Application Guide - NexSens Technology Inc.
Contents
1. Although it often makes sense to purchase systems outright many short term dredging projects make it cost prohibitive Fondriest Environmental offers real time turbidity monitoring systems with weekly and monthly rental rates to accommodate these operations An application specialist can make recommendations on what choice is most cost effective 1 3 Months _ 3 6 Months 6 12 Months _ gt 1Year Please Specify FONDRIEST COM 19 FONDRIEST N ENVIRONMENTAL Fondriest Environmental Inc 2091 Exchange Court Fairborn OH 45324 888 426 2151 937 426 1125 O customercare fondriest com MIX Paper from responsible sources ae FSC C007943 when your PRSRT STD research US POSTAGE demands AID quality data DAvTON OH PERMIT 860 TAKE YOUR PROJECT TO THE NEXT LEVEL CONTACT A FONDRIEST APPLICATION SPECIALIST 888 426 21512. NTU and mg L Unit Conversions For relation to an EPA approved method measurements in NTU an EPA approved turbidity meter can be used to spot sample at regular intervals for quality assurance of the sensor data These data can then be used establish a correlation between the sensor data and the EPA approved data However a calculated model between data sets is only valid for the location where measurements were taken At other locations suspended particles may vary in size material and distribution and any constructed conversion will no longer be accurate 60 50 40 30 20 TURBIDITY FNU NTU 10 SITE NUMBER Likewise models can be created to calculate total suspended solids from turbidity TSS samples will need to be collected and measured to establish a relationship between turbidity and suspended solids In most situations a relationship is derived though a single or multiple linear regression model Once a regression model has been approved it can be used to predict TSS concentrations FONDRIEST COM 5 TYPICAL TURBIDITY imme N EAR Z AM A MONITORING SYSTEM A ns Ak Ags NA Telemetry EN NEP Telemetry provides access to data in real time When dredging it is necessary to monitor sediment RSE The wireless communication can be radio to N re suspension levels to prevent damage to the local NSP shore cellular or satellite based e
3. WHAT S INSIDE 01 Environmental Dredging Overview of USACE Guidelines 02 A Real Time Solution 04 Turbidity Technology 06 Typical Turbidity Monitoring System 08 Points of Compliance 10 Data Management 12 Quality Assurance 14 Recommended Equipment 16 Purchase or Rent 17 About Fondriest Environmental 18 System Configuration Tool WHY MONITORING MATTERS Dredging is a common and economically viable solution for the removal and subsequent treatment of contaminated sediment If executed properly dredging can yield positive environmental results without harming water quality conditions Dredging operations should aim to remove sediment as efficiently as possible while diminishing short term environmental impacts most notably the re suspension of potentially contaminated sediments To minimize sediment re suspension and contaminant release a monitoring system should be established Sediment can easily be dislodged by dredging and dispersed into the water column This re suspension may damage water quality both in the immediate vicinity as well as downstream as it travels with the current Additionally if the suspended sediment is contaminated it can release toxins into the water and air Effective monitoring of re suspended sediments for the duration of dredging operations is crucial to maintaining acceptable water quality levels for both wildlife and humans For this reason the U S Army Corps of Engineers USACE and Environmental P
4. protocols for sampling where to place sampling devices and details about how to interpret the monitor ing data Furthermore the guidelines suggest creating a management plan that describes the specific actions to be taken based on the results of the monitoring This may include increasing monitoring locations sampling fre quency to further assess impacts implementing operational controls i e stopping or slowing down dredge work altering debris management or changing equipment To this end the USACE technical guidelines advise incorporating real time feedback on re suspension into the monitoring plan to make early identification of problems possible The most rapid and effi cient management responses are achievable with this real time data ye eee IJt se a D le avi 1e W a spei wee J eee arses Oa ee ar a Se eT A ore a le el leks a a er yo s et la gt se a TAN Tit anen A REAL TIME SOLUTION Measuring total suspended solids TSS directly is the best method for evaluating sediment concentrations However it is not feasible for real time applications such as monitoring sediment re suspension during dredging operations At present TSS can only be accurately measured by collecting water samples and conducting laboratory tests which require filtering the sediment from the water drying and weighing it This procedure is too time consuming for monitoring dredge sites consider
5. are pulled away from the data buoy by two smaller marker buoys This configuration leaves the water column below the buoy available for sensors without risk of entanglement with anchor lines It also offers greater stability if there are currents or wave action at the location A two point mooring requires a larger deployment area than a single point mooring as the marker buoys are typically set about ten feet away from the data buoy Additional mooring lines run from the marker buoys to bottom chains and anchors at the seafloor The increased system stability from the two anchor setup is well worth the extra equipment as is the expanded area for hanging sensors If there is significant subsurface debris or other risks present deployment pipes or instrument cages can still be used FONDRIEST COM 9 DATA MANAGEMENT A major part of any monitoring project is collect ing and accessing the data While it is possible to simply record measurements onsite the ability to log send and view monitoring data in real time is far more efficient 10 MON TORING TURBIDITY Data Logger As the name implies a data logger is an instrument that stores data In envi ronmental monitoring applications data loggers can be used not only to collect data from sensors and sondes but to control sampling rates and transmit data to a central location in real time While sondes often have the ability to log their own data a separate dedi cate
