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nNrrERmtTrENT SAND FILTER
DESIGN, INSTALLATION & MAINTENANCE MANUAL
PREPARED BY:
EAGLE RIVER ENGINEERING SERVICES
10421 VFW ROAD, SUITE 101
EAGLE RIVER, AR 9957/
(907) 694.5195
iNs 5
I. Introduction ............................................... 1
II. Int...-�mittent Sand Filter Op--rzd nal Characteristics and
VI. Operation of the ISF.......................................... 18
VII. Mamt=znx
A. Monthly Iterm........................................ 19
B. Annual Items ........................................ 19
C. Biannual Items ....................................... 19
VIII. Summary ............................................... 20
Appendix
Operational History in Anchozge
A.
Operational Characteristics ... ..........................
2
B.
Operational Hrstory ..... ............... ......
2
. ...
M.
Design
A.
Sit -Requirements ....... ..............................14
B.
Design Aspects Speafic to Al sLs ............................
4
C.
SampL- Siang Calculation for Filter and Leachfield .................
5
D.
System Mechanical Components and Monitoring System ..............
7
E.
Pcmit Application ......................................
8
F.
Insp-- tions and Asbuils..................................
8
IV.
Material Sptcific tions
A.
ISF Pacizge.........................................
11
B.
Electrical ..........................................
11
C.
Air Pump ...........................................
11
D.
Piping.... . ........................................
11
E.
Bedding Materials .....................................
12
F.
Pea Gravel ..........................................
12•
G.
Sand ..............................................
12
E.
Round P.ock.........................................
12
I.
Insulation ..........................................
12
J.
Filter Fabric .........................................
13
F:
Tank for Lift Sy - ...................................
13
L.
Effluent Pumping Assembly ...............................
13
M.
Substitutions .........................................
14
V.
Con=ction Installation Guidelines
A.
Lift Station .........................................
15
B.
Sand Filter ..........................................
15
C.
Leachfreld..........................................
17
D.
Eloctriml...........................................
17
VI. Operation of the ISF.......................................... 18
VII. Mamt=znx
A. Monthly Iterm........................................ 19
B. Annual Items ........................................ 19
C. Biannual Items ....................................... 19
VIII. Summary ............................................... 20
Appendix
A. Open-ational Chaiacterest a§
Primary tee meat for the ISF system occurs in a conventional septic tank. Raw wastewater is
allowed to settle in an anaerobic environment, and effluent is sc:reend prior to entering a pump
chamber within the tank. A standard MOA approved, two compartment, steed septic tank with
OSI septic tank effluent pumping (STEP) assembly is utilizd. The effluent pump is primarily
controlled by a timer which a.^tiNates the pump at preset, equally spaced intervals. The pump
cycle is timed to apply a small effluent dose to the filter, normally about eight gallons. Pumping
at the specified intenals o=rs 24 hours a day if effluent is available in the tank A low level
override disables the pump when there is insufficient effluent to require pumping. A high water
alarm is included in the reside.ice to alert occupants of possible flooding conditions due to pump
'failure.
The septic tank effluent is pressure dosed to the ISF for secondary, biological treatment in an
a-robic environment and mechanical filtering. Biological degradation tats place when naturally
OccurBag microorganisms re 'siding on the surface of the sand particles utilize the nutrients
contsind in the wa tm-zter. The measured parameters of wastewater effluent quality are BOD,
TSS, fecal coliform, NHrN. Following treatment through a mature sand filter, and prior to
discharge to a drzinfield, the effluent quality parameters an be expected to average:
BOD <5 mg/L
TSS 15 mg/L
Fecal coliform <400 colonies/100 ml
NH3-N < 1.0 mg/L
NO3-N <30 mg/L
The standard design from OSI for a filter bed contains an 1S feet by 20 feet (IS' z 20') internal
filter surface area. FIffiuent loading over the sand filter surface should not exceed 2.0 gpd per
squzre foot, and a lower load rate is preferable. The sand filter can be outfitted with a lift pump
to allow application of the filtered effluent to the leachfield. The filter lift pump is virtually
identical to the primp system utilized in the tank, however, it is controlled by simple level
saitchs. When the ISF contains a pump for a pres:srri=d leachfield, the high water level float
for the ISF will disable the septic tank p.unp until the level in the filter is lowered. High water
level tank alarms will alert the homeov;mzr if problems occur. Final treated effluent disposal is
to a leachfield of reduced size.
B. Ope atiorml l ustuiry in Alaska
Three ISF systems were installed in the Anchorage area in September 1993. The systems area
monitored monthly to record temp-wznrs at four levels in the sand filter and septic tank
temperatures in the two compartments. In addition, water usage and pumping data are collected
to determine usage patterns. Data is presented in the Appendix 1, tables I & 11. Temperatures
2
in the sand filter are a big concern as they affect the treatment process. It is evident that soil
tempcanres just below the top surface of the sand (SF2) reached a low of 40'-41•F in the time
period of D� .^mber to Mach. A delayed tempwzturr response is evident as the cold tempa-atures
migrztzd through-the filtevlayers•000ling the top surface first with the bottom layers retaining
cool whiathe top sxfa: - v=ed lam in-the ssmmerseason. Tho Sh--ndoah, Lot 8 installation
remained approAma�jy 26F warmer than the Lot 140. system. Variatiors in the,filter,operational
characteristics may be attributed to site .spmcific usage patterns and mechanical difficulties
experienced in the air delivery and effluent pump control systems. Filters have esperiwf=l
intsmiTMzntponding of effluent on small ar-,,.s of the sand filter surface. Evaluation of the sand
filter performanr- is in the preliminary stages, but effluent quality test results have been very
enoo=ging.
