HomeMy WebLinkAboutD_Korean_Antioch_Presbyterian_Church_CAE_1701_NE_3rd_St_20240205_FINDEPARTMENT OF COMMUNITY
AND ECONOMIC DEVELOPMENT
D_Korean_Antioch_Presbyterian_Church_CAE_1701_NE_3rd_St_20240205_FIN
PLANNING DIVISION
CERTIFICATE OF EXEMPTION
FROM CRITICAL AREAS REGULATIONS
EVALUATION FORM & DECISION
DATE OF DECISION: February 6, 2024
PROJECT NUMBER: LUA24-000035, CAE
PROJECT NAME: 1701 NE 43rd St Critical Areas Exemption
PROJECT MANAGER: Mariah Kerrihard, Assistant Planner
APPLICANT: Paul Chang
7450 SE 32nd St. Mercer Island, WA 98040
OWNER: Korean Antioch Presbyterian Church
4242 Jones Ave NE Renton, WA 98056
CONTACT: Same as Applicant
PROJECT LOCATION: 1701 NE 43rd St. (APN 3345700059)
PROJECT DESCRIPTION: The applicant seeks approval for a Critical Areas Exemption to facilitate the
maintenance and repair of a broken existing water line on the property situated at 1701 NE 43rd St (Parcel
Identification Number 3345700059). This property falls within a critical area buffer, with the wetland located east
of the subject property and a Type F stream located within unimproved right-of-way north of subject property.
Spanning 102,610 square feet (2.36 acres), the property is within the Commercial Arterial (CA) Zone and Urban
Design District D. It currently houses a religious institution and an associated surface parking lot, accessible via
Jones Ave NE and NE 43rd St.
The applicant has provided documentation from the Washington Department of Fish and Wildlife, along with a
scope of work as part of the master application. The proposed scope of work entails using sandbags to block the
waterway on the west side of the culvert. A sump pump will be employed to drain stream water towards the
existing wetland. Following the drying of the stream bed, a minimum 12-inch trench will be manually dug with a
shovel at the location of the broken water line. Once the repair is complete, the sandbags will be removed, and
everything will be restored to its original state.
Per the Washington Department of Fish and Wildlife (see attachment 4), any diversion device utilized for water
extraction from a lake, river, or stream must be equipped with an approved fish guard to prevent fish passage into
the diversion device, even during temporary water removal (RCW 77.57.010). This guidance provides general
direction for biologists and contractors using water pumps at construction sites, with site-specific conditions
determining its application. The need for pump screens to prevent fish entry may be waived if the supervising
DocuSign Envelope ID: D81771B8-A652-4AD0-B4EA-53C45E9816B0
City of Renton Department of Community & Economic Development Certificate of Exemption From Critical Areas Regulations
1701 NE 43rd St Critical Areas Exemption LUA24-000035, CAE
Permit Date: February 6, 2024 Page 2 of 3
D_Korean_Antioch_Presbyterian_Church_CAE_1701_NE_3rd_St_20240205_FIN
biologist deems fish removal adequate, ensures no threat to fish life, and maintains proper work site isolation and
fish exclusion mechanisms such as coffer dams, block nets, etc., within the work area.
CRITICAL AREA: Wetland and Stream buffers
EXEMPTION JUSTIFICATION: Renton Municipal Code (RMC) 4-3-050 Critical Areas Regulations:
RMC 4-3-050C.3.e.ii Roads, Parks, Public and Private Utilities - Maintenance, Operation, and Repair of existing
Parks, Trails, Roads, Facilities, and Utilities (Emphasis added), and the Construction of New Trails
RMC 4-3-050C.3.f.i. Temporary Wetland Impacts.
