2018 Sanitary System Evaluation

Clive, Iowa

October, 2018

2018 SANITARY SYSTEM EVALUATIONCLIVE, IOWA

October, 2018

I hereby certify that this engineering document was prepared by me or under my direct personal supervision and that I am a duly licensed Professional Engineer under the laws of the State of Iowa.

Michael B. Benham, P.E. No. 24709 (Date)

My license renewal date is December 31, 2019

Pages or sheets covered by this seal:

Report titled “2018 Sanitary Sewer System Evaluation, October, 2018”

Page | i

TABLE OF CONTENTS

0.0 EXECUTIVE SUMMARY ...................................................................................................................A

0.1 INTRODUCTION ............................................................................................................................A0.2 CCTV REVIEW AND FIELD VERIFICATION .............................................................................................A0.3 DATA REVIEW AND ANALYSIS ............................................................................................................A0.4 HYDRAULIC MODEL .......................................................................................................................B0.5 CITY MAINTENANCE PRACTICES ........................................................................................................B0.6 LIFE CYCLE COST, AND COST-EFFECTIVE ANALYSIS ...............................................................................B0.7 RECOMMENDATIONS AND CAPITAL IMPROVEMENT PLAN ........................................................................C

1.0 INTRODUCTION........................................................................................................................1-1

1.1 PURPOSE AND BACKGROUND .......................................................................................................1-11.2 SCOPE.....................................................................................................................................1-11.3 SUMMARY.................................................................................................................................1-1

2.0 HYDRAULIC STRATEGY...............................................................................................................2-3

2.1 STRATEGY DEVELOPMENT .............................................................................................................2-32.1.1 Data Review and Analysis.....................................................................................................2-32.1.2 CCTV Review ......................................................................................................................2-72.1.1 Manhole Field Inspection .....................................................................................................2-72.1.2 GIS Model and Calibration ................................................................................................2-10

2.2 SANITARY HYDRAULIC MODEL .....................................................................................................2-132.2.1 Model Development ..........................................................................................................2-132.2.2 Scenario Analysis...............................................................................................................2-132.2.3 Sanitary Hydraulic Model Results ........................................................................................2-13

2.3 IDENTIFIED HYDRAULIC STRATEGY.................................................................................................2-13

3.0 MAINTENANCE PROGRAM REVIEW ..........................................................................................3-19

3.1 SANITARY SYSTEM MAINTENANCE PRACTICES ..................................................................................3-193.1.1 System Inspection ..............................................................................................................3-193.1.2 Maintenance and Cleaning ................................................................................................3-203.1.3 Pipeline Rehabilitation........................................................................................................3-203.1.4 Manhole Rehabilitation ......................................................................................................3-223.1.5 System Prioritization ...........................................................................................................3-23

4.0 RECOMMENDATIONS .............................................................................................................4-26

4.1 LIFE CYCLE COST, AND COST-EFFECTIVE ANALYSIS ..........................................................................4-264.2 SYSTEM MAINTENANCE PRACTICES ...............................................................................................4-264.3 PROJECT FINANCING ................................................................................................................4-27

APPENDIX

APPENDIX A RECOMMENDED DATA FIELDS

APPENDIX B RECOMMENDED SANITARY PRIORITY RATING SYSTEM

APPENDIX C MANHOLE INSPECTION DATA

Page | ii

TABLE OF EXHIBITS

EXHIBIT 1.1 — PROJECT LOCATION...........................................................................................................1-2EXHIBIT 2.1 — PIPE AGE .........................................................................................................................2-4EXHIBIT 2.2 — PIPE MATERIAL...................................................................................................................2-5EXHIBIT 2.3 — PIPE DIAMETER ..................................................................................................................2-6EXHIBIT 2.4 — MANHOLE INSPECTION SCORES, CITY OF CLIVE .......................................................................2-8EXHIBIT 2.5 — FIELD OBSERVED MANHOLES ................................................................................................2-9EXHIBIT 2.6 — SANITARY DRAINAGE BASINS...............................................................................................2-11EXHIBIT 2.7 — POTENTIAL AREAS OF CONCERN .........................................................................................2-12EXHIBIT 2.8 — PERCENT OF PIPE CAPACITY: BASE FLOWS .............................................................................2-14EXHIBIT 2.9 — PERCENT OF PIPE CAPACITY: 1-YEAR STORM..........................................................................2-15EXHIBIT 2.10 — PERCENT OF PIPE CAPACITY: 5 YEAR STORM ........................................................................2-16EXHIBIT 2.11 — PERCENT OF PIPE CAPACITY: 10-YEAR STORM......................................................................2-17EXHIBIT 2.12 — PERCENT OF PIPE CAPACITY: 25-YEAR STORM......................................................................2-18EXHIBIT 3.1 — PIPE CONDITION RELATIVE TO AGE ......................................................................................3-21EXHIBIT 3.2 — MANHOLE INJECTION GROUTING .......................................................................................3-23EXHIBIT 3.3 — SANITARY SYSTEM PRIORITIZATION SCALE...............................................................................3-24EXHIBIT 3.3— PRELIMINARY SANITARY SEWER RATING...................................................................................3-25

TABLE OF TABLES

TABLE 4.1 — SANITARY CAPITAL IMPROVEMENT PLAN, PERIOD MEDIAN ANNUAL EXPENDITURE; .............................4-27

Page | A

0.0 EXECUTIVE SUMMARY

0.1 INTRODUCTION

The City of Clive, Iowa, has chosen to proactively assess the condition and maintenance practices of the various utility systems. McClure Engineering Co. (MEC) conducted an assessment of the City’s sanitary utility, including evaluation of existing geographic information system (GIS) data and development of a hydraulic model of the sanitary collection system. The City has a system that is in good condition considering the age. MEC’s findings include recommendations of:

Relatively minor changes to the current maintenance practices, Expanding the annual scope of preventative maintenance and rehabilitation, and A projected annual budget to fund current rehabilitation and future sewer replacement

activities.

