Search

CIry OF NASHUA
PROFESSIONAL SERVICES
GENERAL TERMS AND CONDITIONS

By mutual agreement on March 3, 2016
City of Nashua and Woodard & Curran

29. SURVIVAL OF RIGHTS AND OBLIGATIONS. The rights and obligations of the parties that by their
nature survive termination or completion of this contract shall remain in full force and effect.

30. SEVERABILITY. — In the event that any provision of this contract is rendered invalid or
unenforceable by any valid act of Congress or of the New Hampshire legislature or any court of
competent jurisdiction, or is found to be in violation of state statutes or regulations, the invalidity or
unenforceability of any particular provision of this contract shall not affect any other provision, the
contract shall be construed as if such invalid or unenforceable provisions were omitted, and the parties
may renegotiate the invalid or unenforceable provisions for sole purpose of rectifying the invalidity or
unenforceability.

ai. MODIFICATION OF CONTRACT AND ENTIRE AGREEMENT. This contract constitutes the entire
contract between the City and Professional Engineer. The parties shall not be bound by or be liable for
any statement, representation, promise, inducement, or understanding of any kind or nature not set forth
in this contract. No changes, amendments, or modifications of any terms or conditions of the contract
shall be valid unless reduced to writing and signed by both parties.

32. CHOICE OF LAW AND VENUE. This contract shall be governed exclusively by the laws of the

State of New Hampshire and any litigation shall be brought in a court located in the State of New
Hampshire.

GC 13 of 13

THE CITY OF NASHUA "The Gate City"

Purchasing Department

December 29, 2016
Memo #17-086

TO: MAYOR DONCHESS
FINANCE COMMITTEE

SUBJECT: CONTRACT AWARD FOR ENGINEERING SERVICES FOR THE EVALUATION OF
THE WET WEATHER FACILITY (VALUE: NOT TO EXCEED $35,100)
DEPARTMENT: 169 WASTEWATER; FUND: WASTEWATER

Please see the attached communication from Noelle Osborne, Wastewater Department Operations
Supervisor, dated December 29, 2016 for the information related to this purchase.

Pursuant to NRO § 5-83 Frofessicnai Services (A) In the purchase of accounting, architectural, auditing,
engineering, legal, medical and ambulance services and purchases of independent professional
consultant services for personnel, data processing, actuarial, planning, management and other
comparable purchases competitive bidding shall not be required.

The Wastewater Department Operations Supervisor, Board of Public Works (12/29/2016 meeting) and
the Purchasing Department recommend this contact award in an amount not to exceed $35,106 to
Wrighi Pierce of Porismouth, NH.

ep ney
Slo Lob) oo
Ban Kooken

Purchasing Manager

Cc: N Osborne L Fauteux

229 Main Street » Nashua, New Hampshire 03061 © Phone (603) 589-3330 ° Fax (603) 589-3233

To:

From:

Attachments:

Discussion:

Citv of Nashua, Public Works Division
i f

Board of Public Works Meeting Date: December 29, 2016

Noelle Osborne, Operations Supervisor
Wastewater Department

Wet Weather Facility Evaluation

To approve a contract to Wright Pierce for professional services for a complete
evaluation of the wet weather facility in an amount not to exceed $35,100.
Funding will be through: Department: 169 Wastewater; Fund: Wastewater;
Account Classification: 53 — Professional & Technical Services.

Wright Pierce Scope of Work and Fee.

The Nashua Wastewater Treatment Facility (NWTF) has a Wet Weather
Treatment Facility (WWTF) that treats high flow conditions during storm
events that are in excess of the design capacity of the plant. The WWTF was
constructed and put into operation in 2009. This facility only operates when
flows exceed 5OMGD to the main plant, causing very infrequent operation.
The facility can run an average of 10 times a year for a brief period of time
(less than 12 hours at a time, depending on the storm flow). With infrequent
operation, it is difficult to test, trouble shoot and determine appropriate
corrections. Over the years the operational components have failed to work
worked properly. The EPA has recently stated to the City that they do not
consider our Consent Decree for CSO abatement complete until this facility is
fully functioning. Since the WWTF is complex and has many processes
ongoing when in operation, it needs to be evaluated by a qualified engineering
firm to determine the appropriate corrective action.

