request for council direction report -...

PlU MEADOWS

REPORT REQUEST FOR COUNCIL DIRECTION

DATE: July 9, 2015 FILE: 11-5230-07/15

FROM: Operations and Development Services

SUBJECT: Sturgeon Slough Dike

RECOMMENDATION: THAT Council:

A. Authorizes staff to spend up to $25,000 from the Drainage Reserve Fund to complete a temporaryrepair on the sturgeon slough dike; OR

B. Other.

CHIEF ADMINISTRATIVE OFFICER COMMENT/RECOMMENDATION:

REPORT/DOCUMENT: Attached Available N/A

PURPOSE: To inform Council regarding seepage in the dike dividing the Sturgeon Slough and Pitt River.

BACKGROUND: On or about June 8, 2015 City operations maintenance crews noticed water seeping outof the dike toe on the landward side of the Pitt River—Sturgeon Slough Dike. The general area of

concern is depicted in the aerial photograph provided in Attachment A. The leak was starting and

stopping as the water level within the river fluctuated from tidal and freshet influences. Water enteredboth through a joint in an existing culvert that drains the slough and north of the culvert through the

dike structure.

The impacted dike is a primary dike located at the headwater mouth of the Sturgeon Slough along thePitt River. The area of concern is in Drainage Area #4 as detailed in Attachment B. The Sturgeon Sloughitself is completely lined with a secondary dike, also referred to as an agricultural dike, and in the eventof a failure of the primary dike the secondary dike should prevent inland flooding, although this scenariohas never been tested.

This dike area was handed over to the city from the Dewdney Alouette Regional District (DARD) alongwith all other infrastructure in the area in 1998. Little is known about the original construction orconsistency of materials used in the dikes construction. It appears this particular dike is constructed to aslightly higher standard than the typical agricultural dikes but less than the standard dikes elsewhere inthe municipality.

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PITT MEADOWS

ANALYSIS: Thurber Engineering along with City crews investigated to try and determine the source of

the seepage. Surface material of the dike on the landward side was removed and the seepage point was

located closer to the toe. No sources of seepage were found on the water side. The exact path for the

seepage remains unknown. There are no signs of rodent holes, erosion, or failures. There is a large

cottonwood tree nearby that could be contributing to the situation from root growth into the dike, but

this is not expected to be the lone source. This tree is being scheduled for removal after nesting season.

As the river levels are now receding from the freshet the seepage has stopped. For the next few months

seepage is only expected to occur if an extremely high tide event occurs and no such events are

expected in the near future.

Attachment C is a report from Thurber Engineering detailing the field review and identifying possible

solutions for remediation and costs. The engineers estimate for this work is $1.075 million. This

estimate includes replacement of the culvert and associated hardware, including floodgates, access

ramps and extensive dike repair. The detailed cost breakdown by ISL Engineering for the three

components of the repair is in Attachment D.

Also in Attachment Con page 4 of 5 there is a recommendation to make a temporary repair to the dike

this year. The temporary repair would only be a patch, but it would provide the City time to determine

the best course of action for making the full repair which should be completed in August-September

2016. The temporary patch is estimated at $25,000 and could be completed by operations staff.

OPTIONS! ALTERNATIVES: This culvert has been identified for replacement as part of the Drainage Area

4 - Pump Station Replacement Project. A grant application for this work was submitted in February

2015, to the Building Canada Small Communities Program. Staff is still waiting to hear if we have been

successful with this grant application and expect that we will be notified of the outcome of our

application anytime between now and the end of September 2015.

If the grant is approved this larger repair along with the culvert replacement would occur as part of this

larger upgrade to the Drainage Area #4- Pump Station Project and overall conveyance system. Note,

any work completed prior to the awarding of the grant would no longer be eligible for grant funding.

The risk of waiting to learn the outcome of the grant application is low if the temporary repair work is

completed this year. The window for repair is limited by seasonal weather conditions and the optimal

time to complete the both the patch repair and the full repair would be between mid-August through

September.