0.2 CCTV REVIEW AND FIELD VERIFICATION

MEC reviewed closed circuit televising (CCTV) inspection recordings provided by the City and made independent observations, which were then compared against the City’s observations. While the City’s system, as a whole, is in very good condition, the overarching observation of this review was that minor defects are not currently being captured in routine inspections. Defects such as minor cracks or staining at joints are important to document and observe for changes as indicators of system deterioration. Additionally, MEC recommends that routine inspections be carried out during periods of higher ground water, such as the spring and early summer, so that any inflow or infiltration (I/I) is more likely to be directly observed.

MEC also noted that higher likelihood of failure and relative cost of repair/replacement are not factored into manhole or sewer pipe ratings. Ranking manholes and sewer pipes by priority would allow the City to target manpower and preventative maintenance funds more effectively. As the City typically carries out inspections during the winter, and manpower is often dedicated to other tasks during the seasons of higher flows, inspections during this time of year could be reduced to the highest priority assets.

0.3 DATA REVIEW AND ANALYSIS

The City provided available information on the sanitary collection system in the form of separate GIS files for the sanitary collection mains, manholes, and service lines. The City’s GIS data was generally adequate, however, MEC observed some gaps and made mathematical assumptions to fill those gaps for further use of this data in subsequent tasks. The assumptions were discussed with City personnel, and these sites will be prioritized for future data capture activities.

Additionally, the inspection forms were assessed and MEC made recommendations on fields that should be emphasized when filling out the standard forms the City uses for inspections. These recommendations would help to better track the condition of individual elements of the collection system as they age. The recommended updates in data collection and organization are found in Appendix A.

Finally, flow data from the WRA flow meters and City billing data were evaluated against each other and known rainfall data over several years to identify standard flows for base conditions and 1-year, 5-year, and 10-year storm conditions.

Page | B

0.4 HYDRAULIC MODEL

Using the completed GIS data, MEC performed a desktop evaluation of the function of the system, known as a GIS Model. This model was used to identify any further discrepancies in the data, as well as any areas of serious concern in the system.

MEC then developed a sanitary hydraulic model of the entire collection system and WRA trunk sewers using Bentley SewerGEMS. This program uses several flow calculation methods to quickly determine flows at each point throughout the system for user defined conditions. This model was checked for connectivity and updated until proper function was achieved. Flows were then allocated throughout the system, and system function was tested using the previously established Base, 1-Year, 5-Year, and 10-Year conditions and diurnal patterns. Further, growth and redevelopment scenarios were developed to evaluate the current systems suitability for potential growth both within the City, and in other municipalities that share the WRA trunk sewers. (See Exhibit 2.8 through Exhibit 2.12)

City of Urbandale and WRA trunk sewers flow through the City, resulting in few City of Clive sewer runs of significant length before emptying into one or the other system (see Exhibit 2.6). As such, no significant deficiencies were identified in the modeled scenarios. A few minor deficiencies were identified, particularly near Clive Lake (see Exhibit 2.7). These areas are not a cause for significant concern but should be monitored and considered for upsizing if and when the time for sewer and road replacement becomes necessary.

0.5 CITY MAINTENANCE PRACTICES

MEC evaluated the City’s maintenance practices and schedules, and found that, overall, the City’s practices are more than adequate to maintain a well-functioning sanitary collection system. MEC would make the following recommendations to optimize these practices:

Prioritize the City’s sanitary infrastructure based on recommended criteria (see Appendix B) Likelihood of Failure Consequence of Failure

Increase frequency of inspection on highest-tier priority elements Optionally and temporarily reduce frequency of inspection on lowest-tier priority

elements if there is a need to reallocate funds Implement a manhole grouting program in addition to the current sewer lining program Accelerate sewer lining program to approximately 5.5% of total system length per year Complete sewer lining and initiate replacement of sewers as needed to ensure the age

of infrastructure is maintained within the average useful life (approximately 60–70 years)

0.6 LIFE CYCLE COST, AND COST-EFFECTIVE ANALYSIS

The City’s system consists primarily of two types of pipe material: Clay pipe (30% of the system) and Truss pipe (60 % of the system). Clay pipe was installed primarily before 1980 and Truss pipe has been installed primarily since 1980. A mix of PVC, Cast and Ductile Iron, and Reinforced Concrete pipe make up the remaining 10% of the system. Sanitary sewer pipe typically deteriorates exponentially the older it gets (see Exhibit 3.1), with clay pipe having a typical useful life of 60–70 years. The City desires to stay ahead of the curve of deterioration in order to not be overwhelmed with maintenance needs when a large portion of the systems reaches an age of deterioration or failure around the same time. The City proactively began a pipe lining program around 2003. This program has focused on older

Page | C

clay pipes and has addressed approximately 1% of the system per year on average since that time. However, prior to 1980, pipe installation averaged a little more than 1.5% of the current system per year, leaving a gap in the rate of rehab (1% vs. 1.5%).

The total asset value (AV) of the public sanitary collection system, exclusive of any surface or peripheral utility replacement costs (water and storm infrastructure, etc.), is estimated at $172,897,000 (valued in 2018 dollars). Based on this value and the City’s desire to maintain a system in good working order, it is recommended that the annual budget for repairs and replacement of the sanitary system be set at approximately 1.5% of the total AV, or $2,600,000 per year. This value should be adjusted annually to account for inflation to maintain a sufficient budget.

As the City is responsible for all flows to the WRA and sanitary service laterals are a common source of I/I, it may be worthwhile to replace sanitary service connections in combination with any rehabilitation or replacement of the public infrastructure. This would include the lateral connection and service lateral under the pavement up to the full extent within the public right-of-way. This optional replacement would maintain the integrity of service connections.

The City can use discretion as to the specific projects these funds address, but this value would allow for annual rehabilitation of up to approximately 5.5% of total system (both LF and Manholes) per year. If performed successively until completion of a rehabilitation program, a sanitary collection system replacement program could then be initiated at approximately the same annual expenditure. A program of this nature would ensure no pipe or manhole exceeded its useful life before repair and/or replacement. A repair/replacement program at a lesser level would not keep pace with historical pipe installation rates, and pipe age would grow exponentially.

