01_45_10_Sequence_of_Construction_Add1.docx

INFRASTRUCTURE IMPROVEMENTS FOR THE

SOUTH BAY INTERNATIONAL WASTEWATER TREATMENT PLANT

San Diego County, California

SPECIFICATION 01.45.10

SEQUENCE OF CONSTRUCTION

General Summary This document is a supplement to the Plans and Specifications. It establishes a proposed sequence of construction activities and defines constraints that are to be accommodated and specific time restraints associated with the construction activities. Contractor to review this proposed Sequence of Construction and thoroughly familiarize himself with all constraints for maintaining operations of the plant. Contractor to propose a Sequence of construction incorporating these constraints and secure concurrence of Owner prior to starting work. Should the Contractor decide to adopt this proposed Sequence of Construction as his proposed Sequence of Construction, he does so with the understanding that this in no way relieves him from his obligations for preparation of a workable Sequence of Construction and assuming full responsibility for same.

This Sequence of Construction only mentions components of work that are sequence-sensitive, not all portions of work required by Contract.

RELATED REQUIREMENTS

The following may not include all related documents, contract clauses, and technical specifications, and does not relieve the Contractor of the responsibility of performing work associated with this specification in accordance with al terms of the Contract herein.

Specification 01.22.00-Measurement and Payment Specification 01.33.00-Submittal Procedures Contract: Section I “Specifications and Drawings for Construction”.

Work must be performed within an operating plant and must be scheduled and performed to have minimal impact on plant operations.

Plant operational requirements take precedence over Contractor activities. Therefore, interruption of plant operations must be coordinated and are subject to the operational requirements of the plant. Contractor to assume that any interruption of plant operations may be deferred by up to one week from the requested time due to operational constraints.

All electrical power transfers to be performed under unloaded condition.

Definitions “Interruption of plant operations” is defined as any activity that will result in a change in the current method of plant operation or in the position of plant facilities (valves, switches, etc.). Contractor to request such “interruption of plant operations” from the Owner no less than ninety-six (96) hours in advance. Owner may defer the request as allowed by Paragraph 1. 2. Request to be submitted in accordance with Paragraph 1.5. Due to operational constraints, no two interruptions of plant operations that inhibit wastewater flow for longer than two (2) hours are allowed within a single 48-hour period.

“Partial Utilization”, “Substantial Completion”, and “Warranty Period for Items in continuous service”. Refer to Contract Documents for definition. Warranty period will start for the items in continuous service as defined by the Contract Documents.

The terms “open, close, start, stop, operate, verify, energize, de-energize, transfer, Switch-over, etc.” when used in conjunction with the facilities that are in-service or about to be placed in-service are understood to mean: Contractor is to perform the operation under the direct supervision of the Owner’s operation or maintenance staff. For major electrical operations, the Owner will probably elect to perform the activity with their own forces. Contractor is to not abuse Owner’s equipment during these operations, however, it is understood that equipment failure may occur during operation. Contractor will not be held responsible, provided it was not due to abuse or improper means or method.

The term “operational test” refers to the period of specified duration that the installed system is tested to verify operational integrity of a system prior to having the system be placed in-service. Operational testing requires that representatives of all major components for the systems be on-site for timely identification and resolution of system issues.

“Low Flow Period” refers to the time of day when the plant influent flow rate reaches the diurnal minimum. It occurs between the hours of 3 AM and 8 AM.

Full Plant Shutdown: All normally on-line treatment units are stopped and all available storage is used to accommodate the incoming waste flows.

Partial Plant Shutdown: A portion of the normally on-line treatment units are temporarily shut-down and no longer operating.

System Description General The South Bay International Wastewater Treatment Plant is an operational treatment plant, treating a daily capacity of up to 25 MGD. The Work, outlined in Section 01.11.00, generally consists of adding flow equalization tanks and pumps, adding Secondary Settling Tanks (SSTs) and associates facilities, and the complete replacement of the vertical turbine, Return Activated Sludge pumps.

There are multiple points of connection with the existing facilities; structurally, mechanically, electrically, and new instrumentation and controls. Many of these connections will require short plant interruptions and isolated shutdowns. Project work may include:

Demolition of existing concrete structures to facilitate new extensions to the SST influent and effluent channels.

