34 GROSS POLLUTANT TRAPS - Water
34 GROSS POLLUTANT TRAPS34.1PURPOSE AND DEFINITION. 34-134.2PLANNING CONSIDERATIONS . 34-134.334.434.534.2.1Location. 34-134.2.2Planning Issues. 34-1CLASSIFICATION OF GROSS POLLUTANT TRAPS . 34-234.3.1Floating Debris Traps . 34-234.3.2In-Pit Devices . 34-334.3.3Trash Racks and Litter Control Devices . 34-334.3.4Sediment Traps. 34-434.3.5'SBTR' type GPTs . 34-434.3.6Proprietary Traps . 34-5GENERAL DESIGN CONSIDERATIONS . 34-534.4.1Data Collection. 34-534.4.2Hydrology . 34-534.4.3Design Criteria . 34-734.4.4Hydraulic Design. 34-734.4.5Ease of Maintenance . 34-734.4.6Health and Safety . 34-7DESIGN OF SBTR TRAPS . 34-734.5.1Design Standard . 34-734.5.2General Design Parameters . 34-834.5.3Size Calculation. 34-834.5.4Special Design Considerations . 34-1134.5.5Design of Trash Rack for an SBTR Trap . 34-1134.5.6Structural Design . 34-1234.5.7Vehicular Access . 34-1234.6PROPRIETARY DEVICES. 34-1334.7MAINTENANCE . 34-1334.7.1General Maintenance . 34-1334.7.2Maintenance Provisions . 34-14Urban Stormwater Management Manual34-i
Gross Pollutant TrapsAPPENDIX 34.A DESIGN CHARTS FOR 'SBTR' TYPE GPT.34-1534.A.1Average Sediment Retention against Area Ratio R .34-1534.A.2Soil Type Adjustment Factors F1 and F2.34-16APPENDIX 34.B PROPRIETARY GROSS POLLUTANT TRAPS .34-1734.B.1List of Available Devices.34-1734.B.2Sources of Further Information.34-23APPENDIX 34.C RELATIVE EFFECTIVENESS OF GROSS POLLUTANT TRAPS ANDOTHER BMPs MEASURES.34-24APPENDIX 34.D WORKED EXAMPLE .34-2534-iiUrban Stormwater Management Manual
Gross Pollutant Traps34.1PURPOSE AND DEFINITIONGross pollutant traps (GPTs) remove litter, debris andcoarse sediment from stormwater. Some designs alsoprovide oil separation. These substances are collectivelyreferred to as Gross Pollutants.Gross Pollutant Traps may be used as the pretreatment forflow into a pond or wetland to confine the area ofdeposition of coarse sediments.This facilitates theeventual removal of finer sediments. Traps may also beused to keep coarse sediment out of ponds, protecting thevegetation at the head of the pond from the smotheringeffects of sediment. Traps may also be used to removecoarse sediment before the flow enters an infiltrationdevice or filtration device, which would otherwise clog upprematurely.GPTs may also serve the purpose ofcapturing floatable oil, provided that they are designedappropriately.The traps provide little, if any, flow attenuation.Most GPTs will also provide some reduction in otherpollutants. For example, trapping of coarse sediment mayalso provide: removal of particulate nutrients; trace metal removal; oil and grease removal; reduction in bacteria; and reduction in dissolved oxygen demanding substances.All of the above substances can be partly bound tosediments, and will be removed along with the trappedsediment.Booms and other types of litter traps are also included inthis Chapter. These devices do not provide sedimentremoval.34.2PLANNING CONSIDERATIONS34.2.1 LocationGPTs are provided at the downstream end of drains orengineered waterways which discharge to sensitive rivers,water quality control ponds or urban lakes to reducesediment load, litter, oil and chemicals. Ponds receivingrunoff from highways, parking areas or heavy industrialareas are particularly vulnerable.By themselves, traps do not normally provide sufficientstormwater treatment – they should be used in conjunctionwith other treatment devices. Chapter 10 provides anoverview of 'treatment trains'.34.2.2 Planning IssuesA decision needs to be made between centralised anddispersed trapping strategies (see Figure 34.1). Thiswould normally be done at the Master Planning stage – seeChapter 9. In general, large central traps are less suitablefor staged development and are more difficult to clean andmaintain.inMainMaDevelopmentATYPE pmentBTYPE 2SBTRsRiver(a) CentralisedFigure 34.1Urban Stormwater Management Manual(b) DispersedCentralised and Dispersed Trapping Strategies34-1