0.7 RECOMMENDATIONS AND CAPITAL IMPROVEMENT PLAN

The recommendations of this report are as follows:

1. Budget to spend approximately 1.5% of the total sanitary asset value per year on system maintenance, and eventually replacement

2. Modify inspection and maintenance schedules to reflect infrastructure priority

3. Implement manhole grouting in addition to current sanitary system maintenance practices (ring adjustment, boxouts, etc.)

4. Accelerate sanitary main lining program to limit pipe age before lining/replacement to less than 70 years (equivalent to approximately 5.5% of total system LF per year, or 1.5% total asset value expenditure)

Future sanitary collection sewer replacement programs should be coordinated with replacement programs for other utilities and street surfaces. This will allow for the pooling of funds and will greatly reduce the overall costs to the City.

Page | 1-1

1.0 INTRODUCTION

1.1 PURPOSE AND BACKGROUND

The City of Clive, Iowa, has experienced substantial growth in the 60-plus years since incorporation in 1954. The City is nearing full build-out of the incorporated area and does not anticipate significant future growth due to a complete surrounding of other municipalities (Exhibit 1.1).

The City has chosen to proactively assess the condition and maintenance practices of the various utility systems. The City contracted with McClure Engineering Co. (MEC) to conduct a survey and analysis of the City’s sanitary utility and make recommendations to improve and/or optimize maintenance and replacement practices.

1.2 SCOPE

To achieve the tasks set forth by the City, MEC needed to perform the following tasks:

Review all available pre-existing sanitary collection system Closed Circuit Television (CCTV) inspection records and recordings and manhole inspection reports

Review and validation of existing Geographic Information System (GIS) data and make recommendations on data collection and data fields

Compare City and Des Moines Water Reclamation Authority (WRA) flow data to identify typical and peak sanitary flows

Develop a hydraulic model of the sanitary collection system using validated GIS data and evaluate the following scenarios:

o Base Flows

o Average Wet Weather Flows

o 1-Year Storm Flows

o 10-Year Storm Flows

Review and make recommendations on the City’s maintenance schedules and practices Perform a Life-Cycle Cost evaluation and Cost-Effective Analysis on the operation of the

system and any recommended improvements Develop a Capital Improvements Plan that delineates the annual expenditures necessary

to maintain this system effectively in perpetuity

1.3 SUMMARY

The City is looking to the future and acknowledging that the current system– though in generally good condition– will not last forever. The City wants to know what is and will be necessary both today and in the future, to stay ahead of the aging of the system and avoid system failure or emergency expenditures to avoid that at any point in the future. The overall purpose of this study was to provide the City with a clear picture of what is necessary to continue to operate an exceptional sanitary utility.

UNIVERSITY AVE

14

2nd

ST

NW

12

8th

STHICKMAN RD

DOUGLAS PKWY

MEREDITH DR

NW

15

6th

ST

NW

ALI

CE

RD

NW

10

0th

ST

22

nd S

T

N:\

Proj

ects

\CLV

20

31

70

20

-00

\Des

ign\

Exhi

bits

\Exh

ibit1

.1.d

wg

EXHIBIT 1.12018 SANITARY SEWER SYSTEM PLANNING

PROJECT LOCATION

NORTH

CITY OF CLIVE

80

80 35

235

35

CLIVE CORPORATE BOUNDARY

Page | 1-3

2.0 HYDRAULIC STRATEGY

2.1 STRATEGY DEVELOPMENT

There is no on-size-fits-all solution to sanitary system operation and maintenance. Thus, prior to developing a system management plan, MEC conducted a thorough evaluation of the available data on the development, maintenance, condition, and operation of the City of Clive’s sanitary collection system. The steps of this process are discussed in this section.

2.1.1 DATA REVIEW AND ANALYSIS

The City provided available system information on the sanitary collection system in the form of separate GIS files for the sanitary collection mains, manholes, and service lines. The information provided in these files was reviewed and assessed for the following:

Completeness of established data fields Sufficiency of established data fields to provide necessary information Clear inaccuracies in provided data

The City’s GIS data was generally adequate and useful for some purposes. Selected characteristics of the City’s system are presented in Exhibit 2.1 through Exhibit 2.3.

Based on provided information, the City of Clive owns a total of 1,832 manholes and approximately 420,000 linear feet (LF) of pipe ranging from 6” to 30” in diameter. On average, the City has installed approximately 35,000 LF of sanitary sewer pipe every 5 years since incorporation. However, there was a significant lull in the early 1980’s (~6,650 LF from 1980–1984) and a significant development boom in the early 1990’s that extended through the end of the decade (~81,350 LF 1990–1994; ~47,050 LF 1995–1999).

The City’s system consists primarily of two types of pipe material: Clay pipe (30% of the system) and Truss pipe (60 % of the system). Clay pipe was installed primarily before 1980 and Truss pipe has been installed primarily since 1980. A mix of PVC, Cast and Ductile Iron, and Reinforced Concrete pipe make up the remaining 10% of the system.

MEC observed some gaps and apparent inconsistencies in the provided data. Gaps include missing pipe diameters or inlet/outlet invert elevations. Typical inconsistencies included locations where different values were recorded for the same system component, such as different invert elevations or different pipe sizes from different field inspections, or recorded invert elevations that resulted in negative (uphill) pipe slopes that were not evident in CCTV recordings. Further, manhole and sewer pipe data are stored in different tables, which is typical, but no field exists to tie pipe information to the inlets and outlets of each manhole. This is problematic in manholes with more than one inlet or outlet pipe.

Mathematical assumptions, such as assuming invert elevation by averaging known upstream and downstream elevations over the length of pipe between them, were made to fill those gaps for further use of this data. The inferences were discussed with City personnel, and these sites will be prioritized for future data capture activities. Also, MEC recommended that the City add fields to the manhole and collection mains tables. The recommended fields will tie the tables together allowing greater usability of the information the City collects. The recommended updates in data collection and organization are found in Appendix A.

