The text
Footnotes:
--- (10) --- Editor's note— Ord. of 3-9-2010 renumbered Div. 10, §§ 21-131—21-156, as Div. 11, §§ 21-131—21-156.
Sec. 21-131. - Size of sewer.#
(a)
No public, main line gravity sewers shall be less than eight (8) inches in diameter.
(b)
Building sewers shall be a minimum of six (6) inches in diameter.
(c)
Force main sewers shall be sized to provide, at design average flow, velocity in excess of two (2) feet per second. In no case shall force mains be less than four (4) inches (10.2 cm) in diameter.
(d)
Low-pressure sewers shall be a minimum of one and one-half (1½) inches in diameter and be sized to provide, at design average flow, velocity in excess of two (2) feet per second.
(Ord. of 1-2002, Art. X, § 1)
Sec. 21-132. - Depth of sewer.#
(a)
No building sewer shall have less than four (4) feet of cover over the crown of the pipe unless approved by the sewer engineer. No sewer extensions or other public sewers shall have less than five (5) feet cover over the crown of the pipe unless approved by the sewer engineer. The town reserves the right to impose special conditions on such approvals.
(b)
When the vertical distance between the main line sewer and the building/house service, at the location of the main line sewer, is greater than four (4) feet, a vertical pipe riser (chimney connection) shall be used to connect the building/house service to the main line sewer.
(Ord. of 1-2002, Art. X, § 2; Ord. of 3-9-2010)
Sec. 21-133. - Slope.#
(a)
All sewers shall be so designed and constructed to give mean velocities, when flowing full, of not less than two (2.0) feet per second based on Manning's Formula using an "n" value of 0.013. Use of other "n" values may be permitted by the town if deemed justifiable on the basis of research or field data presented. The following are the minimum slope (S) which should be provided; however, slopes greater than these are desirable:
Minimum Slope in Feet
Sewer Size (inch) S (ft per ft)
6 0.0200 (1/4" per foot)
8 0.0040
10 0.0028
12 0.0022
14 0.0017
15 0.0015
16 0.0014
18 0.0012
21 0.0010
24 0.0008
(b)
Under special conditions, if detailed justification is presented, slopes slightly less than those required for the two (2.0) feet per second velocity when flowing full may be permitted. Such decreased slopes will only be considered where the depth of flow will be 0.3 of the diameter or greater for design average flow. Whenever such decreased slopes are selected, the design engineer must furnish with the sewer design plans a report containing detailed justification for the decreased slopes and computations for the depth of flow in such pipes at minimum average, and daily and hourly rates of flow. Decreased slopes may cause additional sewer maintenance expenses. The town reserves the right to impose special conditions when decreased slopes are approved.
(c)
Sewers shall be laid with uniform slope between manholes. Sewers on twenty (20) percent slope or greater shall be anchored securely.
(Ord. of 1-2002, Art. X, § 3; Ord. of 3-9-2010)
Sec. 21-134. - Sewer length.#
No gravity sewer main shall exceed four hundred (400) feet between manholes. Manholes shall be installed at points of direction change or grade change in each sewer main.
(Ord. of 1-2002, Art. X, § 4)
Sec. 21-135. - Alignment.#
All sewer extensions and other public sewers shall be laid true to line and grade so that inspection can be performed by sighting through the pipe from manhole to manhole. Changes in grade or slope shall warrant the installation of manholes for such transitions.
(Ord. of 1-2002, Art. X, § 5)
Sec. 21-136. - Manholes. (See exhibit F and G)#
(a)
Location. Manholes shall be installed at the end of each line; at all changes in grade, size or alignment; at all intersections; and distances not greater than four hundred (400) feet.
(b)
Drop type. An inside drop pipe or an outside drop pipe shall be provided for a sewer entering a manhole at an elevation of twenty-four (24) inches or more above the manhole invert. Where the difference in elevation between the incoming sewer and the manhole invert is less than twenty-four (24) inches, the invert should be filleted to prevent solids deposition. For larger sewers where this would be impracticable, the invert of the manhole shall be so constructed so that there is a smooth transition of flow in the manhole.
(c)
Diameter. The minimum diameter of regular manholes shall be forty-eight (48) inches. Manholes with inside drop pipe shall be sixty (60) inches in diameter. A minimum access diameter of twenty-four (24) inches shall be provided.
(d)
Inverts and bench. The flow channel through manholes shall be made to conform to shape and slope of the sewers entering and leaving the manholes. The bench shall be constructed so that under peak design conditions the flow will remain in the channel.
