A septic tank effluent pump (STEP) system may be installed, when approved by the city, to serve residential and light commercial locations where allowed by Chapter 13.50. A STEP application with a proposed site plan is required for each individual onsite system. A STEP application may be obtained from the public works department.
A STEP system is a facility consisting of a tank or tanks for settling and digesting wastewater solids, and a pressure piping system for conveying the supernatant liquid into the sewer system.
Only sanitary wastewater shall be discharged into the tank. Roof drains and other stormwater sources shall be strictly excluded.
The installer shall be responsible for providing an as-built drawing for the entire system.
Power shall be provided by the customer. The customer shall be responsible for notifying the city when the control panel alarm buzzer is activated. All sewer pipe, drains and plumbing between the tank and the building shall be the responsibility of the customer. The customer shall be responsible for curtailing water usage until city forces respond to the customer's notification. The city will accept no responsibility for damages resulting from a plumbing backup, such as may occur if water usage is not curtailed during an alarm condition or if the customer disables the alarm.
The specifications for a STEP system must be submitted to the city for review and approval.
(Ord. 749, 1997)
The design of any STEP sewer system shall conform to city standards and any applicable standards as set forth herein and in Sections 15.01.025 and 15.01.040.
The layout of STEP system mains shall not interfere with the continuation of the sewer system as outlined in the city of Langley comprehensive sewer plan.
Pump and pipeline sizing shall conform to the criteria as set forth in the Langley comprehensive sanitary sewer plan, most current edition, and Department of Ecology standards.
The applicable general notes shall be included on any plans dealing with pressure sanitary sewer design.
(Ord. 749, 1997)
A. 
Mainline. The minimum pipe size allowed is two-inch inside diameter. This is based on maintenance requirements rather than flow. Pipe shall be PVC Class 200, Schedule 80 PVC or ASTM D 2241, SDR 21 with rubber gasketed joints. Gaskets shall comply with ASTM D 1869. STEP mains shall have a minimum 36 inches of cover to top of pipe. See Section 15.01.370 and DOE criteria for sewage works design G1-1.4(D) for sanitary sewer/water main crossing requirements.
B. 
Service Line. Service connection pipe shall be minimum one-inch diameter, Schedule 40 PVC water pipe, solvent weld joint located at 90 degrees to the mainline unless otherwise approved by the city. Solvent cements and primer for joining PVC pipe and fittings shall comply with ASTM D 2564 and shall be used as recommended by the pipe and fitting manufacturers. Services shall have a minimum 24 inches cover to top of pipe. Pressure services crossing over any water line shall follow DOE requirements.
C. 
Building Sewer. The gravity building sewer between the building and the tank shall be designed and installed in accordance with the Uniform Plumbing Code as adopted in the Langley Municipal Code.
D. 
All pipe shall be installed with continuous tracer tape installed 12 to 18 inches under the proposed finished grade. The marker tape shall be plastic, nonbiodegradable, metal core or backing which can be detected by a standard metal detector. Tape shall be Terra Tape "D" or approved equal. In addition to tracer tape, install 14-gauge coated copper wire, wrapped around the pipe, brought up and tied off at the valve boxes.
(Ord. 749, 1997; Amended during 2013 reformat)
All pipe fittings shall have a minimum working pressure rating equal to the pipe with which they are connected. Fittings shall be PVC 1120, rubber joint complying with ASTM D 1784, D 2466, or D 2467, for pipe larger than one inch. Solvent weld fittings for one-inch pipe shall be socket type Schedule 40 and shall comply with ASTM D 1784 and ASTM D 2466.
(Ord. 749, 1997)
A. 
Ball and Gate Valves. All valves from one to three inches shall be PVC ball valves with preloaded EPDM stem seals, microfinished PVC ball and self adjusting polyethylene ball seat to compensate for wear and prevent over tightening. Valves shall be designed for use with corrosive fluids, for low torque manual operation, and for a working pressure of 150 psi. One- or two-inch valves shall be LT-1000-S or LT-2000-S as manufactured by KBI (King Brothers Industries) or GF500 as manufactured by George Fisher Signet, Inc. Three-inch valves shall be BTU-3000-E as manufactured by KBI or GF346 as manufactured by George Fisher Signet, Inc.
Valves four to 12 inches shall be resilient wedge gate M&H style 820 or Waterous Series 500 plug valves with an epoxy coating to resist corrosion. A ball or gate valve shall be located at every intersection and at a maximum of every 500 feet. Valves may be installed in conjunction with required pigging ports.
B. 
Air/Vacuum Valves. Air release valves and air/vacuum valves shall be located at the high points of the line. Profiles for each pipe run shall be submitted with the hydraulic gradeline for both static and dynamic flow conditions to show where the critical points are for air release valves. Vehicular access to air/vacuum valves is required for maintenance.