With the optimal season for repair immediately upon on is, staff suggests that the temporary repair

work be completed by the City to allow the time needed to learn the outcome of our grant application

and to allow for more time to review repair options for implementation in 2016.

Council also has the following other options:

a. Direct staff to complete the full repair at this time;

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PITT MEADOWS

b. Request staff to do nothing at this time and return to Council in fall 2015 with any further

information we may have with respect to the outcome of the grant application and costs,

remedies and funding options.

IMPLICATIONS OF RECOMMENDATIONS: Seepage through a dike is a serious situation and if allowed to

continue the structure would eventually fail. While there is time to wait for the outcome of the Building

Canada Small Communities Grant Application, staff cautions the temporary patch repair should be

completed prior to the winter rains. Staff estimates the time frame needed to complete the patch work

is a week and can be completed by operation staff.

The complete solution for this area is complete replacement of Drainage Area #4 pump station and its

associated culverts and flood gates. This seepage in the Sturgeon Slough dike reinforces the need for

the upgrades in this drainage area.

a. Organizational: The largest impact to staff time has been in assessing and determiningthe extent of the leakage. The design and construction would be completed by aconsultant. Future staff time would be to monitor the situation, tender the documentsand inspect the repair work when it is underway.

b. Financial: If the repair is done in isolation of the larger pump station #4 project, afunding source in the 2016 budget would need to be identified for the estimated$1.075M repair. The temporary repair is estimated at $25,000.

c. Implementation: To be determined.d. Katzie First Nation considerations: None identified.e. Other: None identified.

OTHER CONSIDERATIONS: None identified by staff.

Prepared by: Randy Evans, Operations Superintendant

Respectfully Submitted by: K. Zanon, Director of Operations and Development Services

Reviewed by: K. Grout, CAO

A1TACHMENT(S):

A. Area Map of the Dike Area of Concern on Sturgeon SloughB. Drainage Area #4 Context MapC. Thurber Engineering Field Inspection ReportD. ISL Engineering Cost Estimate

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Area #4 Dike Repair Location

Man Created: 201 5/07/16

City of Pitt Meadows

0 50 100 200 300 400- 333 -

Area #4 Dike Repair Location Context

1,500 2,000 Mao Created: 2015/07/16 w

City oF Pitt Meadows

0 250 500 1,000 - 334 -

CTHURBER ENGINEERING LTD.

Suite 900— 1281 West Georgia Street FIELD REVIEW REPORT NO.: 1

J Vancouver, BC V6E 3J7Phone: (604) 684-4384 THURBER FILE NO.: 19-598-465

THURBER Fax: (604) 684-5124

FIELD INSPECTION REPORT DATE OF SITE VISIT: June 18, 2015TO: ISL Engineering and Land Services (ISL) ATTENTION: Mr. Kevin Terness, P.Eng.

EMAIL: kternessislenpineerinp.comPROJECT NAME: Sturgeon Slough Dyke (SSD) Seepage, Pitt MeadowsCONTRACTOR(S): City of Pitt Meadows (PM)

PURPOSE OF INSPECTION: Assess dyke seepage.REFERENCE DRAWING / DOCUMENTS:ISL Drawing 989_Stm-01 dated September 13, 2013 (1 page)Figure 1 and 2 (2 pages) Test hole log TH13-02 (1 page)Dyke core zone material grading analysis data sheet (1 page)THURBER PERSONNEL ON SITE: CLIENT/CONTRATOR PERSONNEL TIME ON SITE:Mr. Andy Bowker (AGB), P.Eng., ON SITE: Approximately 1000 to 1100 hoursCGeol.(UK) Mr. Kevin Turness, P.Eng. (KT, ISL) WEATHER: Bright, sunny.