Demolition of the existing vertical turbine RAS pumps at grade, and installation of submersible pumps, including demolition of the existing concrete slab and relocation of pump discharge piping and valves.

Temporary pumping facilities may be utilized to facilitate the replacement of the RAS pumps. There is only one RAS pump station and it cannot be taken out of service for extended periods of time.

Installation of motorized gates within operational site junction boxes and associated structural modifications to facilitate the installation.

Removal of existing pipe isolation and installation and connection of new piping to existing piping.

Installation of new electrical facilities for the proposed equipment. New electrical work includes working within existing Motor Control Centers (MCCs).

SUBMITTALS

Furnish in accordance with Specification Section 01.33.00, “Submittal Procedures”:

Contractor’s Sequence of Construction and plant interruptions/shutdown plan must be submitted to the COR 45 days in advance of plant interruptions/shutdowns, defining work to be performed, including the following items:

Definition of the start date, duration and end date for each segment of work.

For each segment of work, define activities to be performed by or witnessed by Owner and date on which these activities are to be performed.

Scheduling/timing of manufacturers field services, as specified.

Shutdown Plan: Limited interruption(no more than six) interruptions of plant operation isare permitted to perform this work. Define purpose for interruption of plant operation; date and time of interruption; duration of interruption; and hour by hour schedule of proposed work during the interruption. Full plant shutdowns are limited to no more than six times; the Contractor can opt to combine and limit the number of shutdowns.

Provide complete list of equipment and material that is required to perform each segment of work.

MEASUREMENT AND PAYMENT

The work performed by the Contractor under this Specification shall not be measured and paid for directly, but shall be considered to be included in the Lump Sum Bid for this Contract.

ProductS (NOT USED)

Execution General This Section covers six general connections to the existing, operational treatment plant. The Owner will occupy these facilities while modification/renovation work is proceeding. This Sequence of Construction is designed to minimize disruption to the Owner’s operations. The six connections to the existing plant include:

The Bypass Junction Structure The Bypass Metering Structure Tank Drain Junction Structure No.4 Piping Connection to Activated Sludge Tanks (ASTs) Rehabilitation of the RAS Pump Station Connection of the new SSTs to the Existing SSTs Limited interruption of plant operations is anticipated to complete these modifications. The plant will continue to operate, and flow must continue to be treated. All personnel, including electrical personnel, are to be instructed concerning the hazards and precautions to take while working in the vicinity of an operational treatment facility.

The temporary RAS pumping system is to be installed, tested, and substantially complete and operational before the existing RAS pumping system may be taken off-line. Check out and test the temporary RAS pumping system using clean water per the Contract requirements and dispose of the testing water in an appropriate manner. The operational test of the temporary RAS pumping system must be successfully completed prior to final connection of the temporary system to the existing RAS facility.

Contractor shall limit the total number of plant shut-downs required to complete the work defined in this section. Work in multiple areas during a requested shutdown is necessary to accomplish limited shut downs. Coordinate the work with the Owner and Plant Operations Contractor such that work requiring a plant shutdown can be completed in the allotted time without any impacts to plant biological processes due to construction-related activities.

PREPARATION

All material and equipment required to remove the existing facilities/system and install the proposed facilities/system, per the Plans, is to be on-site before installation can begin. This implies that all shop drawings have been submitted to the COR and Owner for review and have been approved for installation.

Notify the Owner at least two weeks prior to the start of a work segment. Construction may occur only after Contractor has complied with preparation requirements defined in this Section.

Verify location of existing facilities prior to construction of facilities proposed in this contract.

All electrical switching, de-energization of loads, energization of loads, etc., to be performed in the presence of, and with the consent of, the Owner.

This Sequence of Construction is a recommended procedure for performing the outlined work. Contractor is solely responsible for verifying that all circuits are dead and tagged out before performing any work under this Section. Comply with OSHA requirements and all applicable codes before throwing the switches to ensure the safety of all employees.

BYPASS JUNCTION STRUCTURE

General The Bypass Junction Structure serves to re-direct influent flows in excess of the downstream treatment facilities’ capacity. During normal plant operations, this structure is not in use and diverts no flow. However, during periods of high influent flow, the structure may be in use. Contractor shall schedule the work such that it is conducted during low flow periods. Contractor shall be aware of any impending wet weather events and plan the work accordingly.