III. DESIGN
A. Site Requirements
In order to qualify for an on-site septic peewit in hfOA fora sand filter system, a site should be
inmpabL- of supporting a conventional leachfield upgrade or initial plus replacement situ. Subject
to umiver, the site should have the following conditions:
1. Two vertical feet (2') of naturally occurring (m situ) soil stztum with Ian
acceptable percolation rate.
2. Four vertical feet (4') of s_-garation to bedrock or an impermeable layer.
3. Two feet (21) of sopa- lion from seasonal high gro=dF-at= tzblc.
4. Sit.- must provide adequ= area to accommodate the installation of septic tank,
BF, and z•achfi-Id. The sand filter box is standzrdiied at 18 feet by 20 feet (18'
x 20'). The ISF sysrm also uses a stan�..ard, two compartment septic tank with lift
station, and small leachfield. Setbacks and horizontal separation distance
applicable to septic tank or field also apply to the filter.
B. Design Aspects Specific to Alaska
The MOA ISF system reins the basic OSI configurtion with the following exceptions:
1. Septic Tank
a. The septic tank is insulated on all sides to help retain any hest energy
enter -ring the tank.
b. The septic tank is a two compartment typ.- tank versus the OSI single
compar'.m.nt system. An additional ea'rity of 250 gallons is added to the
usual tank design volume to accommodate the STEP system.
C. The STEP is contained in the second compartment of the tank. A one
eighth inch (1/8') hole is drilled in the effluent delivery piping within the
tank, above the pump level, to allow effluent line drainback and prevent
ft --s-
blockage during extended periods of inactivity. The effluent line is
sloped to allow positive drainback from the filter to the septic tank where
possible.
2. Sand Filter
a. The sand filter is insulated on all sides exert the bottom to help retain heat
generated within or provided to the filter.
b. An air dispersion line is added within the lower six inches (6') of the sand
layer to supply oxygen required for an aerobic treatment environment and
to provide supplemental heat. The airline is supplied from a small
compressor located within the residence .
C. Flush valves, monitor tubes, sample basin and pump basin (optional) zr.-
insulated to pre%,--zt f e:zing and retain heat in the filter.
4
3. l.eachfield
a. Groundwater and bedrock/impermeaa' lc strata waivers as previously
described, may be acceptabl-, . supported by a positive risk analysis
condo^ted t y-tht-design engineer:
b. Siang of the L-achfield is =M Lased na a v= --water generation rate of 150
gpd per bedroom. Soil application rates are more liberal due to the higher
quality effluent from the sand filter. The design application rate for soil
with a peroration ret, of less than 30 minutes per inch shall be 4.0 gpd per
square foot. The application rate for soil with a percolation rate of 30 to
60 minutes per inch shall be 2.0 gpd per square foot.
Construction of the leazhfield is accomplished in the traditional manner, with the sine required
inspections as a conventional Inchfieid.
C. Sample Siang Calculation for Filter and Leachfield
1. S-tnnle Dts*, n ralcull6ore
a. Calculate Maximum Flow Generztion by Code
ExampL: number of bedrooms (BR) = 4
(4 BR) (150 gallons per day per bedroom CvpdMR)) = 600 gpd
b. Verify rate through sand filter sill be <2.0 gpd/square foot (residential)
Area of filter = 18' x 20' 360 square feet
600 gpd _ 360 square feet = 1.67 gpd/square foot
1.67 gpd/square foot < 2.0 :. acceptable
C. Size leachfidd
E mraple = 600 gpd
Soil pert rate = 39 minutes/inch
Application rate = 2.0 gpd/square foot
Asim.- site requires a 5' wide shallow trench system due to slope and nater table
Assume 0.5' gravel depth below the leachpipe
600 gpd _ 2.0 gpd/square foot = 300 square feet of required absorption area
300 square feet + 5' Aide = 60' length
Reduction factor = 1.0, or no reduction for 0.5' gravel
Use a trench 5' wide by 60' long x 0.5' depth of gravel under leach pipe
d. Calculate Pumping Interval
600 GPD _ 8 gal/cycle = 75 cycles/day
pumping interval = 1,440 min/day _ 75 cycles/day = 19.2 minutes between
cycles
Nota.• Although a four bedroom home is based on 600 gpd, it is recommended that
the ISF pumping cycle be initially set up at 30 minute pumping intervals, which
can then be reduce if not ssaffici—nL
e. Calculate Pumping Cycle Zine
8 gal/cycle is recommended
Volume of delivery pipe is calculated for 1-1/4' ID effluent pipe
Pipe area 0.0085 sq=—e feet P.— foot, asrrm- 40' 1--gt--h
Volume = area x length, (0.0085 square f-, -t) (40') = 0.34 R3
Volume = (0.34 W) (7.48 gallftl) = 2.55 gallons
Pump cycle time = (8 gal + 2.55 gallons) _ 28 gpm = 0.377 minutes
= 23 seconds approximate cycle time
Note: This cycle time should be verified by field tasting the actual set-up prior to
backfilling the sand filter
2. Filter OTificr CalculiicNnq
For a OSI HHF-20 pump, assume flow rata from lift station = 28 CPM