FINDINGS: The proposed development is consistent with the following findings pursuant to RMC section
4-3-050C.2.d:
i. The activity is not prohibited by this or any other provision of the Renton Municipal
Code or State or Federal law or regulation;
Staff Response: The repair of the broken water line is an exempt activity in the City’s
Critical Areas Regulations. The applicant may need separate approval from the
Washington State Department of Fish and Wildlife (WDFW) as the work is in the stream
channel. This certificate does not exempt the applicant from any other agency approvals
needed to repair the water line.
ii. The activity will be conducted using best management practices as specified by industry
standards or applicable Federal agencies or scientific principles;
Staff Response: The applicant has provided guidance for fish screens for construction
dewatering from WDFW. To ensure adequate protection of fish habitat, staff
recommends as a condition of approval the applicant utilize best management practices
and guidance from WDFW applicable for the scope of repair.
iii. Impacts are minimized and, where applicable, disturbed areas are immediately
restored;
Staff Response: See response above.
iv. Where water body or buffer disturbance has occurred in accordance with an exemption
during construction or other activities, revegetation with native vegetation shall be
required;
Staff Response: No vegetation is expected to be removed. Work would occur within the
stream channel for approximately 2-3 hours and then sandbags would be removed and
water allowed to flow toward Lake Washington.
v. If a hazardous material, activity, and/or facility that is exempt pursuant to this Section
has a significant or substantial potential to degrade groundwater quality, then the
Administrator may require compliance with the Wellhead Protection Area
requirements of this Section otherwise relevant to that hazardous material, activity,
and/or facility. Such determinations will be based upon site and/or chemical-specific
data.
DocuSign Envelope ID: D81771B8-A652-4AD0-B4EA-53C45E9816B0
City of Renton Department of Community & Economic Development Certificate of Exemption From Critical Areas Regulations
1701 NE 43rd St Critical Areas Exemption LUA24-000035, CAE
Permit Date: February 6, 2024 Page 3 of 3
D_Korean_Antioch_Presbyterian_Church_CAE_1701_NE_3rd_St_20240205_FIN
Staff Response: No hazardous materials would be utilized for the repair work.
DECISION: An exemption from the Critical Areas Regulations is hereby Approved with Conditions*
and subject to the following conditions:
1. The applicant shall utilize best management practices and guidance from WDFW applicable for the scope
of repair.
SIGNATURE & DATE OF DECISION:
________________________________________ ____________________________________
Matthew Herrera, Planning Director Date
RECONSIDERATION: Within 14 days of the decision date, any party may request that the decision be reopened by the
approval body. The approval body may modify his decision if material evidence not readily discoverable prior to the
original decision is found or if he finds there was misrepresentation of fact. After review of the reconsideration request,
if the approval body finds sufficient evidence to amend the original decision, there will be no further extension of the
appeal period. Any person wishing to take further action must file a formal appeal within the 14-day appeal time frame.
APPEALS: This administrative land use decision will become final if not appealed in writing to the Hearing Examiner
on or before 5:00 PM on February 20, 2024. An appeal of the decision must be filed within the 14-day appeal period
(RCW 43.21.C.075(3); WAC 197-11-680). Appeals must be submitted electronically to the City Clerk at
cityclerk@rentonwa.gov or delivered to City Hall 1st floor Lobby Hub Monday through Friday. The appeal fee,
normally due at the time an appeal is submitted, will be collected at a future date if your appeal is submitted
electronically. The appeal submitted in person may be paid on the first floor in our Finance Department. Appeals
to the Hearing Examiner are governed by RMC 4-8-110 and additional information regarding the appeal process
may be obtained from the City Clerk’s Office, cityclerk@rentonwa.gov.
EXPIRATION: Five (5) years from the date of decision (date signed).