In addition to operational difficulties, there has been an overflow at a manhole
outside of the WWTF for 2 consecutive years. This manhole is for an
incoming interceptor and has an inner diameter vortex in it that is suspected to
not be able to handle excessive flows, causing a backup to ground surface.

The NWTF would like to use the services of Wright Pierce to evaluate our
ongoing issues with this facility. The intent is for them to begin by looking at
the design of the facility and evaluate the influent flows and hydraulics of the
interceptor vortex. From there, the City will determine what the appropriate
next stage will be and how to best approach the WWTF evaluation. Wright
Pierce has been used for numerous projects at the NWTF over the past 5 years.
They have a good understanding of the entire plant and are well qualified to
evaluate and provide the corrective actions needed.

Wright Pierce has provided a total cost of $35,100 which the City proposes to

award in phases to ensure that the evaluation is both fiscally responsible and
provides that the appropriate corrective actions are taken. They are ready to
begin this evaluation immediately.

General Fund

The General Fund is the chief operating fund of the City. At the end of the current fiscal year,
unassigned fund balance of the General Fund was $31.7 million compared to $30.7 million last
year, while total general fund balance was $70.2 million compared to $63.1 million last year. The
$7.1 million change in fund balance is a result of utilizing $4.5 million in unassigned fund balance
toward the FY21 budget, favorable auto permits and intergovernmental revenues, and
approximately $6.8 million in unspent appropriations that were approved to carry forward into
fiscal year 2021.

As a measure of the General Fund’s change in financial position, it may be useful to compare both
unassigned fund balance and total fund balance to tota! fund expenditures over time. Unassigned
fund balance, represents 10.9% of total General Fund expenditures and transfers out, compared to
10.6% in the prior year, while total fund balance represents 24.2% of total General Fund
expenditures and transfers, compared to 21.8% in the prior year.

Debt Service Fund

The Debt Service Fund is used to account for resources and debt service payments associated with
the bond issuance for the acquisition of Pennichuck Corporation. The Debt Service Fund has break
even results as expected as contributed revenue is for the scheduled principal and interest
payments.

Nonmajor Governmental Funds
The nonmajor governmental funds changed by $3.8 million primarily from timing differences
between the receipt and disbursement of grants and permanent financing of capital projects.

Proprietary Funds

The City’s proprietary funds provide the same type of information found in the government-wide
financial statements, but in more detail. Unlike governmental funds, proprietary funds utilize the
accrual basis of accounting. Therefore, no reconciliation is needed between the government-wide
financial statements and the proprietary fund financial statements.

Factors concerning the finances of these two funds have already been addressed in the discussion of
the City’s business-type activities.

General Fund Budgetary Highlights
The following reconciles the City’s adopted budget with the “original budget” columns of the

Budget and Actual Financial Statements on page 39 and the Budget and Actual Detail Schedule on
pages 180 - 181 (in thousands).

Total Adopted Budget $ 282,884,408
Plus: Hillsborough County appropriation 11,993,150
Plus: Appropriation to Solid Waste Fund 5,748,376
Plus: Supplemental appropriations 401,088
Total Original Budget, per Financial Statements/Schedules $ 301,027,022

27

SS.

i BF

‘

A Hey gar ieee ED, en Wp gO Weer
Vv = i ir t m tr i i: hee Ee ee WATER ~ WASTEWATER ~ STORMWATER ~ INFRASTRUCTURE

Dm a

Engineering a Better Environment

November 18, 2016
W-P Project No. T11295

Nis. Noelle Osborne
City of Nashua NWTF
2 Sawmill Road
Nasnua, NH 03060

Subject: Letter Proposal for Influent Hydraulic Analysis & Evaluation of the Wet Weather
Treatment System

Dear Ms. Osborne

We are pleased to respond to your request for assistance with analysis of the Wastewater Treatment
Facility influent hydraulics, and evaluation of the wet weather treatment system. The following
paragraphs cutline relevant project background, our current understanding of the issues, proposed
scope of services, schedule and the estimatec fee.

