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Temporary Rules for Effluent Filters and Access Devices and Other Possible Rule Changes

Joe Lynn

The N.C. General Statutes have been amended by HB-1462, effective August 28, 1998 to require effluent filters and access devices on septic tank systems permitted on or after January 1, 1999. This new law also requires the Commission for Health Services to adopt temporary rules to implement these new requirements by December 1, 1998.

A draft copy of the temporary rules has been sent to all interested parties for comment. Written comments must be received by October 15, 1998. A public hearing will be held in the Acrchdale Building at 512 Salisbury Street, Raleigh on October 28, 1998 at 9:00 a.m.

The Commission for Health Services will take action on the proposed temporary rules at the next scheduled meeting on November 13, 1998 at the Sheraton/RTP.

The latest version of the draft rules for effluent filters and access devices will be available at the conference. I have only listed the paragraphs where changes are proposed.

Over two years ago a “septic tank advisory committee” of local environmental health specialist, on-site wastewater staff, and septic tank manufacturers was created to review the rules and suggest needed changes. Effluent filters and access devices were two items considered by this committee, but many other changes were discussed. Some of the changes are a substitution of one word for another, other are changes that will result in better products, and some are new concepts. A copy of the possible changes follow the draft temporary rules.

POSSIBLE RULE CHANGES WHEN PERMANENT RULES ARE WRITTEN

RULE .1954 MINIMUM STANDARDS FOR PRECAST REINFORCED CONCRETE TANKS

(10)7 All tanks shall be manufactured with a cast-in-place partition so the tank contains two compartments. The partition shall be located at a point not less than two-thirds nor more than three-fourths the length of the tank form the inlet end. The top of the partition, shall terminate two inches below the bottom side of the tank top in order to leave space for air or gas passage between compartments. The top and bottom halves of the partition shall be cast in such manner as to leave a water passage slot four inches high for the full width of the tank. The partition (both halves shall be reinforced by the placing of six inch by six inch NO. 10 gauge welded reinforcing wire. The reinforcing wire shall be bent to form an angle of 90 degrees on the ends in order to form a leg not less than four inches long. When the wire is place din the mold the four inch legs should lay parallel with the sidewall wire and adjacent to it. It is recognized that there are other methods of constructing a partition or two-compartment tank. Any method other than the one described will be considered on an individual basis for approval by the Division of Environmental Health. On-Site Wastewater Section. However, the tank wall thickness must remain not less than two and one-half inches throughout the tank except for the blockouts the pipe penetrations.

(12)9 The concrete tank, lids, risers, and access covers shall be reinforced by using a minimum reinforcing of six-inch by six-inch NO. 10 gage welded steel wire in the top, bottom ends, and sides all exterior faces of the tank. The separate pieces of reinforcing wire fabric shall be lapped at least six inches over one another and tied together. Concrete cover shall be required for all reinforcement. Reinforcement shall be placed to maximize the structural integrity of the tank. The tank and riser shall be able to withstand a uniform live load of 150 pounds per square foot in addition to all loads to which an underground tank is normally subjected, such as the dead weight of the concrete and soil cover, active soil pressure on tank walls, and the uplifting force of the ground water. Additional reinforcement shall be required when the loads of a concrete tank are exceeded by subjecting it to vehicular traffic or when the top of the tank is placed deeper than three feet below the finished grade. The reinforcing schedule for tanks to be installed over three feet deep or subjected to traffic bearing loads must be specifically approved by the state. A tank subjected to traffic bearing loads may have a reinforced concrete slab constructed, or garage over the tank to bear the traffic load instead of the tank. The concrete slab reinforcement shall be designed by a professional engineer and approved by the State.

(14)11 A minimum 28-day concrete compressive strength of 4,000 3,500 pounds per square inch shall be used in the construction of the septic tank and concrete access riser, and the concrete must be mixed using stone with an effective coarse media size no greater than one-fifth of the concrete thickness of the outer wall of the tank. The concrete shall achieve a minim compressive strength of 3,500 3,000 pounds per square inch prior to removal of the tank form the place of manufacture. It shall be the responsibility of the manufacturer to certify that this condition has been met prior to shipment. A septic tank shall be subject to testing to ascertain the strength of the concrete prior to its being approved for installation. Recognized devices for testing the strength of concrete include a properly calibrated Schimdt Rebound Hammer or Windsor Probe Test.Accelerated curing in the mold by use of propane gas or other fuels is prohibited, except in accordance with accepted methods and upon prior approval of the state.