Attachments:
Attachment 1: Master Application
Attachment 2: Site Plan
Attachment 3: Neighborhood Aerial Map
Attachment 4: Washington Department of Fish and Wildlife Fish Screens for Construction Dewatering
cc: None
DocuSign Envelope ID: D81771B8-A652-4AD0-B4EA-53C45E9816B0
2/6/2024 | 11:30 AM PST
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LANDUSEPERMITMASTERAPPLICATIONSQUAREFOOTAGEOFPROPOSEDNON-RESIDENTIALBUILDINGS(ifapplicable):SQUAREFOOTAGEOFEXISTINGNON-RESIDENTIALBUILDINGSTOREMAIN(ifapplicable):NETFLOORAREAONNON-RESIDENTIALBUILDINGS(ifapplicable):NUMBEROFEMPLOYEESTOBEEMPLOYEDBYTHENEWPROJECT(ifapplicable):ISTHESITELOCATEDINANYTYPEOFENVIRONMENTALLYCRITICALAREA,PLEASEINCLUDESQUAREFOOTAGE(ifapplicable):LIAQUIFERPROTECTIONAREAONELIAQUIFERPROTECTIONAREATWOOFLOODHAZARDAREA_______________SQ.FT.0SHORELINESTREAMS&LAKES_______________SQ.FT.0GEOLOGICHAZARD______________SQ.FT.WETLANDS______________SQ.FT.0HABITATCONSERVATION_______________SQ.FT.LEGALDESCRIPTIONOFPROPERTY(Attachlegaldescriptiononseparatesheetwiththefollowinginformationincluded)SITUATEINTHE__________________QUARTEROFSECTION,TOWNSHIPN,RANGE_____W.MINTHECITYOFRENTON,KINGCOUNTY,WASHINGTONAFFIDAVITOFOWNERSHIPI,(PrintName/s)_______,declareunderpenaltyofperjuryunderthelawsoftheStateofWashingtonthatIam(pleasecheckone)thecurrentownerofthepropertyinvolvedinthisapplicationortheauthorizedrepresentativetoactforacorporation(pleaseattachproofofauthorization)andthattheforegoingstatementsandanswershereincontainedandtheinformationherewithareinallrespectstrueandcorrecttothebestofmyknowledgeandbelief.417-----frLSignatureofOwner/RepresntIDateSignatureofOwner/RepresentativeDateSTATEOFWASHINGTON)55COUNTYOFKINGIcertifythatIknoworhavesatisfactoryevidencethatCWA9DPCt(1t’hsignedthisinstrumentandacknowledgeittobehis/hittteTrfreeandvoluntaryactfortheusesandpurp&.bementionedintheinstrument.DatedNotaryPubliclortheStateofWashingtonISACGOIEA[&(5Oe4fNotaryPublicStateofWashingtonNotary(Print):Commission#153572MyComm.ExpiresMay16,2027wwwWWWWMyappointmentexpires:__________________________________________rentonwa.gov/permitservicesIp)jncustomerservice@rentonwa.ov425-430-729410/24/2023IPage2of2DocuSign Envelope ID: D81771B8-A652-4AD0-B4EA-53C45E9816B0
CITYOFRENTONIPERMITSERVICES__CRITICALAREASEXEMPTION(FORSEPAEXEMPTACTIVITIES)INFORMATIONPROJECTNAME:t1-o‘p4k;-:-WAT-Q.p6d.APPLICANTNAME:cH0tPHONE:—9-ic—oCooPARCELNUMBER:,00PROJECFADDRESS9.ePM.4c4T.(1.rroNwABRIEFDESCRIPTIONOFPROJECT:wA-r-ft.IAv’•FPALt-.WORKOCCURSINI]WORKOCCURSINTYPEOFCRITICALAREA:/1vJ?iTLJ(CRITICALAREABUFFERPURPOSEExemptactivitiesprovidedwithaletterofexemptionfromtheAdministratormayintrudeintoacriticalareaorrequiredbuffer(SubjecttoanyconditionsorrequirementsprovidedbytheAdministrator).APPLICABILITYOFEXEMPTIONSThefollowingisagenerallistofactivitiesthatmaybeexemptfromthecriticalareasregulations.MotespecificdescriptionsoftheactivitiesarecontainedintheCriticalAreasRegulations.Someofthelistedactivitiesmaynotbeexemptincertaincriticalareas.ThePlanningDivisionwillevaluateyourequestaccordingtotheCityofRentonCriticalAreasRegulationsinRMC4-3-050C,J,L,andN.IAMREQUESTINGACRITICALAREASEXEMPTIONFORONEOFMOREOFTHEFOLLOWINGACTIVITIESDConservation,Enhancement,andRelatedActivities:•Conservationorpreservationofsoil,water,vegetation,fishandotherwildlife•Enhancementactivitiesasdefinedinchapter4-11RMAD’•Anycriticalarea,bufferrestoration,orothermitigationactivitiesthathavebeenapprovedbytheCityDResearchandSiteInvestigation:•Nondestructiveeducationandresearch•Siteinvestigativeworknecessaryforlanduseapplicationsubmittalssuchassurveys,soillogs,etc.DAgricultural,Harvesting,andVegetatIonManagement;•Harvestingwildfoods•Existing/Ongoingagriculturalactivities’•Removalofdead,terminallydiseased,damaged)ordangerousgroundcoverorhazardoustreeswhichhavebeencertifiedassuchbyaforester,registeredlandscapearchitect,orcertifiedarboristDSurfaceWaterAlteration.NewsurfacewaterdischargesprovidedthedischargemeetstherequirementsoftheStormandSurfaceWaterDrainageRegulations123rentonwa.gov/permftservkesIplannIncustgmrservice@rentonwa.gov1425-430-729410/23/2023IPage1of3DocuSign Envelope ID: D81771B8-A652-4AD0-B4EA-53C45E9816B0
CRITICALAREASEXEMPTIONSHORTFORM•Newormodifiedregionalstormwaterfacilities123•Floodhazardreduction1346)Roads,Parks,PublicandPrivateUtilities:•RelocationofExistingUtilitiesoutofCriticalAreaandBuffer•Maintenance,operation,andrepairofexistingparks,trails,roads,facilities,andutilities12•Installation,construction,replacement,oroperationofutilities,trafficcontrol,andwalkwayswithinexistingimprovedright-if-wayoreasement12•Modificationofexistingutilitiesandstreetsby10%orless125•Managementandessentialtreeremovalforpublicorprivateutilities,roadsandpublicparks’DWetlandDisturbance,Modification,andRemoval•AnyactivityinsmallCategory3wetlands12345•Temporarydisturbancesofawetlandduetoconstructionactivitiesthatdonotincludepermanentfilling1235DMaintenanceandConstructionforExistingUsesandFacilities:•Remodeling,replacing,orremovingexistingstructures12•Normalandroutinemaintenanceandrepairofanyexistingpublicorprivateusesandfacilitieswherenoalterationofthecriticalareaandrequiredbufferoradditionalfillmaterialswillbeplaced12•Constructionactivityconnectedwithanexistingsinglefamilyresidenceorgarage,providedthatnoportionofthenewworkoccursclosertothecriticalareaorrequiredbuffersthantheexistingstructureand/orthedevelopedareaofthesite12•Existingactivitieswhichhavenotbeenchanged,expandedoralteredprovidedtheycomplywiththeapplicablerequirementsofchapter4-10RMC1C]EmergencyActivities:•RemovaloftreesorgroundcoverbyaCitydepartment,agency,public,orprivateutilityinanemergencysituation•Publicinterestemergencyuse,storage,andhandlingofhazardousmaterialsbygovernmentalorganizationsinanAquiferProtectionAreaADDITIONALPERMITS:Additionalpermitsfromotheragenciesmayberequited.Itistheapplicant’sresponsibilitytoobtaintheseotherapprovals.Informationregardingtheseotherrequirementsmaybefoundathttp://apps.ecy.wa.gov/opas/‘ExemptiondoesnotapplyinAquiferProtectionAreas2ExemptiondoesnotapplyinFloodHazardAreas3ExemptiondoesnotapplyinGeologicHazardAreas4ExemptiondoesnotapplyinHabitatConservationAreas5ExemptiondoesnotapplyinStreamsandLakes:Class2to46ExemptiondoesnotapplyinWetlandsI,theundersigned,declareunderpenaltyofperjuryunderthelawsoftheStateofWashington,thattothebestofmyknowledgetheaboveinformationistrueandcomplete.APPLICANT’SSIGNATURE:DATE:_________________rentonwa.gov/pemitseMcesIplanningcustomerserncePrentonwa.govI425-430-729410/23/2023IPage2of3DocuSign Envelope ID: D81771B8-A652-4AD0-B4EA-53C45E9816B0
CRITICALAREASEXEMPTIONSHORTFORMFORCITYUSEONLYDEXEMPTIONGRANTEDDEXEMPTIONDENIEDMatthewHerreraDateInterimPlanningDirectorPlanningDivisionCONDONSOFAPPROVAl:rentonwa.gov/permitservices)pIanningcustomerservicerentonwa.govI425-430-729410/23/2023IPage3of3DocuSign Envelope ID: D81771B8-A652-4AD0-B4EA-53C45E9816B0
Fish Screens for Construction Dewatering