Mr. Randy Evans (RE, PM) + 3 labourersACTIVITIES/OBSERVATIONS:

1. In response to ISLs request of June 17, 2015, Thurber Engineering Ltd. (Thurber) visited the SSD site onJune 18 to inspect seepage on the Jandward dyke face, centred on approximate UTM coordinate 525089 m E,5460206 m N.

2. Previously ISL had prepared drawings for lining 3 existing culverts to the south of the site, and lining theexisting 1200 mm diameter (dia.) corrugated steel pipe (CSP) culvert at the site. The ISL Drawing 989_Stm_01dated September 13, 2013 (attached) provides a site base plan.

3. During the site visit, RE of PM noted the following:

i. PM staff had observed piping at the above location approximately 10 days ago (c. June 8).ii. The piping had been brought to the attention of RE on June 15.

iii. The Pitt River is currently in freshet, elevating seasonal river water levels, and that the freshet seasonmay continue for another 2 to 3 weeks.

iv. The SSD was likely constructed in the 1950s.v. In the recent past, the SSD had been widened, marginally, on the river side to accommodate crane

outrigger feet. (It is understood that occasionally a crane had been positioned on the SSD to facilitatelifting of a lock block from the dyke crest to the river end of the existing culvert to block culvert flows.)

4. The SSD geometry and water levels as shown on Figure 1 were constructed from tape and clinometer sitemeasurements. Water levels were recorded at 1050 am on June 18, 2015. The 1200 mm dia. CSP culvertand Thurber July 26, 2013 test hole TH13-02 (attached) have been approximately located on Figure 1 fromDrawing 989_Stm_01 and Thurber records, respectively. TH13-02 has also been located onDrawing 989_Stm_01.

5. Seepage was observed at approximately 3.6 m below the SSD crest elevation from the SSD landward face atthe approximate location shown on ISL Drawing 989_Stm_01 and Figure 1. The seepage was a trickle’ flow.

6. During the site visit PM used a backhoe to excavate into the landward SSD face at the seepage location. Theexcavation encountered approximately 0.3 to 0.5 m thick, 600 mm minus rip rap dyke armouring over inferredcompact sandy GRAVEL with some silt and some cobbles, considered to represent the dyke fill material.Thurber collected a sample of this material and completed a grading analysis to ASTM Cl 36 and Ci 17. Thetest data sheet is attached.

7. Seepage flows pooled into a concave portion of the excavated face. Clear seepage flows from the SSD facedisplaced silt laden pooled water indicating that, under the conditions at the time of the observed seepage flowsat this location, piping and loss of fine material was not occurring from the SSD.

Report To: ISL Engineering and Land Services.File No.: 19-598-4

Date: June 18, 2015Page 1 of 5

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PHOTOS:

Report To: ISL Engineering and Land Services.File No.: 1 9-598-465


ru to 2 (1€ Landward face of ting 1200 mm . r ..

Photo 3 (right). Seepage location (red circle, enlarged in Photo 4).it and flap valve in foreground.

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Report To: SL Engineering and Land Services.File No.: 19-598-465

.,..Photo 3 enlargement.

Photo 5 (right). SSD core zone material.


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Report To: ISL Engineering and Land Services.File No.: 19-598-465


:.: ‘-‘

• • /(eft).3 landward face. Dyke core zone material exposed below £J mm minus rip rap armouring. Samplefor grading analysis recovered from red circle.Photo 8 (right). Pooled silt laden waters pooled in SSD landward face excavation displaced by clear seepage flows (redcircle)

INSTRUCTIONS I RECOMMENDATIONS / REMARKS:

The water level on the Pitt River side of the SSD was roughly 1 m higher than the water level in the SturgeonSlough (SS) at the time of the site visit. Seepage occurred from the SSD landward face at about 0.4 m belowthe Pitt River water level and 0.6 m above the SS water level, respectively.

