Structure excavation & Backfill

Question 1

What material is to be used flowable backfill be used around structures.

Answer 1

NO–> Only for VERY special cases

Question 2

Moisture content for backfill material

Answer 2

Looking for shiny, sticky, muddy and holds shape well.

Question 3

What question should I be asking as I look at backfill material?

Answer 3

Is clay content high in this material?
Any indication of expansive soils?

Question 4

BEFORE DIGGING WHAT NEEDS TO BE DONE?

Answer 4

Dig Alert submitted 2 full working days before operation
delineated high risk utilities

Question 5

How far back are spoils from edge?

Answer 5

2 ft

Question 6

Competent Person

Answer 6

Inspects face for failure
Enforses CSO
Enforces submittals

Question 7

How deep of excavations are allowed before needing to follow OSHA regulations?

Answer 7

5 ft

Question 8

Egress Rules

Answer 8

-4 feet or deeper, need egress ever 25 ft
-3 feet above grade for ladder

Question 9

5-4-3-2-1 pneumonic

Answer 9

5-anything over 5 feet needs a plan stamped by an engineer
4-anything deeper than 4 needs a degree every 25 ft
3-The egress ladder needs to extend 3 ft above grade
2- spoils are 2 ft away from excavation
1- one competent person

Question 10

If the buried man-made object is discovered and is not shown on the plan

Answer 10

Change Order work

Question 11

When to take photos

Answer 11

Prior to excavation operations

Question 12

Is the bottom of footing for any structure final?

Answer 12

No, it is approximate.

Question 13

Slurry backfill is defined as

Answer 13

2 sack cement

Question 14

Sand Equivalent Definition

Answer 14

Sand vs Clay ratio per CT 217

Question 15

Beyond structure backfill graduation requirements and compaction requirements

Answer 15

100% passing 3” and 90% compacted

Question 16

Thickness of lifts

Answer 16

8”

Question 17

Do not place backfill against structures until they have reached a compressive strength of?

Answer 17

2,500 PSI

Question 18

When backfilling an abutment, what needs to be placed on bridge’s back wall for protection?

Answer 18

bumpers

Question 19

Is compaction method damaging the structure?

Question 20

What is compaction below approach slabs or sidewalks, or roadway?

Answer 20

95% to a distance of 2.5’ below these surfaces. But is 95% under all approach slabs. full width and depth due to compaction specifications.

Question 21

How far back is 95% compaction from the centerline of the abutment?

Answer 21

150 ft