phase 1 part 2 cso control plan ... - city of newport · war monument in from of newport bay club...

Technical Memorandum

Phase 1 Part 2 CSO Control Plan Wellington Avenue CSO Facility Sewer Catchment Area 6 Flow Metering Investigation Prepared for: City of Newport Public Works Department 70 Halsey Street Newport, RI 02840 Prepared by: Earth Tech, Inc. 300 Baker Avenue Concord, Massachusetts 01742 October 6, 2006 J.N. 82372

INTRODUCTION

This Sewer Catchment Area 6 wastewater flow metering Technical Memorandum (TM) has been

prepared to describe the investigation procedure used, results of the investigation, and recommendations

for rehabilitation of observed defects. Figure 1 presents the meter locations along the Thames Street

Interceptor, the primary sewer conduit in the catchment area.

METERING OF WASTEWATER FLOWS

The flow metering program was designed to provide a general understanding of the hydraulics of Sewer

Catchment Area 6, which is tributary to the Thames Street Interceptor, to evaluate the dry weather and

wet weather flow characteristics of the catchment area, and to determine infiltration and inflow sensitivity

of the catchment.

The program included measurement of flows from the southern tributary areas, the Wave Avenue Pump

Station from Middletown, RI, the America’s Cup Avenue relief sewer, and the terminus of the Thames

Street interceptor at the twin 54” sewer conduit near Touro Street which directs wastewater flows to the

Long Wharf Pump Station. The metering manholes were selected to provide a snapshot of the flows

entering and exiting Catchment Area 6, enabling a more precise analysis of flows generated within the

catchment area. Once the metering manholes were identified, ADS Environmental Services (formerly

Severn Trent Pipeline Services, Inc. (STPS)) installed four flow meters. The locations of each flow meter

are presented in Table 1.

TABLE 1

METER LOCATIONS, PIPE AND CATCHMENT AREA DATA

Site No. Meter Location

1 Thames Street near Washington Square 2 America's Cup Ave. at Thames Street 3 24 Memorial Blvd. 4 Lee Avenue

Notes: 1. Flow Metering Location 2 was installed to measure flows discharging from the high level

connection of the Thames Street Interceptor to the relief sewer on Americas Cup Avenue.

1 Catchment Area 6 Flow Metering Investigation

ADMIRAL KALEBUS ROAD

HILL

SIDE

AVEN

UE

MAPLE AVENUE

J.T. C

ONNE

LL R

OAD

FARE

WELL

STR

EET

WASH

INGT

ON S

TREE

T

BREN

TON

ROAD

HAZA

RD RO

AD

HARRISON AVENUE

CARR

OLL A

VENU

E

CARR

OLL A

VENU

E

COGGESHALL AVENUE

BELLEVUE AVENUE

RUGGLES AVENUE

VICTORIA AVENUESHEPARD AVENUE

LEROY AVENUE

LAWRENCE AVENUE

WEBSTER STREET

NARRAGANSETT AVENUE

WELLINGTON AVENUE

MARC

HANT

STRE

ET

PARKER AVENUE

DIXON STREET

SPRING STREET

THAM

ES S

TREE

T

EAST BOWERY STREET

BELL

EVUE

AVEN

UE

MIDD

LETO

N AV

ENUE

ANNA

NDAL

E RO

AD

RHOD

E ISL

AND A

VENU

E

OLD BEACH ROAD MEMORIAL BOULEVARD

CATHERINE STREET

MEMORIAL BOULEVARD

BELLEVUE AVENUE

CHURCH STREET

TOURO STREET

LONG WHARF

HARRISON AVENUE

MEMORIAL BOULEVARD

KAY S

TREE

T

BROA

DWAY

BLISS ROAD

VAN ZANDT AVENUE

METER #4 THAMES STREETAT LEE AVENUE

NARRAGANSETT AVENUE84" STORAGE CONDUIT

WELLINGTON AVENUECSO FACILITY

METER #2 AMERICA'S CUP AVENUEAT THAMES STREET (IN YARD BEHIND

WAR MONUMENT IN FROM OF NEWPORTBAY CLUB AND HOTEL) METER #3 24 MEMORIAL BOULEVARD

FROM WAVE AVENUE PUMP STATION

METER #1 THAMES STREETNEAR TOURO STREET/WASHINGTON SQUARE

LONG WHARFPUMP STATION

20" FORCE MAIN FROMWAVE AVENUE PUMP STATIONMIDDLETOWN, RHODE ISLAND

FORT ADAMS AREA

NEWPORTHARBOR

MIDDLETOWN

NEWPORT

Easton Pond

Almy Pond

Lily Pond, Newport

Green End Pond

3

2

6 1

4

7

FIGURE 1SEWER CATCHMENT AREA 6

FLOW METER LOCATIONSAND SEWER CATCHMENTS

PHASE I PART 2 CSO CONTROL PLAN

SCALE 1" = 2,000'0 2,0001,000 Feet

SEPTEMBER 2006

m:\w

ork\ne

wport

_ri\m

aps\c

so_ph

asei\fi

g1_M

eterL

ocati

onsA

rea6.m

xd

Sewer District BoundariesBuildingsDocksPaved Roads and ParkingUnpaved Roads and Parking

LEGEND:Metering Locations


The flow meter installation was completed on April 18, 2006 and the meters recorded data between April

18 and May 30, 2006, at which time they were removed. The meters measured depth and velocity and

recorded the data at 15-minute intervals in the meter’s computer memory. The recorded data were

uploaded from the meters periodically using a laptop computer. During the metering period, the meters

were checked weekly for routine maintenance to ensure that they were operating properly. The routine

maintenance inspections indicated that the meters were operating as intended and that any minor

problems encountered were corrected. Data from the flow monitoring for Catchment Area 6 is located in

Appendix A.

3.2 RAINFALL MONITORING

Rainfall data was obtained from a tipping bucket collector rain gauge with an electronic data logger

installed by ADS on the roof of the Long Wharf Pump Station. Rainfall was recorded in 15-minute

intervals during the entire flow metering period. During the metering period, eight rainfall events

exceeding 0.25 inches of precipitation were measured and are summarized in Table 2.

TABLE 2 RAINFALL SUMMARY

Storm Events Exceeding 0.25 inches During the Metering Period Start End

Date Time Date Time

Peak Hourly

Intensity (in/hour)

Total Rainfall (in) Duration (hr)

4/23/2006 16:30 4/23/2006 23:30 0.38 1.09 7 5/2/2006 2:45 5/2/2006 9:45 0.15 0.56 7 5/2/2006 20:45 5/3/2006 19:45 0.13 0.66 23 5/9/2006 10:00 5/9/2006 19:45 0.18 0.59 9.75

5/12/2006 12:00 5/13/2006 5:45 0.18 1 17.75 5/13/2006 13:15 5/15/2006 13:15 0.96 4.08 48 5/16/2006 2:30 5/16/2006 10:30 0.22 0.35 8 5/19/2006 9:30 5/19/2006 13:00 0.30 0.49 3.5


3.3 TIDAL MONITORING

The tide level in Newport Harbor was measured using a tide gauge behind the Long Wharf pumping

station. The recorded data was then uploaded from the data logger to a laptop computer. The data loggers

were checked weekly to retrieve the recorded data.

Figures 2 through 5 present the sum of the flows recorded at the two inlet points (Meter 3 – Flows from

the Wave Avenue Pump Station and Meter 4 - Lee Avenue) and at the two outlet points (Meter 1 –

Terminus of the TMI and Meter 2 – America’s Cup Avenue relief sewer). For the purpose of this

analysis, the sum of meters 1 and 2 shall be referred to as the downstream flow and the sum of meters 3

and 4 shall be referred to as upstream flow

The tide does not appear to influence the sanitary sewage flow during the April 23, 2006 storm event used

in the following analysis. The comparison of the wet weather flow and the tide is shown in Figure 2. The

flow in the sanitary system does appear to reflect changes in the level of the tide during the dry weather

period used in our analysis. The comparison of dry weather flows and the tide level is shown in Figure 3.

Earth Tech will continue to compare the tide and the metered flow data over the metering period to

determine if the tide is affecting the volume of infiltration in the system.

ANALYSIS OF METERING PROGRAM

For the analysis of inflow, the April 23, 2006 storm was selected because it was a large, short duration

wet weather event in the metering period which did not trigger a surcharge in any of the metered

manholes; occurred during a period of generally dry weather; and was completely confined to the

collection system (this event did not cause a CSO at any city facility). The storm occurred at about 4:30

PM on Sunday, April 23, with a duration of about 7 hours, a peak hourly intensity of 0.38 inches per hour,

and total rainfall of 1.09 inches. Based on the storm’s characteristics, April 23 (Sunday) from 12:00 PM

through April 24 (Monday) at 6 AM was considered an acceptable representative wet weather period. To

provide a representative dry weather period to use with the analysis of inflow for the April 23 storm, the

period from Sunday, April 30 through Monday, May 1, was selected as the representative dry weather

period. This period covered both a weekend and weekday flow pattern; had a 7 day antecedent rain-free

period; and was deemed acceptable. Base flows during the storm event were generally similar during the

representative dry weather period. A comparison of wet weather and dry weather flows is shown in

Figure 4.