Habitat Program, Fish Screening Section
September 20, 2021
Fish Screens for Construction Dewatering 1
Purpose
A diversion device used for conducting water from a lake, river, or stream for any purpose shall be
equipped with a fish guard approved by the director to prevent the passage of fish into the diversion
device (RCW 77.57.010), even when the water is only temporarily removed.
This guidance is intended to give general direction to biologists and contractors when using water
pumps at construction sites. Site specific conditions will dictate how this guidance is used. Pump
screens sized to prevent fish entry may not be necessary if the supervising biologist determines that fish
removal was adequate, that fish life is not at risk and there is adequately maintained work site isolation
and fish exclusion mechanisms such as coffer dams, block nets, etc. in the work area.
Block net guidance is not included in this document because the size and configuration of block nets
depends on location, channel morphology, species and size of fish expected to be present, debris likely
to be encountered, etc. The local biologist should work with the contractor to determine appropriate
block net mesh size based on the size of the smallest fish expected to be present and to ensure that the
layout and sturdiness of the block net system is adequate to withstand expected water volume and
velocity, size of debris, and other site-specific conditions that might impact the ability of the block net
system to exclude fish.
This document may also assist biologists in assessing the compliance of fish screens; however, a more
detailed compliance document is in development. A foot valve or backflow preventor is not an
acceptable fish screen unless it is placed inside a screen that meets the other criteria listed below. When
fish life may be present a fish screen must be used and the standard state screening criteria must be
met, unless determined otherwise by the department.
To select an appropriate fish screen for your construction project you will:
1) Determine the area of the fish screen required using calculations provided below to ensure
approach velocity criteria are met.
2) Determine the best fish screen design or configuration based on the screen area calculations
and site-specific and other considerations.
Determine the screen area of the fish screen.
Use the equation below to calculate the required Minimum Effective Screen Area. Please note that the
Minimum Effective Screen Area works in combination with other fish screen features to provide required
maximum approach velocities that both protect fish life and prevent excessive debris occlusion. 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝑀𝑀𝐸𝐸𝐸𝐸 𝑆𝑆𝐸𝐸𝑆𝑆𝐸𝐸𝐸𝐸𝑀𝑀 𝑆𝑆𝑀𝑀𝑆𝑆𝐸𝐸𝑆𝑆𝐸𝐸𝐸𝐸 𝐴𝐴𝑆𝑆𝐸𝐸𝑆𝑆 (𝐸𝐸𝐸𝐸2 )= 𝑀𝑀𝑆𝑆𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝐷𝐷𝑀𝑀𝐸𝐸𝐸𝐸𝑆𝑆𝐸𝐸𝐸𝐸𝐷𝐷 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 (𝐸𝐸𝐸𝐸𝑐𝑐)𝑀𝑀𝑆𝑆𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝐴𝐴𝐴𝐴𝐴𝐴𝑆𝑆𝐹𝐹𝑆𝑆𝐸𝐸ℎ 𝑉𝑉𝐸𝐸𝐹𝐹𝐹𝐹𝐸𝐸𝑀𝑀𝐸𝐸𝑉𝑉 (0.33 ft/s)
Where:
Minimum Effective Screen Surface Area – The total wetted screen area (the area of the screen
submerged in the water) minus the area(s) occluded by major supporting structural elements of the
screen. Screen size should be based on the maximum expected pumping rate and water volume/depth
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Fish Screens for Construction Dewatering 2
and is expressed in square feet (ft2).