Gross Pollutant TrapsCurrent overseas practice appears to favour the use ofsmaller underground devices, which can be located inroads, footpaths or other public areas. Note that thecentralised and dispersed strategies are alternatives – it isnot necessary or cost-effective to provide both.decision support system for GPTs (see Allison et al., 1998).This may be of assistance in selecting the most suitabletypes of traps, however it would require adjustment withlocal data. Contact details for the CRCCH are provided inAppendix 34.B.In Figure 34.1, the Local Authority needs to make adecision whether to adopt Strategy (a) or (b). Thisdecision involves engineering, planning and administrativeconsiderations. Strategy (b) would be favoured if there isexpected to be a time delay between developments (a)and (b), and if the traps are to be developer-funded.Appendix 34.C provides a comparison of the relativepollutant removal efficiencies of different types of GrossPollutant Traps. The traps are also compared with severaltypical housekeeping and educational quality controlmeasures. The final columns give an indication of relativecost per hectare of catchment area, and of relativeeffectiveness.Large open traps may be unsightly and require to belocated away from public areas, screened by landscaping,or covered. Covering involves a considerable increase incost and maintenance complexity.34.3CLASSIFICATION OF GROSSPOLLUTANT TRAPSThere is a very wide range of devices for the treatment ofgross solids. Selection of suitable devices depends onmany factors including catchment size, pollutant load, thetype of drainage system and cost.Table 34.1 provides an overall classification of the types ofGPTs that could be used in Malaysia, and the range ofcatchment areas for which they are suitable.Thisclassification is followed in the text of this Chapter.No information is available on construction and operatingcosts of most structural devices under Malaysianconditions. Costs depend on a number of economic andsocial factors, the assessment of which is outside the scopeof this Manual. It is expected that over time, informationwill be compiled to allow comparative cost assessments tobe undertaken.34.3.1 Floating Debris Traps(a)BoomsBooms are used primarily on streams and rivers wherethere is permanent water. Booms have been used inMalaysia, including on Sg. Klang for more than ten years.The Australian CRCCH (Co-operative Research Centre forCatchment Hydrology) markets a spreadsheet-basedTable 34.1GroupOverall Classification of Gross Pollutant TrapsDescription and FunctionCatchmentArea RangePurpose-built orProprietaryDetails inSectionFloating DebrisTraps (booms)Litter capture on permanentwaterbodies 200 haProprietary34.3.1In-pit devicesLitter and sediment capture inexisting pits0.1 – 1 haProprietary34.3.2Trash Racks &Litter ControlDevicesHard or soft litter capture devices ondrains2 – 400 hausually purpose built frommodular components34.3.3Sediment TrapsSediment removal only, on drains 200 haPurpose built34.3.4'SBTR' TrapsSediment and litter capture fordrains or pipes5 – 2000 haPurpose built34.5Proprietary devicesRange of devices, mainly for pipes2 – 40 haProprietary34.634-2Urban Stormwater Management Manual
Gross Pollutant TrapsBooms are only effective as a pollution control measureunder certain conditions. The requirements for a suitablesite include (Willing & Partners, 1989): favourable currents, location relative to major sources, such as tributarystormwater drains, access for maintenance, ability to handle the effects of water level changes, suitable locations for attachment and anchorage, no interference to river traffic.Booms are generally not effective unless there is a steadycurrent to force trapped material into the boom. Tidal flowreversals or strong adverse winds may disperse thetrapped material, rendering the boom ineffective. TheBandalong Trap, discussed below, aims to overcome thisproblem.Installation of the boom will mainly be governed by siteconditions. Sufficient slack must be provided to allow theboom level to rise and fall with tide and/or flood waterlevel variations.The material collected in urban areas includes potentiallyoffensive, hazardous or infectious wastes includingdiscarded syringes which necessitates the implementationof arrangements for mechanical cleaning.Nielsen and Carleton, 1989 concluded that the decision toinstall a boom or a trash rack was governed by a numberof factors including:(i)the type of trash to be collected. Booms were foundto be effective in retaining both smaller floating andpartially submerged objects and larger objects.