Michael Pacholok, Director Purchasing and Materials Management Division City Hall, 18th Floor, West Tower 100 Queen Street West Toronto, Ontario M5H 2N2

Joanne Kehoe Manager Construction Services

Addendum No. 1, RFP 9117-16-5043

June 29, 2016 Via Website posting (12 pages)

ADDENDUM NO. 1 REQUEST FOR PROPOSAL NO. 9117-16-5043

Re: Professional Services for Dufferin Sanitary Trunk Sewer (STS) System Improvements at G. Ross Lord Reservoir Municipal Class Enviromental Assessment Study

EXTENDED CLOSING: 12:00 NOON (LOCAL TIME) JULY 13, 2016

Please refer to the above Request for Proposal (RFP) document in your possession and be advised of the following: I. REVISED: CLOSING DATE A1-1: Revised Closing Date:

The closing date has been extended from July 6, 2016 to July 13, 2016, and the deadline for questions will be July 6, 2016. Please note that there will be no further extensions of the closing date.

A1-2: Section 5.3 – Table 5-1: Proposal Evaluation Form

Replace points to be awarded for Item "c. Project Management, Project Understanding and Approach" to 15 points. Revised table is attached.

A1-3: Section 7.3 – Base Scope of Work and Provisional Items

Table 7-1 was revised as follows (Revised table is attached): Item A8: Class EA public consultation including two (2) PICs. Item B3: Stage 2 Archeological Assessment.

A1-4: Section 3.3.23 – Provisional Item No. 1 Replace Section 3.3.23 with the following: In the event that a more detailed Archeological Assessment is required due to implementation

of the preferred solution, a Stage-2 Assessment Study should be conducted in accordance with the Ontario Ministry of Culture’s “Archaeological Assessment Technical Guidelines, 1993”. Payment for an Archaeological Assessment will be in accordance with Section 7.3 from the Provisional Allowance for this item.

A1-5: Section 3.6.3.5 – Flow Monitoring

1 of 12

Addendum No. 1, RFP 9117-16-5043

Replace Section 3.6.3.5 with the following:

Duration of at least ten (10) consecutive months.

II. QUESTIONS AND ANSWERS Q1: Due to the RFP requirement for a brief turnaround of proposals and, given the

technical nature of the scope of this project, would the City please provide a 2 week extension on the proposal submission deadline?

A1 Answer: See Revision A1-1. Q2: Can you please clarify the number of PICs to be included. Page 27 notes “ two (2)

public consultation meetings and one (1) additional public meeting and comment tracking”, while Table 7-1 Upset Limit Cost Breakdown has only one(1) PIC under item A8

A2 Answer: The Proponent is required to participate in two (2) public consultation meetings including

preparation of display materials, attendance with presentations at the sessions and debriefing with City staff along with performing other related tasks specified in RFP. Table 7-1 has been revised to include two (2) PICs. See Revision A1-3.

Q3: Can you please confirm if a Cultural Heritage Assessment is required in addition to

a Stage 1 Archaeological Assessment? A3 Answer: Cultural Heritage Assessment is not required as the sewers alignment is not expected to

affect above ground heritage structures. Table 7-1 has been revised accordingly. See Revision A1-3.

Q4: The WSP Report included in Appendix E of the RFP refers to an SPL being

retained by Wardrop to complete a Geotechnical Investigation as part of their work to complete Technical Memorandum No. 1. Can the City provide us with the geotechnical investigation report?

A4 Answer: The requested document is not available at this point. The City staff will assist the

Successful Vendor to obtain the required background documentation if needed. Q5: Wardrop’s Technical Memorandum No. 1 refers to a number of Figures and

Appendices. They have not been included as part of the RFP. Can the City provide us with this information?