2. At the time of the site visit an approximately 1 m piezometric head appeared to be driving seepage flows fromthe Pitt River into the SS. It is unknown if, when the piezometric head is elevated higher than that observed onJune 18, seepage flows contain fines indicative of piping.

3. Temporary Dyke Repair Recommendations.

We recommend that a temporary repair be made to the SSD andward face to reduce potential piping of finesthrough the dyke. We recommend the temporary repair adopt the following procedure:

i. On the SSD landward face, excavate the existing rip rap armouring to expose dyke core zone materialfrom low water level to 2 m above, 2 m to the left and 2 m to the right of the centre of the observedseepage location.

ii. Place non-woven geotextile Nilex 4545 or Nilex 4547 or approved equivalent in accordance withmanufacturers’ instructions.

iii. Carefully key in and place 600 mm minus rip rap material to rebuild dyke armouring to pre-repairgeometry.

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4. Preliminary Permanent Dyke Repair Recommendations — Sheet Pile Seepage Cut-Off Wall (SPSCW).

We understand it proposed that instead of lining the culvert, as was originally proposed, it is currently proposedto excavate and replace the existing 1200 mm dia. CSP culvert. We understand that it proposed to usetemporary and permanent sheet piles to construct dams during the replacement works. We recommend that apermanent SPSCW be installed to reduce the risk of local seepage/piping issues through the dyke. Our keypreliminary recommendations in relation to a permanent SPSCW are listed below and indicated on Figure 2.

i. Culvert trench backfill to comprise clay or silt with a permeability in the order of lxi 0-8 ms-1.ii. Culvert trench to be locally widened at south end of SPSCW and backfilled with low permeability trench

back fill material to a minimum of 2 m north of the north culvert sidewall over a minimum plan length of4 m.

iii. South end of SPSCW to be keyed in a minimum of 1 m, in plan view, into the widened trench back fillzone.

iv. North end of SPSCW to extend to north end of SSD.v. Sheet piles to be driven to be embedded a minimum of 1 m into the native silt material underlying the

dyke encountered in TH13-02. On this basis minimum sheet pile lengths are anticipated to beapproximately 6.5 m.

FURTHER EXAMINATION REQUIRED: Q YES NO NOT APPLICABLE

COPIES TO: REPORT BY: Andy Bowker, P.Eng. REVIEWED BY: David Hill, P.Eng.EMAIL: [email protected] EMAIL: dhilkthurber.ca

Report To: ISL Engineering and Land Services. Date: June 18, 2015File No.: 1 9-598-465 Page 5 of 5

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C MENT DFT - PAGE 4

STURGEON SLOUGH OUTFALL PROJECT

DRAINAGE IMPROVEMENTS

SUMMARY SHEETAMOUNT

1.0 STURGEON SLOUGH NORTH OUTFALL (RELINE PIPE ONLY) $ 601,452.50

2.0 STURGEON SLOUGH NORTH OUTFALL (REBUILD 40M OF DIKE ONLY) $ 662,640.00

3.0 STURGEON SLOUGH NORTH OUTFALL (REBUILD 40M OF DIKE AND REPLACE CULVER1 $ 1,074,865.00

TENDERER’S INITIALS

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FT-PAGE 4

1.0 STURGEON SLOUGH NORTH OUTFALL (RELINE PIPE ONLY)

ITEM MMCD DESCRIPTION UNIT QUANTITY UNIT PRICE AMOUNTNO. REF.