Mechanical/Civil Isolate the 66-inch Emergency PE Bypass Line into the structure. Record Drawings indicate a flap gate is currently installed on the 66-inch discharge into the structure.

After isolation, perform the structural modifications to the Bypass Junction Structure required for the gate installation. This includes installing the wall penetration for the 48-inch EQTI line and the slab modifications for the installation of PEG-SG-001.

Install gates PEG-SG-001 and PEG-SG-002 complete in place. Gate PEG-SG-002 shall be fully operational, and in the closed position, before placing the structure back in service. This avoids directing flow to the new equalization tanks prior to their commissioning. Gate PEG-SG-001 shall be in open position.

After gates have been tested and confirmed to be fully operational, remove isolation of the 66-inch Emergency Bypass Line and place the Bypass Junction Structure into service. Coordinate with the Owner for final gate positions.

Electrical Contractor shall install conduit and wire per PLAN from the existing DAF building to the junction box at the Bypass Junction Structure.

Complete final connections to gates PEG-SG-001 and PEG-SG-002 as required.

BYPASS METERING STRUCTURE

General The existing Primary Effluent Bypass Metering structure contains the flow meters necessary to measure the influent flow that is bypassing the normal treatment facilities. During normal plant operations, this structure is not in use. Currently, the plant Record Drawings indicate the bypass metering structure is isolated from the primary effluent channel.

The Primary Effluent Channel is in operation during normal plant operations. A full plant shutdown will be required for work contained within the primary effluent channel. The maximum duration for this shutdown, for work within the Primary Effluent Channel is four (4) hours.

Prior to initiating the work, Contractor shall field verify the installation of the existing flow meters, determine what components will be required to place the flow meters into service, and have these components on-site prior to beginning the work.

Mechanical/Civil Record Drawings indicate a slide gate has been installed within the Primary Effluent Channel to isolate the 66-inch PE Bypass to the Bypass Metering Structure. However, field investigations have indicated that a blind flange is installed instead. Contractor shall field verify actual conditions prior to initiating work.

Contractor shall confirm the PE Bypass Metering Structure is isolated completely prior to initiating the work. After isolation, reconnect existing flow meters to the existing power and I&C points and confirm all connections.

Once all meter connections are made and confirmed to be operational, recalibrate each flow meter in accordance with the manufacturer’s recommendation.

After Contractor confirms flow meters have been re-calibrated and are ready for service, coordinate with plant operations staff to schedule a plant shutdown during the low flow period.

After the plant has been shut down, remove existing blind flange on the 66-inch PE Bypass line in the Primary Effluent Channel, and place into service.

Electrical Disconnect existing flow meter from existing power and controls. Reconnect existing flow meter to existing power and controls as required.

TANK DRAIN STRUCTURE NO. 4

General Tank Drain Structure No. 4 is a cast in place, concrete structure, collecting drain flow from the majority of the treatment plant and routing it back to the headworks of the plant. This structure is always in service. Reference the Plans for additional information regarding the tank drain structure.

Mechanical/Civil Contractor shall provide for Owner’s review of his plan to work in the structure while the drain system remains operational. Contractor’s plan may include a temporary bypass of the structure, temporary pumping, or other means of allowing access into the drain structure. After Owner’s review and concurrence, implement plan.

After the incoming flow to the structure has been accommodated, complete the penetration of the tank drain structure per the details shown in the Plans.

Place Tank Drain Structure No. 4back4 back in service after all installed piping has been tested, and all structural repairs are complete.

Piping Connection to Activated Sludge Tanks (ASTs) General To utilize the proposed equalization basinstanks, a new connection to the existing Activated Sludge Tanks (ASTs) must be made. The ASTs are vital to the proper functioning of the facility. A short duration, full plant shutdown, during low flow periods will be required to complete the proposed connection. This plant shutdown shall be combined with other planned plant shutdowns.

Mechanical/Civil Contractor shall coordinate with plant operations to schedule the required shutdown during low flow periods. The maximum duration of this shutdown shall be four (4) hours.

After coordination with the plant operations staff, and with their assistance, close the existing slide gate installed on the 72-inch PE Line at the Primary Effluent Channel.