(e)
Frames and covers. Provide standard manhole frames and covers.
(f)
Watertightness. Watertight covers shall be used in areas where the top of the manhole will be below FEMA flood levels and in areas known to be subject to flooding.
(Ord. of 1-2002, Art. X, § 6)
Editor's note— It should be noted that Exhibits F and G referenced above are not set out at length herein, but are on file and available for inspection in the office of the town clerk.
Sec. 21-137. - Materials for public sewer construction.#
(a)
Requirements for public sewers shall be applicable to sewer extensions and sewer systems in developments and subdivisions. All plans for public sewers, sewer extensions, and proposed developments and subdivisions shall be submitted for review. The following material specifications shall be used as guidelines for submittal of plans for review. Changes in these specifications may be required if the nature of wastes carried or design/construction problems require a change in materials used. These changes are to be reviewed and approved by the sewer engineer designated by the town.
(b)
Reference in the specifications to any article, device, product, materials, fixture, form or type of construction etc. by name, make or catalog number is included to establish a standard of quality. Any article, device, product, material, fixture, for or type of construction which, in the judgment of the town, is equal to that named may be substituted.
(c)
Each straight pipe and standard fitting shall have cast upon it, or stamped on the pipe, the manufacturer's name and trademark, nominal pipe size and material designation.
(d)
Materials:
(1)
Polyvinyl chloride pipe—Gravity sewer. Polyvinyl chloride (PVC) gravity sewer pipe and fittings shall conform to SDR35 (standard dimension ratio), and conform to ASTM D3034 (Type PSM polyvinyl chloride sewer pipe and fittings). Joints shall be elastomeric gasket joints, providing a watertight seal, conforming to ASTM D3212 (Joints for Drain and Sewer Plastic Pipes Using Flexible, Elastomeric Seals).
(2)
Polyvinyl chloride pressure pipe.
Force main: Polyvinyl chloride force main shall be Class 150-DR18 push-on joint pressure pipe conforming to AWWA C900 (polyvinyl chloride (PVC) pressure pipe, four-inch through twelve-inch for water). Fittings shall be mechanical joint ductile iron conforming to ANSI A21.10 (grey-iron and ductile-iron fittings, three-inch through forty-eight-inch, for water and other liquids). Pipe and fitting joint shall conform to ANSI A21.11 (rubber-gasket joints for ductile-iron and grey-iron pressure pipe and fittings) and shall include plain rubber gaskets suitable for use with raw sewage. Fittings shall be cement lined and seal coated inside and out in accordance with ANSI A21.4 (cement mortar lining for ductile-iron and grey-iron pipe and fittings for water).
Low pressure sewers: Polyvinyl chloride sewers shall be push-on joint pressure pipe meeting ASTM 2241 with wall thickness rating of SDR 21, pipe sizes from one and one-half-inch to eight-inch. Fittings shall be push-on pressure type meeting ASTM D3139 rated wall thickness of SDR 21. Pipe gaskets shall meet ASTM F-477.
(3)
Ductile iron pipe and fittings. Ductile iron pipe and fittings shall conform to ANSI A21.51. (ductile iron pipe, centrifugally cast in metal molds and sand-lined molds -thickness class 51 minimum). Fittings shall be class C and conform to ANSI 21.10. Ductile iron pipe shall be a bell and spigot joint. Ductile iron pipe shall have nominal laying length of at least sixteen (16) feet. Pipe and fittings shall be given an exterior coating of bituminous paint and an inside cement mortar lining in accordance with ANSI 21.4 (cement-mortar lining for ductile-iron and gray-iron pipe and fittings). The cement mortar lining shall be given a protective coating of bituminous paint.
(4)
Valves: Gate, air release, corporations, curb stops.
a.
Gate valves for force main drains and cleanouts, shall be ductile iron solid wedge gate valves made in accordance with AWWA specification C-500 or resilient-seated gate valves made in accordance with AWWA specification C-509. Valves to be rated for one hundred twenty-five (125) psi working pressure. Valve body and bonnet to be coated inside and out with fusion bonded epoxy.
b.
Air release and vacuum release valves are to be installed at high points in force mains and shall be designed for use in sewage and shall have a cast iron body conforming to ASTM A48, class 30 or A126, class B with stainless steel floats and stainless steel trim conforming to ASTM A276 or bronze trim conforming to ASTM B62, and pressure rated for 0 to 300 psi.
c.