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Pip

e A

ges.

dwg

EXHIBIT 2.12018 SANITARY SEWER SYSTEM PLANNING

PIPE AGES

PROJECT LEGEND

1965-1969

1970-1974

1975-1979

CLIVE CORPORATE BOUNDARY

NORTH

1250 25000

GRAPHIC SCALE

1980-1984

1985-1989

1990-1994

1995-1999

2000-2004

2005-2009

POST 2010

PRE 1965

PIPE AGE ASSUMED(Based on Available Data)

USSD TRUNK LINES

WRA TRUNK LINES

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Pip

e M

ater

ials

.dw

g

EXHIBIT 2.22018 SANITARY SEWER SYSTEM PLANNING

PIPE MATERIALS

CLIVE CORPORATE BOUNDARY

PROJECT LEGEND

CAST IRON

VITRIFIED CLAY

DUCTILE IRON

PVC

REINFORCED CONCRETE

TRUSS

UNKNOWN

WRA TRUNKS

USSD TRUNKS

NORTH

1250 25000

GRAPHIC SCALE

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Pip

e D

iam

eter

s.dw

g

EXHIBIT 2.32018 SANITARY SEWER SYSTEM PLANNING

PIPE DIAMETERS

LEGEND

6" Dia.

8" Dia.

10" Dia.

12" Dia.

15" Dia.

16" Dia.

18" Dia.

20" Dia.

21" Dia.

24" Dia.

27" Dia.

30" Dia.

UNKNOWN

CLIVE CORPORATE BOUNDARY

NORTH

1250 25000

GRAPHIC SCALE

USSD TRUNK SEWERS

WRA TRUNK SEWERS

Page | 1-7

Additionally, the inspection forms used by the City were assessed and MEC made recommendations on fields that should be emphasized when filling out the standard forms the City uses for inspections. These recommendations can help to better track the condition of individual elements of the collection as they age.

Finally, flow data from the WRA flow meters and City billing data were evaluated against each other and known rainfall data over several years to identify standard flows for dry, wet, and storm periods. Further, WRA flow meter data was used to determine a diurnal flow pattern for the individual meters and the City as a whole.

2.1.2 CCTV REVIEW

The City provided MEC with digital video files of CCTV inspections, and inspection data sheets for the pipes and manhole inspections that have been conducted over the last decade. The results of the City’s inspections were compiled and tabulated in spreadsheet format and categorized and sorted by score on various responses and overall ranking or score. MEC personnel then reviewed the most recent available footage for each pipe segment and recorded independent observations of the condition and any defects using the National Association of Sewer Service Company’s (NASSCO) Pipeline Assessment Certification Program and Manhole Assessment Certification Program (PACP/MACP) standards for the criteria and ratings. These observations were then compared with the compiled observations made by the City. Any significant or consistent discrepancies were noted.

While the City’s system is generally in very good condition, the overarching observation of this review was that minor defects are not currently being captured in routine inspections. Defects such as minor cracks or staining at joints are important to document and observe for changes as indicators of system deterioration, yet these early indicators were not consistently documented.

MEC also recommends that routine inspections be carried out during periods of higher ground water, such as the spring and early summer, so that any inflow or infiltration (I/I) is more likely to be directly observed. Additionally, location and failure risk factors are not factored into manhole ratings. Thus, no manhole carries a higher priority than others for the purposes of maintenance and inspection. As the City typically carries out inspections during the winter, and manpower is often dedicated to other tasks during the seasons of higher flows, inspections during this time of year could be reduced to the highest priority pipes and manholes.

2.1.1 MANHOLE FIELD INSPECTION

The City’s Manhole inspections use a grading system that ranges from 0 to 100, with 0 signifying no observed deficiencies. Of the City’s 1,832 manholes, the vast majority score 5 or less (see Exhibit 2.4). Upon evaluating the inspection results, a threshold of 30 points was identified as the threshold for field observation/verification of manhole condition. Additionally, a number of locations where pipe junctions occur but no manhole was present and locations where there appear to be multiple downstream pipes were observed to determine system function. MEC personnel accompanied City staff in the field over two days to observe these locations (see Appendix C).

Page | 2-8

Exhibit 2.4 — Manhole Inspection Scores, City of Clive

91.8% 0.082288828

4.0%

0.8%

0.8%

2.6%

0.1%

0.1%

0-5

6-10

11-20

21-30

31-40

41-50

>50

Exhibit 2.4Manhole Inspection Scores,

By Percent of Total

DOUGLAS PKWY

HICKMAN RD142th

ST

NW

156th

ST

CLIVE LAKE

NW

128th

ST

UNIVERSITY AVE

SE B

OO

NE

DR

JORD

ON

CRE

EK P

ARK

WA

Y

SWANSON BLVD

NW

100th

ST

22N

D S

T86th

ST

VA

LLEY

WES

T D

RIV

E

HICKMAN RD

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Ins

pect

ed M

Hs.

dwg

NORTH

1250 25000

GRAPHIC SCALE

EXHIBIT 2.52018 SANITARY SEWER SYSTEM PLANNING

FIELD INSPECTED MANHOLE LOCATIONS AND REASON FOR SELECTION

LEGEND

CLIVE TRUNK SEWERS

CLIVE COLLECTORS

MANHOLE OF INTEREST- PIPE INTERSECTION WITH NO APPARENT MANHOLE

MANHOLE OF INTEREST- MULTIPLE DOWNSTREAM PIPES

MANHOLE OF INTEREST- POOR INSPECTION SCORE

CLIVE CORPORATE BOUNDARY

Page | 2-10

As was noted in the review of CCTV inspections, the general condition of the system is very good. Most of the manholes selected for field observation were rated poorly due to cleaning needs or surface deterioration that had subsequently been rectified prior to our visit. However, the manholes also exhibited many minor indicators of deterioration that are not recorded in the City’s regular inspections. The following observations are examples of early signs of deterioration or underlying issues:

Surface Efflorescence– Indicative of moisture wicking through concrete Surface Staining– Indicative of I/I during higher groundwater periods Minor Spalling– Early deterioration of concrete structures, often starts with large

aggregate becoming loose and/or displaced Grouted Bench Deterioration– Indicative of I/I at the joint between the precast barrel

and base sections, often first appears as minor cracking or fracturing of a grouted in place bench structure

2.1.2 GIS MODEL AND CALIBRATION

In addition to simple system data validation, the system function and sufficiency can be evaluated using the GIS data. Upon completion of existing data validation and cleanup, MEC used this data to perform a desktop evaluation of the function of the system, known as a GIS Model. This model is useful for identifying any further discrepancies in the data, as well as any areas of serious concern in the system. In a GIS model, flow paths are identified, and slopes and resulting pipe capacities are calculated. This model is typically calibrated by checking known problem areas and flows against calculated capacities and industry standard demands.