A5 Answer: The requested information is not available at this point. The City staff will assist the

Successful Vendor to obtain the required background documentation if needed. Q6: WSP’s Report is missing Preliminary Drawings as part of Section 6 and Section 7 is

missing in its entirety. Can the City provide us with this information? A6 Answer: The requested information is not available at this point. The City staff will assist the

Successful Vendor to obtain the required background documentation if needed. Q7: Section 3.6.3.5 asks for a duration of at least 12 consecutive months for flow

monitoring, and it is also stated in Section 3.6.1.2(b) that the monitoring and

2 of 12

Addendum No. 1, RFP 9117-16-5043

analysis will be used to calibrate the update to the City’s hydraulic model. Given the anticipated schedule outlined in Section 3.2.4(b), the entire 12 months of data cannot be used for this purpose, and only a subset of what is captured. Please confirm the intended use of the flow monitoring data, and whether a specific minimum amount of information is expected for input into the calibration/hydraulic modelling assessment.

A7 Answer: The City wants to capture flow monitoring information to calibrate the model. The plan is

to install the flow monitor at the commencement in August 2016 and capture information up to June-July 2017 in order to capture all seasonal dry weather flows and a couple of major rain events. Allow for 10 months of flow monitoring. The remaining raw data from flow monitoring can be utilized by the City for the detailed design stage and to further calibrate the model at the preliminary design stage. Refer to Revision A1-2.

Q8: Section 3.6.1.2(a) indicates that the City has a hydraulic model that incorporates the

study area. In order to estimate level of effort, please confirm the type (spreadsheet, hydrodynamic, static) and extent of the model’s coverage. If possible, can a copy of the model or screen-capture of its extents be made available during the RFP process? Can the expected model simulations to be evaluated be elaborated, in terms of design storms, future growth, etc.?

A8: Answer: The hydraulic model is an InfoWorks model, and a map showing the drainage area to be

analyzed as part of the project is attached. For the model simulations, see attached the Criteria for Trunk Sewer Capacity Assessment Memo.

Should you have any questions regarding this addendum contact Joan Blake by email at jblake2@toronto.ca. Please attach this addendum to your RFP document and be governed accordingly. Proponents must acknowledge receipt of all addenda in their Proposal in the space provided on the Proposal Submission Form as per Appendix A, Section 4 - Addenda of the RFP document. All other aspects of the RFP remain the same. Yours truly,

Joanne Kehoe Manager, Construction Services Purchasing and Materials Management

3 of 12

Addendum No. 1, RFP 9117-16-5043

Revised

Table 5-1 Proposal Evaluation Form

EVALUATION CRITERIA AVAILABLE

POINTS TO BE AWARDED

a. Proponents Profile and Corporate Experience 10

b. Project Team Relevant Experience and Team Structure and Experience Working on Similar Projects

15

c. Project Management, Project Understanding and Approach 15

d. Project Workplan, Time Task Breakdown and Proposed Schedule 15

e. Innovation strategy(ies) or value added 5

f. Proposal Structure and Overall Quality of the Proposal 5

g. QA/QC Plan and Staffing for QA/QC 5

h. Project team experience working in TRCA controlled lands, dams, reservoirs, rivers, and woodlands (Project reference and other materials provided will be used to assess this qualification)

5

TOTAL Technical Proposal Score 75

Proponent must score a minimum of 56.3 points to qualify for the short-list and further evaluation.

Cost of Services – Proponent's fees

Proponent’s fees are calculated as described in Table 7-1

25

TOTAL SCORE 100

Stage 3. INTERVIEW (If applicable)

Proponent must score a minimum of 56.3 points out of the maximum possible 75 points for the Technical Proposal Score to qualify for the short-list and further evaluation as described in Section 5.3.3.

Should an interview be scheduled, the interview will be used to review /refine / revise Proponent’s scores assigned in categories a, b, c, d, e, f, g and h above.

4 of 12

Addendum No. 1, RFP 9117-16-5043

Revised

Table 7-1 Upset Limit Cost Breakdown

Item No. Description Cost ($)

A BASE SCOPE OF SERVICES:

A1 Project management, project monthly progress meetings, workshops and all other general requirements during the project.