Maximum Diverted Flow (rate of flow, flow/pumping rate, or pump capacity) – The maximum volume of
diverted flow over a given unit of time. For end of pipe or pump screens, it is the volume of water
flowing through a pipe inside a particular time unit (e.g. cubic feet per second [cfs] or gallons per minute
[gpm]). Formulas to convert flow rates between units are provided on page 9 of this document.
1. Determine the Maximum Diverted Flow. This can be done a few different ways, listed in order of
preference:
a. Get this information from the contractor.
b. Determine the make and model of a particular pump and look up the rating curve or
maximum pump capacity on the manufacturer’s website. This information may also be
available through various retail websites.
c. Measure the outside diameter of the ports (pump intake and discharge). Typically, trash
pumps have the same sized intake and discharge ports.
If you are unable to determine the exact maximum capacity of a pump, you can use information in Table
1 to determine the Minimum Effective Screen Surface Area required based on some common trash
pump sizes/capacity. Trash pumps are commonly used for construction and related dewatering. Trash
pumps can pass debris and ‘dirty’ water without damaging the equipment. Trash pumps are typically
sized based on the diameter of the intake and discharge ports. Other types of pumps such as
submersible, diaphragm, or other types of centrifugal pumps may be used for construction dewatering.
This table is not intended for these pump types and instead you should refer to the manufacturers
specifications or other resources to determine the pump capacity.
Table 1. Quick reference guide for common trash pump sizes used for construction dewatering and the
Minimum Effective Screen Surface Area required. Please note that the screen sizes listed assumes a fully
submerged and clean screen.
Pump Size (in) Pump Capacity Minimum effective screen surface area (ft2) gpm cfs
6 1,162 2.59 7.8
4 565 1.26 3.8
3 342 0.76 2.3
2 179 0.40 1.2
Maximum Approach Velocity – The water velocity component perpendicular to the screen surface
(Figure 1). For construction dewatering, 0.33 feet per second (ft/s) is the Maximum Approach Velocity.
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Fish Screens for Construction Dewatering 3
Figure 1. Simple illustration of approach velocity. A note regarding screen approach velocities:
The size of the fish screen, the pumping rate and maintaining a clean fish screen are the most critical
elements for maintaining appropriate screen approach velocities for construction dewatering. A
correctly sized screen chosen following the guidelines in this document and an appropriate level of
operational oversight and maintenance will, in most cases, result in appropriate approach velocities. In
field application for construction sites, WDFW strongly recommends that contractors use a pump screen
area that is sized considerably larger than the minimum required. Doubling, or even tripling the screen
area will significantly reduce maintenance time and costs for the contractor while the additional fish
screen costs will be relatively minimal. A screen designed to the absolute minimum screen area criteria
will be rendered out of criteria with any amount of debris accumulation on the screen face.
Accurately measuring approach velocities at fish screens is difficult in field settings. Simply observing the
area near the screen can help discover excessive approach velocities. Excessive debris accumulation on
the screen, obvious swirling, and signs of debris being drawn towards the screen from further than 3
inches away from the screen can all be signs of excessive approach velocities. This problem can be
exacerbated as water levels drop during dewatering and debris or sediment consolidate around the
screen. Generally, cleaning the screen, adjusting the screen placement, or adjusting pumping rates can
help alleviate excessive (> 0.33 ft/s) approach velocities.