Contractor shall drain the 72-inch PE line to facilitate the proposed connection. Reference the Plans for anticipated water surface elevations at the Primary Effluent Channel, the AST Influent Channel, and the invert elevation of the piping. Due to the plant's biologic process needs, the ASTs cannot be fully drained and must be isolated from the incoming 72-inch PE line. At Contractor's option, the individual AST basin isolation valves/gates may be used, or Contractor may develop and install a temporary isolation device in the riser box connecting the 72-inch PE line to the AST Influent Channel. Provide final Isolation Plans with Contractor's Sequence Submittal.

Complete the connection of the 24-inch FM to the 72-inch PE. Record Drawings indicate a 48-inch x 24-inch connection. However, alternative information exists suggesting this fitting is not present. Contractor to field verify the existence of the 48-inch pipe prior to initiating the work.

After connection has been completed and tested, place the plant back into operation by re-opening the existing gate on the 72-inch PE line. Confirm all required ASTs are ready to accept influent.

Rehabilitation of the RAS Pump Station General There is only one Return Activated Sludge (RAS) pump station serving the needs of the entire South Bay IWWTP. This station cannot be taken out of service without shutting down the entire treatment facility. In order to facilitate the construction within the existing RAS pump station, this sequence anticipates the use of temporary storage and pumping.

The rehabilitation of the RAS pump station generally consists of demolishing the existing vertical turbine pumps and replacing them with submersible pumps. Rehabilitation includes structural, mechanical, electrical, and I&C improvements. All work will be conducted within the existing, operating facilities.

The following sequence requires construction of the RAS pump station improvements prior to installation of SST-11, SST-12, and SST-13.This is due to the potential routing of temporary pipes, electrical lines, and tanks. Contractor’s proposed sequence of construction shall take into account the location of any temporary facilities and coordinate with the other work of this Contract.

The following sequence includes the temporary storage and pumping of the RAS effluent from the existing SSTs, No.1 through 10. Several different, full plant shutdowns will be required to complete the improvements to the RAS pump station, and these shutdowns are defined below. All shutdowns shall occur during low flow periods, and the maximum duration of any one shutdown shall not exceed eight (8) consecutive hours.

Mechanical/Civil Install a temporary RAS/WAS bypass pumping wet well (tanks), temporary RAS bypass pumps, and temporary WAS bypass pumps at a location adjacent to the northwest corner of existing SSTs. Perform clean water testing using effluent to verify operability.

RAS Rate = variable, up to 21.6MGD Storage Volume = minimum working volume of 13,500 gallons WAS Rate = variable, up to 500 gpm Coordinate the demolition of the existing effluent channel knock-out wall, emergency ladder, etc. with that shown on the Plans. Install stop logs at west end of SST effluent channel to prevent effluent from the existing SSTs from leaking into the excavation. Stop logs shall be provided by the Contractor.

Saw-cut and remove non-hydraulic portion of block-out in west wall of SST effluent gallery (below elevation 48.00).

Install temporary RAS surcharged gravity lines: (2) 24-inch RAS, and (1) 20-inch RAS to temporary RAS/WAS wet well (tanks) from locations near connection points in SST effluent gallery. These three lines will connect the existing SSTs to the temporary wet well. Temporary piping may be solid wall piping or flexible piping, provided the operating pressure requirements are met. The existing RAS lines are gravity fed from the SSTs. Alternate piping configurations and sizes may be proposed by the Contractor based on the available work space and final sequence.

Extend temporary RAS discharge line from temporary RAS bypass pumps to a location adjacent to connection point at west end of existing buried RAS pumps 42-inch header. Perform preparatory excavation to make ready for connection to buried 42-inch RAS header. The existing 42-inch RAS line is located parallel to the north wall of the existing RAS pump station.

Extend temporary WAS discharge line from temporary WAS bypass pumps to a location adjacent to connection point in SST effluent gallery. Isolate the existing WAS pumps using the existing valves once the final connection is made.

After the temporary pumps and wet well have been installed, and as much of the temporary RAS and WAS piping as possible has been installed, coordinate with the Owner and schedule a single, full plant shutdown. This shutdown shall not exceed 8 hours in duration. During this shutdown install the following:

(2) 24-inch tee and plug valve on the existing RAS lines into the east wall of the wet well. The tee and valve will provide the ability to route RAS flow to either the existing wet well or through the temporary RAS pipe to the temporary wet well. Connect the previously installed temporary 24-inch piping.