Configuration recommended by OSI = standard 18' x 20' ISF has 7 laterals, 16' Iong
7 Iaterals from one central manifold = 4 GPM per lateral
I,at..zal length = 16' (off central manifold)
From OSI: Recommend 3/4' diem -t -x manifold lines with 1/2' lat_--zls
I' ateral distribution holes will be 1/8' (orifice)
Assuming 5' pressure drop from across orifice (see not-)
Orifice arm (A) 0.00009 ft=
Q = CdA %r 2gH (orifice equation Cd = 0.6)
Q = 0.6 (A) 164.4 H
Q = 0.6 (0.00009) 164.4 (5) (5' head, 1/8' orifice hole)
Q = 0.00092 fN/sec
Q = 0.41 gpm
4 gpm per lateral requires:
4 gpm _ 0.41 gpm/hole = 10 holes per 16' lateral Q 2.0' spacing along lat=21 pipe
Note: 1) This calculation should be accomplished as a backup to OSI standard design
which specifies the number of orifices and spacing. 2) Minimum ac -ptabIe 'vsquirt'
height during inspection shall be 49.
3. Efrluent Tine Sizing
The effluent line is typically sized at one and one quaff inch (1-1/4') diameter for the
standard effluent pump size. This should beengin=-.d to d t—, -mine if excessive head loss
occurs for large grade changes and/or long effluent piping distances.. The volume of
dminback liquid should also be armd--red in the design for long effluent piping distznces.
6
D. System Mechanical Components and Monitoring System - .
An important design aspect of the ISF'is the consiistzat-dosing of the filter bed. Dosing is
primarily controlled by a timer, with float controls providing high alarms and 16w overridis.
a. Septic Tank Dosing Effluent Pump. This pump is activated by the OSI control
panel timer at preset intervals. The tank also contains two level switches. If the
1evl in the tank becomes too high, the upper flcai will activate a high water alarm.
The pump continues to cycle on the timed intervals. If the Level in the tank
bermes too low, the low Level shut-off switch will override the timer.
b. Sand Filter. I.n some cases, the ISP bed also contains an effluent pump. This
pump basin also has two level switches. The lower switch is a simple on/off
switch set for an approximat two inch (L') drawdown. The upper float switch
dsabL-s the seac tztk dosing pump and awaits a high water alarm if the effluent
level in the filter reaches the sand layer.
C. Air Pump. The ISF is quipped with an air diffuserline to promote aerobic
ba..••*—ial aeon and raise the filter temperature. This pump is designed to operate
continuously, year round. The pump itself is generally located within the interior
of the house or c.awlspax, wh_- s p^- warmed air is available. Air delivery to the
filter is through a small diameter insuktutd pipe.
d. Sampling. A provision should be made for sampling of sand filter effluent. This
is ac:complished through the pumping basin, if one is required, or by fas~.lfing a
s --,=m sampling basin.
e. Monitoring Tuns. Moaito3ng of the sand filter is axomplished through six inch
(6`) PVC tubes placed to- the top of the sand surface layer in the filter. These
tubes allow monitoring of any surfi= ponding in the filter.
2. Des'=
Specificetioas for control pan -!s require the OSI Simplex SICMTMRO, or two pump control
panel SSFICTLrMRO1RO as appropriate. Use of a pump in the ISF will require the duplex
control. Ali electrical service and compm= should meet or exceed applicable local, State, and
NEC codes. The instsIlation should be completed by a locally fins. -d electrician. All
components should be severe weather proof (Nema 4x rated or equal), and suitable for - in
conte with efilueai, if applicable. If possffiIe, all control panels should be mounted within -view
of ft septic tank/lift station and filter. Alarms must be mounted in the house, where audible to
the oxupaats of the home. Dedicated electrical circuits should be installed'for the septic tank and
sand filler pumps. The air pump iqu:r-s a 2.2 amp/84 watt, 110 volt supply. The manufacturer
of the ISF pzlage and controls mn provide a detailed schematic for electrical operation.
Commenial establishments are required to utilize explosion proof, intrinsically safe controls for
lift station operation.
E. Permit Applications
Application for a permit to co: =.-t the ISF system requires a submittal similar to a conventional
system. Include design calculation Tor sizing of septic tank, and leachfield. Provide calculations
and plan for pump timing and operation: Include pump specifications and curves, product
sp-.,,^ifieation'sheets, earth material spwifications and proposed suppliers, pressure system and
orifice calculations. A rarrative description and formal waiver request, if appropriate, soil test
logs and percolation tests, groundwater monitoring, and a site plan will be required.. The site plan
must include neighboring well and septic development, and general topography. Profile and plan
drawings of the ISF shall be included, with detail sketches. Anchorage Municipal Code (AMC)
15.65 should be consulted for appropriate code requirements.