(15)12 After curing, tanks manufactured in two sections and as required, concrete risers shall be joined and sealed at the their joint joints by using a mastic, butyl rubber, or other pliable sealant that is waterproof, corrosion- resistant, and approved for use in septic tanks. The sealant shall have a minimum size of one inch nominal diameter or approved equivalent, approved by the state. Before sealing, the joint shall be smooth, intact, and free of all deleterious substances. Tank sections halves shall be properly aligned to ensure a watertight seal. Mortar Mix, hydraulic cement, or other appropriate concrete sealant shall be fully applied over the outside seam of the sealed joint. The sealants Sealants shall be provided by the septic tank manufacturer. Tanks and access risers shall be subject to watertightness testing.

(16)13 All tanks produced shall bear an imprint identifying the manufacturer, the serial number assigned to the manufacturer’s plans and specifications approved by the state, and the liquid or working capacity of the tanks. This imprint shall be located to the right of the blockout made for theoutlet pipe penetration point on the outlet end of the tank. All tanks shall also be permanently marked with the date of manufacturer adjacent to the tank imprint or on the top of the tank directly above the imprint.

(b) Pump tanks shall meet the construction requirements of Paragraph (a) of this Rule with the following modifications.

(1) Tanks shall be cast with a single compartment, or is a partition is provided, the partition shall be cast to contain a minimum of two four-inch diameter circular openings or equivalent, located no more than 12 inches above the tank bottom.
(2) There shall be no requirements as to tank length, width, or shape, provided the tank satisfies all other requirements of this section.
(3) The invert of the inlet openings shall be located within 12 inches of the tank top. No freeboard shall be required in the pump tank.
(4) After joining, tanks manufactured in two sections shall be plastered along the joint with hydraulic cement, mortar, or other waterproofing sealant. Methods of waterproofing tanks may be used as specifically approved in the plans and specifications for the tank. Prior to backfilling, the local health department shall make a finding that a two section midseam tank is water tight if a soil wetness condition is present within five feet of the elevation of the top of the tank.(5) Pump tank risers must have a pipe penetration point constructed in accordance with paragraph (a)(4) of this rule to allow for routing of electrical wire conduit out of the tank.

(6) Tanks shall be vented and accessible for routine maintenance, if located more than 150 feet form the facility. A water tight manhole access riser with removable cover shall be provided over the pump with a minimum diameter of 24 inches opening or other equidimensional opening with at least 576 square inches. The manhole access riser shall extend at least six inches above finished grade and be designed and maintained to prevent surface water inflow. Larger or multiple manholes risers shall be provided when two or more pumps are required. Pumps shall be removable without requiring entrance into the tank. Manhole Tank lids, access covers, and electrical controls shall be secured against unauthorized access. Manhole Risers shall be sealed watertight where they join the top of the pump tank and constructed to prevent water inflow through the lid or cover, joined to the tank top and sealed in accordance with paragraphs (a)(12) and (b)(14) of this Rule.

(7) All pump tanks shall bear an imprint identifying the manufacturer, pump tank serial number assigned by the Division of Environmental HealthOn-Site Wastewater Section and the liquid or working capacity of the tank. The imprint shall be located to the left of the outletblockout pipe penetration pointAll tanks shall also be permanently marked with the date of manufacturer adjacent to the tank imprint or on the top of the tank directly above the imprint.

(c) Plans for prefabricated tanks and risers, other than those approved under Paragraphs (a) or (b) of the Rule for precast reinforced concrete tanks, shall be approved on an individual basis as determined by the information furnished by the designer which indicates the tank or riserwill provide equivalent effectiveness as those designed in accordance with the provisions of Paragraphs (a) and (b) of this Rule.
Add rules for fiberglass, PVC, and plastic tanks here.

(d) Replace provisions for built in place tanks with, Built in place septic tanks or pump tanks must be designed by a Professional Engineer and approved by the State.

These are additions to Rule .1954
(1) Prior to shipping, the tank manufacturer shall certify that all tanks meet the requirements of Rules .1952, .1953, and .1954.