Remove 42-inch blind flange and connect temporary RAS bypass pumps discharge line to west end of buried 42-inch RAS pumps header. (Temporary RAS bypass pumps to be isolated by discharge valves and remain out of service).

Disassemble existing WAS piping in SST effluent gallery and connect (1) 10-inch temporary WAS line to point of connection.

A second, full plant shutdown will be required to complete the remaining connections to the existing RAS piping inside the effluent gallery. SSTs7, 8, 9 and 10 have individual lines of 12-inch and 16-inch diameter, connected to the existing RAS wet well. During this second shutdown install the following:

Reconfigure these discharge lines to connect to the previously installed, 20-inch temporary piping. Install the necessary tees and valves to allow the RAS flow to route to either the existing wet well or the temporary piping, depending on the needs of plant operations.

Relocate the existing plug valves on the discharge of the RAS pumps per the Plans.

After all the temporary piping has been connected to the existing piping and the discharge plug valves moved, install pipe plugs or blind flanges as required to isolate wet well from normal SST operation, routing all RAS flow from the existing SSTs to the temporary pumping systems.

Confirm existing RAS pumps are isolated by relocated discharge valves. Open suction and discharge valves of temporary RAS and WAS bypass pumps and place temporary RAS and WAS bypass pumping facilities in service.

Continue operation of temporary RAS and WAS bypass pumping facilities during construction of proposed modifications to the existing RAS pump station. Perform modifications of existing RAS pumping facilities per the Plans and Specifications. Temporary RAS and WAS pumps operation mode during bypass pumping shall be controlled as nearly as possible to be compatible with the mode of operation and process control of the existing RAS and WAS pump station.

With the temporary bypass RAS and WAS pumps remaining connected and operable, perform clean-water operational readiness testing of proposed RAS pumps. Dewater the existing wet well following successful testing.

During a third, full plant shutdown of not more than 8 hours duration complete the following:

Disconnect the temporary RAS pumps discharge line from the buried 48-inch RAS discharge header, and re-install 48-inch blind flange. Temporary RAS pumps discharge line to remain in place and available for reconnection.

Using the valves installed previously, isolate the temporary RAS and WAS piping, and remove the previously installed plugs or blind flanges installed in the wet well, routing all RAS flow through the existing wet well connections.

Install new valve SST-PV-017 at west exterior wall of existing RAS wet well per the Plans.

Confirm new RAS pumps and existing WAS pumps valves are open. Open valves allow wet well to fill with RAS and place modified RAS and WAS pumping facilities in service.

Temporary RAS and WAS bypass pumping facilities are to remain in place available for reconnection throughout the Performance Acceptance Testing period. Following completion of Performance Acceptance Testing and acceptance of modified facilities by Owner, remove temporary bypass pumping wet well, temporary RAS and WAS pumps, and temporary piping.

Electrical Provide power and controls at temporary RAS/WAS bypass pumping wet well for temporary RAS/WAS bypass pumps.

Disconnect existing power and controls from existing RAS pumps. Once pumps have been replaced with submersible type pumps, reconnect all power and controls as required.

CONNECTION OF THE NEW SSTS TO THE EXISTING SSTS

Influent Channel General Several modifications are required to the existing SST influent channel to connect the proposed SST-11, 12, and 13 to the existing SSTs. These include a 48-inch influent pipe, 8-inch air pipe, 8-inch scum pipe, structural, electrical, and I&C modifications.

One full plant shutdown will be required for several of these connections. All plant shutdowns must be coordinated with plant operations, and must occur during low flow periods. The maximum duration of each shutdown shall not exceed eight (8) hours. Additional, partial shutdowns may be acceptable, provided the safety of all staff and plant operations can be addressed.

Contractor shall coordinate with plant operations to confirm the number of SSTs that are required to process the influent plant flow during a partial shutdown. It is anticipated that nine (9) SSTs will be required.

It is anticipated that all new construction of SST-11, 12, and13 will be complete before commencing with the final connections to the existing system. If Contractor chooses a different sequence, isolation of the connections must be provided until construction is completed.