(ii) hydraulic considerations.The trash retainingperformance of booms decreases at higher flowsbecause trash is forced under and over them. Theminimum flow velocity at which trash escapes bybeing forced underneath a boom depends largely onthe weight of the boom and has been observed to beas low as 1 m/s.(b)Bandalong TrapBandalong traps are a type of floating boom for collectedlitter and debris being transported in rivers, streams andestuaries. The trap is typically moored to the bank of astream, river or canal. In plan view the trap is "fish"shaped with floating litter and debris being funnelled (viathe tail) into the main body of the trap where it is caught.A floating gate at the throat of the entry closes when a tidereverses direction to ensure that floating debris is retained.These traps originated in Australia where a number havebeen installed on rivers and urban creeks.Urban Stormwater Management Manual34.3.2 In-Pit DevicesThese litter and sediment traps are located in inlet pits.While their effectiveness is limited, they are economical touse in locations where they can be installed in existing inletpits.The application of inlet pit traps in Malaysia is likely to belimited, at least in the near future, as most of the existingurban drainage systems do not have inlet pits.(a)Trap Gully PitsTrap gully pits are deeper than standard pits to storetrapped sediment. Some designs also direct flows beneathan underflow weir to trap floating trash and debris. InNorth America they are known as ‘catchbasins’.Trap gully pits are of course only useful where thedrainage system contains pits – i.e. a piped system. Theireffectiveness is limited because of the tendency for highflows to entrain and wash out the collected sediment andlitter.(b)Litter BasketsSeveral local authorities in Australia, including NorthSydney Council and Banyule City Council in Victoria, havedeveloped simple perforated or mesh baskets that areinstalled in existing side entry pits to collect leaves andlitter. The size of the basket is chosen to suit the existinginlet pit dimensions: baskets are smaller than the sideentry pit area so when the baskets clog or fill with litterstormwater overflows the edge of the basket thus reducingthe risk of flooding. Their low cost and easy installationmake them attractive in existing piped drainage systems.Materials can be either plastic or steel. This type of deviceis mainly intended for pipe systems.34.3.3 Trash Racks and Litter Control DevicesA variety of trash racks have been trialled in severallocations in Australia. The trash racks have ranged fromrelatively small screens installed at the outlets ofstormwater pipes to large steel trash racks on rivers andopen channels and more recently "soft" trash racks (littercontrol devices) that are installed in open channels and atthe outlets of piped drains.(a)Trash RacksSince 1979, fixed steel trash racks have been installed inthe stormwater drainage systems in the ACT (AustralianCapital Territory) to trap trash and debris. The trash rackarrangement, which has evolved over recent years, is avertical trash rack with vertical bars at 60 mm centres. Arange of trash racks has been trialled (Figure 34.2). It hasalso been suggested by a number of researchers that atrash rack with horizontal bars set at an angle to the flow34-3
Gross Pollutant Trapsshould be self-cleansing, since the flow would push debristowards the sides of the rack. The effectiveness of suchan approach would appear to depend on the shape andsurface finish of the bars and their angle relative to theflow.