Valves for low pressure sewers shall be bronze conforming to ASTM B62 alloy C83600 for corporation stops and curb stops and shall be full ported ball valves with threaded AWWA taper or AWWA I.P.T. conforming to AWWA C300 standard for underground service lines. Valves to be as manufactured by Mueller Co., Ford or equal. Valves to have large operating head, one piece body and be rated by AWWA for three hundred (300) psi working pressure.
d.
Check valves for low pressure services shall be bronze, swing check type, conforming to ASTM B62 Alloy C83600 as manufactured by Mueller Co. or equal, pressure rated to two hundred fifty (250) psi, or PVC housing with Buna-N flapper gasket and stainless steel hardware as manufactured by Environment One Corporation, or equal.
e.
Curb boxes shall be steel extension type, with cast iron lid with brass pentagon head plug, with stationary rod, and cast iron arched base. All boxes to be coated with asphalt base paint. Cast iron sewer cleanout covers marked "SEWER" shall be placed over all low pressure curb boxes for proper identification.
(5)
Other pipe materials. As technology changes, other materials may be considered for substitution by the town.
(6)
Manholes.
a.
Barrels and cone sections. Manhole barrels and cone sections shall be precast reinforced concrete and shall conform to ASTM C478 (precast reinforced concrete manhole sections) except as specified otherwise.
b.
Base section. Manhole base sections shall be monolithic to a point six (6) inches above the crown of the incoming pipe and shall conform to ASTM C478, except as specified otherwise. For inside or outside drop manholes, openings for pipes shall be a minimum of six (6) inches from any horizontal joint.
c.
Inverts and shelf. Manhole inverts and shelf shall provide a smooth sloped channel constructed to conform to the size and the shape of the inlet and discharge pipe or pipes. The invert shall be constructed of brick grade SS meeting ASTM C32 (sewer and manhole brick) and shall be constructed with mortar using type II Portland cement. The base work below the brick shall be suitable materials consisting of cast-in-place concrete or solid brick construction, subject to the approval of the sewer superintendent.
Alternate invert construction may include a one-piece fiberglass flume, shelf and bells precast into the manhole base. Channels shall be at least the same depth as the pipe diameter and the shelf shall have a non-skid surface. The bells shall either accept the "boot" connector or a properly sized rubber ring to seal the pipe to the manhole connection in accordance with ASTM C 923 and ASTM C 1244.
d.
Horizontal joints. Horizontal joints between sections of precast concrete barrels shall be of a type approved by the sewer superintendent, and shall have an elastomeric or mastic-like gasket for watertightness.
e.
Corbel of manhole (between manhole cone and frame and cover) shall be constructed of brick grade SS meeting ASTM C32 (sewer and manhole brick) and shall be constructed with mortar using type II Portland cement. Outside of corbel shall be coated with mortar and sealed. Care shall be made to provide watertight construction. Flexible gaskets or mastic-like gasket shall be placed between the manhole frame casting and the top coarse of brick to provide added sealing against leaks, which may be caused by thermal or frost action against the manhole cover. Frame chimney seals may be required as specified in [subsection (d)(10)].
(7)
Manhole rings. Manhole rungs shall be steel reinforced copolymer, polypropylene plastic of an approved design. Rungs shall not be less than twelve (12) inches wide. Rungs shall be manufactured by M.A. Industries, Inc., East Point, Georgia or Improved Construction Method, Inc., Jacksonville, Arkansas.
(8)
Cast iron manholes frames and covers. Cast iron manhole frames and covers shall be heavy duty suitable for a minimum H-20 loading or more at the discretion of the town and conform to the standards of the town as regards pattern, dimensions and weight. They shall be gray cast iron. Castings shall be true to pattern and free from flaws. The bearing surfaces of manhole frames and covers shall be machined to give continuous contact along the entire perimeter. Manhole frames and covers shall be manufactured by E.L. LeBaron Foundry Company (LB268-3), or Neenah Foundry Company, or equal with twenty-four-inch clear opening and twenty-six-inch covers. All covers shall have the word "SEWER" cast into the top surface.
(9)
Watertight cast iron manhole frames and covers. Watertight manhole frames and covers shall be used in sewers constructed in floodplain or floodway areas. Manhole covers shall be type BW or SW manufactured by E.L. LeBaron Foundry Company (LBW268-1), or Neenah Foundry or equal with twenty-six-inch diameter covers, and twenty-four-inch diameter clear openings and shall be supplied with inner cover and locking bar. Covers shall have the word "SEWER" cast into the top surface.