6. equipment chosen to monitor a dredging site periodic maintenance and calibration is required Instrument maintentence includes cleaning the instruments especially if a sensor is not self wiping and replacing any deteriorating o rings to prevent water ingress If using additional parameter sensors such as conductivity further field servicing may be required Maintenance intervals are largely dependent on site con ditions and other variables such as the potential for biofouling Common calibration and maintenance intervals are on a weekly or bi weekly basis Turbidity sensors usually require a two point calibration one at 0 NTU FNU and another at a higher turbidity value often 126 NTU 124 FNU The 0 NTU value can be obtained using de ionized water though 0 NTU FNU stan dard solutions do exist The high range calibration should use an approved standard such as a commercial or prepared Formazin or commercial AMCO AEPA standards For greater accuracy and a wider range turbidity sensors can follow a three point calibration e g 0 NTU 100 NTU and 1000 NTU Regardless of the number of points used it is important to always include O NTU FNU as the first point For best results use only freshly prepared or purchased turbidity standard as they degrade over time Any diluted stan dard should only be used on the day it is made In case of sensor failure or damage it is useful to have spare sensors or sondes on hand These can be field
7. regarding water quality during a dredg ing operation Radio telemetry is recommended when all equipment is in close proximity If equipped with a license free spread spectrum radio a data logger can com municate with a shore side radio base station This range may vary depend ing on the logger and base station used Spread spectrum radio technology may allow a range as far as five miles line of sight or a few hundred feet non line of sight The radio base station serves as a central hub for any buoy based data logger in range with the ability to send the collected data to a project computer Cellular telemetry offers more geographic flexibility than radio though it does require a cellular data plan This small additional cost permits data transmissions from anywhere that receives a cellular signal With cellular telemetry monitoring stations do not need to be in close proximity nor is a shore side base station required Instead all the data can be accessed wire lessly via the Internet Data loggers may be equipped with cellular modems from different providers including AT amp T Verizon and Sprint For remote applications where radio and cellular telemetry are not feasible satellite telemetry can be used The Iridium communications network main tains a dynamic cross linked constellation of Low Earth Orbiting LEO sat ellites providing coverage all over the world This means that data loggers with an Iridium satellite modem c
8. such as sensors and data datacenter Monitoring data can be viewed in real time or as a graph to see loggers In addition to housing the monitoring equipment the buoy trends Real time automated alerts can Dredge Dredges are excavators used to remove contaminated sediment A data buoy is a floating platform limits are exceeded l q supplies all power and can transmit be sent via text or email when turbidity sensor data in real time levels exceed pre defined limits L 1 _ i 7 Turbidity Sensor Turbidity data are substituted m for TSS as it can be measured if instantaneously Most turbidity 00 sensors are compliant with ISO 7027 and have a wiper to prevent fouling Sensors can hang at multiple levels in ji Mooring Hardware the water column alone or in a multi l Data buoys can be anchored with a parameter sonde single or two point mooring based on H application requirements a 2 gy t 2 Dg x E FONDRIEST COM 7 MONITORING TURBIDITY POINTS OF COMPLIANCE Where turbidity monitoring systems should be located will depend largely on the site conditions of the dredging project The number of monitoring loca tions required for a dredging operation can vary but a common monitoring setup relies on three measure ment locations The chosen measurement locations are known as points of compliance At these points the USACE suggests using stationary or towed turbid ity sensors in conjunct
9. systems may still be cost effec tive for the larger dredging applications as well Turbidity monitoring equipment can be rented instrument by instrument or as an entire system calibrated and ready to deploy on arrival Rental equipment can include sensors sondes handheld displays data buoys and web based datacenter access Real time telemetry via radio to shore cel lular and satellite can also be incorporated A large rental pool also means that most turbidity monitor ing equipment can be shipped same day for quick deployment and emergency situations Just as with Fondriest purchases rental projects have access to a knowledgeable support staff who will provide personalized service before during and after the project Fondriest Environmental Inc 2091 Exchange Court Fairborn OH 45324 tel 888 426 2151 fax 937 426 1125 customercare fondriest com 16 MONITORING TURBIDITY ABOUT FONDRIEST Company Located in the Lower Great Lakes and Ohio River Valley region Fondriest Environmental is a leading distributor and integrator of equipment for natural resource professionals and outdoor enthusiasts Our team of spe cialists can help customers understand the products they are buying and make the correct decisions out in the field We seek to understand project needs devise a comprehensive solution provide the equipment and know how to implement it and then offer long term project support for whatever needs arise Cap