(c)Fish Net (Net Tech) DeviceThe Fish Net (Net Tech) device consists of a frame thatinstalled on a pipe headwall with a net “sock” attached.The sock fills with litter until it becomes so full that arelease is triggered and the sock is released. While thesock is still attached to the unit it ties itself and falls free ofthe stormwater flow (subject to there being sufficient roomfor the sock to be displaced away from the stormwaterflow). After the sock is cleaned it is re-attached to itsframe.34.3.4 Sediment TrapsSedimentation traps function by providing an enlargedwaterway area and/or reduced hydraulic gradient toreduce flow velocities and allow bedload sediment to betrapped and suspended sediments to settle out ofsuspension. They do not provide litter removal.Figure 34.2Trash RackNielsen and Carleton, 1989 also undertook laboratory teststo try and establish the necessary conditions for trashracks to be self-cleansing. The laboratory investigationfailed to identify a self-cleansing design.Design principles for fixed trash racks are the same asdescribed under SBTR-type traps, in Section 34.5.5.(b)Prior to the late 1970s, a number of sedimentation basinswere constructed in Australia (primarily the ACT) usingprimarily gabions or masonry walls to create unlinedsedimentation ponds. Difficulties were experienced in dewatering and de-silting these structures.Until theconstruction of a series of GPTs and water pollution controlponds upstream of the pond, it also acted as asedimentation basin.The design of sediment traps is not covered in detail in thisManual, as they would mainly be used outside urban areas.In urban areas, the presence of litter makes it preferableto build a 'SBTR'-type GPT.Litter Control Devices34.3.5 'SBTR' type GPTsMore recently a number of litter control devices have beeninstalled in open channels and at the outlets to pipeddrains in Australia. These devices collect litter, as do trashracks, and they therefore can be described as "soft" trashracks. "Soft" trash racks are a series of nylon mesh"socks" which are attached to a rectangular metal framethat is mounted vertically and perpendicular to the flow.The "sock" is laid out downstream of the metal frameparallel to the direction of flow. A series of these socks aremounted side by side across a channel to form a "soft"trash rack. The nylon socks have been found to effectivelycapture and retain floating litter, debris and vegetativematter. The litter and debris is captured in the "socks" andis retained even if the trash rack is overtopped.The socks are cleaned by removing each sock in turn,undoing the tie at the base of the sock and dumping thecollected material into a truck. The base of the sock isthen re-tied and it is slotted back into place. Due to theeffectiveness of the socks it has been found that duringperiods of rainfall that the soft trash racks may need to becleaned every two to three days.34-4SBTR traps combine the functions of a Sedimentation Basinand a fixed Trash Rack. The device is named after theinitial of the two components. 'SBTR' type traps havepreviously been referred to in some literature as GPTs.The difficulties in de-watering and de-silting thesedimentation basins in Canberra led, in 1979, to theconstruction of the first major SBTR trap in Canberra,Australia. The trap was a major concrete lined basin thatwas designed to both intercept litter, debris and coarsesediment during storm flows and to act as an efficientretarding basin. This trap drew on the previous experienceof sedimentation basins but also incorporated additionalfeatures to intercept trash and debris. It marked thecommencement of the development and refinement ofgross pollutant traps in Australia.The on-going development of SBTR type traps in Australiahas focused on improving these facilities for ease ofmaintenance and simplifying the design elements to reducecapital costs.Urban Stormwater Management Manual
Gross Pollutant TrapsFigure 34.3Major SBTR (Type 1) traps are typically located in majorchannels and engineered waterways to intercept mediumto high stormwater flows from large urban catchments.They are visually unattractive and generally should beplaced away from residential areas, or screened (seeFigure 34.3).Covered in-ground (Type 2) traps are used at thedownstream end of pipe or open drains. They are lessvisually intrusive and hence are more suitable forresidential or urban areas. Due to the cost of the structurethey are usually smaller in size than Type 1 traps and areonly suitable for treating small catchment areas, mainly onpipe drains.Indicative ‘standard’ arrangements for Type 1 and Type 2SBTR traps are given in Figures 