PROJECT BACKGROUND

The Nashua Wastewater Treatment Facility includes a wet weather treatment system that was put in
service in 2009. The Wet Weather Fiow Treatment Facility project included modifications of the
treatment facility’s influent piping system, a below grade diversion structure, a wet weather pump
station, a wet weather sedimentation facility, and modifications to the City’s existing hypochlorite
contact chamber. More specifically, these improvements included:

e Site Piping Modifications — Installation of a drop shaft vortex manhole and new 48” piping to
connect the 48” Salmon Brook Interceptor to the 72” Merrimack Interceptor just upstream
of the Main influent Pump Station.

® Wet Weather Pump Station — Hydraulically actuated influent gates, two mechanical bar
screens, four 21 mgd submersible pumps, and a magnetic flow meter on the 42-inch force
main to the wet weather sedimentation facility.

Wet Weather Sedimentation Facility - A Kruger Actiflo System that includes chemical and

ballasted floc mixing, coagulation and maturing tanks, prior to lamella clarifiers. The system
discharges to a 48-inch gravity line to the chlorine contact tank.

@

® Hypochlorite Contact Chamber — The modification to the chlorine contact tank included new
influent piping with isolation sluice gates, new rotating scum collection pipes and fixed FRP
weirs.

On October 21°, Nashua experienced a rain event of nearly 3 inches over a time of 3 hours. During one
hour they received 1.8 inches. The plant influent hydraulics were overwhelmed by this flow, surcharging

Recognized for Engineering Excellence ~ Selected for Service & Value 230 Commerce Way, Suite 302
Portsmouth, NH 03801

www.wright-pierce.com
Phone: 603.430.3728 | Fax: 603.430.4083

Ms. Osborne
November 18, 2016

Page 2of5

and overflowing the influent sewers. The overflow flooded the paved parking area on the north side of
the wet weather pump station, significantly eroded the adjacent banking, and flowed into the adjacent
wetlands. A large electrical transformer was undermined and taken off line.

Wright-Pierce met with the Plant Operations Staff to discuss their observations of the rain event:

@

The drop shaft vortex manhole on the 48-inch Salmon Brock Interceptor (connected to the
72-inch North Merrimack Interceptor) was overflowing; it flooded the adjacent parking area,
and eroded the adjacent bank. The manhole rim is at about elevation 33.0.

The main influent pump station was receiving up to 56 mgd at one point, and was unable to
keep up with the peak flow.

The influent pump station wet well flooded the lower level to about elevation 15.0, within
approximately 3.6 feet of the intermediate floor level.

In response to the wet well flooding, the 72-inch influent gate to the main influent pump
station was closed from about 24 inches open to about 10 inches open. This further restricted
the flow to the pump station.

According to the level trending information in SCADA, the water surface elevation upstream
of the wet weather pump station influent gate and mechanical screens was 22.0.

Two wei weather influent pumps were operated (each pump rated at 21 mgd and 51-foot
TDH), and lowered the wet weather pump station wet well to below normal operating levels
(elevation of about -5.0). However, the recorded total peak flow rate of the wet weather
pump siation was measured at only 25 mgd. The total rated flow capacity of this pump
station is 60 mgd with 3 pumps operating. This indicates a possible hydraulic bottle neck
associated with either the influent gate or mechanical screens.

PROJECT OBLECTIVES
Based on our initial investigation of the rain event and existing conditions, we have identified seven
project objectives:

1.

Identify the issues that resulted in the overflow of untreated influent wastewater, and the
reasons why the wet weather pump station was only able to receive/pump about 25 mgd;

Evaluate modifications and control strategies that will minimize the potential for future
untreated wastewater overflcws;

Identify the necessary modifications required to facilitate the desired flow handling capacity;

Evaluate possible operational issues or limitations with the wet weather flow treatment
facility (Actiflo System) to effectively treat pumped wet weather flows up to 60 mgd;

Recommend modifications and operational changes to the wet weather flow treatment
system;

Mis. Osborne
November 18, 2016

Page 30f5

6.

identify equipment, structure, piping, controls or operations related issues affeciing tne Wet
Weather Facility’s capacity to effectively handle and treat the identified design peak flows
reaching the facility;

Develop a capital upgrade plan to address identified issues.