If more precise documentation of excessive approach velocities is needed, any flow meter used for
stream discharge may be used. However, the accuracy of these measurements depends on the exact
device used. Please contact the fish screening section for more information on measuring approach
velocities at fish screens. A note regarding trash pumps and capacity:
Table 1 was developed using the total pump capacity of approximately 30 different commercially
available trash pumps at each size listed. The max capacity of each pump under optimum conditions was
used to produce the information in the table. However, there are many variables affecting pump
capacity, including but not limited to: the type of pump used (electric, gasoline, or diesel), the engine or
motor size of the pump, the pipe or line diameter, debris load or silty water, altitude, and water
temperature. The contractor will use the total head (sometimes called “lift”) required to dewater the
Approach velocity
Pump screen
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Fish Screens for Construction Dewatering 4
site to choose the best pump for a given project. A simple illustration (Figure 2) and brief description of
common pump terminology follows.
Figure 2. Simple illustration of trash pump and common pump terminology. Adapted from
www.briggsandstratton.com
Head or Lift – Gains or losses in pressure caused by gravity and friction as water moves through a
system. Depending on how the measurement is taken, lift and head may also be referred to as static or
dynamic. Static indicates the measurement does not consider the friction caused by water moving
through the hose or pipes. Dynamic indicates that losses due to friction are factored into the
performance.
Total Suction Head – The static suction lift plus the friction in the suction line.
Static Suction Lift – The vertical distance from the waterline to the centerline of the pump suction line.
Total Discharge Head – The static discharge head plus the friction in the discharge line.
Static Discharge Head – The vertical distance from the discharge outlet to the point of discharge or
water surface elevation when discharging into another body of water.
Total Head – The sum of the total suction head and total discharge head.
Determine the best fish screen for use on your project.
After determining the fish screen area needed using the methods above, you can choose more details
about the appropriate fish screen based on site-specific and other considerations. Fish screens for
construction dewatering may be off-the-shelf designs or custom fabricated. The fish screen must be
sturdy enough to not compromise the integrity of the screen during pumping if the screen becomes
clogged with debris. The goal is to find a fish screen that is sized to match your maximum pumping
conditions and water depth. Typically, it will be difficult to find an ‘off the shelf’ screen that exactly
matches your project conditions. It will most likely be a larger size than the minimum pumping capacity
or flow rate. Again, a larger fish screen will require less maintenance and provide greater protection of
fish life. Figures 3 and 4 show various fish screens used in construction dewatering projects and some
examples of things that are not fish screens.
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Fish Screens for Construction Dewatering 5
Figure 3. a) Custom fish screen barrel. b) Two off-the-shelf screens manifolded together. c) Custom fish screen box. d) Foot valve (not a fish
screen), and e) Trash pump and slip-over style mesh screen. A and C are examples of custom screens where the pump intake (likely with a foot
valve or backflow preventor) is placed inside the screen.
a
e d c
b
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Fish Screens for Construction Dewatering 6
Figure 4. a and e) Custom fish screen boxes. b, c, and d) Custom fish screen barrels. f) Foot valve wrapped in wire mesh (not a fish screen).
e
c
b
a
d
f
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Fish Screens for Construction Dewatering 7
Site-specific and other Considerations:
1. Screen shape and geometry – Standard screen shapes are a barrel, cylinder, or box (Figure 5).
While screen shape may not matter, site specific conditions may favor one screen shape over
another for both protecting fish and removing water. For example, a small diameter screen may
be necessary for dewatering in shallow water where no sump is used or needed.
Figure 5. Some typical screen shapes.
2. Cleaning – Fish screens for construction dewatering do not need to have an automated cleaning
system; however, an operator must regularly check and clean the screen during the entire
pumping operation to prevent the screen from becoming occluded with debris. As water levels
decrease, the screen must continue be monitored for fish that may not have been rescued
during fish removal and site isolation. Again, a larger screen will require less maintenance and
will provide a greater level of fish protection.