The City’s sanitary collection system was evaluated graphically and major collectors and collection areas were identified. The City’s system was broken down into 22 general sanitary collection areas, commonly referred to as Sanitary Drainage Basins (see Exhibit 2.6). These basins typically have a number of pipes that all come together to a single outlet pipe, or is sometimes a conglomeration of several short pipe runs that all drain to a single trunk. Sanitary drainage basins are useful for identifying common areas where discrete flows can be identified and addressed if necessary.

The model was tested using flow values from the City’s billing records and WRA flow meter data. As the WRA trunk sewer runs through the City of Clive, the City’s sanitary collection system has very few locations where a single pipe is a collector for a very large area. Also, the City does not have any significant known problem areas, and the GIS model was used primarily to evaluate pipe capacity and system connectivity.

To check the system against “worst-case” conditions, the system was run with DNR standard flows per capita (for residential areas) and per acre (for industrial and commercial areas). As these values are much higher than the flow currently recorded in the City, some potential bottlenecks were identified. In these areas the standard flows are close to or even exceed the calculated pipe capacity. These locations are presented in Exhibit 2.7. It is important to reiterate that these flows are based on DNR standard flows, and not the City’s actual water use. These standard values assume high sanitary demand customers, and a generous allowance for I/I. Due to the actual businesses and industries currently located in the City of Clive, these peaks are unlikely to be met, or even approached. However, Exhibit 2.7 does identify a reach that MEC recommends be increased in size/capacity when the road or pipe is replaced.

CLIVE CORPORATE BOUNDARY

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

22

21

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Dra

inag

e Ba

sins

.dw

g

NORTH

1,250 2,5000

GRAPHIC SCALE

EXHIBIT 2.62018 SANITARY SEWER SYSTEM PLANNING

SANITARY DRAINAGE BASINS

LEGEND

CLIVE TRUNK SEWERS

CLIVE COLLECTORS

CLIVE CORPORATE BOUNDARY

WRA TRUNK SEWERS

#

SANITARY COLLECTION BASINS

USSD TRUNK SEWERS

WRA Flow Meter C2

WRA Flow Meter UWH-7

WRA Flow Meter C1

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Pip

e C

apac

ities

.dw

g

EXHIBIT 2.72018 SANITARY SEWER SYSTEM PLANNING

AREAS OF POTENTIAL CONCERN

LEGEND

CLIVE CORPORATE BOUNDARY

NORTH

1250 25000

GRAPHIC SCALE

USSD TRUNK LINES

WRA TRUNK LINES

6" Dia.

8" Dia.

10" Dia.

12" Dia.

15" Dia.

16" Dia.

18" Dia.

20" Dia.

21" Dia.

24" Dia.

27" Dia.

30" Dia.

UNKNOWN

POINT PEAK FLOWS* PERCENT OF CAPACITY

*Peak Flow based on Iowa DNR per acre flows for land use, not City use Data.

1 0.07 MGD (0.33 MGD) 14% (Up to 66% at full development)

2 0.20 MGD 40%

3 0.25 MGD (0.53 MGD) 50% (Up to 105% at full development)

4 0.15 MGD 30%

5 0.45 MGD** 90%

6 0.55 MGD** 110%

7 1.01 MGD** 126%

8 0.33 MGD** 66%

9 0.47 MGD** 93%

10 0.38 MGD** 76%

11 0.31 MGD** 39%

12 0.47 MGD** 93%

** Flow value assumes redevelopment of current commerncial/industrial area.

INDUSTRIAL / REDEVELOPABLE

UNDEVELOPED

RESIDENTIAL

HIGH DENSITY RESIDENTIAL / COMMERCIAL

RECOMMENDED FOR SIZE

INCREASE AT REPLACEMENT

Page | 2-13

2.2 SANITARY HYDRAULIC MODEL

2.2.1 MODEL DEVELOPMENT

Using the completed GIS data, a sanitary hydraulic model of the entire collection system and USSD/WRA trunk sewers was created using Bentley SewerGEMS. SewerGEMS uses several flow calculation methods to iteratively determine flows at any and every point throughout the system for user defined conditions. Once the system is built in the model, this process is able to perform flow calculations for hundreds or thousands of pipes.

This model was checked for connectivity and modified until proper function was achieved. Known flows from WRA flow meters and City billing data were calculated per pipe-foot, and distributed throughout the system as inflow per manhole. System function was then tested and evaluated.

2.2.2 SCENARIO ANALYSIS

The City requested that a hydraulic model be used to evaluate the system function under the Base Flow, 1–Year, 5–Year, and 10–Year flow conditions. To more accurately evaluate flows, diurnal patterns were developed, and 25–Year flow conditions were also evaluated. Further, growth and redevelopment scenarios were developed to evaluate the current systems suitability for potential growth both within the City, and in other municipalities that share the WRA trunk sewers.

2.2.3 SANITARY HYDRAULIC MODEL RESULTS

The sanitary hydraulic model results show how much pipe capacity is utilized under each of the various flow conditions. These results are presented in Exhibit 2.8 through Exhibit 2.12. Due to the good condition, adequate pipe sizes, and relatively short runs of pipe, no significant deficiencies were identified in any modeled scenario. Additionally, no significant difference is noted between current development levels, or if higher demand businesses or redevelopment were to occur. There may be potential minor surcharge conditions if upstream development were to utilize a significant portion of trunk sewer capacity but this is not likely to cause backups for the City’s customers.