10. tem perature increases output intensity brightness will decrease which in turn affects the measured turbidity reading Some turbidity sensors include an 1 04 NOT TEMPERATURE COMPENSATED 1 03 TEMPERATURE COMPENSATED 1 02 1 01 0 09 0 08 NORMALIZED TURBIDITY OUTPUT 0 07 A ane 28 30 32 34 36 38 40 42 44 46 TEMPERATURE C internal thermistor to compensate for these effects while others offer the ability to make adjustments in the software For sensors that do not com pensate for temperature a minor drift can be seen in the turbidity readings as the temperature of the LED rises In addition to the longevity and stability of an LED light source near infrared LEDs 780 900 nm offer further advantages by reducing color interference Near infrared wavelengths are less likely to be absorbed by particles in the water and thus will have a lower error value than broadband light which can be partially absorbed This means that colored dissolved material in the water such as a dye or humic stain will not affect ISO 7027 compli ant sensors White Broadband light instruments however including EPA Method 180 1 turbidity meters will be affected if color is present Due to the advantages of a near infrared LED most nephelometric turbidity sensors follow ISO 7027 guidelines While other designs including backscat ter also use a near infrared LED ISO 7027 compliance ensures accurate and comparable turbidity data
11. the buoy Data buoys with 150 to 450 lb net buoyancy are generally adequate for monitoring projects on rivers inland lakes and protected waters Larger platforms may be required in coastal and Great Lakes deployments that are subject to more extreme conditions and wave action Towed sensors are known as floating points of compliance as they move with the dredging operation While these can be attached directly to the dredging equipment they can also be deployed on a buoy system a set distance away from the dredge location The buoy systems then move with the dredge as the project progresses remaining the same distance away from the active dredging site For accurate data all sensors should be calibrated shortly before the project begins If using a buoy based system the platforms should be fully assem bled on shore prior to deployment This includes attaching any sensors towers solar panels and additional ballast weights if needed Furthermore the complete turbidity monitoring system sensors data logger telemetry software should be tested before the buoy is put in the water While this process ensures that all equipment is functioning within specifications it also gives everyone the chance to familiarize themselves with the system prior to deployment Issues are always easier to deal with before the buoy platform is deployed in the water A buoy based system must be moored to ensure that it remains stationary The buoy is u
12. 0 180 degrees from the transmitted light can be accepted as a backscatter sensor Without a standardized quality guide for these instruments any data received are not comparable to any other instrument Method Compliance Many turbidity monitoring projects want data to be EPA compliant However no true EPA 180 1 compliant submersible turbidity sensors exist For in situ monitoring the USGS instead recommends ISO 7027 compliant sensors The requirement of a tungsten lamp light source makes any dynamic EPA Method 180 1 instrumentation impractical Tungsten lamps have a high power draw require warm up time and have an energy output that deterio rates with age This means that instruments in compliance with this method will require frequent calibrations and bulb replacements While this is simple enough with a handheld meter it becomes impractical in a submersible sensor On the other hand LED light sources are compact and have a smaller power draw LEDs also have a longer lifetime than tungsten lamps no warm up period and they can be modulated to reject ambient light Modulating or rapidly pulsing a light source reduces errors due to ambient light This makes LED light sources ideal for long term deployments However sensors with an LED light source should be compensated for temperature While turbidity itself is not affected by temperature the LED is Changes in the internal temperature will affect the optical power output of the LED As
13. abilities We work closely with NexSens Technology a company that specializes in the design and manufacture of real time environmental measurement systems A variety of sensor platform and telemetry options are available to fit the unique needs of each project We can provide complete integrated solutions and support projects from conception to completion An extensive fleet of rental equipment is also available for short term project needs Certifications Fondriest Environmental is a Certified Repair Center for YSI NexSens amp Fish Sens offering quick turnaround affordable labor rates and personalized service Our knowledgeable technicians are available for phone email and onsite support when the need arises Publications We cover many customer projects in our Environmental Monitor magazine which is updated daily online and printed quarterly We also produce Lake Scientist an interactive online resource providing research articles and news on lake ecology Informational pages on environmental parameters and applications are available in the Measurement Sciences section of our website And FishSens Magazine available online provides anglers boaters and fisheries professionals with the latest fish science news Commitment A commitment to integrity and longstanding customer relations are the standard rather than the exception at Fondriest Environmental We support professionals educators and researchers who continuously work