34.4 and 34.5,respectively. Many design variations are possible to suitsite conditions. Design principles for the SBTR type trapsare discussed in Section 34.5.34.3.6 Proprietary TrapsThe realisation that large numbers of traps are needed tocontrol water pollution has led to commercial developmentof a range of devices for trapping gross pollutants.Some of the proprietary GPTs that are currently availableoverseas are described in Section 34.6.Urban Stormwater Management ManualType 1 SBTR Trap34.4GENERAL DESIGN CONSIDERATIONS34.4.1 Data CollectionDesign of GPTs requires data on: Catchment area, Hydrology of inflows, Survey details of the site, Hydraulic conditions at the GPT outlet, which maycreate tailwater, Soil type, and Estimates of sediment loads and other pollutantloads from the catchment.34.4.2 HydrologyPeak inflows shall be computed using the Rational Methodor one of the hydrograph methods in Chapter 14.Normally these calculations will be done as part of thehydraulic design of the drainage system. The shape andvolume of the hydrograph is not important for GPT design.The magnitude of sediment and other pollutant loads willdetermine the frequency of cleaning.Pollutant loadcalculations, if required, can be performed using themethods described in Part D, Chapter 15.34-5
Gross Pollutant Traps34-6Figure 34.4Type 1 SBTR Trap ConfigurationFigure 34.5Type 2 SBTR Trap ConfigurationUrban Stormwater Management Manual
Gross Pollutant Traps34.4.3 Design CriteriaFor each GPT, albeit as part of a "treatment train", aprimary treatment objective or performance criteria relatedto a specific pollutant shall be ascribed. This is the targetpollutant that is to be reduced to a nominated level.34.4.4 Hydraulic DesignThe GPT must be designed so as to prevent any additionalsurcharge in the stormwater system in the event of partialor complete blockage. Tidal influence and backwatereffects must be considered. Refer to Chapter 10 and 16for a discussion of stormwater system design.The pollutant reduction performance must be maintainedup to the design discharge. If design flows are exceeded,the GPT should not allow any significant re-mobilisation oftrapped material.34.4.5 Ease of MaintenanceSediment must be removed from the traps on a frequentbasis. In the past, the design has often not allowed foreasy cleaning. Problems with cleaning can be partlyovercome by appropriate design.Maintenance considerations should be addressed duringthe preliminary design stage of a GPT, to ensure: Sudden drops into deep water; Sudden changes in flow velocities or water levels; and Raised structures that children can fall off.Therefore GPTs should be fully enclosed if possible, orfenced off. Such fencing should be designed so that itdoes not interfere with the hydraulics of the flow structure.Provision shall be made to minimise mosquito hazard asfollows: keeping the sediment trap wet with a low or trickleflow; or using biodegradable slow release larvicides (note: fullenvironmental impact assessment of the larvicidewould be needed prior to the adoption of thisalternative).34.5DESIGN OF SBTR TRAPSThe Type 1 SBTR traps are designed as open traps onlarge, open channels or engineered waterways where theyare installed at or below ground level.The Type 2 SBTR trap is enclosed, and is installed belowground. Type 2 traps are intended for pipe drainagesystems.SBTR traps permit coarse sediment to settle to the bottomby decreasing the stormwater flow velocity by increasingthe width and/or depth of the channel. cost effective maintenance; maintenance staff to follow occupational health andsafety procedures. This includes the avoidance, wherepossible, of entry by personnel into the device; avoidance of direct human contact with debris andtrapped pollutants; minimisation of environmental impacts duringmaintenance (e.g. the disposal of water in the GPT);34.5.1 Design Standard avoidance of the necessity for routine tenance (e.g. unblocking the outlet structure)may be required;The 'SBTR'-type GPTs should be designed to retain all litterand debris in the water quality design storm of 3 monthARI, and to comply with the size requirements in DesignChart 34.1. monitoring the pollutant build-up to