FIGURE 2 - Comparison of Wet Weather Wastewater Flows and the Newport Harbor Tide

April 23 to April 24, 2006

0

2

4

6

8

10

12

4/23/0

6 12:0

0

4/23/0

6 13:0

0

4/23/0

6 14:0

0

4/23/0

6 15:0

0

4/23/0

6 16:0

0

4/23/0

6 17:0

0

4/23/0

6 18:0

0

4/23/0

6 19:0

0

4/23/0

6 20:0

0

4/23/0

6 21:0

0

4/23/0

6 22:0

0

4/23/0

6 23:0

04/2

4/06 0

:004/2

4/06 1

:004/2

4/06 2

:004/2

4/06 3

:004/2

4/06 4

:004/2

4/06 5

:004/2

4/06 6

:004/2

4/06 7

:004/2

4/06 8

:004/2

4/06 9

:01

4/24/0

6 10:0

1

4/24/0

6 11:0

1

4/24/0

6 12:0

1

4/24/0

6 13:0

1

4/24/0

6 14:0

1

4/24/0

6 15:0

1

4/24/0

6 16:0

1

4/24/0

6 17:0

1

Date/Time

Flow

(mgd

)

0

20

40

60

80

100

120

Tide

Lev

el (i

n)

Upstream Flow 4/23

Downstream Flow 4/23

Tide

5

FIGURE 3 - Comparison of Dry Weather Wastewater Flows and the Newport Harbor Tide

April 30 to May 1, 2006

0

1

2

3

4

5

6

7

4/30/2

006 1

0:04

4/30/2

006 1

1:05

4/30/2

006 1

2:05

4/30/2

006 1

3:05

4/30/2

006 1

4:05

4/30/2

006 1

5:05

4/30/2

006 1

6:05

4/30/2

006 1

7:05

4/30/2

006 1

8:05

4/30/2

006 1

9:05

4/30/2

006 2

0:05

4/30/2

006 2

1:05

4/30/2

006 2

2:05

4/30/2

006 2

3:05

5/1/20

06 0:

05

5/1/20

06 1:

05

5/1/20

06 2:

05

5/1/20

06 3:

05

5/1/20

06 4:

05

5/1/20

06 5:

05

5/1/20

06 6:

05

5/1/20

06 7:

05

5/1/20

06 8:

06

5/1/20

06 9:

06

5/1/20

06 10

:06

5/1/20

06 11

:06

5/1/20

06 12

:06

5/1/20

06 13

:06

5/1/20

06 14

:06

5/1/20

06 15

:06

5/1/20

06 16

:06

5/1/20

06 17

:06

5/1/20

06 18

:06

5/1/20

06 19

:06

5/1/20

06 20

:06

5/1/20

06 21

:06

Date/Time

Flow

(mgd

)

0

20

40

60

80

100

120

Tide

Lev

el (i

n)

Upstream Flow

Downstream Flow

Tide

6

FIGURE 4 - Comparison of Wet Weather (April 23 to 24, 2006) and Dry Weather (April 30 to May 1, 2006) Wastewater Flows

0

2

4

6

8

10

12

4/23/0

6 12:0

04/2

3/06 1

3:00

4/23/0

6 14:0

04/2

3/06 1

5:00

4/23/0

6 16:0

04/2

3/06 1

7:00

4/23/0

6 18:0

04/2

3/06 1

9:00

4/23/0

6 20:0

04/2

3/06 2

1:00

4/23/0

6 22:0

04/2

3/06 2

3:00

4/24/0

6 0:00

4/24/0

6 1:00

4/24/0

6 2:00

4/24/0

6 3:00

4/24/0

6 4:00

4/24/0

6 5:00

4/24/0

6 6:00

4/24/0

6 7:00

4/24/0

6 8:00

4/24/0

6 9:01

4/24/0

6 10:0

14/2

4/06 1

1:01

4/24/0

6 12:0

14/2

4/06 1

3:01

4/24/0

6 14:0

14/2

4/06 1

5:01

4/24/0

6 16:0

14/2

4/06 1

7:01

Date/Time

Flow

(mgd

)

Upstream Flow 4/23Downstream Flow 4/23Upstream Flow 4/30Downstream Flow 4/30Rain

7


The total inflow for the Thames Street Interceptor and upstream tributary area can be observed as the area

between the wet weather flow meter data and the dry weather metering data. Based on the correlation

between the wet and dry weather flows shown, infiltration does not appear to be a major concern at the

time of the flow metering in Catchment Area 6. This corresponds with the low volumes of infiltration

observed in the CCTV inspection of the Thames Street Interceptor (TMI) performed prior to this metering

period. The CCTV inspection of the TMI was summarized and submitted under the technical

memorandum titled “Thames Street Interceptor Television Inspection” dated August 30, 2006.

