Attachments_1-6_rvsd_06-24-17.pdf

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ATTACHMENT 1

PROJECT LOCATION AND CONTRACTOR ACCESS

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CONTRACTOR ACCESS

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PROJECT LOCATION

g6edxbjl Callout Santa Fe Drive g6edxbjl Callout W. Riverview Pkwy g6edxbjl Text Box Hwy C-470 g6edxbjl Callout Asphalt Recreation Road g6edxbjl Callout

CONTRACTOR ACCESS

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CHATFIELD DAM & LAKE

Callout

CONTRACTOR WORK & STAGING AREA

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ATTACHMENT 2

CONTRACTOR WORK AREA, STAGING AREA

& ACCESS

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CONTRACTOR ACCESS

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DOG PARK

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DEWATER FROM STILLING BASIN TO D/S OF GRADE CONTROL WEIR ~ 900 FEET

DDD

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ATTACHMENT 3

OUTLET WORKS STILLING BASIN

AS-BUILT DRAWING

(HIGHLIGHTING SELECT DRAINAGE FEATURES)

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ATTACHMENT 3

OUTLET WORKS STILLING BASIN

AS-BUILT DRAWING

(HIGHLIGHTING SELECT DRAINAGE FEATURES)

Chatfield Dam & Lake Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 1

ATTACHMENT 4

Summary of 2007 Dewatering/Cleaning/Inspection of the Stilling Basin, Manholes and South Platte River Channel at Chatfield Dam and Lake.

The Stilling Basin, Manholes and Channel at Chatfield Dam and Lake were last dewatered/cleaned by contract and inspected by USACE personnel in November 2007.

All flows were shut off through the outlet works flood conduit for the duration of the contract and inspection work. The channel was allowed to drain down to the level of the Weir. A mobile crane was used to place a large diameter, high capacity, pump into the Stilling Basin area, adjacent to the Channel. Irrigation piping was placed on the right (east) side of the Stilling Basin area from the Stilling Basin downstream to the Channel below the Weir (a distance of approximately 900 feet). The pump operated for several days to remove the initial volume of water from the Stilling Basin and Channel.

Additional water that entered the Stilling Basin and Channel (due to leakage of the service gates and from the inflow of groundwater) was continuously removed by a smaller pump placed in the dewatering sump of the Stilling Basin until the USACE inspections were completed. An estimated 300 pounds of fish were transferred from the Stilling Basin to Chatfield Lake by Chatfield State Park personnel at the beginning of the dewatering effort. Photos of the November 2007 dewatering/cleaning/inspection activities are included on Pages 2 through 17 of this Attachment (4). These photos include the setup for the November 2007 dewatering/inspection effort as well as general physical condition of the Stilling Basin, Manholes, Channel and Weir. Additional photos are available from the Tri-Lakes Project Office upon request.

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Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 2

Photo No. 1 – General view of the outlet works stilling basin and downstream channel after flows thru Chatfield Dam were shut off and before dewatering. View is looking downstream from the right (east) side of the stilling basin.

Photo No. 2 – General view of the stilling basin and downstream channel following dewatering. View is looking downstream from the left (west) side of the stilling basin.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 3

Photo No. 3 – Another view of the right (east) side of the stilling basin and the pump, generator and piping used for the dewatering operation.

Photo No. 4– Another view of the right (east) side of the stilling basin and the pump, generator and piping used for the dewatering operation.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 4

Photo No. 5 – Close-up of the pump and generator used for the dewatering operation.

Photo No. 6 – General photo of the dewatering operation looking upstream towards the stilling basin from the downstream channel.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 5

Photo No. 7 – View of the downstream channel just upstream of the grade control weir. Note the dewatering pipe on far bank and the grade control weir in left center of photo. Also note piping for the exposed gaging station used by the State of CO for discharge measurements in the center of channel.

Photo No. 8 – General view, looking downstream, of the downstream channel from just upstream of the grade control weir.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 6

Photo No. 9 – View of the downstream side of the grade control weir. Note the dewatering discharge pipe on far bank.

Photo No. 10– View, looking downstream, of the downstream channel from atop the grade control weir.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 7

Photo No. 11 - Fish removal operation by the State of Colorado.

Photo No. 12 - Fish removal operation by the State of Colorado.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 8

Photo No. 13 – View of riprap/sediment removal operations within walls of the stilling basin structure.