$

A2 Data gathering, background information (drawings, reports, growth projections, modeling, analysis and other information as necessary)

$

A3 Modelling, analysis and all other studies to assess impacts and present viable options and alternatives for the MCEA including the preferred = solution

$

A4 All Technical Memorandums as listed in the RFP; including submission of draft and final reports

$

A5 Flow and rain monitoring as per Section 3.6.3 $

A6 All other studies and remaining Class EA activities – as required per MCEA Schedule B including submission of draft and final reports* (See Note 1)

$

A7 Agency consultation and all other required meetings as mentioned in the RFP

$

A8 Class EA public consultation, all other meetings identified in the RFP, and coordination including two (2) PIC

$

A9 Field Investigation and natural environment inventory including arborist report, natural environment report (aquatic biologist and other staff), Subsurface Utility Engineering (SUE) report, and topographical survey to complete the EA and preliminary design.

$

A10 Archeological assessment Stage -1 for the study area $

A11 Geotechnical, hydro-geological and soils investigations including ESA Phase -1 (See Section 3.6.2)

$

A12 Preliminary design (See Section 3.6.4) $

A13 Disbursements $

SUBTOTAL - BASE SCOPE (A) $

B PROVISIONAL SCOPE OF SERVICES *(See Note 2)

B1

If required, additional studies and activities required for a MCEA - Schedule C including one (1) additional PIC meeting and all other additional studies and reports required as per the MCEA process (Section 3.3)

$

B2

Complete CCTV inspection, including coding of defects as per NAASCO and COT standards and providing data as per COT format and requirements – 1,000 meter CCTV inspection under low flow conditions (Could be for West Don STS, Dufferin STS, or collection system), including procurement of vendor with 3 quote process, review of CCTV, permits and preparing a report. (Cost will be adjusted based on actual length of CCTV)

$

5 of 12

Addendum No. 1, RFP 9117-16-5043

Item No. Description Cost ($)

B3 Stage-2 Archeological Assessment $

B4 Environmental Impact Assessment/Study for the preferred solution $

B5 Allowance - Specialized Disbursements for Public Consultation Activities

$ 10,000.00

B6 Allowance - Health and Safety Equipment $ 10,000.00

B7 Allowance for DSL testing and report (3 quotes will be required) $ 10,000.00

B8 Allowance - Respond to comments received during the review period and any Part II Order requests

$

B9 Traffic control, paid duty police officer allowance to inspect valve chamber or engineering study within road allowance (not for geotechnical work)