F. Inspections and Asbuilts
The usual code ins,=. icons are required, including tank leveling and relative Level; bottom of
Ieachfield excavation for location, uniform excavation depth, soil condition, and relative depth.
The sand filter system adds a third component to a regular tank/leachfield system, requiring
additional inspections. (Refer to AMC 15.65.)
a. The bottom of the filter excavation will need to be examined for relative level and
L—. PI condition, ±1.5 inches. The hole is over-exca-ated and a layer of leveling
sand placed over the bottom to protect the filter liner. Inspect to verify that no
sharp objets or stones could damage the liner at this point. The floor of the filter
should be Level ±1/2'. If an interior lift pump is planned, the sump should be
bend excavated and the edges of the opening smoothed with wet sand and tamped
to provide a curved transition to the filter bad.
b. Verify adequacy of perimeter wall form and absence of nails or other sharp
protrusions. Verify the seal of all boot flange penetrations: Air line, drain line,
pump line. This is accomplished visually.
C. Inspect gradation depth and level condition of first layer of pen gravel, and
condition of under drain. Slots on underdrain pipe face up. Verify round rock is
adequately mounded over underdrin. Pea gravel should be relati rely free of fine
soil material.
d. After a six inch (6') portion of sand is plate, leveled, and the air diffuser is
installed, check for Level condition, relative lev-..1, and uniform coverage'ofthe air
diffi:ser. Uniform coverage is critical to the success of the filter.v a sand
sample and obtain a sieve analysis for suitability regarding grain six-. Submit to
MOA for approval. The percentage of fines and overall gradation of particles is
critical to the su== and life expectancy of the filter. Absolutely no contaminant
soil or materials, such as leaves or debris shall be allowed in the filter sand.
e. After all sand is placed, cieck for corre t depth, an absolute level surface condition
and general sand condition.
f. After upper pea gravel and piping is instmIled, and tank fined vih water:, perform
an operational check of pressure at the filter (squirt test) with orifice shields
removed. Check for 1--.Im at tank pump plumbing and all connections. Rexrd
•-level of orifice s above pipe•(minimuun a,,..eptable head is four feet (4'), and
verify that oriflw s 'holds a.,e aplad znd covered Kith pea gravel cover. Inspect
lateral flush piping, and accessibility of valve. ,
g. If a sample basin is installed, verify that samples can easily be obtained without
contamination.
h. Verify pla=m=t of appropriate amo.mt and type of insration. Require close
fitting of insulation around standpipes. Cheek filter fabric for type and placement
over the insulation.
L Final soil cover, grading and seeding. Check relative level and grade on slope.
j. Dependent on location in the Municipality, a Municipal elec-trical inspection shall
be made a part of the specifications. The contractor should submit a copy of the
satisfactory inspection report to the engineer, and a copy is to be submitted to
MOA with system asbuilts.
If a Municipal iasp, tion is not required, a locally licensed el.—trician shall be
r_spo'ble for verifying the quality and adequacy of the work. The electrician
shall also verify proper operation of the control timer and flit switches. The
contra= shall submit a leets' signed by the electrician, stating that the installation
mets all applicable codes and industry s"ndards. This letter shall be submitted
to the MOA with the asbu lts. This letter shall be submitted to the MOA with the
system asbuilt
2. T=;c 1 Con -sanction inrn-:21on Schedy_+1.
a. After septic tank/lift =tion is in pia--, but not bacL-tilled. Sewer piping from
building to tank is complete, and bedded to springline.
b. After sand filter pit is excavated and prepared for filter construction. Prior to
plaxment of filter liner material.
C. During construction of the sand filter there should be intermittent insp--cion to
vwify construction compliznce as described in Section F.1.
d. Inspection of open =ch ezca%ztion of Itachfield as per MOA Code.
e. Inspection of leachfield prior to final bacUll with all piping in pax. Insp---don
will require pressure testing of lcachfield piping with sand filter pump in place if
applicable.
L Inspection of final grading.
3. Asb? It qi?bmittnl
The following information should be included on the current Municipal Inspection Report form
(MOA25) in addition to all information required with a standard installation :
a. Locations of sand filter and 211 associated standpipes. Provide elevation of ISF
floor, gravel layer, sand layers, airline, and piping. Provide elevation and location
of outlet piping.
b. In addition to the usual required swing ties for one tank cleanout, and one
leachfield monitor tube, provide swing ties for all ISF standpipes.
C. Provide results of pressure test, pump cycle time and pump interval setting.
td
IV. MATEtLAL. SPECIFICATIONS
A. ISF Paclmge ..
The primary filter -liner, pressure lines, flushing piping and valve; pump basin, •pamps•and
2ssociaL� timers, ssvitrhes and alarms shall be obtained from OSI or a rrppfier of their products.