Based on the close correlation between wet and dry weather flows, our analysis of the meter data centered

on inflow sources within Catchment Area 6. Our analysis was based on comparing upstream flow and

downstream flow and observing the difference in flows. In Figure 5, a reaction in both the upstream and

downstream flows is evident at or immediately following the first recorded rainfall measurement.

Measured downstream flows generally appear to fluctuate with the rainfall intensity. The upstream and

downstream flows quickly diverge with increases in rainfall intensity and converge with decreases in

rainfall intensity. This trend is observed at approximately 5:45 to 6 PM, 8:15 PM, and finally at 9:15 to

9:30 PM as the storm event ends. The drain down period extends approximately 7 to 8 hours after the

storm event. This extended drain down period is likely caused by indirect sources of inflow, such as

sump pumps.

The volume of inflow estimated to have entered the system during this storm is approximately 500,000

gallons. This amount is considered significant for a storm event of short duration (about 7 hours) with a

relatively low peak hourly intensity of 0.38 inches per hour.

Based on conditions observed in other areas of the city; lack of infiltration flow at the time, as observed in

both the CCTV inspection of the TMI and in the metering data; and the frequency of inflow sources

encountered in other areas of the city (i.e. rain leaders, roof drains, catch basin, yard drains), Catchment

Area 6 appears to generate significant volumes of inflow.

PRELIMINAY RECOMMENDATIONS

Based on a preliminary analysis of flow information obtained during the metering period, the conditions

encountered in the TMI CCTV inspection, the building inspections, and the results of the smoke testing in

other priority inflow areas in the city, the city should consider performing a full sewer system evaluation

study (SSES) of Sewer Catchment Area 6. Additional recommendations may be included in the


Wellington Avenue CSO Control Plan, Phase I Part 2 report after all field work is completed and the

information is evaluated by Earth Tech.

COST ESTIMATE FOR SSES FIELD WORK FOR SEWER CATCHMENT AREA 6

A preliminary cost estimate to complete a SSES of Sewer Catchment Area 6 is shown in Table 3 below.

The SSES would consist of performing smoke testing of the entire sanitary sewer system and performing

a house to house survey of all buildings in the catchment area. Sewer Catchment Area 6 consists of

approximately 1,354 buildings and 57,610 linear feet (LF) of sanitary sewer pipe. Based on the

conditions encountered in the other priority catchment areas in the city, Earth Tech would recommend a

minimum of 100 dye tests to confirm suspect connections to the sanitary sewer as observed in the smoke

testing and the house to house surveys.

TABLE 3 ESTIMATED COST FOR SSES FOR SEWER CATCHMENT AREA 6

Item Assumption Source Unit Cost Quantity Estimated Cost

Smoke Testing 100% of Area 6 Sanitary Sewer Inflow $0.50 57,610 $28,805 House to House Survey 100% Buildings in Area 6 Inflow $45.00 1,354 $60,930

Dye Testing 100 Tests Inflow $95.00 100 $9,500 Subtotal $99,235

Contingency 25% Inflow $24,809 1 $24,809 Engineering 20% Inflow $19,847 1 $19,847

Total $143,891 Estimated Cost For SSES in Area 6 $144,000

FIGURE 5 - Comparison of Upstream and Downstream Flows for April 23-24, 2006 Storm Event

0

2

4

6

8

10

12

4/23/0

6 12:0

0

4/23/0

6 13:0

0

4/23/0

6 14:0

0

4/23/0

6 15:0

0

4/23/0

6 16:0

0

4/23/0

6 17:0

0

4/23/0

6 18:0

0

4/23/0

6 19:0

0

4/23/0

6 20:0

0

4/23/0

6 21:0

0

4/23/0

6 22:0

0

4/23/0

6 23:0

04/2

4/06 0

:004/2

4/06 1

:004/2

4/06 2

:004/2

4/06 3

:004/2

4/06 4

:004/2

4/06 5

:004/2

4/06 6

:004/2

4/06 7

:004/2

4/06 8

:004/2

4/06 9

:01

4/24/0

6 10:0

1

4/24/0

6 11:0

1

4/24/0

6 12:0

1

4/24/0

6 13:0

1

4/24/0

6 14:0

1

4/24/0

6 15:0

1

4/24/0

6 16:0

1

4/24/0

6 17:0

1

Date/Time

Flow

(mgd

)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Rai

nfal

l (in

)

UpstreamDownstream

Rainfall

10


CONCLUSION

Based on the results of the wastewater flow metering of Sewer Catchment Area 6, it is recommended that

the City of Newport perform a SSES program to identify inflow sources to reduce total inflow entering

the sanitary sewer system during storm events in an effort to provide additional system capacity for

sanitary flow and reduce combined sewer overflows.

phase 1 part 2 cso control plan ... - city of newport · war monument in from of newport bay club...

Documents