Page 1 of 2 Calleguas MWD Engineering & Construction Committee Agenda March 17, 2015

CALLEGUAS MUNICIPAL WATER DISTRICT ENGINEERING & CONSTRUCTION COMMITTEE

www.calleguas.com

March 17, 2015

NOTICE AND CALL OF A MEETING OF THE CALLEGUAS ENGINEERING & CONSTRUCTION COMMITTEE

An Engineering & Construction Committee Meeting of Calleguas Municipal Water District is hereby called and notice of said meeting is hereby given for 5:00 p.m. on Tuesday, March 17, 2015 at Calleguas Municipal Water District, 2100 Olsen Road, Thousand Oaks, California. The Calleguas Municipal Water District’s Engineering & Construction Committee meeting is noticed as a meeting of the Board of Directors for the purpose of compliance with the Brown Act. Members of the Board who are not assigned to the Engineering & Construction Committee may attend only as observers and cannot participate as members of the Board, whether or not a quorum of the Board is present. In order to preserve the function of the committee as advisory to the Board, members of the Board who are not assigned to the Engineering & Construction Committee will not vote on matters before the Engineering & Construction Committee.

A G E N D A A. CALL TO ORDER AND ROLL CALL Steve Blois, Chair Andres Santamaria, Committee Member B. PUBLIC COMMENTS

Opportunity for members of the public to address the committee on matters within the committee’s jurisdiction (as required by Government Code Section 54954.3(a)). Please limit comments to three minutes.

C. COMMITTEE ITEMS

1. Discussion regarding Pressure Surge Analysis of Oxnard-Santa Rosa Feeders and Las Posas Feeders

2. Discussion regarding Change Order approval policies

D. OTHER COMMITTEE ITEMS E. FUTURE AGENDA ITEMS

Page 2 of 2 Calleguas MWD Engineering & Construction Committee Agenda March 17, 2015

F. ADJOURNMENT NOTE: At the discretion of the committee, all items appearing on this agenda, whether or not expressly listed for action, may be deliberated and may be subject to action by the committee. This committee reviews items and makes a recommendation for final action to the full Board of Directors. Final action will be taken by the Board of Directors. Agendas for the meeting of the Board of Directors may be obtained from the Clerk of the Board. This committee will not take any action that is binding on the Board, even when a quorum of the Board is present. Writings relating to open session agenda items distributed to Directors less than 72 hours prior to a meeting are available for public inspection at Calleguas’ Administrative Office Building. Requests for a disability related modification or accommodation, including auxiliary aids or services, in order to attend or participate in a meeting should be made to the Clerk of the Board in advance of the meeting to ensure availability of the requested service or accommodation.

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Engineering & Construction Committee Meeting March 17, 2015

Overview

Background What is Pressure Surge? Western System Previous Work

Modeling Scenarios and Results Recommended Improvements Recommended Next Steps

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BackgroundWhat is Pressure Surge?

A pressure wave that is caused when a fluid in motion is forced to stop or change direction suddenly. (Also known as water hammer.)

Most common causes include: Pump failure (due to power loss) Hydro failure (due to power loss or “load rejection”) Valve closure and modulation

BackgroundWhat is Pressure Surge?

Consequences of Surge: Upsurge: High positive surge pressures can rupture

pipe and pump casings. Downsurge: Large negative surge pressures

(vacuums) can collapse pipe and cause intrusion of ground or other water at leaks.

Pipe, valve, and fitting displacement and support failure.

Damage to appurtenances. Vibration, cavitation, column separation, and fatigue

failure of pipe, pumps, and appurtenances.

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BackgroundWestern System

BackgroundPrevious Work

The need to address surge in the Western System was originally identified by the O&M Manager in 2001.

Although initial surge analysis work was done at that time, subsequent changes in operating assumptions required that the surge analysis be revisited.

Additionally, the project was put on hold for several years due to other workload priorities.

surge-related failure

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BackgroundPrevious Work

Work was resumed in 2011 and NHC has since: Reviewed existing facilities and identified and

analyzed potential operating scenarios. Developed and calibrated the surge model. Run surge model for operating scenarios and

identified system improvements needed.