$ 10,000.00

SUBTOTAL – PROVISIONAL ALLOWANCE (B) $

SUBTOTAL – UNIT PRICE ITEMS (FROM TABLE 7-2 Below) (C) $

TOTAL (D) = SUBTOTAL (A+B+C) $

HST – 13% of TOTAL (D) $

GRAND TOTAL (TOTAL (D) + HST) $

6 of 12

��468ha

HEPC

C N

R

KE

EL

E S

T

FINCH AVE W

BA

TH

UR

ST

ST

STEELES AVE W

SHEPPARD AVE W

DU

FF

ER

IN S

T

SE

NT

INE

L R

D

AL

NE

SS

ST

SE

NL

AC

RD

REINER RD

FL

INT

RD

ACTON AVE

PALM DR

SEARLE AVE

EL

DE

R S

T

WIL

SO

N H

EIG

HT

S B

LV

D

CODSELL AVE

MA

XW

EL

L S

T

FA

YW

OO

D B

LV

D

THE POND RD

WIL

LIA

M R

AL

LE

N R

D

HO

VE

ST

GO

DD

AR

D S

T

BETTY ANN DR

HORSHAM AVE

ELLERSLIE AVE

DREWRY AVE

OVERBROOK PL

YORKVIEW DR

FISHERVILLE RD

PATRICIA AVE

TO

RRESDALE A

VE

MCALLISTER RD

ALMORE AVE

DE

HA

VIL

LA

ND

DR

PE

TR

OL

IA R

D

HOUNSLOW AVE

PLEWES RD

ALEXIS BLVD

CARL HALL RD

COOK RD

BOMBAY AVEINVERMAY AVE

CA

NU

CK

AV

E

DELHI AVE

NASH DR

TORO RD

HIGHWAY 401 C

E

DE

RR

YD

OW

N R

D

GILLEY RD

BAINBRIDGE AVE

AR

MO

UR

BLV

D

CHURCHILL AVE

PLANNING BOUNDARY

SH

AF

TE

SB

UR

Y S

T

HID

DEN

TR

L

ROCKFORD RD

PE

CK

HA

M A

VE

CLANTON PARK RD

BR

YA

NT

ST

RA

DIN

E R

D

CAINES AVE

STEEPROCK DR

LAURELCREST AVE

STA

FF

OR

D R

D

TAVISTOCK RD

VICTORY DR REGENT RD

BEVDALE RD

DALLAS RD

DIANA DR

FOUR WINDS DR

WILDCAT RD

MAG

NETIC

DR

LURGAN DR

BE

FF

OR

T R

D

DE QUINCY BLVD

HU

CK

NA

LL R

D

HOME RD

ASHWARREN RD

RIMROCK RD

LANGHOLM DR

EVANSTON DR

EA

ST

ON

RD

PURDON DR

KENTON DR

YO

NG

E B

LV

D

DEVONDALE AVE

SPALDING RD

TIMBERLANE DR

DOLOMITE DR

KATHERINE RD

CHAMPAGNE DR

BRISBANE RD

TIL

LP

LA

IN R

D

GREENWIN VILLAGE RD

LE PAGE CRT

ROMNEY RD

TILBURY DR

SH

AR

PE

CR

OF

T B

LV

D

CA

RS

CA

DD

EN

DR

FESTIVAL DR

DELABO DR

BA

NT

ING

AV

E

YORK BLVD

FINE ARTS RD

ELYNHILL DR

HANOVER RD

KILLAMARSH DR

KEELEGATE DR

YUKON LANE

WHITBURN CRES

CA

NY

ON

AV

E

GA

MB

ELLO

CR

ES

CA

RP

EN

TE

R R

D

THE CHIMNEYSTACK RD

LIMESTONE CRES

FIN

DLA

Y B

LV

D

BRENTHALL AVE

NE

LS

ON

RD

DO

N R

IVE

R B

LV

D

LISSOM CRES

CATFORD RD

TU

SC

AN

GT

CA

ND

IS D

R

RIDEAU RD

VILLATA GDNS

DOLLERY CRT

SANDRINGHAM DR

ASSINIBOINE RD

PLANNING BOUNDARY

Addedum No. 1, RFP 9117-16-5043

7 of 12

To: Jian Lei

From: Grace Lin

Date: August 12, 2014

Subject: Criteria for Trunk Sewer Capacity Assessment

To answer the question about what criteria should be used to assess the trunk sewer capacity, this

memo will firstly review the criteria documented in the Metro Works Report (October 1993) by

the Water Pollution Control Division of the Metropolitan Toronto Works Department, secondly

review the criteria used in the recent trunk sewer studies, and lastly recommend the criteria to be

used for future trunk sewer studies and improvement projects.

1. Metro Works’ criteria for trunk sewer capacity assessment (Ref.1)

Analyzing Trunk Sewer Capacity

• When analysing the capacity of an existing sanitary trunk sewer, if it can convey the peak

DWF plus I/I of 0.26 l/s/ha without surcharging the pipes, it is considered to have sufficient

capacity and no upgrade is required.