For Anchorage, the basic 18' z 20' ISF with PVC liner is specified. In addition to the filter
paclzge, the OSI linear air diffuser is required, with a suitable air pump. .
1. Liner - OSI Model LI or equivalent. 30 mil PVC cut and fabricated to provide
water tight enclosure of filter sand volume. Seams to be permanent as per
Manufacturer's recommendations. All connections, such as boot flanges, through
sand filter to be permanently bonded to the liner.
2. Manifold Assembly - OSI Model SFM 1036 or equivalent with orifice shields and
flushing assembly. All drilled holes to be cleaned of burrs and pipes flushed prior
to assembly.
3. Pump Basin, if required - Sand filter pump basin is to be OSI Model PBSF1561FI
with flow inducer and matching 15 inch diameter riser s. -^tions as needed to extend
12 inch above finish grade maintaining a water tight seal through the full length
of conduit riser. PVC splice box to be installed with a conduit seal rat.
4. Filter Secondary Pump Cif rquircd) - OSI Mode120 OSI 05 = with appropriate
float assembly and high pressure discharge assembly.
5. Linear Air Diffuser - Available at OSI, no model number available.
B. Electrical
Required timing and control devices shall be those sLpplied by OSI for us-- with their sand filter
pacl2ge. All necessary conduits, buried electrical wires, connections, and snitches shall meet
National Electrical Code sp-.,.ifications and be listed by Underwriters Laboratories or a similar
agency. Connections to existing electrical service must be designed and fabricated by a licensed
electrician.
C. Air Pump
The air compressor and punp shall be a Thomas Indus, Inc. model No. 5070 linear air pamp,
or equal product Fittings must be air tight and capable of withstanding a 20 psi ra=i gum.
Operating pressure is three to five prig delivering 2.4-1.6 cubic feet per minute.. A port for
measuring line'pressure utilizing a'standard low range air gaud is recommended.
D. Piping
Gravity drain pipe shall be four inch (4') diameter ASTM 3034 PVC or MOA approved equal
produce. Pressure piping shall be schedule 40 PVC conforming to ASTM D-2241 or polyethylene
pipe shall conform to ASTM D-2239-74 at 160 psi. Air diffuser line shall be three quarter inch
11
(314') HDPE as supplied by OSI. Arctic air line, external to the filter shall consist of minimum
R-4 dual Rall HDPE constructed with un thane foam, three quarter inch (3/4") HDPE with one
inch (1') foam pip- insulation jackets and four inch (4') PVC outer shell, or an approved
alt_ -^Rate All p1p: shall have two inch (2") insulation, two feet (2') wide over areas which have
less than four feet (4') of soil cover. Additional "amination may be Rarrrnted under driving
s; rfac.-s or snow -cleared ar-,.s. Fittings for 211 piping shall conform to industry standards and
sazufactu-s's r:commendations.
E. Bedding- Materials
Materials used for bedding below the spring line of pip -,s shall be MASS Class 'B" material or
equiN?I=L This material need not meet the stringent standards of the filter sand. Material used
for fill over the spingline shall be free of large stones or Iarge inorganic materials, and shall be
plate in a thawed condition.
F. Pea Gravel
IOMIiy zmilable, Qashed thr- eighths rich (318') round pea gravel is suitable for use in the ISF.
mist have 1000 passing the three eighths inch (318') sieve, and must have less L' -tan 20
pe:~...nt (LO o) passing the one quarter inch (114') sieve, and 1ss than one per=t (1 o) passing
the R sieve. One quarter inch (1/4') pea gravel with round particles and less than one percent.
(l o) mec^g the j`8 sieve is an approved substitute, if available.
G. SF Sand
Currently, the only 2pp.ove3 souree of ISF filter sand is Central Paving Product's 'Winter Road
Sand' azaLabL- at the Palmer yard. Substitutes must have less than two percent (2 0) passing the
if100 sieve, less than one percent (1 o) passing the £'200, and have 100 percent (100o) passing
the r4 sieve. A coefficient of uniformity Cuc4 is recommended.
Washed, three quarter inch (3/4') to one and one half inch (1-112') septic rock with no fines
p^esettt will be a3�.iaL-. This material is utilized to szgrega� the pea gravel from the one quarter
inch (1/4') slots in the four inch (4') underdrain. Rock is piled around and two inches (2") over
the four inch (4") pipe.
L Insulation
Two inch (2') thick extruded polystyrene foam with a +35 psi direct burial rzdng.
12
J. Filter Fabric
OSI product LIFT or an alternate product meeting the following specifications: Minimum 80
pond t=sile strength (ASIM-D=:632) and minimum 2.5 per second permittivity rating (ASTM -
D -4491).
K. Tani: for Lift Systems
1. Septic tank should be a two compartment steel tank specifically for the use of OSI
for their pat=ted lift station assembly Model 4200.
2. The tanks shall be designed for soil loading conditions as required by Municipal
and State regulations. The design or analysis shall be in accordance with accepted
engineering practice and local regulatory agencies.