Modeling Scenarios and Results

Conditions Modeled: 2011 Maximum Day Demand Condition 2035 Future Demand Condition Winter Low Demand Condition Emergency (or Scheduled Shutdown) Demand

Condition

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Modeling Scenarios and Results

Surge-Causing Events Modeled: Load rejection at the hydro facilities (Conejo, Santa

Rosa, Springville) Loss of power to Calleguas pump stations (Fairview,

Grandsen Phase 1) and purveyor pump stations that take suction off turnouts (Price Rd. – Cal Am, Sand Canyon, and Solano Verde)

Closure of certain purveyor turnouts (to evaluate pressure trapped between reg stations observed under winter low demand conditions)

Example of Modeling Results(without surge improvements)_

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Example of Modeling Results(with surge improvements)

Modeling Scenarios and Results

The results of the analysis show that: Following power loss at the hydro facilities and pump

stations, the minimum HGL will drop sufficiently low to create large magnitude negative pressures downstream of Conejo and Springville Hydros.

Following a loss of power to GPS1, the minimum HGLwill drop low enough in Tierra Rejada Feeder to open an existing combination air valve and create negative pressure just upstream.

High pressure may develop and be trapped between closed regulating stations.

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Recommended Improvements

Install 4-inch controlled venting vacuum relief valve on the downstream side of the turbine outlet valve at Conejo Hydro.

Install 4-inch controlled venting vacuum relief valve on the 42-inch pipeline between Springville Hydro and Reservoir.

Recommended Improvements

Install 12-inch surge check valve on the inlet of an existing combination air valve on Tierra Rejada Feeder to prevent air valve slam upon pipeline repressurization.

Install 6-inch controlled venting vacuum relief valve on Tierra Rejada Feeder to prevent the formation of a vacuum.

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Recommended Improvements

Construct a 10-inch bypass pipeline with a pressure relief valve from the upstream to the downstream side of Regs 4, 5, 6, and 6A.

The bypasses will produce a cascade effect to prevent high pressures from developing and being trapped by safely relieving pressure downstream and ultimately to Springville Reservoir.

Recommended Next Steps

Finalize surge report. Identify design engineer and develop scope of work to

perform preliminary design for recommended improvements.

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Questions and Discussion

Pressure surge – Valve Closure

LPF-1

Turnout PRS-2

PRS-3

1.Low flow/low demand –winter; T.O. and PRS’s initially closed2. Turnout opens between closed PRS’s3. PRS-2 opens in response to drop in d/s pressure

4. T.O. closes, pressure builds in LPF-1 (PRS-2 still open)

5. PRS-2 attempts to respond by closing (slow closure), but too late, “trapped pressure” in LPF-1

6. “Trapped high pressure” slowly relieved by manually opening PRS-3

“Trapped pressure ”

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Mitigating Pressure Surge –Step 1: Surge Analysis

Definitions1. What is cavitation?

The sudden formation and collapse of low-pressure bubbles (vapor cavity formation) in liquids by means of mechanical forces.

Can occur at pumps and valves

Causing pitting damage and potential failure

Mitigating Pressure Surge –Step 1: Surge Analysis

Definitions1. What is column separation?

Following downsurge in pipeline; the transient state where vapor pressure temporarily forms in a pipeline (ie, vacuum)

Water boils and forms large pockets of vapor

On upsurge, vapor pockets collapse as two liquid columns rejoin, giving potentially damaging upsurge in pressure.

Pipe Failure Modes:(1) At vapor pocket formation

– pipe collapse (2) At vapor pocket collapse

- pipe rupture

Calleguas Municipal Water District Engineering & Construction Committee

March 17, 2015 Discussion Regarding Change Order Approval Policies

Item Staff Authorization Limits

Project Managers Manager of Engineering

General Manager

Professional Services1 $2,500 $34,999 $99,999 Construction Services/

Materials Procurement1,2 $2,500 $34,999 $34,999

Change Orders (current)3 $0 $0 $25,000 (cumulative on project)

Change Orders (proposed)4 $2,500 $34,999 $99,999 or 25% of the original contract

amount, whichever is less

1 Authorization limits are set forth in the Administrative Code (Procurement Policy) and Ordinance No. 18.

2 Above $34,999 must be competitively bid, unless an emergency under the Public Contract Code.

3 Authorization limit established by practice in 1993, not documented in any policy.

4 Proposed change order approval limits are per individual change, not per change order (which typically consists of a group of changes being processed at once), nor cumulatively per project as currently handled. An “individual change” would typically be associated with a specific work change directive. Change order summary reports would be provided to the Board (1) quarterly for all active construction projects with change orders and (2) for a single project any time a change order is presented to the Board for approval.