• When analysing the capacity of an existing combined trunk sewer, if it can convey 2.5 times

of the average daily DWF without surcharging the pipes, it is considered to have sufficient

capacity and no upgrade is required.

• If the existing trunk sewers are at or near capacity, new trunk relief sewers will be required.

Designing a new Relief Trunk Sewer

New trunk relief sewers would be installed such that, in addition to providing capacity for future

sanitary flows, maximum relief of the existing system in wet weather would be provided, as well as the

flexibility to divert flows for inspection and maintenance of the system. In situations where trunk sewer

improvement works have effects on CSO, reducing CSO frequency to the watercourse to once per year

on average is required.

The relief for existing I/I is limited to the following:

• The I/I from the 5-year design storm, where the existing I/I in the trunk sewers contributes

to basement flooding, or flooding out the top of maintenance holes on the streets; and

• The I/I from the 1-year design storm or the 0.26 l/s/ha allowance, whichever is greater, in

all other cases. For this, sufficient capacity is provided so that the trunk sewer does not

surcharge to ground level.

When designing a new relief trunk sewer, future peak sanitary flows are calculated, by applying the

Harmon Peaking factor to the average flow which is calculated using 450 l/cap/d for residential

population and 337.5 l/cap/d for new employment population. The flow generated from predicted

increases in employment population is added to the existing flow from

Memorandum

John Livey Deputy City Manager

Toronto Water Water Infrastructure Management Metro Hall, 18th Floor 55 John Street

Toronto, Ontario M5V 3C6

Tel: 416-338-2841 Fax: 416-338-2828 E-Mail: glin@toronto.ca

Addendum No. 1, RFP 9117-16-5043

8 of 12

2

Industrial/Commercial/Institutional (ICI) areas. Employment populations are used to estimated

future ICI flows because of the observed trend is for wet industries such as breweries, metal

finishing, etc., to leave the Metropolitan Toronto area. It is expected that new industries would be

more of the commercial type.

To better understand the rationales of the above criteria, following side notes were also quoted from

Metro Works Report, the Water Pollution Control Division of the Metropolitan Toronto Works

Department, October 1993:

• Storm water entering the trunk sewer system occupies capacity that would otherwise be

available for sanitary flows. It is also the cause of treatment plant by-passes and combined

sewer overflows.

• The usual practice was to design the combined sewers with ample capacity to convey the

runoff from a storm with a 2 to 5 year return period, plus the daily sewage flows. The

treatment of all storm flows was not economically feasible; consequently the usual practice

was to convey an amount up to 2.5 times the daily wastewater flow to the treatment plant,

and to allow the surplus to overflow to nearby watercourses.

• Sewers, unlike treatment plants which can be expanded as flows increase, are designed for

ultimate flows expected from the sewershed. It is not economical, and in most cases not

practical to construct a sewer for existing flows then to construct another sewer in another

10 years for increased flows that has occurred. The cost to oversize a sewer is marginal

compared to the cost of construction (i.e. excavation, tunnelling, disruption of the

community, etc.).

• Therefore, the method of determining design flows for sewers is different from the

method for determining design flows for treatment plants. The design criteria also are more

conservative.

2. Criteria used in the recent trunk sewer capacity studies (Ref.2)

The following criteria were used in the Don River and Central Waterfront Trunk Sewers and

CSO Control Strategy EA which was completed in 2012.

Don Sanitary Trunk Sewers:

Analyzing Trunk Sewer Capacity

• City's planned growth up to 2031;

• Calibrated with flow monitoring data under DWF and WWF conditions;

• Trunk sewer capacity was checked with the 2031 peak DWF, ie. 2031 peak sanitary sewage

flow plus baseflow. It was found that the trunk sewers can convey the flow without

surcharging the pipes.

• Trunk sewer capacity was checked with the 2031 peak DWF plus I/I allowance of

0.26L/s/ha. It was found that some reaches in the trunk sewers were surcharged.