14. achieved with the use of a dynamic turbidity instrument also known as a turbidity sensor These sensors are submerged in a body of water for continuous turbidity monitoring Turbidity meters on the other hand use a water sample instead of measuring in the water directly This means they cannot be used in situ for real time data While tur bidity meters can be used to check data quality they are not recommended as primary monitoring sources for dredging applications Most turbidity sensors are connected to a buoy based sonde or a data logger for recording data This is the preferred turbidity monitoring method by the U S Geological Survey as in situ measurements more accurately represent surface water conditions than sampling methods In addition the real time availability of data from submersible sensors improves control measure response times when turbidity levels change TRANSMITTED LIGHT BEAM gt oap LIGHT 90 APERTURE LENS SCATTERED S LIGHT DETECTOR Turbidity sensors can use nephelometric 90 degree or backscatter gt 90 degree technology to measure the amount of light scattered by particles in water The sensor is designed with two optical windows generally located on the same flat surface of the sensor The light source and the photode tector are located below the optical windows and are tilted to achieve the desired scattered light angle The single flat surface means that a turbidity sensor ca
15. an transmit data in real time from any where on Earth As with cellular networks the data are sent to a central gateway which then transfers the data over the Internet to any project computer or cell phone Real Time Online Datacenter The easiest way to share and view turbidity monitoring data is through a web based datacenter An online datacenter offers 24 7 instant access to project data via any web browser Turbidity monitoring and other data can be exported into the datacenter directly from the data logger or through the project software This project management service can be password protected or public and allows users access to the collected data in real time In addition to any dredging specific information the online interface can provide dynamic area maps overlaid with weather information recent and historical data time series graphs and statistical summaries Visitors can interact with the project maps and view real time monitoring data or turbidity level trends over time But these cloud based datacenters are more than just a pretty face Many can be programmed to send out automated alarm notifications when tur bidity levels exceed pre defined limits These limits are determined by col lecting background data prior to dredging using spot sampling equipment Once an allowable turbidity range has been set the data are entered into the online database If turbidity levels exceed this recommended range during dredging opera
16. cosystem and minimize the spread of contaminants NSO This is usually done with a turbidity monitoring station N upstream for background data and two stations TSE downstream at locations affected by the dredging NSE A BY To be effective measurement data should be provided ENG Ar in real time The easiest and most efficient way to do IHE A this is with a buoy based turbidity monitoring system TVA AA Nes A data buoy can house sensors at multiple depths in EAA HES the deepest part of the waterway providing more E AS comprehensive data than a shore based system This op PS C system can then securely transmit the data to the O maa AS AAW Internet in real time for access from any computer OOE NO wO O a ne 4 Buoy systems are flexible and customizable based on the dredging project requirements They can house as many sensors as needed and all equipment is powered via a marine battery and recharging solar panel system With multiple telemetry options to from the water They can be l choose from continuous real time data are available hydraulic mechanical or a hybrid Data Buoy Live Data from any computer This ensures that the dredging Most are mounted on a spud 24 7 instant access to project data operations progress smoothly and any control mea barge An additional barge may be that supports real time monitoring is available through a cloud based sures can be implemented immediately if parameter needed for sediment disposal instruments
17. d data logger can gather data from any and all attached sensors while ensuring that no data are lost If telemetry wireless communication is avail able the logger can remotely control sensor sampling rates and transmit collected data to a central project computer Data loggers with telemetry technology can provide real time turbidity data and remote access via a cellular modem radio transmission or satellite modem When housed in a data buoy a data logger is charged by the buoy s solar power system If a solar panel system or external battery is not available the logger can be self powered using alkaline batteries Data loggers can be configured with a number of sensor ports for connection to industry standard digital and analog interfaces including RS 485 SDI 12 or 0 2 5 VDC Turbidity sensors can connect to a logger directly or through a multi parameter sonde A data logger can also handle additional water quality sensors temperature strings or Doppler velocity meters if they are required for the dredging application Telemetry Telemetry or wireless communication is a useful tool for monitoring turbid ity in real time Common telemetry options are cellular and radio though satellite telemetry can be used in more remote locations The deciding factor when determining the most cost effective telemetry option should be the local site conditions and proximity to a project computer All three of these options permit real time updates
18. e to the sea floor An application specialist can develop the best mooring plan to accomodate the approximate water depth C lt 5 ft C Between 5 and 25 ft Between 25 and 50 ft _ Between 50 and 100 ft gt 100ft Water Column Measurements Measuring turbidity at a single mid level depth is often sufficient for dredge monitoring In some cases however regulatory agencies may require readings at multiple depths Single Depth Multiple Depths Please Specify Telemetry License free spread spectrum radio telemetry allows communication with a shore side NexSens radio base station as far as five miles line of sight from the monitoring site Cellular telemetry allows greater geographic flexibility and is able to transmit from almost anywhere in the U S but it includes the cost of a cellular data plan Satellite telemetry can be used nearly anywhere in the world but it tends to have the highest data cost compared with cellular telemetry Cellular Radio Satellite None Quality Assurance A multi parameter sonde with turbidity sensor connected to a handheld display is an ideal way to verify the accuracy of a turbidity monitoring system and uses the ISO 7027 method Alternatively there are portable turbidimeters that can measure using the EPA approved 180 1 method C Multi parameter sonde amp handheld display ISO 7027 Method C Portable turbidimeter EPA 180 1 Method Project Length Rental vs Purchase