enablemaintenance before the GPT becomes overloaded; provision of disposal facilities for debris and liquidpollutants during maintenance; and provisionforadditional,non-programmedmaintenance if problems arises (e.g. odours).Adequate provision for road access to the site bymaintenance vehicles and equipment must be made.Suitable walkways, ladders and plinths shall be providedwithin the structure for access.34.4.6 Health and SafetyThe trash rack is intended to collect floating andsubmerged debris. Experience has shown that it should belocated at the downstream end of the sediment trap.Traps designed according to these criteria are expected toremove, on an annual average basis, 70% of the sedimentwith a grain size 0.04 mm. This sizing criterion may notbe attainable in the case of very fine-grained soils (siltsand clays). A further discussion of sizing criteria is given inChapter 4.The pollutant removal efficiency η of a trap is calculatedas: AMC proposedη AMC existing (34.1)Open GPTs can present a hazard because of:Urban Stormwater Management Manual34-7
Gross Pollutant TrapsTable 34.2where AMC annual mean concentration.Thedetermination of average annual load and annualvolumetric runoff will be normally be required to obtainAMCs (annual mean concentration) for the existing andproposed situations. Methods of doing this calculation aredescribed in Chapter 15. Alternatively, computer modellingmethods can be used as described in Chapter 17.Grain Size (mm)% finer0.004120.01250.063600.30921.1810034.5.2 General Design ParametersThe 'SBTR' trap relies on reducing the flow velocitysufficiently to allow settling by gravity. These principlesapply to both Type SBTR-1 (major) and SBTR-2 (minor)traps.Grading of Reference Soil used in GPTDesign ProcedureSediment Trap1.Determine the required removal efficiency of coarsesediment 0.04mm diameter, P0.04*.Velocity though the sediment trap should not exceed1.0 m/second, to minimise re-suspension.2.For a sediment trap volume greater than 5 cubicmetres, a sediment drying area with a minimum areaequal to 1.5 square metres for each cubic metre oftrap volume shall be provided, where sediment maybe dried prior to transportation. The area shall besurfaced with 300 mm of compacted gravel or otherapproved surfacing;Determine the catchment area Ac (m2) served by thesediment trap and the applicable degree ofurbanisation [U] within that catchment. Allow forfuture catchment development, if appropriate.3.Select a trial trap area ratio R: Bar spacing shall be capable of retaining a smallplastic bottle or an aluminium drink can, with amaximum clear spacing of 50 mm between bars;4. Trash racks shall be sized to operate effectively whilstpassing the design flow without overtopping and with50% blockage; Trash racks shall be structurally stable whenovertopped by flood events up to the major designstorm when fully blocked; The ratio length: width of the sediment trap should bebetween 2 and 3. Trash racks and their supporting structures shall bedesigned to withstand log impact together with dragloads or debris loads (100% blocked); and The design must allow water to flow past or over thetrash rack when the trash rack is blocked. Vehicular access must be provided for maintenance, inaccordance with Section 34.5.7.34.5.3 Size CalculationThe sediment basin size is determined using the followingprocedure. A flowchart of the procedure is given inFigure 34.6.The procedure was developed for a ‘Reference Soil' whichis a silty loam. The grading of the Reference Soil isdefined in Table 34.2. The efficiency of the trap will varywith soil type. Adjustment factors for different soils aregiven in Design Chart 34.2 in Appendix 34.A. The chartshows typical soil gradings and the relevant adjustmentfactors FA and FV.R AtAc(34.2)Find P0.04 for the reference soil from the appropriateDesign Chart 34.1 in Appendix 34.A, and Factor F1from Design Chart 34.2. Calculate actual trap removalefficiency for the site soil:P0.04* P0.04 F 1(34.3)Adjust R if necessary by trial and error to obtain therequired performance.5.Select the length Lt (m) and width Wt (m) of thesediment trap to give the required area At such thatthe length to width ratio is between 2 and 3 and thewidth is not less than 2 metres.Depth of the Sediment Trap6.Determine the average annual export M (tonne) ofsediment with grain size 0.01 mm from equations inChapter 15.7.Determine the average annual percentage retentionP0.01 of sediment 0.01 mm for the reference soilfrom the applicable Curve B in Design Chart 34.1 forthe selected trap area ratio (At /Ac). Then determinethe adjusted average annual percentage retentionP0.04* of sediment 0.01 mm from the equation:P0.01* P0.01 F 2(34.4)where,F2 Factor from Design Chart 34.2.34-8Urban Stormwater Management Manual