3. All welding shall be in accordance with applicable codes and standards.
4. An additional second compartment outlet riser shall be 12 gaup sheet steel, and
shall extend 12 inches (12') minimum, above surfa grade, shall have a minimum
nominal diameter of 24 inches (24'), and shall be capable of being equipped with
the following:
a. A junction (Noma 4x) boa or equal, bonded and attached to the riser.
b. UL listed electrical cord grips, installed in the J -box.
5. A lid shall be furnished with the rises. It shall be constructed of fiberglass or
equivalent aggregate finish. Meet H-10 loading requirements and have a s -^sur
latching mechanism.
6. Riser installation - each riser shall be sealed or welded to the top of the tank in
such a manner as to prevent infiltration of groundwater.
7. Insulation - four inches (4') of rigi4 extruded polystyrene shall be placed in the
riser directly below and attached to the lid.
8. Insulation - two inches (2') sprayed shop applied urethane on circumference of
riser with 46465 Tnemec coating.
L. Effluent Pumping Assembly
1. Effluent pumping assembly shall be OSI Model 20 -OSI -05-= series consisting
of the following:
a. 1/2 HP 110 volt or equal UL listed effluent pump.
b. Sae ed ;ramp Nzult (US patent No.4439323) 59 inches (59') deep, three
sixteenths inch (3/16') thick high density PVC cylinder houses the pump,
Level controls and screen and serves as a baffle to prevent the screen from
clogging.
c. 'All piping shall be PVC or other non -corroding material.
2. Pump controls and alarm system - control shall be OSI SICTETMRO or
SSFICTE12YIRO1RO, as appropriate, 110 volt with the following options:
a. Event counter.
b. ELpsed time meter.
13
C. Program timer.
d. 10 watt heater.
e. Remote zk=..panrl _option with a minimum of 80 DB sound press=e at 24
inches (241), op-=adng tem . „ -30AC to 65AC, continuous sound to
be located in the home.
f. Oil tight visual alum with push-to-silenae feature. Automatic audio zlarm
reset.
g. 15 amp motor rated toggle switch, double pole, double throw with dir—.
positions; manual (man), automatic (auto), and center (ofi) (HOA).
h. Nema 4x rated, fiberglass, or equal, enclosure with hinged cover.
M. Substitutions
The De arnnent will consider substitute saterials if adequate product information is supplied to
the On -Site Services program manager.
14
V. COl\'STRLTCTION GUIDELINES
A. Lift Station
1. Fs2czir to proper depth to allow gtavity flowTrbm iesidenw and drinbaek from the sand
filt-; install tank level, tol aria 0.01 -foot (0.01'), on undisturbed earth-orclassified NPS
fill r-;,!ci21 compacted to 95 percent (95%). Line tank excavation walls with two inches
(2') +35 psi burial foam full depth of tank. BaciZill between tank and foam insulation
with sand material and compact, in a manner to prevent damage to the tank surfar~
coating.
2. After inspec ion, cr-e.te a Level sand s rfac-e over the tank and add two inches (20) burial
foam +35 psi directly over the tank. Mound unclassified soil over tank location to a depth
of two feet (2') above finish grade to allow positive drainage away from the tank and
counteract buoyancy, if applicable.
3. Exracate to Level of tank inlet and outlet installing inlet and outlet piping properly bedded
on undisturb:d or compacted fill material. Pressure effluent line is recommended to be
one and one quarter inch (1-1/4') ID pipe installed with positive drainback to tank.
--ial for the at may be HDPE or Schedule 40 PVC.
4. All connections to he as per MOA-DBES and UPC requirements, PVC 3034 piping with
caulder or equivalent couplings for inlet riser pip -,s. All tank connections are to b--
complevely water tight.
B. Sand Filter
A 19 feet by 21 feet (19' x 21') area is staLd out utilizing reference stakes around the perimeter
of the excz-.ation:
1. Verify grade ntcessary for gravity flow to the leachfield portion if not utilizing a pump
basin. Determine the eL-cation of the sand filter bottom and reference to a bench mark.
2. Exca atz sand filter area to proper depth, plus two inches (2"). Place two inches (2') of
Feuding material in bottom of sand filter. If a pump basin will be included, excavate the
depression. Ruud Level to a uniform surfaw, level ± one half inch (1/2"). Smooth
transition from floor to pump basin depression and radius basin edges with tamped, wet
sand. The sand provides a smooth, stone fr-- surface for the liner to contact
3. Cms== and install perimeter fuming support walls to specified dimensions. If the filter
is buried, the support frame is constructed of untreated two by four inch (2' x 4")
dun-mmonal lumber and one half incl (IR') plywood. Strength requirement is dependent
on filter size and soil ba l --fill chamcLeristics. Temporary bracing is recommauded until
b3zIM is compItted. E^suur no nails or staple points can contact the PVC liner. Install
two inches (20y'bf 35 psi rigid polystyieine insulation over interior plywood perimeter
walls, ftst=ing to wood with construction adhesive.