2.3 IDENTIFIED HYDRAULIC STRATEGY

There are no specific immediate hydraulic improvements indicated as a result of these analyses. A few minor deficiencies were identified, particularly near Clive Lake (see Exhibit 2.7). These areas are not a cause for significant concern but should be monitored and considered for upsizing if and when the time for sewer and road replacement becomes necessary.

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Pip

es P

erce

nt F

ull.d

wg

EXHIBIT 2.82018 SANITARY SEWER SYSTEM PLANNING

PIPES PERCENT FULL: BASE FLOWS

NORTH

1250 25000

GRAPHIC SCALE

PROJECT LEGEND

0-15%

15-30%

30-45%

45-60%

60-75%

Greater than 75%

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Pip

es P

erce

nt F

ull.d

wg

EXHIBIT 2.92018 SANITARY SEWER SYSTEM PLANNING

PIPES PERCENT FULL: 1-YEAR STORM

NORTH

1250 25000

GRAPHIC SCALE

PROJECT LEGEND

0-15%

15-30%

30-45%

45-60%

60-75%

Greater than 75%

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Pip

es P

erce

nt F

ull.d

wg

EXHIBIT 2.102018 SANITARY SEWER SYSTEM PLANNING

PIPES PERCENT FULL: 5-YEAR STORM

NORTH

1250 25000

GRAPHIC SCALE

PROJECT LEGEND

0-15%

15-30%

30-45%

45-60%

60-75%

Greater than 75%

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Pip

es P

erce

nt F

ull.d

wg

EXHIBIT 2.112018 SANITARY SEWER SYSTEM PLANNING

PIPES PERCENT FULL: 10-YEAR STORM

NORTH

1250 25000

GRAPHIC SCALE

PROJECT LEGEND

0-15%

15-30%

30-45%

45-60%

60-75%

Greater than 75%

N:\

Proj

ects

\CLV

20317020-0

0\D

esig

n\D

wgs

\Pip

es P

erce

nt F

ull.d

wg

EXHIBIT 2.122018 SANITARY SEWER SYSTEM PLANNING

PIPES PERCENT FULL: 25-YEAR STORM

NORTH

1250 25000

GRAPHIC SCALE

PROJECT LEGEND

0-15%

15-30%

30-45%

45-60%

60-75%

Greater than 75%

Page | 2-19

3.0 MAINTENANCE PROGRAM REVIEW

The City provided MEC with the following Operations and Maintenance (O&M) program documents:

Sanitary System Operations and Maintenance Manual Sewer Cleaning Schedule Priority Cleaning Segments List and Exhibit CCTV Inspection Schedule

These documents were reviewed and evaluated to determine the sufficiency of the City’s O&M program to facilitate the City’s goals for the system.

3.1 SANITARY SYSTEM MAINTENANCE PRACTICES

The current O&M program as currently implemented and evaluated documents have served to maintain the system in its current condition. These documents and practices are a good starting point and will help to meet the City’s goals with a few relatively minor modifications.

3.1.1 SYSTEM INSPECTION

System inspection is an integral part of a good maintenance system. Routine inspection is necessary to maintain a current knowledge of the condition of the system as a whole, and of the individual components. Additionally, regular inspection affords the opportunity to identify and address any acute issues before they can become catastrophic and interfere with the function of the system.

The City currently conducts sanitary sewer CCTV inspections on a rolling 5-year schedule, where all pipes in a defined area (pipes that fall on specific pages of the City’s map book of the system) are inspected approximately every fifth year. The City owns and utilizes their own CCTV equipment for these inspections.

The City’s O&M manual specifies that all manholes are to be inspected every year. It may be possible that City personnel do visually inspect every manhole every year. However, the inspection data provided did not record formal survey results in all four years provided for any manhole. Approximately half recorded formal inspections in each two and three of the four years provided, and less than 5% were inspected only once in that period.

It was noted in conversation with City staff that manhole and sewer inspections are commonly carried out during the winter due to the availability of manpower. It is commonly recommended that these inspections be carried out during periods of high ground water so that I/I can be directly observed. These conditions commonly occur in the spring and early summer.

It is considered best practice to only have personnel conduct inspections that are trained in using and put into practice a standardized inspection and defect rating coding system, such as NASSCO’s PACP/MACP program (see Section 2.1.1). This system has codes for nearly every conceivable defect including those that seem very insignificant. MEC recommends all personnel that conduct CCTV inspections be certified in PACP/MACP inspection techniques and coding.

Page | 2-20

3.1.2 MAINTENANCE AND CLEANING

The City’s O&M Manual presents the following activities as, “the day-to-day activities undertaken by staff to ensure that the collection system continues to function as intended.”

Root Control Jet Cleaning Grease Control

These activities are all worthwhile and if properly and regularly implemented, will serve the City well to achieve this goal.

The City’s current Maintenance and Cleaning practices as currently defined are likely adequate to meet the City’s goals for system operation.

3.1.3 PIPELINE REHABILITATION

Pipeline maintenance is important to operate a well-functioning sanitary collection system. A wide range of factors can impact the performance of sanitary sewers, though they can be roughly categorized as Structural and Operational factors. Operational factors include surface and/or debris buildup, and other degradation that is generally addressed by routine cleaning and maintenance. Structural factors are those that would impact the function of the system by physically impacting the carrying capacity; factors such as pipe shape and integrity, material quality and condition, and root intrusion, and construction grade and external support. Most structural defects can result in the introduction of I/I to the system, and minor to moderate structural defects are typically able to be addressed through pipeline rehabilitation, whereas major defects typically call for excavation and replacement of the failed infrastructure.

Sanitary sewer pipe typically deteriorates exponentially the older it gets (see Exhibit 3.1), with clay pipe having a typical useful life of 60–70 years. The City desires to stay ahead of the curve of deterioration in order to not be overwhelmed with maintenance needs when a large portion of the system reaches an age of deterioration or failure around the same time. To that end, the City proactively began a pipeline rehabilitation program in 2003. This program utilizes Cure-In-Place Piping (CIPP) to line the existing sewer line without any need for excavation or trenching.