Gross Pollutant Traps1. Determine required % removal1. Determine required % removal2. Determine catchment area,2.urbanisationDetermine catchmentarea,%and soil type% urbanisation and soil typeAdjust R asrequired3. Select trap area ratio R3. Select trap area ratio R4. Determine average annual retention4.sedimentDetermineaverage annualretentionof 0.04mmfrom Designof sediment 0.04mmCharts34.1, 34.2from DesignCharts 34.1, 34.25. Select trap length, widthand area At Lt x Wt6. Determine average annual sediment6. Determineaverageseeannualsedimentexportfrom catchment,Chapter15export from catchment, see Chapter 157. Determine average annual retentionDetermineaverage annualretentionof7.sediment 0.01mmfrom Designof sediment 0.01mmCharts34.1, 34.2from DesignCharts 34.1, 34.2No8. Determine dep
34.3.3 Trash Racks and Litter Control Devices A variety of trash racks have been trialled in several locations in Australia. The trash racks have ranged from relatively small screens installed at the outlets of stormwater pipes to large steel trash racks on rivers and open channels and more recently "soft" trash
means of a thermo drain or pop drain. Also, when multiple traps are installed in a trap station, insulating the traps can provide freeze protection. Thermo Drains are installed in a Tee ahead of 200 Series traps or replace the drain plug directly in the body of specially machined 800 Series traps
types of traps: swim-in bait traps, swim-in bait traps with de- coys, floating bait traps, and decoy traps. Most of the ducks were captured in the spring with Mallard the most numerous species followed by Blue-winged Teal and Wood Duck. Trap- ping mortality averaged 4.5% with mink and raccoon respon- sible for most known causes of death. METHODS
Fish are breed in spawning traps. There are two different types of traps, 1.5-liter transparent traps that can be used to spawn up to 8 fish per trap and 2-liter opaque traps that can hold 12 fish. In H221, clean traps are located below the workspace in the center of the laboratory. In
TRAPS LITE wasn't my idea. I wanted to do HEAVY METAL TRAPS, a collection of all those SIX-skull traps they wouldn't let me print in my previous four books. I was ready to kick butt and take names. I figure you're ready for it. But, noooooooooo. the publishers are stuck on this TRAPS LITE notion, and there'
GIS Pollutant Loading Application— Users Manual 1. Pollutant Loading Application Overview PLOAD is a simplified, GIS-based model to calculate pollutant loads for watersheds1. PLOAD estimates nonpoint sources (NPS) of pollution on an annual average basis, for any user-specified pollutant. The user may calculate the NPS loads using either the .
¾ Two or more traps placed next to each other will capture more mice than single traps. 44. ¾ Probably the biggest mistake made in mouse trapping is not using enough traps. Use enough to quickly eliminate the mice. ¾ Great care must be taken to place traps out of the public view and to check them regularly.
Outlet Fittings, Flash Arrestors and Check Valves 85 Cylinder Brackets 86 Bottle Holder 89 PIGTAILS 90 TRAPS 92 Moisture Traps 94 Oxygen Traps 96 Hydrocarbon Traps 97 Gas Purifiers 98 Micron Filters 99 Gauges 100 MEDICAL EQUIPMENT 101 Model 301/1501 102 Model 301P/301 103 Model 25P/25 104
on the two sites. Of these, 55 were captured in traps with a dead rabbit (63%), and 32 were captured in traps with a live rabbit. Of the 13 radio-collared female ferrets available on both sites, 10 were captured. Seven (70%) were captured in traps using dead rabbit as a lure, and three were captured in traps using live rabbit as a lure.