Designing Relief for Existing I/I

• Criteria: convey the 2031 peak sanitary sewage flow with I/I allowance of 0.26L/s/ha plus

the wet weather response associated with the 1-year design storm without surcharging pipes.

Four off-line storage facilities are proposed.

• The storage faculties are designed to relieve the surcharged trunk sewers by spilling peak

flows under wet weather conditions. As the I/I response recedes, the detained flows are

then pumped back to the trunk system. Addendum No. 1, RFP 9117-16-5043

9 of 12

3

Central Waterfront Combined Trunk Sewers:

Analyzing Trunk Sewer Capacity

• City's planned growth up to 2031;

• Calibrated with flow monitoring data under DWF and WWF conditions;

• Trunk sewer capacity was checked with the 2031 peak DWF, ie. 2031 peak sanitary sewage

flow plus baseflow. It was found that the trunk sewers can convey the flow without CSO.

• Trunk sewer capacity was checked with the 2.5 times of 2031 average DWF. It was found

that the trunk sewers can convey the flow without CSO.

Designing a CSO Control Storage System

• Criteria: reducing CSO frequency from each location to the receiving water to once per year

on average, using 1991 as a typical average year.

3. Criteria to be used for future trunk sewer capacity studies and improvement projects

Sanitary Trunk Sewers:

Analyzing Trunk Sewer Capacity

• Population and employment: use the available longest City's planned growth at the time of

analysis;

• Sanitary f sewage low rate: use 240 L/cap/d, or the calibrated with flow monitoring data if

available, whichever is greater;

• Sanitary sewage flow peaking factor: Harmon's formula , or use the calibrated with flow

monitoring data if available;

• Baseflow rate: use 0.08 L/s/ha, or the calibrated with flow monitoring data if available,

whichever is greater;

• Sanitary trunk sewer capacity should be checked with:

a) the future peak DWF, ie. future peak sanitary sewage flow plus baseflow. The trunk

sewers should be able to convey the peak DWF without surcharging the pipes.

b) the future peak sanitary sewage flow plus I/I allowance of 0.26L/s/ha. The trunk sewers

should be able to convey the peak DWF without surcharging the pipes.

• If the existing trunk sewers are at or near capacity under the condition in a), this indicates that

new trunk relief sewers for sanitary flow conveyance are required.

• If the existing trunk sewers are at or near capacity under the condition in b) but have sufficient

capacity for condition a), this indicates that new trunk relief sewers, in-line or off-line storage

are required depending on the extent of the pipes lacking of free flow capacity.

Designing a Relief Facility

The following design criteria should be used in the design of the new trunk relief sewers, in-line

or off-line storage:

• Population and employment: use the available longest City's planned growth at the time of

analysis;

• Sanitary sewage flow rate: use 450 L/cap/d. This is applied to the drainage area where a

relief is required.

• Sanitary sewage flow peaking factor: Harmon's formula;

• I/I allowance and Hydraulic Grade Line (HGL) requirement:

Addendum No. 1, RFP 9117-16-5043

10 of 12

4

a) The new relief sewers and the existing trunk sewers after being relieved should be able

to convey the peak future sanitary sewage flow plus I/I allowance of 0.26L/s/ha without

surcharging the pipes, in all cases.

b) In the situations where the surcharge level in the trunk sewers would not cause

basement flooding or flooding out the top of maintenance holes on the streets, the new

relief sewers and the existing trunk sewers after being relieved should be able to convey

the peak future sanitary sewage flow plus the I/I from the 1-year design storm or the 0.26

l/s/ha allowance, whichever is greater, without surcharging the pipes.

c) In the situations where the surcharge level in the trunk sewers would cause basement

flooding or flooding out the top of maintenance holes on the streets, the new relief sewers

and the existing trunk sewers after being relieved should be able to manage the peak

future sanitary sewage flow plus the I/I from all the rainfall conditions without causing

basement flooding or flooding out the top of maintenance holes on the streets.