Because the air released by these valves will contain hydrogen sulfide, the valves and their enclosures shall be constructed of corrosion resistant materials. The valve vaults shall have insulated lids to prevent freezing. Vents shall be equipped with an odor control system such as activated carbon filters impregnated with sodium hydroxide.
C. 
Check Valves. Check valves used on service lines shall be a tee or wye pattern swing check, PVC, with a working pressure of 150 psi. Valves shall be designed for use with corrosive fluids. A check valve shall be installed at the end of the service stub-out at the property line to be installed in a valve box located at the center of the lot. Check valves shall be King Brothers, KSC or approved equal.
D. 
Pressure Sustaining Valve Assembly. Pressure sustaining valves are sometimes required in the design of STEP systems to keep the pipeline full during periods of low or no flow or when siphoning conditions exist.
E. 
Valve Box Lids. Valve box lids shall be specified to be marked with "SEWER" so they can quickly be distinguished from valves in the water system.
All service connect boxes shall be Carson Model 1419 with hinged bolt down cover and 1419E extension box as required, or approved equal.
(Ord. 749, 1997)
A pipeline pig is a projectile that is forced through the inside of a pipe to clean pressure pipelines. A pigging port is used as a point to send or retrieve the pig.
Pigging ports may be required:
A. 
At every change in pipeline size;
B. 
At the end of every dead-end line;
C. 
No farther than every 3,000 feet.
These locations are subject to review and approval by the city.
(Ord. 749, 1997)
Approved STEP tanks are as follows: 1,000 gallon, Evergreen Precast and Northwest Cascade, Inc.; 1,200 gallon, Central Reddi-mix, Inc.; and 1,700 gallon, Evergreen Precast.
Tanks for single-family residential use shall be rectangular, 1,000-gallon precast concrete, single chamber, and shall have been designed by a registered structural engineer. Fiberglass or polyethylene tanks shall not be allowed. Dual chamber tanks may be allowed in certain instances as approved by the director of public works. All tanks shall be manufactured for acceptance of pump assemblies or effluent filters and have a precast groove one inch wide by one-half inch deep, 24 inches in diameter to allow positive attachment of the riser. The manufacturer shall provide the structural design and certification to the city for review. The design or analysis shall be in accordance with accepted engineering practice. Tanks up to four feet in depth shall be designed for the following loading conditions:
A. 
Top of tank 400 pounds per square foot.
B. 
Lateral load of 62.4 pounds per square foot.
C. 
The tank shall be designed to support a 2,500-pound wheel load.
D. 
The tank shall be designed to withstand hydrostatic loading equal to the maximum depth of bury, in addition to the soil loading. Maximum depth of bury shall be measured from the ground elevation to the invert of the sewer line entering the tank.
Deeper installations, if required by local conditions, will require special consideration, as will tanks located where a vehicle might be driven over them. Tanks approved as traffic bearing tanks shall be designed to withstand an H-20 live load with a minimum soil cover of 18 inches.
All tanks shall be guaranteed in writing by the tank manufacturer for a period of two years from the date of delivery to the project. Manufacturer's signed guarantee shall accompany delivery.
Systems installed on a site where an existing septic tank exists may use the existing tank if it meets DOH and/or city requirements.
Concrete material and construction shall meet the requirements of section 6-02 of the WSDOT/APWA Standard Specifications for Road, Bridge, and Municipal Construction, most current edition.
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. The walls and bottom slab shall be poured monolithically. Concrete shall achieve a minimum compressive strength of 5,000 psi in 28 days.
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.
The concrete mix shall not be modified unless the mix design is reviewed and approved by the city.
Tanks shall be protected by applying a heavy cement-base waterproof coating, Thoroseal or equal, on both inside and outside surfaces.
Tanks shall be manufactured and furnished with 18-inch diameter access openings of the size and configuration shown on the standard drawings. Modification of completed or existing tanks will not be permitted for structural, warranty, and liability reasons. Tanks shall be furnished without concrete access hole lids. In order to demonstrate watertightness, tanks shall be tested prior to acceptance. Each tank shall be tested at the factory, by filling with water to the base of the riser 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 hours. The two-hour water loss shall not exceed one gallon.
Tanks shall not be moved from the manufacturing site to the job site until the tank has cured for seven days and has reached two-thirds of the design strength.
Tanks shall be bedded on six inches sand or pea gravel. Sides shall be compacted in two-foot lifts to the same or greater density than the surrounding area.
After the tanks have been set in place and the riser installed, but prior to backfilling, each tank shall be tested by filling the tank to two inches above the base of the riser for a two-hour period. Water loss shall not exceed one gallon.
Tanks installed where ground water levels are above tank bottom require precautions to prevent flotation. In general, tanks shall immediately be filled with water and shall not be pumped down more than three feet below top of tank.
Tank excavation shall be backfilled with select material free of boulders and compacted to a dry density equal to or greater than that of the adjacent, undisturbed soil. City inspection shall be required of the backfill and compaction of any tank that is abandoned in place. Finish grading, cleanup, and restoration shall be completed prior to final acceptance by the city.