(10)
Watertight covers and standard covers subject to flooding or covers in cross country sewers shall be installed with a flexible manhole frame chimney seal consisting of an internal or external rubber compound conforming to ASTM C923 standards, with a minimum fifteen hundred (1,500) psi tensile strength, maximum eighteen (18) percent compression set and hardness (durometer) of forty-eight (48). Bands shall be used to compress the rubber seal to the corbel and shall be 16-gauge stainless steel conforming to ASTM A240, type 304 with screws conforming to ASTM F593 and 594, type 304.
(11)
Ductile iron manhole frames and covers shall be manufactured of flake graphite (gray iron) complying with the requirements of ASTM A48-83 or spheroidal or nodular graphite iron (ductile iron) complying with the requirements of ASTM A536-80. Frames and covers shall be round model GTS, class 400 as furnished by Quality Water Products, Inc. or equal. Frames and cover shall meet a test load rating of eighty-eight thousand (88,000) pounds. Frames and cover shall be of the locking type with blocking keys. Frames shall have a polyethylene gasket. Covers shall have cast in the word "SEWER". Watertight covers shall have a watertight "0"-ring and shall be rated to fifteen (15) psi external pressure. Cover shall be secured by means of six (6) cams and stainless steel bolts.
(12)
Pipe joint lubricant shall be as provided by the pipe manufacturer. The use of automotive grease and/or petroleum based lubricants is not permitted.
(Ord. of 1-2002, Art. X, § 7; Ord. of 3-9-2010)
Sec. 21-138. - Materials for pipe installation.#
(a)
Pipe bedding. Material for pipe bedding shall be washed and screened sharp gravel, well graded in sizes from one-quarter-inch to one and one-half-inch inclusive. It shall be clean, hard, durable and free from dust, clay or organic matter. It shall be well compacted in place. Pipe bedding shall be used to cover the pipe to a height of six (6) inches above the crown of the pipe.
(b)
Blanket materials. Material to be installed from six (6) inches above the crown of the pipe to one (1) foot above the crown of the pipe shall be clean sharp sand or the following:
(1)
Subsoil. Material excavated on site which is friable, natural soil composed of gravel, sand, or silty or clayey gravel and sand; free from debris, concrete or other rubble, organic matter, muck, peat, excavated rock and boulders over six (6) inches in maximum dimensions; or
(2)
Crushed gravel. Crusher run gravel consisting of inert material that is hard durable stone and coarse sand, free from loam or clay, surface coatings' and deleterious material. Gradation shall be in conformance with RIDOT specification for processed gravel for sub-base.
(c)
Backfill materials. Material to be used as backfill shall be common fill defined in subsection (b)(1) above as subsoil.
(d)
Unsuitable materials. Materials unsuitable for use as backfill materials include cut or broken pavement, debris, concrete or other rubble, organic materials, muck, peat, silty soils or clayey soil, rock over six (6) inches in maximum dimension and any material which will not provide sufficient support or maintain the installed sewers or appurtenant construction in a stable condition.
(e)
Excavation support. Lumber used for sheeting, walers, struts, shores, bracing, and other system members shall be free from loose knots and other defects that may impair its strength or durability. Lumber shall be spruce, fir or equal.
(f)
Rip-rap material. Stone for rip-rap shall be sound, of approved quality, nearly cubical in shape and consist of field stones, boulders, quarry stones or rock fragments. At least fifty (50) percent shall be not less than twelve (12) inches in the least dimension. The remainder shall be graded to form a compact mass when installed.
(Ord. of 1-2002, Art. X, § 8)
Sec. 21-139. - Notification and permits.#
(a)
Utility companies shall be notified in writing at least seventy-two (72) hours (excluding Saturdays, Sundays and legal holidays) before excavation in a public way. Such notification gives the companies the opportunity to cooperate in protecting underground cables, pipe, structures, etc., from possible accidental damage or resulting service interruption.
(b)
Excavation required in a public way or street under the town's jurisdiction shall be made only with the permission of the town highway department. Excavation required in a public street under the jurisdiction of the State of Rhode Island Department of Transportation (RIDOT) shall not begin until a permit has been obtained from the department. Excavation near or under railway structures shall not begin until a permit has been obtained from Amtrak or the governing rail authority.