19. his method reports in FNU or FBU based on the sensor used While FNU readings are approved by ISO 7027 neither option is approved by the EPA The second method uses a handheld turbidity meter This method requires taking a water sample and then inserting it into the meter for a reading As this method uses a sample instead of an in situ measurement it is often not representative of the surface water as a whole This is especially a hindrance when quality checking monitoring systems that measure turbidity at mul tiple depths along the water column While handheld meters are not sub mersible many styles are compliant with EPA method 180 1 This means that the long term data can be cross checked against an EPA approved method However while correlations can be made between data sets care should be taken when comparing data between the meter and the buoy based monitoring system Turbidity instruments are inherently not comparable and comparative models are only accurate for the specific sample location FONDRIEST COM 13 RECOMMENDED EQUIPMENT While there are plenty of turbidity monitoring instruments on the market some stand out above the rest Fondriest Environmental has selected these products as the best in their field for their quality reliability and value Together they provide an advanced and powerful real time turbidity moni toring system For a sensor or sonde accuracy is of utmost importance and the YSI EXO2 doe
20. ible digital and analog sensor interfaces include RS 232 RS 485 SDI 12 VDC mA and pulse count The top of the instru ment well includes 8 pass through ports for power and sensor interface Each port offers a UW receptacle with double O ring seal for a reliable waterproof connection eats Ax be hae Sor Z SE 7 Steve R Log Out Oe i VOD atat E OVERVIEW SITES v FIELDBOOK MEDIA REPORTS si S w le daa EO wr wt E ae TAI z feynaide fit 6 gt Y MO BONITA SPRINGS WQData LIVE is a web based project management service that allows users 24 7 instant access to data collected from NexSens remote environmen tal data logging amp telemetry systems More than just an online database WQData LIVE offers the ability to generate automated reports configure alarms to notify project personnel when data values exceed threshold limits create FieldBooks to store calibration forms notes and media and much more Projects are password protected with the ability to configure a public portal or presentation view to share data with the general public Project Administrators have the ability to edit project descriptions and informa tion while users given Collaborator access are limited to data viewing and form entry The Google Maps view shows all project sites on a map with zoom scroll and drag capability Mousing over a site on the map displays the most recent data values and clicking on the site na
21. ing the quick feedback required to allow timely control measures This is particularly true in cases when the dredged sediment contains contaminants that pose an added risk to wildlife and people To achieve this real time monitoring turbidity a measure of water clarity is substituted for TSS MONITORING TURBIDITY Measuring Turbidity Turbidity data can be substituted for total suspended solids because it is an indirect measure of the particle density in the water When monitoring dredging operations turbidity readings can approximate levels of re sus pension and indicate the likelihood of released contaminants in real time As an optical measurement turbidity monitoring requires a light source and a photodetector The light source in the instrument generates an incident light beam which is scattered in all directions by particles in the water The more particles present in the water the more the light will scatter A photodetector is set up to measure the amount of light scattered at a specified angle Most tur bidity instruments use nephelometry which requires a 90 degree angle for measurement This is considered the most accurate method and is approved by both the Environmental Protection Agency EPA and International Orga nization for Standardization ISO quality design standards Other detector angles such as backscatter can provide useful data but they are not con sidered approved methods Real time turbidity data are
22. ion with water column sampling Wmi coo op ro aD a oa oo mu B wo MONITORING TURBIDITY As suggested by the name stationary systems are set at fixed locations These systems can be placed on structure or on an anchored buoy in the water Seawalls are a common example of a structure that can be used as turbidity monitoring sensors can be mounted in a perforated PVC pipe along the seawall However site conditions often make it difficult or impractical to mount the monitoring equipment along the shore In addition relying solely on shoreline solutions may not accurately represent re suspension levels and sediment transport due to the nature of water currents For these reasons buoy based systems offer the most comprehensive and cost effective solu tion Data buoys provide a stable platform for turbidity monitoring with the ability to house multiple sensors at different depths in the water column In addition they can carry a data logger solar powered battery pack and telemetry wireless communications systems for extended deployments Anchored buoys are usually located both up and downstream of the dredg ing operation The downstream buoy s measure re suspended sediment and sediment transport in areas at risk while the upstream and off site buoy serves as a control for suitable turbidity levels These buoys can come in different sizes based on the environmental conditions and the number of sensors suspended from