SCOPE OF SERVICES

Based on the present conditions and project objectives listed above, we have developed the following
proposed scope of services:

A. Influent Hydraulic Analysis:

1.

8.

Meet with City staff to confirm the hydraulic basis and objectives, including plant influent flows
ana anv other observed hydraulic limitations (e.g. hydraulic bottlenecks, or unequal flow split
issues).

Review wet weather flow influent pumping systems operational information for the present
operational approach, and key wet weather flow equipment systems.

Review the existing record drawings to verify dimensional and layout information of structures
and flow path elements, such as piping, valves, instrumentation, weir locations and heights.

Review existing information on the projected peak flows from the three influent sewers to the
plant, and evaluate the effective hydraulic capacities of the existing influent sewer system in the
immediate vicinity of the Wastewater Treatment Facility (considering pipe size and slope).

Investigate the rated capacity of the drop shaft vortex manhole, as well as possible operational
issues and subsequent modification options.

Evaluate the operation, control and calibration of the wet weather flow pumping facility,
including gates and equipment (influent screens and pumping system).

Develop a hydraulic model of the plant influent systems, including the influent sewers (on the
treatment facility property), and the influent hydraulics of the main pump station and wet
weather pump station. The model will be developed using the record drawings information.

a. Obtain historic data and cbservations on the water surface elevations, and flow data at
the wastewater treatment facility. Calibrate the model using available historic water
surface elevation and flow information.

b. Based on the projected flows, evaluate the design conditions for the wet weather systems
to flag what is undersized and robbing the needed system’s capacity.

c. Use the model to evaluate specific modification options to the structures and piping, or
control strategies to minimize future untreated wastewater overflows.

identify equipment, structure or piping capacity issues that are reducing the treatment facility’s
capability to satisfactorily handle the peak flows reaching the facility.

Ms. Osborne wn ,
(PER cscs

November 18, 2016
Page 4o0f5

OD ecees

S. Develop specific recommendations for wet weather flow system modifications, as well as
possible operational/controls changes required to minimize future overflow of untreated
wastewater.

B. Wet Weather Treatment System:

1.

Evaluate operation and control system modifications for improving the performance to the
wet weather flow treatment facility (Actiflo System) ideally so it can effectively treat pumped
wet weather flows of up to 60 mgd. This includes evaluation of the chemical and blast feed
systems, mixing/coagulation/maturing, effluent clarification, and sludge handling systems.

Identify any equipment, structure, piping, controls or operations which affect the Wet
Weather Facility’s capacity to effectively nandie and treat the design peak flows reaching the
facility.

Develop recommendations for wet weather treatment system modifications to improve the
effective treatment of identified design flows.

C. Summary Reports: Each of the above phases of work (Influent Hydraulic Analysis and Wet Weather
Treatment Systems) will result in:

1.

SCHEDULE

A technical memorandum summarizing the findings of the evaluations, and a capital upgrade
plan to address identified issues, including budgetary cost estimates associated with the
suggested modifications.

A technical workshop with City staff to review the preliminary modifications list, and
incorporate City comments in the final memoranda.

W-P will commence work on this project immediately upon receipt of authorization to proceed. We
expect to complete the above scope items within 16 weeks, and will be ready to move quickly into the
desired implementation phase selected by the City.

ESTIMATED FEE

Based on our proposed project scope, we estimate the effort to complete the various aspect of the work,

as follows:

@

influent Hydraulic Analysis - approximate effort of 120 staff hours and a total engineering fee
of $18,700.

Wet Weather Treatment System Evaluation - approximate effort of 100 staff hours and a
total engineering fee of $16,400.

Ms. Osborne
November 18, 2016
Page 5o0f5

We trust this proposal addresses your needs to evaluate the Wet Weather Facility. We are available to
further discuss this project and fine tune the associated tasks to meet your budgetary constraints or
expectations. We look forward to the opportunity to serve the City.

Very truly yours,
WRIGHT-PIERCE

Timothy Vadney, P.E.
Senior Project Manager