Photo No. 14– Stockpile of riprap removed from the stilling basin structure.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 9

Photo No. 15 - Cleaning out the sump at the downstream end of the stilling basin adjacent to the end sill.

Photo No. 16 – General view of the baffle blocks in the stilling basin from atop the west stilling basin wall.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 10

Photo No. 17 – Another close-up view of the baffles from the floor of the stilling basin.

Photo No. 18 – Close-up view of the upstream side of the end sill from the floor of the stilling basin

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 11

Photo No. 19 – Minor scrape/spall on the upstream face of the end sill on the left (west) side of the sump.

This scrape was caused by the excavator cleaning the riprap/sediment out the stilling basin.

Photo No. 20 – View, looking east, of the downstream edge of the end sill of the stilling basin. Note minor spalls on the upper edge. Again, these spalls are believed to be caused by riprap churning around in the basin during discharges through the conduit.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 12

Photo No. 21 – General view of the sloping floor slab of the stilling basin looking downstream from the downstream end of the flood conduit. Note numerous small spalls on concrete surface, believed to be from vandals throwing riprap from above. Also note the upper slab drain outlet in bottom center of photo.

Photo No. 22 – Close-up of the slab drain shown in the previous photo. This drain appeared to be flowing at the time of the photo.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 13

Photo No. 23 – View of one of the middle drain outlets on the east side of the sloping floor slab. No flow was noted at the time of this photo.

Photo No. 24 – Close-up of the drain outlet shown in the previous photo. No flow was noted at the time of this photo.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 14

Photo No. 25 – View of the drainage manhole on the left (west) wall of stilling basin. Project personnel are removing the manhole cover to allow for visual inspection.

Photo No. 26 – View looking down inside the drainage manhole on the left (west) wall of stilling basin.

The manhole was mostly clear of debris or sediment. No sediment or debris was removed from this manhole during the contract/inspection.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 15

Photo No. 27 – View of the outlet for the drainage manhole on the left (west) wall of the stilling basin. This outlet is located at the base of the wall on the inside of the basin. A small amount of drainage was noted coming from the outlet following dewatering.

Photo No. 28 – View of the drainage manhole on the right (east) wall of stilling basin. Project personnel have removed the manhole cover to allow for visual inspection.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 16

Photo No. 29 – View looking down inside the drainage manhole on the right (east) wall of stilling basin.

Note the rock, wood, and metal fence post at the bottom of hole. This material could not be retrieved during the inspection.

Photo No. 30 – Close-up view of the bottom of the drainage manhole shown in previous photo. Note rock, wood and fencepost. This material was left in manhole.

Stilling Basin Dewater/Clean (Nov2007) Attachment 4 - Page 17

Photo No. 31 – View of the outlet for the drainage manhole on the east wall of the stilling basin. This outlet is located at the base of the wall on the inside of the basin. A small amount of drainage was also noted from this outlet following dewatering.

Photo No. 32 – Close-up view looking inside the outlet shown in the previous photo. Note the rock, wood and fence post at bottom of manhole. This material was left in manhole.

Attachment 5 – Page 1

ATTACHMENT 5

Photos of Abandoned Steel Pipe to be Removed on West Side of Stilling Basin

Attachment 5 – Page 2

Existing Steel Pipe to be Removed

Existing Steel Pipe to be Removed

Attachment 6 – Page 1

ATTACHMENT 6

Page 2 -- Photos of Existing Steel Covers on Drainage Manholes in Stilling Basin

Page 3 -- Photos of New Manhole Cover Design Example or Equivalent (on Existing Manhole)

Page 4 -- Photo Examples of Side Rail Ladders and Ladder Climbing Devices (in Existing Manholes)

Page 5 -- Example Specification Sheet for New Manhole Cover Design or Equivalent

Attachment 6 – Page 2

Existing Steel Manhole Cover

Attachment 6 – Page 3

New Manhole Cover Design Example with Locking Mechanism or Equivalent (on Existing Manhole)

Attachment 6 – Page 4

Example of New Side Rail Ladder and Ladder Climbing Device (in Existing Manhole)

Example of Side Rail Ladder and Ladder Climbing Device (in Existing Manhole)

Attachment 6 – Page 5

Example Specification Sheet for New Manhole Cover Design or Equivalent