23. iple sensors in one sonde and distribute to various other sondes in the field Wet mateable connectors allow for swaps in wet conditions while active port monitoring automatically detects each sensor and veri fies operation A ae ia J p i LN s J The NexSens CB 450 Data Buoy is designed for deployment in lakes rivers coastal waters harbors estuaries and other freshwater or marine environ ments The floating platform supports both topside and subsurface envi ronmental monitoring sensors including weather stations wave sensors thermistor strings multi parameter sondes Doppler current profilers and other monitoring instruments The buoy is constructed of an inner core of cross linked polyethylene foam with a tough polyurea skin A topside 20 tall stainless steel tower includes three 10 watt 12VDC unbreakable solar panels and a center 10 ID x 18 tall instrument well accommodates batteries data loggers sensors and more Three 4 pass through holes with female NPT bottom threads allow for quick connection of instrument deployment pipes and custom sensor mounts The stainless steel frame supports both single point and multi point moorings HURRAH Ree Ae BERREEEEEEEE l zs gt EERRRRERREEE The CB 450 Data Buoy is optimized for use with NexSens data loggers Wireless telemetry options include Wi Fi spread spectrum radio cellular and Iridium satellite Compat
24. n be wiped or cleaned remotely during a deployment Regularly wiping the sensor windows prevents fouling attachment of inorganic mate rial such as silt or biological material such as algae or barnacles Wipers can be built into the sensor or attached to a separate brushing mechanism Fouling on the sensor windows can yield artificially high turbidity readings as the material can block light from entering the water or from returning to the detector Turbidity Units and Reporting Thanks to the multitude of instrument designs turbidity reporting can quickly become confusing There is also a large amount of misinformation regarding approved standard compliance and which turbidity units should be used in reporting Turbidity units are only useful and accurate if they are reported correctly with correspondence to a specific instrument design On their own turbidity units including NTU and FNU have no inherent value physical or otherwise They are a qualitative rather than a quantita tive measurement Turbidity and thus particle density is a function of the amount of light that is scattered at specific angles However the physical properties of these particles shape color and distribution can affect the measurement This means that two water samples with the same level of suspended solids but with varying particle compositions could result in different turbidity read ings In addition longer and shorter light wavelengths in
25. nsity is fairly linear However it becomes non linear above 40 NTU and inaccurate at higher turbidities To account for this some sensors offer a secondary algo rithm for measurements over 1000 NTU This yields less precise readings but the accuracy is improved over non adjusted nephelometric sensors NEPHELOMETRIC 90 SCATTER DETECTOR BACKSCATTER DETECTOR SIGNAL REACHING THE DETECTOR 0 2000 4000 6000 8000 10000 TURBIDITY NTU Backscatter A backscatter sensor uses a photodetector centered past the 90 degree angle 90 180 degrees from the transmitted light Backscatter sensors have several advantages 1 a wide measurement range 2 improved accuracy at higher turbidities over 1000 NTU 3 a tolerance for a varying particle sizes Between 1000 4000 NTU backscatter technology is nearly perfectly linear However during periods of low turbidity a backscatter sensor will not be as accurate as a nephelometric instrument Backscatter sensors are also more prone to color interference due to particle darkness value the ability to reflect near IR bands The largest disadvantage for backscatter sensors however is the lack of comparability The USGS and several backscatter sensor manufacturers have attempted to define appropriate backscatter angles e g 135 180 degrees from the incident light At this time no current design standard has been set for these sensors As such any scattered light detection centered between 9
26. rotection Agency EPA offer extensive guidelines for estimat ing the environmental consequences of a dredge The guides also emphasize the need to monitor these effects as the dredging operation occurs in order to keep any re suspension and transport under control These monitoring efforts allow project managers to respond if re suspended sediment levels exceed pre established parameters by slowing down or altering the dredging For the complete USACE s Technical Guidelines for Environmental Dredging of Contaminated Sediments visit http el erdc usace army mil elpubs pdf trel08 29 pdf For the complete EPA s Contaminated Sediment Remediation Guidance for Hazardous Waste Sites visit http www epa gov superfund health conmedia sediment pdfs guidance pdf FONDRIEST N ENVIRONMENTAL ENVIRONMENTAL DREDGING Overview of USACE Guidelines Environmental dredging is defined as the removal of contaminated sedi ments from a water body for purposes of sediment remediation USACE While there are several approaches to dealing with contaminated sediment dredging is frequently the cleanup method of choice for projects under the Comprehensive Environmental Response Compensation and Liability Act CERCLA also known as the Superfund program As no two projects are identical the specific environmental limits set for a dredging project will vary Several influencing factors include location sediment composition acting regulato