(c)
The owner of any particular underground structure shall be notified promptly of damage to the structure. Whenever the town or public utility companies may require, pipes or other underground structures encountered in excavating or trenching shall be properly supported across the excavation or trench. Obtain locations of other public utilities of the town that may be encountered in the sewer installation. All requirements of these utilities in the form of, and not limited to, fees, permits and repair methods shall be met. The town utilities are not registered under "Dig-Safe", therefore notification of each utility not covered by "Dig-Safe" is required.
(Ord. of 1-2002, Art. X, § 9; Ord. of 3-9-2010)
Sec. 21-140. - General requirements.#
(a)
All excavations required for building sewers and public sewers shall be open trench work unless otherwise approved by the town. Pipe laying and backfill shall be done in accordance with the standard practice to provide proper support, drainage and freedom from rock damage in backfilling. No backfill shall be placed until the pipe has been inspected.
(b)
Before excavation is started, the bituminous or concrete street surface shall be cut vertically in a line parallel to the center line of construction, and slightly wider than the trench width, using an approved hand or power operated tool, so as to allow for trench excavation without further disturbing the surface on either side of the trench. All excavation shall be of sufficient width and depth with proper allowance for sheathing and bracing.
(c)
Excavation, concrete work, backfill, embankments and paving shall not be performed during freezing weather or upon frozen material and are subject to approval by the town director of the department of public works. New work shall be bonded to old or existing work, all subject to the approval of the town. The town shall have the right to decide when the weather is unsuitable.
(Ord. of 1-2002, Art. X, § 10; Ord. of 3-9-2010)
Sec. 21-141. - Permits and use of explosives.#
(a)
Obtain all required licenses, permits and insurance for the use of explosives.
(b)
Use explosives only in compliance with local regulations, laws and ordinances and as approved by the town. Blasting shall be conducted with all possible care so as to avoid injury to persons and property. Cover all blasting charges with mats or heavy timbers and take every precaution for the adequate protection of all persons, traffic, building, trees and other property. Sufficient warning shall be given to all persons in the vicinity of the work before blasting. Caps or other exploders shall not be kept in the same place in which dynamite or other explosives are stored.
(Ord. of 1-2002, Art. X, § 11; Ord. of 3-9-2010)
Sec. 21-142. - Excavation.#
(a)
Entrances and exits to abutting properties, private ways, alleys, and streets for ordinary traffic in and out of all premises shall be provided and maintained. Carry out the work in such a manner so as to minimize the interference and inconvenience to business concerns on account of the construction work. Truck away excavated materials to a stockpile and truck the materials back to the construction site for use as backfill if the town deems it necessary as a means of minimizing interference and inconvenience of business firms.
(b)
Length of trench allowed to be open:
(1)
The length of trench allowed to be open shall be subject to approval by the town. The total running length of all work in each section shall be kept as short as practical.
(2)
At traveled way areas, trenches shall not remain open overnight or weekends, trenches to be safely barricaded and lighted and checked regularly.
(c)
Excavation shall be carried to a point at least six (6) inches below the bottom of the pipe. If the bottom of any excavation has been removed below the required grade, it shall be brought to grade by refilling with gravel or other selected material which shall be well compacted. Materials shall be compacted to ninety (90) percent maximum density (modified proctor) at optimum moisture content.
(d)
Where the excavation is close to existing underground structures or utilities, the excavation shall be dug by hand to insure against damage of utilities or against disturbing load bearing soil.
(Ord. of 1-2002, Art. X, § 12; Ord. of 3-9-2010)
Sec. 21-143. - Dewatering trenches.#
The trenches and all other excavations shall be kept entirely free of water at all times until the sewers are laid, backfilled and tested and all other structures are finished ready for operation. Sand, silt, and debris entering the building sewer, sewer extensions or other public sewer due to improper removal of water or by neglect of the work shall be removed. During excavation the installed pipe shall be capped at all times to prevent the entrance of groundwater, silt, mud, debris, and overflow of septic tanks, dry wells, leach fields, storm drains and any other inflow.
(Ord. of 1-2002, Art. X, § 13)
Sec. 21-144. - Excavation support.#
(a)
Furnish, put in place, and maintain such sheeting, shoring and bracing, as may be required to support the sides of the excavation and to prevent any movement which could in any way injure the work, cause safety hazard, diminish the necessary width of trenches or other excavations, or otherwise delay the work or endanger adjacent structures.
(b)
All sheeting, shoring and bracing shall be of the sizes and strength needed to properly support the superimposed loads and to prevent any movement, displacement or settlement of adjacent structures, properties and utilities, pursuant to OSHA regulations 20 CFR, Part 1926.
