(A) Select backfill. Select backfill material shall contain no human-made or organic material or clay pockets and shall be free of rocks, clods or other materials larger than two inches in nominal diameter. Materials from on-site excavations may be used for select backfill; provided, they meet the specific requirements and contain optimum moisture content for proper compaction. Water saturated material shall not be used as select material. If sufficient on-site select backfill material is not available, acceptable material from an off-site borrow area shall be secured.
(B) Backfill. Backfill shall be free of all organic materials and shall not contain any rocks larger than four inches in diameter or be in a water saturated condition.
(C) Crushed stone or screened gravel. Crushed stone or screened gravel shall meet the requirements of the State Department of Transportation Standard Specifications (latest revision). Crushed stone or screened gravel shall conform to standard size No. 5. Any rock excavated on site which meets this graduation may be used. Specifically, the stone shall meet the following gradation.
Sieve Size | Percentage Dry Weight Passing Designated Sieve Size |
1-1/2-inch | 100 |
1-inch | 90 - 100 |
3/4-inch | 20 - 55 |
1/2-inch | 0 - 10 |
3/8-inch | 0 - 5 |
No. 200 | 0 - 0.6 |
(D) Pipe bedding. All materials used for pipe bedding shall conform to State Department of Transportation Standard Specifications (latest revision) for standard size 67 material. Any rock, run-of-bank sand or gravel excavated on site which meets the following gradation may be used.
Sieve Size | Percentage Dry Weight Passing Designated Sieve Size |
1-inch | 100 |
3/4-inch | 90 - 100 |
3/8-inch | 20 - 55 |
No. 4 | 0 - 10 |
No. 8 | 0 - 5 |
No. 200 | 0 - 0.6 |
(E) Riprap. The stone for riprap shall consist of field stone or rough unhewn quarry stone. The stone shall be sound, tough, dense and resistant to the action of air and water. The riprap shall be class I as specified in the NCDOT Standard Specifications (latest revision). The stone shall vary in weight from five to 200 pounds. At least 30% of the total weight of the riprap shall be in individual pieces weighing a minimum of 60 pounds each. Not more than 10% of the total weight of the riprap may be in individual pieces weighing less than 15 pounds.
(Ord. passed 6-21-2011)