3. Uniform flow – Screens should be designed to draw water relatively uniformly over the entire
screen area to prevent excessive debris occlusion and to prevent fish impingement. If site
conditions allow, screens should be elevated or suspended off the stream bed to ensure the full
use of the screen area. Please note that sections of the screen that are occluded or blocked by
the stream bed, screen structural components or any other natural or constructed features does
not count towards the Minimum Effective Screen Surface Area.
4. Screen Material
a. Screen material must be corrosion-resistant and sufficiently durable to maintain a smooth,
uniform surface over the course of use. Screen surfaces must be smooth to the touch, with
the openings punched through in the same direction as the water flow ('smooth' side out).
Screen materials commonly used include stainless steel, aluminum, or durable plastics (not
PVC).
b. The screen material must have a porosity (open area) of at least 27%. The maximum screen
opening allowed is based on the shape of the opening.
5. Screen Opening or Hole Size (Figure 6). These are the maximum sizes allowed unless there is site-
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specific biological rationale for doing so.
a. Square and circular openings must not exceed 3/32 inch (0.094 inch or 2.4 mm). Measure
square openings on a diagonal.
b. Slotted screen face openings must not exceed 0.069 inch (1.75 mm). Measure slotted
openings in the narrow direction. Slotted screens should be oriented vertically.
Figure 6. Screen mesh sizes and the direction to measure them.
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Fish Screens for Construction Dewatering 9
How to Measure Screen Opening Size.
Screen opening size can be measured using a taper measuring gage with metric or imperial graduation
marks. A tool with an imperial measurement range of 1/32 to 5/8-inch measurement capacity with 1/64
Inch graduation and metric with a range of 1 mm to 15 mm long with 0.10 mm graduation readings is
preferred. A 3/32” drill bit can also be used as an inexpensive sizing gage.
Relevant Calculations and Formulas: Converting flow rates
Converting from cfs to gpm: cfs x 448.83 = gpm
Converting from gpm to cfs: gpm ÷ 448.83 = cfs Calculating Surface Areas.
Formulas for calculating surface areas (Figure 7) are generally intended for closed shapes. However,
most fish screens will likely have some ends blocked off, open, or not otherwise count towards the
Minimum Effective Screen Surface Area requirement. An example of a blocked end would be a screen
side placed in direct contact with the streambed or any other obstruction. Therefore, these formulas
must be modified to measure the Minimum Effective Screen Surface Area.
Figure 7. Illustration of different shapes and how to calculate area.
Surface Area of a Cylinder.
The formula for calculating the surface area of a closed cylinder is: 2πrh + 2πr², where r = radius and h =
height. Do not count blocked areas or open ends towards the Minimum Effective Screen Surface Area
requirement. Therefore, the formula to calculate the surface area of a cylinder excluding the ends is:
2πrh.
Surface Area of a Cube.
The formula for calculating the surface area of a closed cube is: 6a², where a is the length of the side of
each edge of the cube. Do not count blocked areas or open ends towards the Minimum Effective Screen
Surface Area requirement. Therefore, the formula to calculate the surface area of a cube is like
calculating the surface area of a square. To calculate the surface area of a square fish screen, multiply
the number of screened sides by a².
Surface Area of a Rectangle.
The formula for calculating the surface area of a closed rectangle is: 2lw + 2lh + 2wh, where: l=length,
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Fish Screens for Construction Dewatering 10
h=height, and w=width. Do not count blocked areas or open ends towards the Minimum Effective Screen
Surface Area requirement. To calculate the surface area of a rectangular fish screen, omit the blocked or
open side of the screen from the formula. For example, if the larger rectangle is open on the top, and
the screen is placed on the stream bed the formula would not calculate the top or bottom of the
rectangle. In this case the formula would be: 2lh + 2wh.
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