(c)
Sheeting shall be driven where needed for stability, and excavation work conducted in such a manner as to prevent the material in back of the sheeting- from running under the sheeting and into the excavation. Care shall be taken to prevent voids outside of the sheeting, but if voids are formed, they shall be immediately filled, and well compacted. Sheeting shall not cross the pipe line nor shall it be driven to such a depth at manholes that it will bear upon the pipe.
(d)
Sheeting shall not unnecessarily be driven below the sewer invert. But where this is necessary, it shall not be removed, but cut two (2) feet higher than the top of the pipe and left in place.
(e)
The sheeting, shoring, bracing or parts thereof, shall be left in place after the completion of the work in locations where necessary to support existing structures. All sheathing, which is left in place, shall be cut off at least two (2) feet below the surface. Lumber removed may not be reused.
(f)
The town has the right to order sheeting and bracing installed and/or left in place, but shall not be construed as creating any obligation on its part to issue such orders, and its failure to exercise its right to do so shall not relieve the excavating contractor from liability for damages to persons or property occurring from or upon the work occasioned by negligence or otherwise growing out of a failure on the part of the excavating contractor to install or leave in place in the excavation sufficient sheeting and bracing to prevent any caving or moving of the ground adjacent to the sides of the excavation.
(Ord. of 1-2002, Art. X, § 14; Ord. of 3-9-2010)
Sec. 21-145. - Pipe bedding, pipe installation and blanket placement.#
(a)
All building sewers, sewer extensions, and other public sewers shall be bedded in clean gravel or other selected material, acceptable to the town. Blocking under the pipe is not permitted. Bedding material shall be properly compacted and shaped to fit the barrel of the pipe.
(b)
Each pipe shall be laid true to line and grade and in such manner as to form a close concentric joint with the adjoining pipe and to prevent sudden offsets of the flow line. As the work progresses, the interior of the sewer shall be cleared of all silt, mud, debris and materials.
(c)
Pipe laying shall proceed upgrade with the spigot ends pointing in the direction of flow. Joining pipes shall be performed in accordance with the manufacturer's recommendations.
(d)
After installing the pipe on the bed, the bedding material shall be placed and compacted to the spring line (horizontal center line) of the pipe. Bedding material shall be then placed to a level of six (6) inches above the crown of the pipe. Pipe/trench shall be inspected by the engineer designated by the town.
(e)
Blanket. Blanket materials shall be placed from the top of the bedding material to a level twelve (12) inches above the crown of the pipe and compacted.
(f)
Compaction. Place and compact bedding and blanket material in continuous layers not exceeding six (6) inches loose depth. Materials shall be compacted to ninety (90) percent maximum density (Modified Proctor) at optimum moisture content.
(Ord. of 1-2002, Art. X, § 15; Ord. of 3-9-2010)
Sec. 21-146. - Backfilling trenches.#
(a)
As soon as practicable after the pipe has been installed and the blanket material has been installed and compacted, the backfilling shall begin and shall thereafter proceed expeditiously.
(b)
Backfill. Material for backfilling shall be placed and compacted to depths, contours and grade required. Backfill systematically and as early as possible, to allow maximum time for natural settlement. Each layer of backfill shall be compacted after it is placed.
(c)
Place and compact backfill in continuous layers from the top of the blanket as follows:
(1)
Under grassed areas. Twelve (12) inches loose depth to four (4) inches below finish grade.
(2)
Under paving. Six (6) inches loose depth to underside of road base or sub-base.
(d)
Hydro-hammers used to prepare the base or sub-base for the road surface shall not be used within three (3) feet of the top of the pipe. Hydro-hammers may be used at distances greater than three (3) feet above the top of the pipe if the backfill has been compacted to ninety (90) percent maximum density (modified proctor) at optimum moisture content.
(e)
No stone or rock fragment shall be backfilled into the trench nor shall masses of backfilling material be dropped, as from a bucket on excavating equipment, into the trench in such a manner as to endanger the pipe.
(f)
Care shall be taken to prevent stones and lumps becoming nested. All voids between stones shall be completely filled with fine material.
(g)
Any voids left by the removal of sheeting shall be completely refilled with suitable materials thoroughly compacted.
(h)
Pieces of bituminous pavement shall be excluded from the backfill unless expressly permitted by the town in which case the bituminous pavement pieces shall be broken up as directed.
(i)
If, in the opinion of the town, the material to be used in the backfilling is unsuitable material, the material shall be removed and replaced with suitable material.