(2) The local health department shall comprehensively inspect and test the septic tanks, pump and grease tanks installed in their respective county or district for conformance with the approved plans and specifications and the provisions of the Rule, including:
(a) Concrete compressive strength using a properly calibrated Schmidt Rebound Hammer, Windsor Probe, or other approved device.
(b) Reinforcement using a metal detector.
(c) Measurement of relevant tank dimensions.
(d) Concrete consolidation, tank access, reinforcement placement, sealant, and structural integrity by visual inspection of tanks.
(e) If field inspections reject over ten percent of a manufacturer’s tanks then a manufacturing facility visit shall be required. This inspection will consist of the following:

(1) Inspection of the production facilities
(2) Raw materials records or ready mix records must be checked
(3) Sampling of inventory for concrete strength, wire reinforcement, measuring relevant tank dimensions, concrete consolidation, manufacturer information, tank access, sealing and sealant, and structural integrity.
(4) Rejection of over ten percent of sampled tanks will be cause for a follow up inspection within 45 days.


(3) The local health department shall test a representative sample of the pump tanks manufactured or installed in their county or district for Watertightness. Acceptable methods of Watertightness testing shall include a static water test by ASTM standard C1227-93a which is hereby adopted by reference in accordance with G.S. 150B-14(c) or vacuum test in accordance with state quidelines. State vacuum-testing guidelines are seal they empty tank and apply a vacuum of:

(1) Three inches of mercury held for one hour;
(2) Five inches of mercury held for 10 min.;
] (3) Ten inches of mercury for 1 minute;
Allow a 10 percent variance.

(4) All local Health departments shall have an inspection program plan which shall detail how the inspection requirements of this Rule shall be met, including documentation of ownership or access to necessary equipment and supplies.

PROPOSED CHANGES TO RULE.1955 DESIGN CRITERIA FOR CONVENTIONAL SYSTEMS

1. RULE .1955 (J) Effluent distribution devices, cluding distribution boxes, flow dividers, and flow diversion devices, shall be of sound construction, watertight, not subject to excessive corrosion, and of adequate design as approved by the local health department. Concrete distribution devices must meet the standards of Rule .1952 (a)(14). Effluent distribution devices shall be separated from the septic tank and nitrification lines by a minimum of two feet of undisturbed or compacted soil and shall be placed on a solid foundation of soil or concrete to prevent differential settlement of the device.

2. RULE .1955 (k) Grease traps, move to RULE .1952 (f) Grease traps tanks or grease interceptors shall be required for all food service facilities, meat markets, and other places of business where the accumulation of grease and oil can cause premature failure of a soil absorption system. The following design criteria shall be meetThe following are minimum standards of design and construction of Grease Tanks and Grease Traps:

(1) The grease trap tank shall be plumbed to receive all wastes associated with food handling or industrial processes and no toilet waste;
(2) The grease trap liquid capacity shall be sufficient to provide for at least five gallons of storage per meal served per day, or at liquid capacity, or a capacity as determined in accordance with the following: 

LC=D x GL x ST x HR/2 x LF
where
LS= grease trap tank liquid capacity (gallons)
D = number of seats in the dining area
GL = gallons of wastewater per meal (1.5 single-service; 2.5 full services)
ST = storage capacity factor = 2.5
LF = loading factor = (1.25 interstate highway, 1.0 other highway and recreation area, 0.8 secondary roads)

3. Move to RULE .1954 (f) Grease tanks shall meet the construction requirements of Paragraph (a) of this Rule with the following modifications.

(1) Two or more chambers must be provided, with the total length-to-width ratio at least 2:1. Chamber opening and outlet sanitary tee shall extend down at least 50 percent of the liquid depth. Alternately, the outlet may be through a specially designed grease filter.
(2) Access manholes riser shall extend at least to finished grade and be designed to prevent surface water infiltration. The manholes access covers shall also have be readily removable covers to facilitate inspection, filter maintenance and grease removal.
(3) Where it has been demonstrated that specially designed grease interceptors will provide improved performance, the grease trap tank liquid capacity may be reduced by up to 50 percent.
(4) Where the design liquid capacity exceeds gallons multiple tanks will be required.

4. RULE .1955 DESIGN CRITERIA FOR CONVENTIONAL SYSTEMS

(1) The soil cover over the nitrification field and backfilling around the tank(s) cannot occur until an inspection of the system has been made by an authorized agent of the state. The soil cover over the nitrification field shall be to a depth of at least six inches.


Please address any questions to Dr. David Lindbo.


This page (https://www.ces.ncsu.edu/plymouth/septic/98lynn2.html) created by
Vera MacConnell, Research Technician, I on February 16, 1999.
Last Updated on 7/17/00 by Roland O. Coburn, Research Tech. I

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