4. The 30 mil PVC liner is unfolded from the center of the excavation and stretched over the
top edges of the support frame. - Ensues that the liner is in full contact with the bottom and
sides and that no bridging occurs. No•.e: Installation of remainder of sand filter interior
should be accomplished during warm ambient temperatur (+40°), and should
15
be completed within one day. If this is not possible, the excavation must be covered to
prevent the intrusion of leaves or other contaminants. If temperatures are below 40°, the
excavation should be tented and heated at night. Stockpiled materials must be Impt
covered. Under no circumstances should frozen soil materials be placed within the filter.
Remove all debris such as leaves and sticks from the filter.
5. Place underdrain and pump basin in prepared area if required (pressure system). Basin
must be placed with a bottom cap installed to prevent damage to liner. Install boot flange
and seal to underdrain pipe, if underdrain penetrates perimeter (gravity system). Use
nanufacuuer's r^toomm-.idei method for bonding PVC liner and sealing to four inch (4')
underdrain. Underdrain is installed with slots facing up. Provide and cover stub-out for
later connection to leachfield, if a gravity system.
6. Install additional boot flanges and pipe stub-ins to interior of filter at correct elevation.
Install boot flanges for pressure inlet, air line, and any other required transitions. Relieve
perimeter insulation at pipe transition areas.
7. Place layer of washed three quarter to one and one half inch (3/4" to 1-1/2") septic round
rock around and two inches (2') over the underdrain to prevent pea gravel and finer
material from entering slots. Remaining sand and gravel elevations are marled arled on
interior walls of the liner before adding materials.
S. Place six inches (6") of pea gravel. Level ± one half inch (0.5"). Place fill around
outside perimeter of framing as necessary to avoid "blow-out' of the firming sidewalls.
9. Place six inches (6") filter sand. Level to ± one half inch (0.5'). Place fill around.
outside perimeter of filter as necessary.
10. Place air diffuser line. Penetrate and seal to previously installed boot flario . Lay air
diffuser line in a concentric spiral with approximately one foot (1') separation between
passes. Use sand piles to hold the position of the air line. Seal end of the air line with a
brass compression fitting.
11. Plate remainder of twenty-four inch (24") total filter sand layer. Sand is placed damp to
allow for compaction. Wet sand if necessary and place in six inch (6') lifts, do not
mechanically compact Level sand surface with six foot (6') carp.—iters level and a
straight edge. Place monitor tubes on said surface. Place fill around perimeter frzining
during filling to help support the frame shape.
12. Place two inches (2") of pea gravel over top of sand to support distribution system. Install
pressure lints, manifold, and flush valves. Connect to pressor effluent line from septic
tank through boot flange.
13. Fill septic tank with clean water and conduct pressure test. Verify minimum squirt height
of four feet (4') and check for leaks in pressure piping. Verify trickle hole in tank end of
pressure line allows drain back of pressure line
14. Install snap on orifice shields, and cover piping with remaining three inches (30) of pea
gravel. Level to one half inch (0S').
15. Extend six inch (6") monitor tubes, let zl cl- -outs and valve boxes, and add pump basin
riser, if necessary. All risen s'rall extend above finished grade. Install two inch (2") 35
psi burial foam insulation and standpipe- covers before placing fill. Cover iisulation with
approved filter fabric material, relieved to fit monitors and standpipes. Hand fit gzslwu
made of filter fabric around standpipe penetrations to provide an eff=dve silt barrier.
16
Install two inch (2") 35 psi burial foam in sump risme lid. Attach with construction
adhesive.
16. Place unclassified fill over sand filter utilizing excavator. Do not drive on or over filter
bed with maa'urayor w :•-Fstabiish rough grading:. Ins'...I1 gravity or pressure line
to ka--hfield, if applicable. Compiwrnnection znd pressure test line before backfilling.
17. Install thee- inches (3") topsoil and establish finish grade. Fertilize and seed.
C. LeachfieId
Install leachfi-eld using the same materials, twhniques and tolerances required for conventional
leaching syst-.nes. Referenx AMC Code 15.65..
D. Electrical
The electrical portion must be i^stalled and insp.--ted by a locally licensed els: tricfan. It is
recommended that elwtrical service work be coordinated in advance to allow testing of the
controls and electrical panel during the squirt test. The electrician shill be responsible for
obtaining the proper inspections and a copy of the inspection report shall be submitted to the MOA
with the system asbuilts.
17
IV. OPERATION OF THE ISF
The ISF system has a simple operating sequence requiring little attention besides the regulation
of water use. Families with exp----nm=t-,l versions in Anchorage experienced o,:—msional high
coater alarms and probably rationed coater use more than needed at other times. The ISF system
pumps a specified amo.mt at regular time intervals, normally six to 10 gallons every 30 minutes.
If the septic tank received an inflow of seccage which exceeds the capacity of the dosing pump by
more than 80 gallons, the high mater alarm will sound to notify the owner that they need to reduce
water use. The system works effectively when the occupant can control coater usage by
distributing the Rater demand over the full day. Concentrated water use such as laundry should
be done on alternate afternoon or evenings to avoid a high water alarm. Average daily flows for
the test homes gradually increased during the test period due to the adaptation made by the system
users from a holding tank to leaching systems.