27. ry agencies and environmental laws To assist with this effort the U S Army Corps of Engineers USACE has generated a comprehensive set of guidelines to evaluate environmental dredging as a solution for sediment remediation projects While the EPA s remediation guide addresses all possible steps and alternatives for dealing with contaminated sediment the USACE s guide focuses specifically on the dredging component These guidelines provide detailed steps regarding the establishment of a dredging operation from the preliminary evaluation to the process methods and control procedures In doing so this guide establishes a hier archy of objectives regarding the technical aspects of a remedial dredging operation These objectives aim not only to minimize sediment re suspen sion release and residuals but also to maintain a cost effective strategy in both the short and long term Both of these guidelines stress the importance of implementing a moni toring strategy that provides rapid feedback allowing dredge operators to respond to high re suspension levels before they become problematic Established limits for sediment re suspension maximum allowable levels for water quality and released contaminants may be a part of dredging regulations established in consultation with stakeholders or by federal acts and regulatory agencies The USACE recommends drafting a comprehensive monitoring plan that includes equipment and techniques to use
28. s not disappoint The rugged NexSens CB 450 offers long term durability with 30 W of solar power 450 pounds of buoyancy and a choice of instrument mounts for multiple sensors Alone real time data are good but with remote data collection 24 7 access from any computer instant alarm notifica tions and trend tracking the intuitive WQData Live takes real time data to the next level 14 MONITORING TURBIDITY The YSI EXO represents the next generation of water quality instruments from YSI The advanced sonde platform offers a wide range of capabili ties to those dedicated to monitoring natural aquatic environments such as oceans estuaries rivers lakes and groundwater With a highly efficient power management platform robust construction and chemistry free anti fouling system EXO allows accurate data collection for up to 90 days between service intervals The EXO2 sonde includes six sensor ports and a central anti fouling wiper option Sensor parameters include temperature conductivity depth dis solved oxygen pH ORP total algae phycocyanin and chlorophyll turbidity and fluorescent dissolved organic matter f DOM The sonde can also output 4 calculated parameters including salinity specific conductance total dis solved solids TDS and total suspended solids TSS All EXO sensors are digital sensors with onboard signal processing and memory Built in sensor diagnostic and calibration data allow users to cali brate mult
29. stems will use a submersible sensor to monitor for sediment re suspension These turbidity sensors can use nephelometry or backscatter technology to measure the amount of light scattered by particles in the water Regardless of the sensor chosen it is important to use the same sensor model throughout a project for internally consistent data While inter instrument rela tionship models can be developed data from different instrument designs are not directly comparable Each sensor will read varying amounts of light scatter from suspended particles due to the differences in light source and measurement angle In turn the sensors will output varying results despite measuring the same water sample In addition to cost considerations sensor choice should be based on expected or poten tial turbidity readings low high or a wide range and whether or not compliant and comparable data would be useful MONITORING TURBIDITY Nephelometry Nephelometry is a measurement method with a light source and a photode tector set at a 90 degree angle from each other This is the angle that is most sensitive to light scatter as it is not affected by particle size Most nephelometric turbidity sensors comply with ISO 7027 guidelines While other sensor designs exist compliance with ISO 7027 ensures accu rate and comparable turbidity readings In addition to the high sensitivity the relationship between nephelometric light scatter and particle de
30. sually moored via a stainless steel mooring line bottom chain and anchor It is recommended to moor the buoy in the deepest part of the waterway to ensure the most inclusive measurements This allows for multiple measurement depths and will best reflect the characteristics of the water body as a whole Buoy based systems are typically moored as either a single point or two point mooring based on environmental and application specific factors Single point moorings are not common but they require the least amount of mooring equipment This setup can be deployed in very calm waters with minimal instruments A single point mooring should only be used when all sensors and equipment are housed within an instrument cage or deploy ment pipe Hanging sensors risk getting damaged or entangled with the anchor line A cage or pipe protects the instruments from entanglement subsurface debris and currents without affecting sensor readings In a single point configuration a mooring line connects the buoy directly to a bottom chain and anchor The sensors are typically housed within a central deployment pipe or attached to a rigid instrument cage The anchor bottom chain and mooring line are assembled and attached to the buoy prior to deploying the system Two point moorings are the most common deployment configuration This is the recommended setup if sensors will be hanging at multiple depths in the water column In a two point setup the mooring lines
31. swapped during calibration or routine maintenance checks Having a spare turbidity sensor available will reduce downtime due to unforeseen sensor failure which could cause critical and costly interruptions to safe dredging operations For greater details regarding maintenance requirements and sensor calibra tion the manufacturer s user manual should be referenced Performance Verification In addition to keeping turbidity equipment calibrated it s important to peri odically verify that the sensors are providing accurate turbidity data The best way to achieve this is by checking turbidity in the same area using a separate portable monitoring system This is also known as spot sampling There are two portable turbidity measurement methods available for spot sampling The first method uses a sensor much like the one used in the buoy based monitoring system and a handheld display The turbidity sensor can be attached directly to a handheld display or through a sonde to the display to show real time data Sondes are useful instruments if other parameters such as pH dissolved oxygen or conductivity should be recorded as well The sonde or sensor can be lowered into the water column to a depth that matches the in place sensors While it is at that depth a turbidity measurement can be taken The data from this portable system can then be compared to the in place monitoring system and checked for discrepancies As with the buoy based system t