Emergence overflows to a nearby watercourse may be needed for the I/I from the rainfalls

greater or equal to the 5-year design storm. Otherwise, it would require a large storage

facility to store the I/I from large and extreme rainfall events and large volumes of wet

weather flows would be sent to the treatment plant.

• The new relief sewers and the existing trunk sewers after being relieved shall not increase the

peak flows to the wastewater collection system downstream.

Replacing an Existing Sanitary Trunk Sewer

Sometimes an existing trunk sewer is needed to be reconstructed due to conditional and/or

structural, or relocation reasons. In this case, the criteria of designing a relief facility can be used.

Combined Trunk Sewers:

Analyzing Trunk Sewer Capacity

• Population and employment: use the available longest City's planned growth at the time of

analysis;

• Sanitary sewage flow rate: use 240 L/cap/d, or the calibrated with flow monitoring data if

available, whichever is greater;

• Sanitary sewage flow peaking factor: Harmon's formula , or use the calibrated with flow

monitoring data if available;

• Baseflow rate: use 0.10 L/s/ha, or the calibrated with flow monitoring data if available,

whichever is greater;

• Combined trunk sewer capacity should be able to:

a) Convey the peak future DWF, ie. peak future sanitary sewage flow plus baseflow,

without CSO.

b) Convey 2.5 times of the average future daily DWF, without CSO.

• If the existing trunk sewers are at or near capacity under the condition in a) or b), this indicates

that a new trunk relief sewer or diverting flow within the combined sewer system is required.

Note that new combined trunk sewers are not allowed to be constructed; therefore, the new

relief sewer in this case should be a new sanitary trunk sewer.

Designing a CSO Control Storage System

• Criteria: reducing CSO frequency from each location to the receiving water to once per year

on average. The City uses 1991 as a typical year for the average wet weather flow condition.

Addendum No. 1, RFP 9117-16-5043

11 of 12

5

Reference:

1. Metro Works Report, the Water Pollution Control Division of the Metropolitan Toronto

Works Department. October 1993

2. Don River and Central Waterfront Trunk Sewers and CSO Control Strategy EA, MMM

and BPR, 2012

Definitions:

The definitions for the following terms are used throughout this document.

Dry Weather Flow

Dry weather flow is the combination of the base flow, and sanitary sewage flow from domestic and trade

(institutional, commercial and industrial) sources during dry weather.

Base Flow

The base flow is a constant flow entering sanitary and combined systems representative of some inflow and

infiltration from foundation drains and sewer pipes. It typically also has a seasonal variation.

Infiltration/Inflow (I/I)

During wet weather flow conditions, flows in sanitary sewers are exceeded with I/I, which refers to extraneous

water from infiltration and inflow to the sanitary sewer, additional to the sanitary flow from residential or

institutional, commercial and industrial land uses. Infiltration takes place through pipe material degradation and

at joints. Inflow refers to the stormwater that enters the system through roof leaders, footing drains, yard drains,

manhole covers or illegal connections with storm sewers.

Sanitary Trunk Sewer

Sanitary Trunk Sewers collect discharges from local separated sanitary sewers and/or a portion of

intercepted flows from combined trunk sewers. They convey sanitary sewage, some storm runoff from

inflow/infiltration, and combined flows that are intercepted from combined trunk sewers.

Combined Trunk Sewer

Combined Trunk Sewers collect discharges from local combined sewers and carry both sanitary sewage and

storm runoff. A portion of flows in combined trunks are intercepted and sent to the treatment plant, while flows

exceeding the interception capacity can be diverted to another sewer or to the receiving waters.

Combined Sewer Overflow

Combined sewer overflow (CSO) is flow originating at a regulator from a combined sewer that exceeds the

interceptor capacity and is conveyed to receiving waters.

.

Addendum No. 1, RFP 9117-16-5043

12 of 12