MMCD 015301 - TEMPORARY FACILITIES

1.01 015301 Dewatering of work area Lump Sum 1 $ 50,000.00 $ 50,000.0027.IS

• MMCD 033053 - CAST-IN-PLACE CONCRETE

1.02 033053 Concrete Headwall (Single Culvert North) Lump Sum 1 $ 15,000.00 S 15,000.001.5.3

1.03 03 30 53 Concrete Headwall (Single Culvert North) Lump Sum 1 $ 15,000.00 $ 15,000.001.5.3

MMCD 312301 - EXCAVATING, TRENCHING Ar.D BACKFILLING

1.04 31 23 01 Overexcavating including 19mm clear crush backfill Cubic Metre 30 $ 85.00 $ 2,550.001.10.3 “Optional)

MMCD 312413 - ROADWAY EXCAVATION, EMBANKMENT & COMPACTION

1.05 31 24 13 Excavation includes all removals and restoration Lump Sum I $ 7,500.00 $ 7,500.001.8.4

MMCD 32 1123 - GRANULAR BASE

1.06 32 11 23 19mm minus Clear Crush Base - variable thickness Tomse 45 $ 55.00 $ 2,475.001.4.3 includes placement, grading adjustment of moisture

‘ontent and compaction1.07 32 11 23 19mm minus Crushed Granular Base - variable thickness Tonne 50 $ 45.00 $ 2,250.00

1.4.3 includes placement, grading adjustment of moisturenontent and compaction (Optional)MMCD 313710 - RIPRAP

1.08 31 37 10 Supply and place 300 minus Rip Rap, c/w geotextile and Tonne 50 $ 45.00 $ 2,250.001.4.1 related excavation and disposal (Optional)

MMCD 334213 - PIPE CULVERTS

1.09 3342 13 Relining of existing 1200mm DIA culvert c/w 1015mm Lineal Metre 28 $ 1,700.00 $ 47,600.001.5.1 dia. threaded Weholite and non-shrink grout

1.5.2SMMCD 3399 99S - MISCELLANEOUS

1.10 33 99 99S Supply and Delivery 1050mm Combiantion Gate Each 2 $ 30,000.00 $ 60,000.001.1.1

1.11 3399 99S Install 1050mm Combiantion Gate Each 2 $ 10,000.00 $ 20,000.001.1.1

1.12 33 99 99S PermaGuard Debris Screen Lineal Metre 20 $ 600.00 $ 12,000.001.1.2

1.13 33 99 99S Treated Timber Walkway clw stairs Lump Sum I $ 32,000.00 $ 32,000.001.1.3

1.14 3399 99S Steel Piling 323mm dia x 9.5mm thick Lineal Metre 150 $ 420.00 $ 63,000001.1.4

MMCD 4000 OOS - SHEET PILING1.15 400000S TypeAZ26-700steelsheetpiles Square 188 $ 650.00 $ 122,200.00

1.5.1 Metre1.16 40 00 OIlS Type AZ 26-700 steel sheet piles (temporary) Square 143 $ 650.00 $ 92,950.00

1.5.2 Metre

Total Construction Costs $ 546,775.00

10% Contingency $ 54,677.50

Grand Total $ 601,452.50


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FT-PAGE 4

2.0 STURGEON SLOUGH NORTH OUTFALL (REBUILD 40M OF DIKE ONLY)


MMCD 01 5301 - TEMPORARY FACILITIES2.01 01 5301 Dewatering of work area Lump Sum I $ 50,000.00 $ 50,000.00

27.1SMMCD 312413 - ROADWAY EXCAVATION, EMBANKMENT & COMPACTION

2.02 312413 Excavation of existing dike cu.rn 4000 $ 50.00 $ 200,000.001.8.4

2.03 3124 13 Dike Fill Tonne 8500 $ 25.00 $ 212,500.001.8.4 -

MMCD 32 1123 - GRANULAR BASE

2.04 32 1123 19mm minus Clear Crush Base - variable thickness Tonne 60 $ 55.00 $ 3,300.001.4.3 includes placement, grading adjustment of moisture

mntent and compaction2.05 32 1123 75mm minus Crushed Granular Subbase - vaiable Tonne 70 $ 45.00 $ 3,150.00

1.4.3 thickness includes placement, grading adjustment ofmoisture content and compaction (Optional)MMCI) 3137 10 - RIPRAP