(Ord. 749, 1997)
Outlet risers shall be fiberglass or ribbed PVC as manufactured by Orenco Systems, Inc., 2826 Colonial Road, Roseburg, Oregon 97470, or approved equal. Outlet riser shall be a minimum of 18 inches high or as otherwise shown on the engineering drawings, and have a diameter of 24 inches. Outlet risers shall be factory equipped with the following:
A. 
Two one-inch or one one-quarter-inch diameter (IPS) neoprene grommets, one for the pump discharge, installed no less than eight inches from the top of the riser and one for the splice box conduit.
B. 
A PVC splice box, with four cord grips and one-inch outlet fitting, Orenco Model No. SB4i or approved equal.
A lid shall be furnished with each riser. It shall be latching and shall be constructed of fiberglass with an aggregate finish. Riser and lid combination shall be able to support a 2,500-pound wheel load. PVC risers are not allowed in traffic areas.
Each riser shall be bonded to the top of the concrete tank with a two-part epoxy that shall be supplied with the riser by the manufacturer. The epoxy shall be applied in accordance with the manufacturer's recommendations. A generous bead of epoxy shall be laid completely around the bottom of the riser prior to mounting the riser on the top of the tank. After the riser is in place, a generous fillet shall be run completely around the inside base. The epoxy shall be allowed four hours curing time at 64 degrees Fahrenheit; otherwise a greater time shall be allowed based on the manufacturer's recommendations before backfill is placed over tank. Care shall be exercised during the curing period to avoid dislodging the riser or disrupting the watertight seal between the riser and tank.
(Ord. 749, 1997)
Pumps shall be stainless steel, thermoplastic, or coated inside and out with baked-on epoxy paint, UL listed for use in effluent. All pumping systems shall be Orenco Systems Model OSI S 4000 Series High Head Pumping Assemblies or approved equal comprised of:
A. 
Standard vault: 15-inch by 48-inch PVC Vault and Flow Inducer, Orenco Model No. SV 1548FI with eight one-and-three-eighths-inch diameter inlet holes or approved equal.
B. 
Hose and valve assembly includes one-inch diameter flexible PVC hose with quick-disconnect fittings and PVC ball valve. Orenco Model No. HV 100 Bfc or approved equal.
C. 
Mercury Switch Float Assembly, Model MF-ABR or approved equal, with three mercury floats mounted on a PVC stem which attaches to vault.
D. 
Pump: OSI High Head, 1/3 hp or 1/2 hp, 115V, single phase Model 8 OSI 03 HH or 8 OSI 05 HH, with eight-foot cord and one-eighth-inch bypass orifice for effluent application, or approved equivalent.
All pumping systems shall be installed in accordance with the manufacturer's recommendations.
(Ord. 749, 1997)
All STEP systems shall be wired to a dedicated 20-amp breaker which supplies power to the STEP system control box only. This is required to avoid damage or overload to system and appliances. All buried power shall be installed with continuous tracer tape installed 12 inches above the buried power. The marker tape shall be plastic nonbiodegradable, metal core backing marked "Power."
Positions on the PVC 3 float assembly are to be set at the following levels: High tank level alarm is to be set nine inches below underside of tank top, "on" at three and one-half inches below alarm, and "off" in same float as "on" set three and one-half inches below "on," and redundant off with low level alarm set four inches below off.
Control panels shall be Orenco Systems Model S-IRODS (redundant off with disconnect assembly) or approved equal with the following features:
A. 
Rating: 1 hp/115 VAC, 2 hp/230 VAC, single phase, 60 Hz. Motor start contact shall be rated for 25 FLA, single phase, 60 Hz.
B. 
Audible alarm, panel mount with a minimum of 80 db sound pressure at 24 inches continuous sound.
C. 
Oil-tight visual alarm, red lens, with push-to-silence feature.
D. 
Automatic audio-alarm reset.
E. 
Fifteen-amp motor rated toggle switch, single-pole, double-throw with three positions: manual (MAN), automatic (AUTO) and center (OFF).
F. 
NEMA 4X-rated fiberglass enclosure with gasketed, hinged cover, and locking latch. Padlock will be installed by city at time of city's acceptance of the completed installation and shall signify final acceptance.
G. 
Alarm circuit shall be wired separately from the pump, so that if the internal pump overload switch is tripped, the alarm will still function.
H. 
Twenty-amp power disconnect assembly toggle switch to de-energize entire control panel, to permit servicing panel without access to the customer's breaker switches. The pump control panel shall be mounted on the side of the house nearest the tank and pump, within sight of the tank in all cases and of the street where practical at no less than four feet but no more than five feet above finished grade.
I. 
There shall be a dedicated 20-amp circuit breaker serving the pump control panel.
J. 
Control panel shall contain hour meter and event counter bases so the meter and counter may be moved from one installation to another.
(Ord. 749, 1997)