source of leakage and make repairs as necessary to eliminate leakage. Air testing shall be in addition to infiltration tests specified in Paragraph 3.03.A.4
4. Mandrel Test of Sewers
All PVC sewer lines shall be tested by the Contractor at his expense for diametric deflection using a GO-NO-GO type mandrel or other approved method. The mandrel shall have an outside diameter of not less than 95 percent of the PVC pipe inside diameter. This testing shall be accomplished prior to final acceptance, but after the pipe has been backfilled completely.
Leakage into the sewer shall not exceed 100 gallons per mile of sewer per inch of inside diameter of the sewer per 24 hours to any section between successive manholes. The amount of leakage shall be measured by a suitable weir or other device. All equipment and labor for measuring the infiltration shall be furnished by the Contractor.
If the infiltration exceeds the above specified amount, the Contractor shall make the necessary corrections to bring it within the acceptable limits. All visible leaks or points of infiltration shall be repaired even though the infiltration is below the maximum specified.
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