Whet a high coater alarm is encountered, coater use must be sharply curtailed for as long as needed
to provide ample drawdown. The alarm is silenced by pushing the button on the control panel.
If the alarm sounds and operator knows that inflow has been minimal, or suspects any other
problem, a technician should be consulted as there may be an uncontrolled water usage such 25
a leaking toilet valve.
The same general rules of use for any on-site septic system apply to the ISF. Care should be
taken to prevent undesirable substances from entering the septic tank. Septic tank additives are
not recommended, nor is pumping mor_ frequently than every two y -.ars. Low phosphate
detergents minimize adverse affa^ts on the system.
is
VII. MAINTENANCE
A. . Monthly Items -
1. R=d pump ehpsed d= m -e ear and pumping event counter.. Compute the.zverage daily
. pamping time and number of events per day for each month. Compare number of evens
per day to number of evens computod for previous month. Compare daily pumping time
since last checked interval. Any inconsistency in numbers should be investigated. Be
familiar with the timer set-up and determine if acetal evens and elapsed time are
reasonable.
2. Monitor the filter bed and verify that no water is ponding in the six inch (6-) monitor
tubes. It is important to detect any ponding as early as possible to prevent anaerobic
conditions and eventual &lure of the filter. Obtzm the assistance of a quzlif--d t=hnician
or engineer if ponding occurs.
3. Verify that Levels in tank and ISF pump baan Cif so egstip-- ) zee near their normal Levels,
and that float switches are not entangled.
4. Verify operation of the air pump and delivery pressure.
B. Annual Items
1. Perform flushing of pressure dosing lines in the ISF. This is accomplished by op -ening the
flushing valve located in the filter field.
2. Perform pressure check on ISF pressure lines utilizing a pressure gauge attached to
pressure lat ntl end. If p.--=ine is too high, clean pr -issue lines with a bottle brush or jet
cleaning device, and re -test.
3. Remove STEP system filter bzslWt and clean one eighth inch (1/8') mesh s= -.-n with a
high pressure hose.
4. Remove, clean and inspect the air cleaner element on the top of the air pump.
C. BiannuA Uaiaten2nce Items
1. Pump septic tank and I=p file copy of receipts to satisfy MOA requirements.
2. Monitor levels of effluent in leachfield.
19
VIII. SUAOL.4RY
Use of an In# mitr=t Sand Filter aM may allow development of prop -.sties which do not have
conditions suitable for conventional leachfield disposal systems. The ISF may also allow
upgrading of properties currently utilizing folding =Ii to an on-site leaching system. For design
purposes, the following benefits are realized:
1. Reduction of required separation distance from the bottom of the leachfield to
groundwater table and bedrock For a leachfield servicing an ISF, groundwater
separation may be waived from the required four feet (4') to two feet (2') from the
seasonal high, and bedrock or impermeable strata separation distance may be
waived from the required six feet (6') separation to four feet (4').
2. Thr, ISF produce a much higher quality effluent, desirable for higher population
densities or waiver situations.
3. I.eachfields serving an ISF are much smaller than a standard leachfield, requiring
less usable lot area.
Although - of the ISF provides design flexibility, there are inherent drawbacks associated with
the basic operation and complexity of the system. The following disadvantages may apply:
1. inflow of effluent has an absolute limit based on regular, timed pumping cycles.
Surge capacity is limited to that provided in the septic tank lift station. Intenal
pumping over 24 hours provides a reserve only during the morning hours. This
may forte the suers to ration or schedule water use.
2. Cost of the ISP system is significantly higher than conventional systems.
3. Adaptation of the ISF system to Alaslam climate conditions requires a more
extensive design process, intensive inspection during construction, and a regular
program of monitoring and maintenance.
4. Operational history of the ISP in Anchorage is limited.
Studies are currently in progress to determine the most effective sand media size and optimum
dosing techniques to improve filter effluent quality. Long term monitoring of the Anchorage area
filters may result in the ISF being considered a conventional design for DEES approval.
20
APPENDIX
INDEX
1.
Sand Filter with Pump Di=h=gr
2.
Sand Filter with Gravity Disch-,rgz
3.
Profit- Drauing - Sand Filter Kith Putnp Discharge
4.
Profile Draviing - Sand Filter with Gravity Discharge
5.
Sample Basin Detail
6.
Table I = Lot 140 Op==zting Record
7.
Chart I - Lot 140 Temperature Profile
S.
Table II - Lot 8, Shenendoah Operating Rxord
9.
Chart H - Lot 8, Shenendoah Temp=zture Profile
10.
jns»aWon photos - Lot 8, Shenendoah
21
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DWGJ94-055$ -DATE: -1 18 95 I SCALE: N.T.S.
L-AEAGLE RIVER ENGINEERING SERVICES
P.O. Box 773294.
EAGLE RIVER, AK. 99577
(907) 694-5195 FAX: (907) 694-3297
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DWG�'94-055A DATE: 1 18 95 I SCALE: N.T.S.
EAGLE RIVER ENGINEERING SERVICES
P.O. Box 773294
EAGLE RIVER, AK.' '98-077
(907) 694-5195 FAX: (907) 694-3297
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