2.06 31 37 10 Supply and place 300 minus Rip Rap, c/w geotextile and Tonne 900 $ 45.00 $ 40,500.001.4.1 related excavation and disposal (Optional)

MMCD 3342 13 - PIPE CULVERTS2.07 40 00 OOS Type AZ 26-700 steel sheet piles (temporary) Square 143 $ 650.00 $ 92,950.00

1.5.2 Metre



Grand Total $ 662,640.00


___________

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FT-PAGE 4

3.0 STURGEON SLOUGH NORTH OUTFALL (REBUILD 40M OF DIKE AND REPLACE CULVERT


MMCD 015301 - TEMPORARY FACILITIES

3.01 01 5301 Dewatering of work area Lump Sum 1 $ 50,000.00 $ 50,000.00

27.1S

MMCD 033053 - CAST-IN-PLACE CONCRETE

3.02 033053 Concrete Headwall (Single Culvert North) Lump Sum 1 $ 15,000.00 $ 15,000.00

1.5.3

3.03 03 30 53 Concrete Headwall (Single Culvert North) Lump Sum 1 $ 15,000.00 $ 15,000.00

1.5.3

MMCD 312413 . ROADWAY EXCAVATION, EMBANKMENT & COMPACTION

3.04 31 24 13 Excavation of existing dike cu.m 4000 $ 50.00 $ 200,000.00

1.8.4

3,05 31 24 13 Dike Fill Tonne 8500 $ 25.00 $ 212,500.00

1.8.4

MMCD 312301 - EXCAVATING, TRENCIHNG AND BACKFILLING

3.06 31 23 01 Overexcavating including 19mm clear crush backfill fCubic Metre 30 $ 85.00 $ 2,550.00

1.10.3 (Optional)

MMCD 321123 . GRANULAR BASE

3.07 32 11 23 19mm minus Clear Crush Base - variable thickness Tonne 60 $ 55.00 $ 3,300.00

1.4.3 includes placement, grading adjustment of moisture

content and compaction

3.08 32 11 23 19mm minus Crushed Granular Base - variable thickness Tonne 70 $ 45.00 $ 3,150.00

1.4.3 includes placement, grading adjustment of moisture

content and compaction tOptiona1)MMCD 313710- RIPRAP

3.09 31 37 10 Supply and place 300 minus Rip Rap, c/w geotextile and Tonne 900 $ 45.00 $ 40,500.00

1.4.1 related excavation and disposal (Optional)MMCD 3342 13 - PIPE CULVERTS

3.10 3342 13 Replace of existing 1200mm DIA culvert c/w 1050mm Lineal Metre 30 $ 1,100.00 $ 33,000.00

1.5.1 dia. threaded Weholite

1.5.2S

MMCD 3399 99S - MISCELLANEOUS3.11 3399 99S Supply and Delivemy 1050mm Combiantion Gate Each 2 $ 30,000.00 $ 60,000.00

1.1.1

3.12 33 99 99S Install 1050mm Combiantion Gate Each 2 $ 10,000.00 $ 20,000.001.1.1

3.13 33 99 99S PennaGuard Debris Screen Lineal Metre 20 $ 600.00 $ 12,000.00

1.1.2

3.14 33 99 99S Treated Timber Walkway c/w stairs Lump Sum I $ 32,000.00 $ 32,000.00

1.1.33.15 3399 99S Steel Piling 323mm dia x 9.5mm thick Lineal Metre 150 $ 420.00 $ 63,000.00

1.1.4

MMCD 4000 OOS - SHEET PILING3.16 40 00 OOS Type AZ 26-700 steel sheet piles Square 188 $ 650.00 $ 122,200.00

1.5.1 Metre

3.17 40 00 OOS Type AZ 26-700 steel sheet piles (temporary) Square 143 $ 650.00 $ 92,950.001.5.2 Metre



Grand Total $ 1,074,865.00


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