I. Excavation

• A. Be sure of outside dimensions of tank
• 1. Must have a minimum of 12" of clear space all the way around tank.
• 2. Take into account the base material and inlet elevation for hole depth
• a. The incoming line must have a minimum of 1/4" per foot slope from facility to tank.
• b. Allow a minimum of 4"-6" bedding material in bottom of hole; allow for over excavation if there are unstable soils.
• c. Must know the distance from outside bottom of tank to the invert of the inlet.
• B. Place excavated material in an area that will not be in the way of the delivery truck.
• 1. Most tank delivery vehicles require to be within about 6' of the hole.

II. Check area leading into the excavation site before delivery

• A. Check for low hanging wires.
• B. Check for trees, buildings, etc., that may be in the way of the boom.
• C. Look for mud, soft spots, steep grades, or tight corners.

III. Setting the tank in the hole

• A. Take safety measures.
  1. Do not stand in hole while tank is being placed.
  2. Watch for water coming into the hole and walls sliding off in the hole.
  3. Stay away from edge of hole and watch the equipment operator.
• B. Be sure the tank is level.
• C. Check for proper alignment between inlet pipe and tank inlet.

IV. Backfill instructions for 3000 gallon 2-piece

• A. Follow same guidelines for excavation
• B. Set bottom half in prepared hole and make sure it is level
• C. Place kent seal aroundthe tank and set top half onto bottom half ensuring the inlet is in the correct position.
• D. Backfill should be of proper size and gradation.
  1. No stones over 4" in diameter.
  2. Thick sand or pea gravel should be used as backfill to provide uniform support for the tank walls.
  3. Make sure the backfill contains sufficient moisture for proper compaction

V. Water testing instructions for 1-piece tanks

• A. After proper placement and backfill ensure the inlet and outlet are sealed from any infiltration or exfiltration.
• B. Bring the water level to a point 2" above the point of riser connection to the top of the tank.
  1. To prevent uplift damage to the top of the tank, do not put more than 2" of water into the riser.
• C. Measure the water loss, if there is no water loss during the first 24 hours the test is complete.
  1. Some water absorption may occur within the first 24 hours, if so, refill the the tank and determine the exfiltration over the next 24 hours.
  2. The water level should not drop over 1" in the riser.

VI. Water testing for the 3000 gallon 2-piece tank

• A. Make sure the inlet and outlet are sealed off from infiltration and exfiltration
• B. Backfill to a point just below the mid rib seam
• C. Bring the water level just above the mid rib seam (no more than 2") and check the seam for any leaks.
• D. If there are no leaks finish backfilling the tank and bring the water level to a point no more than 2" into the riser.
• E. If there is no water loss in the first 24 hours the test is complete
  1. Some water absorption may occur, if so, refill tank and measure the water loss over the next 24 hours and determine the amount of exfiltration.
  2. The water level should not drop over 1" in the riser.

*  Peak day bedroom flows (Qp) are based on typical administrative rules.
**  Occupancy is based on typical usage of two occupants for the first
bedroom and one occupant per additional bedroom.

Concrete Tanks

• a. Walls, bottom and top of reinforced concrete tanks shall be designed across the shortest dimension using one-way slab analysis. Stresses in each face of monolithically constructed tanks may be determined by analyzing the tank cross-section as a continuous fixed frame.
• b. The walls and bottom slab shall be poured monolithically; alternatively, water stops may be provided.
• c. Reinforcing steel shall be ASTM A-615 Grade 60, fy = 60,000 psi. Details and placement shall be in accordance with ACI 315 and ACI 318.
• d . Concrete shall be ready-mix with cement conforming to ASTM CI50, Type II. It shall have a cement content of not less than six (6) sacks per cubic yard and maximum aggregate size of 3/4 inch. Water/cement ratio shall be kept low (0.35±), and concrete shall achieve a minimum compressive strength of 4000 psi in 28 days. The Contractor shall submit a concrete mix design to the Engineer for review and approval. Three (3) concrete sample cylinders shall be taken and tested for each tank manufactured until the manufacturer and Engineer are satisfied that the minimum compression strength is being obtained. To ensure compliance, the manufacturer shall then make and set three (3) sample cylinders for a minimum of 20% of the remaining tanks at the discretion of the Engineer. If the minimum compressive strength is not being obtained, the manufacturer shall be required to make and test sample cylinders for each tank manufactured. Calcium chloride will not be allowed in the mix design. The cost of testing cylinders shall be the tank manufacturer's responsibility. The tank manufacturer may supply a Swiss hammer for compressive testing in the field in lieu of sample cylinders.
• e. Tanks may be protected by applying a heavy cement-base waterproof coating (Thoroseal® or equal), on both inside and outside surfaces, in compliance with Council of American Building Officials (CABO) report #NRB-168; 6181, however the tank should be watertight without the addition of seal coatings.
• f. Form release used on tank molds shall be Nox CreteTM or equal. Diesel or other petroleum products are not acceptable.
• g. Tanks shall not be moved from the manufacturing site to the job site until the tank has cured for seven (7) days or has reached two-thirds of the design strength.
• h. Tanks shall be manufactured and furnished with access openings of the size and configuration to accommodate individual packaged pump systems. For 24-inch diameter access risers, the tank manufacturer shall cast in place a flanged tank adapter to facilitate the bonding of a 24inch diameter access riser. The flanged tank adapter shall be made of 1/4" thick ABS and shall have an outside diameter of 27 inches and an inside diameter of 22-3/4 inches. The flanged adapter shall be Orenco Systems©, Inc. Model PRTA24 or engineer-approved equal. The adapter must have an overall height of no less than 3 inches to allow 1-1/2" exposed for sufficient bonding area once the adapter is installed in the tank. For 21-inch and 30-inch diameter access risers, either a grooved tank adapter plate (Model RRFTA or RRFTA30) or a flanged tank adapter (Model FRTA30) may be installed in the tank. The adapter shall be manufactured of fiberglass or ABS and shall accommodate either a 21-inch or 30-inch diameter access riser.
• i. The septic tank and the top slab shall be sealed with a preformed flexible plastic gasket. The flexible plastic gasket shall be equal to the flexible butyl resin sealant congeal CS-102 or CS202 as manufactured by Concrete Sealants, Inc. of New Carlisle, Ohio, and shall conform to federal specification SS-S-00210(2i0A) and AASHTO M-198.
• j.  In order to demonstrate watertightness, tanks shall be tested twice prior to acceptance.  Inlets to the septic tank will be watertight pipe seal Cast-A-Seal™ (Manufactured by Press-Seal Gasket Corporation) or equal as approved by the Engineer.  Each tank shall be tested at the factory, prior to shipping, by filling with water to the soffit and letting stand.  After 24 hours, the tank shall be refilled to the soffit and the exfiltration rate shall be determined by measuring the water loss during the next two (2) hours.  Any leakage shall be cause for rejection.  After installation is completed, each tank shall be filled with water to the point two inches into the access riser and retested as previously described (the field test period may be reduced to not less than two (2) hours).  Backfill of a depth equal to the water height in the riser must be in place over the tank to prevent damage due to hydrostatic uplift.  No tank will be accepted if there is any leakage over the two (2) hour period.