The City currently rehabilitates approximately 1% of the total linear feet (LF) of the sanitary collection system per year. Due to the historic rate of installation of sanitary sewer pipe, a program that rehabilitates less than 1.5% of the system annually is not adequate to stay ahead of rehabilitation and replacement needs in the long-term. MEC recommends that the City budget approximately 1.5% of the total asset value (discussed in Section 4.1) for rehabilitative maintenance every year. This value will allow the City to rehabilitate up to 5.5% of the total LF of the system, or replace up to 1.5% of the total LF of the system, or any combination between the two. At this level of investment, the City should be able to maintain a well-functioning system in perpetuity.

Page | 3-21

Exhibit 3.1 — Pipe Condition Relative to Age

0 10 20 30 40 50 60 70 80 90 100 110 1200

10

20

30

40

50

60

70

80

90

100

Years From Installation

Perc

ent o

f Lik

e-N

ew C

ondi

tion

CIPP Lining & Manhole Rehabilitation returns Capacity and Useful Life back to 90%+

Page | 3-22

3.1.4 MANHOLE REHABILITATION

The main parts of a manhole can be simplified to the Surface interface and the Underground Structure. The surface interface consists of the concrete interface surrounding the manhole cover in streets (boxout), frame and cover, and adjustment rings. The underground structure is made up of the cone section, barrel sections, base section and bench, and the effluent and influent pipe junction(s). Typically, the surface interface is responsible for manhole inflow, and the underground structure for manhole infiltration. MEC recommends manhole rehabilitation options that work from the outside in, as these options have proven to be more effective, and work with positive hydrostatic pressure, rather than against it.

Surface Interface

The City’s O&M Manual briefly discusses Manhole Sealing as a tool to eliminate I/I in the system. This is specified as a means to address deficiencies noted during regular inspections. This practice is aimed at the surface interface, specifically at the adjustment rings between the cone and casting. This is a good practice, and many opportunities exist to add to this practice and improve the condition and watertightness of the City’s manholes. The boxout can also be a major source of I/I once it begins to deteriorate, and repairs and maintenance of this structure is a good investment. The potential for I/I at the surface interface increases exponentially if the surface conditions around the manhole direct surface runoff toward the manhole, such as low points in the street or ground. Sealing the adjustment rings will also help reduce this I/I.

Underground Structure

It is important to also address the underground structure of the manhole, as all joints in the sections of the manhole, where pipes enter and exit a manhole, and even wicking through the concrete if not sealed externally can all contribute to substantial I/I. Injection grouting is a practice that can help to significantly reduce this source of I/I. Injection grouting is typically accomplished by drilling a hole in the manhole and using a pressure injection system to introduce a hydrophilic grout into the soil and/or void outside the manhole. This grout bonds with any moisture present and creates a water tight barrier that is conformed to the external surface of the manhole.

Page | 3-23

Exhibit 3.2 — Manhole Injection Grouting

3.1.5 SYSTEM PRIORITIZATION

Prioritizing system elements is a strong tool that can be used to help the City more effectively direct funds to where they will have the most impact toward the function of the system. This does not mean that low-priority areas are ignored, but rather that high-priority areas receive additoinal attention. Elements should be prioritized based on both the likelihood of failure (LOF) and the consequence of failure (COF). Likelihood of failure considers any factors in the area at and upstream of the element that can contribute to the accelerated degradation of sanitary sewer infrastructure as well as any known recurring issues in the system. Consequence of failure takes into account the location of the element in relation to the system as a whole and in the surrounding environment. A visualization of this prioritization scale is shown in Exhibit 3.3.

Page | 3-24

Exhibit 3.3 — Sanitary System Prioritization Scale

The City’s O&M Manual indicates areas that have had recurring incidence of the following issues are prioritized and categorized on the list and exhibits found in Appendix X:

Root Growth Grease Buildup Creek Crossings Pipeline buried along creeks or other places prone to flooding Poor Pipe Grade or Debris Accumulation

These categories are consistent with MEC’s recommended LOF prioritization categories.

Additionally, it is recommended to proactively rate all system elements based on the impact they would have if they were to fail. This impact can be on the community and/or environment (e.g.– creek or railroad crossings, or along major transportation corridors) and also relate to the constructability/accessibility or transportation impact of any repairs (e.g.- a manhole in a residential backyard, a residential street, or an arterial roadway). Use of a robust rating scale would allow for the optimization of inspection and maintenance funds. An example of the City’s system using this rating system is shown in Exhibit 3.4. The rating system used in this analysis is provided in Appendix B.

N:\

Proj

ects

\CLV

20

31

70

20

-00

\Des

ign\

Exhi

bits

\Exh

ibit3

.4.d

wg

EXHIBIT 3.42018 SANITARY SEWER SYSTEM PLANNING

PRELIMINARY SANITARY SEWER RATING

NORTH

80

35

NOTE: Pipe Locations are ranked by potential Environmental or Community Impact and likely Constructability or Transportation Impact . Numerical scores are Low (1) to High (5).