(j)
Excavated material, which is acceptable for surfacing or pavement sub-base shall be placed at the top of the backfill to such depth as, may be specified elsewhere by the highway surveyor or as directed. The surface shall be brought to the required grade and stones raked out and removed.
(Ord. of 1-2002, Art. X, § 16; Ord. of 3-9-2010)
Sec. 21-147. - Backfilling around structures.#
As soon as practicable after the pipes and manholes have been placed, leakage tests shall be made after which backfilling shall begin and shall thereafter be prosecuted expeditiously. Unequal pressure shall be avoided by carrying the backfill material up evenly. The materials shall be placed and compacted in accordance with [subsection 21-146(c)].
(Ord. of 1-2002, Art. X, § 17)
Sec. 21-148. - Surplus material.#
All surplus material is to be removed as directed by the town, or property owner.
(Ord. of 1-2002, Art. X, § 18; Ord. of 3-9-2010)
Sec. 21-149. - Pavement.#
(a)
Road pavements constructed over pipe trenches shall match the existing road surface and be installed after the backfill has been thoroughly compacted. All work shall be done as directed by the town highway department, and shall be in accordance with the town road standards. For state roads all work shall be done in accordance with Rhode Island Department of Transportation Standards.
(b)
Where the sewer is laid in a paved shoulder, or in a gravel shoulder, or in existing or new rights-of-way including private property, the area disturbed by construction shall be resurfaced to match the original conditions and surface. All sewers laid within right-of-ways shall be provided with a surface, which is capable of having full access maintained by the highway department, and shall be approved by the highway surveyor.
(c)
Where there is reinforced concrete slab under bituminous concrete top, the reinforced concrete slab shall be restored.
(d)
Where the trench is in a paved road or shoulder or sidewalk or pavement of any kind, after the trench is backfilled, apply a temporary bituminous concrete patch, which shall be maintained so as not to create a nuisance or a traffic hazard until the final surface is applied. All patching and paving work on the town roads subject to approval by the town highway department.
(Ord. of 1-2002, Art. X, § 19)
Sec. 21-150. - Protection of slope.#
(a)
Any slope of the filled-in area, exposed to flooding shall be protected by rip-rap at finished grade. Thickness of rip-rap layer shall be not less than twelve (12) inches.
(b)
All other slopes shall be covered with six (6) inches of loam and properly seeded.
(Ord. of 1-2002, Art. X, § 20)
Sec. 21-151. - Leakage testing.#
(a)
The installed sewer and manholes shall be gas and water tight. Leakage tests shall be made.
(b)
Infiltration shall not exceed one hundred (100) gallons per inch diameter in twenty-four (24) hours per mile of sewer; measured during maximum groundwater conditions.
Calculations:
Infiltration in gallons per day
GPD = Pipe Diameter-inch × Distance - Ft. × 100 gallons
5280 ft/mile
(c)
Manhole leakage shall not exceed one-eighth (⅛) inch drop per hour, after absorption, during a twenty-four-hour water drop test. Manhole testing to be completed prior to construction of invert channels where practicable.
(d)
Building/house services shall be tested by either a dye test of each pipe joint during new construction or a pressure test of the entire line as described in [section 21-152].
(Ord. of 1-2002, Art. X, § 21)
Sec. 21-152. - Pressure testing—Gravity sewers.#
(a)
Pressure testing of gravity sewers shall be of the following methods:
(1)
Water drop test. The sewer shall be subjected to internal pressure by plugging the pipe at the lower end and then filling the sewers and the high manhole with clean water to a height of eight (8) feet above the top of the pipe. The leakage from the sewer will be measured by the volume of water added to the high manhole to maintain the water level in the manhole. Ex-filtration shall not exceed one hundred (100) gallons per inch diameter per twenty-four (24) hours per mile of pipeline [see subsection 21-151(b)].
(2)
Air testing (preferred method). If low pressure air testing of the pipe lines is used, air is to be applied slowly until the pressure reaches four (4) psi. Allow two (2) minutes for temperature adjustment. The test, made between two (2) manholes three hundred (300) feet apart, shall conform to the following requirements:
a.
Air pressure at start 3.5 psi. Air pressure shall be adjusted 0.433 psi for each foot below ground water table. Water drop test will be adjusted in same manner. Infiltration test may be substituted for air test in high groundwater areas subject to the approval of the sewer superintendent.
b.
Air pressure at stop 2.5 psi or better for the testing time listed below:
Pipe Size Time
6' 5 min. 40 sec.