Structural The existing influent channel serving SST-1 through SST-10 is equipped with a stop log groove and knock-out wall at the far west end, adjacent to SST-10. Contractor shall remove this knockout and install the connecting 48-inch pipe for the new SSTs.

The Owner does not currently have a stop log for use at this end of the SST influent channel. Contractor shall provide the stop log, or any other means to isolate flow within the existing influent channel.

Contractor shall demolish the existing ramps on the west of SST-10, per the requirements shown in the Plans.

Mechanical/Civil Four piping connections must be made between the existing SST Influent Channel and the proposed SST Influent Channel. These are (1) 48-inch Influent pipe, (2) 8-inch Channel Air pipes, and (1) 8-inch Scum pipe. A full plant shutdown is required for these connections.

Contractor shall coordinate with plant operations to shut down the SSTs. Once the influent flow to the SSTs has been stopped, Contractor shall complete any dewatering of the influent channel to facilitate the above connections.

During the first plant shutdown, contractor shall install a stop log, or selected means of isolating the west end of the existing influent channel, to facilitate the structural modifications necessary for the through-wall piping connections. With the Owner’s consent, SST-10 may be removed from service for an extended period of time.

Install the 48-inch influent connections and the two, 8-inch CA through-wall connections. Complete the connections of these pipes to the existing CA piping.

Contractor shall confirm the location of the existing 8-inch scum connection. Record Drawings indicate there is an existing wall pipe and plug in place at SST-10. While the scum skimming system is inoperable, remove the plug and make the connection.

Complete the miscellaneous NPW connections between SST-10 and SST-11.

Electrical Provide conduit and wire from MCC-SST to the new SST’s 11, 12, 13. Power and controls shall be installed at skimmers, skimmer valves, and secondary sludge collectors.

Effluent Channel General The SST Gallery of SST-11 will be connected to the existing SST Gallery. The Effluent Channel of SST-11 will be connected to the SST outfall box through a 48-inch pipe connection.

Contractor shall coordinate the work within this area with the proposed sequence for the rehabilitation of the RAS Pump Station and the Influent Channel modifications to complete as much work as possible during a single plant shutdown. It is anticipated the excavation for this connection will be completed and the temporary RAS pump station installed prior to construction of the new SSTs.

Structural Reference the Plans for the necessary structural modifications to the SST Gallery. After excavation, demolish the existing emergency access and SST Gallery wall.

After completion of the RAS Pump Station rehabilitation, and removal of the temporary system, complete the final connections of the SST Gallery.

Mechanical/Civil Several piping connections are required to complete the installation of SST-11, 12 and 13 and make the connection to the existing facility. These connections include the 48-inch effluent pipe, a 24-inch RAS pipe, a 12-inch drain pipe, and several small diameter NPW and a sump pump discharge pipes. These connections shall be made during a full plant shutdown.

Coordinate with plant operations to shut the plant down. The maximum duration of shutdown is 8 hours. Confirm the water level in the effluent box is below the proposed effluent channel connection, and at a level sufficient to facilitate the required work.

Record Drawings indicate an existing 72-inch wall pipe is installed in the west wall of the effluent box. Confirm installation of the 72-inch wall pipe and blind flange on the exterior of the box prior to initiating the connection. Remove the blind flange, install a 72-inchx48-inch reducer and complete the connection of the 48-inch effluent pipe.

Isolate the 12-inch drain line from SST-10. Record Drawings indicate the existing 12-inch drain line terminates at SST-10 with a blind flange. Contractor shall confirm the final connections, and install the proposed 12-inch drain line.

Complete the miscellaneous NPW connections during the plant shutdown.

Install the proposed sump pump discharge. Record Drawings indicate the existing sump pump discharge terminates with a tee. Connect the proposed discharge to the tee and place in service.

The previous RAS sequence installed valve SST-PV-017 on the 24-inch RAS connection at the RAS wet well. The 24-inch RAS connection can be made at any time, provided the valve was installed.

After all piping connections are complete and tested, place the plant back in operation.

Electrical Provide conduit and wire from MCC-SST to the new SST’s 11, 12, and 13. Power and controls shall be installed at sump pump and flow meters.

- End of Specification -

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