PROJECT LEGEND

CREEK CROSSING (5);ARTERIAL STREET (4 TO 5)

CREEK CROSSING (5);RESIDENTIAL BACKYARD (3 TO 4)

CREEK CROSSING (5);RESIDENTIAL STREET (2 TO 4)

CREEK CROSSING (5);OPEN GRASS (1)

PARALLEL TO CREEK (3);ARTERIAL STREET (4 TO 5)

PARALLEL TO CREEK (3);RESIDENTIAL BACKYARD (3 TO 4)

PARALLEL TO CREEK (3);RESIDENTIAL STREET (2 TO 4)

PARALLEL TO CREEK (3);OPEN GRASS (1)

NO CROSSING (1);ARTERIAL STREET (4 TO 5)

NO CROSSING (1);RESIDENTIAL BACKYARD (3 TO 4)

NO CROSSING (1);RESIDENTIAL STREET (2 TO 4)

NO CROSSING (1);OPEN GRASS (1)

PRIMARY THOROUGHFARE (5);ARTERIAL STREET (4 to 5)

WITHIN OR CROSSES RAILROAD ROW (5);ARTERIAL STREET (4 TO 5)

WITHIN BRIDGE FOOTPRINT (4);ARTERIAL STREET (4 TO 5)

Page | 3-26

4.0 RECOMMENDATIONS

4.1 LIFE CYCLE COST, AND COST-EFFECTIVE ANALYSIS

The total asset value (AV) of the public sanitary collection system, exclusive of any surface or peripheral utility replacement costs (water and storm infrastructure, etc.), is estimated at $172,897,000 (valued in 2018 dollars). This is the estimated cost to replace the entirety of the City’s sanitary sewer system, if this were to be undertaken at one time. This is also a good benchmark to budget against for incremental repairs and replacement of the system. Based on this value and the City’s desire to maintain a system in good working order, it is recommended that the annual budget for repairs and/or replacement of the sanitary system be set at approximately 1.5% of the total AV, or roughly $2,600,000 per year.

The City can use discretion as to the specific projects these funds address, and these funds can be spent on any combination of rehabilitation and replacement that is desired or necessary. If this value was spent exclusively on rehabilitation, this would allow for annual rehabilitation of up to approximately 5.5% of total system (both LF and Manholes) per year. If rehabilitation was performed successively until completion of a rehabilitation program, a sanitary collection system replacement program could then be initiated at approximately the same annual expenditure. A program of this nature would ensure no pipe or manhole exceeded its useful life before repair and/or replacement. A repair/replacement program at a lesser level would not keep pace with historical pipe installation rates, and pipe age would grow exponentially.

As the City is responsible for all flows to the WRA and sanitary service laterals are a common source of I/I, it may be worthwhile to replace sanitary service connections in combination with any rehabilitation or replacement of the public infrastructure. This also can save the City money on other public infrastructure as it can greatly reduce the necessity to cut into serviceable road surfaces to perform spot repairs, and can extend the life of road infrastructure. This practice would include replacing the private lateral connection to the City’s sewers and the length of private service lateral under the pavement up to the full extent within the public right-of-way. This is wholly optional and at the City’s discretion. However, pairing this replacement with replacement of other public infrastructure would help to maintain the integrity of service connections and has shown to reduce the overall repair and replacement costs to the community.

4.2 SYSTEM MAINTENANCE PRACTICES

As discussed in Section 3.0, there are a number of additional practices that the City can implement to optimize the annual maintenance practices. MEC recommends the following specific updates:

Prioritize the City’s sanitary infrastructure using the following criteria (see Appendix B)- Likelihood of Failure Consequence of Failure

Increase frequency of inspection on highest-tier priority elements Optionally and temporarily reduce frequency of inspection of lowest-tier priority

elements if there is a need to reallocate funds Implement a manhole grouting program in addition to the current sewer lining program Accelerate sewer lining program to approximately 5.5% of total system length per year Complete sewer lining and initiate replacement of sewers as needed to ensure the age

of infrastructure is maintained within the average useful life (approximately 60–70 years)

Page | 3-27

4.3 PROJECT FINANCING

As discussed earlier in this section, MEC recommends the City set the annual budget for sanitary system rehabilitation and maintenance at 1.5% of the total asset value, currently $2.6 million. This value should be adjusted annually to account for inflation to maintain the same level of maintenance and operation in perpetuity. A Capital Improvement Plan (CIP) demonstrating how these funds may be adjusted for inflation and dispersed between Rehabilitation and Replacement projects is shown in Table 4.1. This CIP assumes that the City will complete a rehabilitation program on the entirety of the system before beginning any systematic replacement program.

Table 4.1 — Sanitary Capital Improvement Plan, Period Median Annual Expenditure;Full System Rehabilitation Before System Replacement

2018Dollars

FY 2020-2024

FY 2025-2029

FY 2030-2039

FY 2040-2059 FY 2060+

MH Rehabilitation $ 539,314 $ 539,314 $ 673,164 $ 840,234 $ - $ -

MH Replacement $ 234,780 $ - $ - $ - $ 569,873 $ 887,843Sewer Main Rehabilitation $ 2,054,141 $ 2,054,141 $ 2,563,949 $ 3,200,285 $ - $ -

Sewer Main Replacement $ 2,358,675 $ - $ - $ - $ 5,725,123 $ 8,919,556

PUBLIC SYSTEM TOTAL $ 2,593,455 $ 3,237,113 $ 4,040,518 $ 6,294,996 $ 9,807,399

As discusses previously, if the City chooses to begin to implement a systematic replacement program before completion of a rehabilitation program, these funds could be divided between the two tasks, and the recommended investment would remain the same. An example of how this may break out is shown in Table 4.2.

Table 4.2 — Sanitary Capital Improvement Plan, Period Median Annual Expenditure;Mixed Rehabilitation and Replacement Program;2018

DollarsFY 2020-

2024FY 2025-

2029FY 2030-

2039FY 2040-

2059 FY 2060+MH Rehabilitation $ 539,314 $ 539,314 $ 323,711 $ 404,052 $ 629,500 $ -

MH Replacement $ 234,780 $ - $ 161,856 $ 202,026 $ 314,750 $ 887,843Sewer Main Rehabilitation $ 2,054,141 $ 2,054,141 $ 1,132,990 $ 1,414,181 $ 2,203,249 $ -

Sewer Main Replacement $ 2,358,675 $ - $ 1,618,557 $ 2,020,259 $ 3,147,498 $ 8,919,556

PUBLIC SYSTEM TOTAL $ 2,593,455 $ 3,237,113 $ 4,040,518 $ 6,294,996 $ 9,807,399

APPENDIX A

RECOMMENDED DATA FIELDS

APPENDIX B

RECOMMENDED SANITARY PRIORITY RATING SYSTEM

APPENDIX C

MANHOLE FIELD INSPECTION DATA