8" 7 min. 36 sec.
10" 11 min. 52 sec.
12" 17 min. 05 sec.
15" 26 min. 42 sec.
18" 38 min. 27 sec.
(b)
Should the sections under test fail to meet the requirements, the leak shall be located and the repairs necessary to eliminate the leak shall be accomplished. The sewer shall then be retested.
(Ord. of 1-2002, Art. X, § 22)
Sec. 21-153. - Pressure testing—Force mains.#
(a)
Force mains shall be tested for pressure and leakage in accordance with AWWA C600—Installation of Ductile Iron Water Mains and Their Appurtenances, except as amended or added below:
(1)
Test duration. Two (2) hours.
(2)
Test pressure. One hundred fifty (150) percent of maximum operating pressure.
(3)
Allowable pressure loss. Pressure shall not vary more than ± five (5) psi for the duration of the pressure test.
(4)
Allowable leakage. Allowable leakage shall be determined by the following formula:
L = SD (P)^1/2
133200
L = allowable leakage, in gallons per hour.
S = length of pipe tested, in feet.
D = nominal pipe diameter, in inches.
P = average test pressure, in psi (gauge).
(5)
Allowable leakage, in gallons per hour, per one thousand (1,000) feet of pipeline can be determined from the following chart.
Nominal Pipe Diameter-inches
Average
Test Pressure psi 3 4 6 8 10 12 14
250 0.36 0.47 0.71 0.95 1.19 1.42 1.66
225 0.34 0.45 0.68 0.90 1.13 1.35 1.58
200 0.32 0.43 0.64 0.85 1.06 1.28 1.48
175 0.30 0.40 0.59 0.80 0.99 1.19 1.39
150 0.28 0.37 0.55 0.74 0.92 1.10 1.29
125 0.25 0.34 0.50 0.67 0.84 1.01 1.18
100 0.23 0.30 0.45 0.60 0.75 0.90 1.05
(Ord. of 1-2002, Art. X, § 23)
Sec. 21-154. - Relation to water mains and/or water services.#
(a)
Whenever possible, sewers shall be installed with a minimum of ten (10) feet horizontal separation between the sewer and potable water lines. Should a lateral separation of ten (10) feet not be possible, one of the following methods of protection shall be employed. In both methods, the water main invert shall be eighteen (18) inches above the sewer crown. Sewer main shall be installed with minimum vertical separation of eighteen (18) inches below water main.
(1)
Lay sewer and water main in separate trench.
(2)
Lay the sewer and water main in same trench with the water main at one (1) side on a bench of undisturbed earth.
(b)
Whenever sewers must cross under water mains, the sewer shall be laid at such an elevation that the top of the sewer is at least eighteen (18) inches below the bottom of the water main. When the elevation of the sewer cannot be varied to meet the above requirements, the water main shall be relocated to provide this separation or reconstructed with mechanical-joint cement lined ductile iron pipe for a distance of ten (10) feet on each side of the sewer. One (1) full length of water main should be centered over the sewer so that both joints will be as far from the sewer as possible.
(c)
When it is impossible to obtain horizontal and/or vertical separation as stipulated above, both the water main and sewer shall be constructed of mechanical-joint cement lined ductile iron pipe or other material based on equivalent watertightness and structural soundness. Both pipes shall be pressure tested by an approved method to assure watertightness or both pipes shall be encased in concrete.
(Ord. of 1-2002, Art. X, § 24)
Sec. 21-155. - Cleanouts.#
(a)
Cleanouts shall be made of durable corrosion resistant materials conforming in size and thickness to that required for pipe and fittings to which the cleanout will be connected. The design shall be such that the closure plug when properly secured will make a gas-tight and watertight seal.
(b)
Cleanouts shall be installed in building sewers not more than one hundred (100) feet apart and at each change of direction, which is greater than forty-five (45) degrees.
(c)
Cleanouts shall have removable plugs or caps and a cast iron cover at finished grade.
(Ord. of 1-2002, Art. X, § 25)
Sec. 21-156. - Elbows—Bends.#
No elbow or bend greater than forty-five (45) degrees shall be installed in building sewers. The use of two (2) or more forty-five (45) degrees elbows may be used upon the approval of the town. In such cases a two-foot minimum straight section of pipe shall be installed between each elbow with a cleanout for a practical length to facilitate sewer rooting and cleaning equipment.
(Ord. of 1-2002, Art. X, § 26; Ord. of 3-9-2010)