32. teract with and reflect off of particles in different ways This means that two instruments with different light sources may not measure the same level of turbidity in the same water sample Finally the measurement angle within an instrument is only accurate within a specific turbidity range Some angles are accurate for lower turbidity levels while others are intended for very high measure ments The solution to all of these variables is in the turbidity unit The USGS and ASTM have developed a list of ten different turbidity units each intended for use with a specific instrument design As turbidity instrument designs vary by light source and measurement angle these factors will determine which units should be used If the light source or the angle changes so will the recommended unit Three of these units are commonly used in dredge turbidity monitoring listed at the bottom of this page Each instrument design has its own designated unit and the misappropria tion of turbidity units particularly NTU diminishes their accuracy and useful ness Unfortunately most turbidity data in the U S have been reported in NTUs over the past two decades regardless of their light source or detec tor geometry The USGS s revised turbidity protocol 2004 is working to improve the comparability of turbidity data by requiring that reported units match the instrument design As mentioned earlier the U S Environmental Protection Agency USEPA and
33. the International Organization for Standardization ISO have established specific requirements for turbidity instrument designs The quality design standards are known as EPA Method 180 1 and ISO 7027 As the EPA Method 180 1 requires a tungsten lamp light source and a 90 degree measurement angle it falls under the nephelometric white light turbidimeter category Thus instruments in compliance with EPA Method 180 1 report in NTU Nephelometric Turbidity Units ISO 7027 requires a near infrared LED light source and a nephelometric mea surement angle so instruments in compliance with this design report in FNU Formazin Nephelometric Units Formazin is the recommended calibra tion standard for many of these instruments The third well known design is not compliant with any approved design standards Instruments that follow the backscatter near IR turbidimeter design should report in FBU Formazin Backscatter Units Most submersible turbidity sensors use a near infrared LED light source due to the low power draw and thus should report in FNU or FBU Turbidity meters used for data quality assurance may contain a white light 400 680 instead of a near infrared light These instruments report in NTU Common Turbidity Monitoring Instrument Design Unit Nephelometric white light turbidimeter Nephelometric near IR turbidimeter FONDRIEST COM 3 4 TURBIDITY TECHNOLOGY The most commonly used turbidity monitoring sy
34. tions the datacenter will immediately issue an alert text and or email to the appropriate project manager or operator With the availability of real time data and the datacenter s auto alert system dredge operators can be notified immediately when turbidity levels rise This means that timely control procedures can be implemented to slow down alter or stop the dredging operation until levels fall below the maximum allowable limit The online datacenter can also transmit this alert back to the data logger in order to respond to the exceeded turbidity range Automated responses may include taking more frequent readings during high turbidity periods then resuming regular log intervals when levels return to normal East River Buoy 01 e600 Verizon LTE 294 Friday October 3 wadatalive nexsens com WQData LIVE Alert High Turbidity The turbidity at Buoy 01 has exceeded 100 NTU FONDRIEST COM 11 QUALITY ASSURANCE Accurate data ensure that dredging operations remain in compliance with set regulations To main tain that accuracy and keep equipment function ing within specifications best practice recommends cleaning and calibrating the instruments at regular intervals It is also recommended to cross check sensor accuracy against a separate instrument This cross checked data can then be used to show com pliance against an EPA approved method if needed eee a System Maintenance Regardless of the turbidity
35. to monitor and protect our global resources by providing them with the products and services needed to face today s environmental challenges Our team of solu tion driven experts has years of field experience and a keen eye for finding the best equipment for each application Contact Information To reach an application specialist please call 888 426 2151 or email customercare fondriest com T D Z U i zM iy m Z lt J O Z E4 m SYSTEM CONFIGURATION TOOL Fondriest application specialists will assist with tailoring buoy configuration and equipment choices on a site by site basis to ensure reliability and proper data management The ques tionnaire below can help you get started Once completed this form can be faxed to 937 426 1125 or if completed digitally emailed to customercare fondriest com Contact Information Name Organization Telephone Email Site Conditions Describe the site conditions in a paragraph or two Please include details regarding levels of wind waves and boat traffic experienced in the area 18 MONITORING TURBIDITY 4 gt Site Location The location of a monitoring system can affect what buoy configuration best suits the conditions Please select in what type of water body the system will reside C Lake C River Coastal Other Please Specify Approximate Depth The mooring hardware and cable lengths used for a deployment depends on the distanc
36. vigates to a display showing the last reading or tabular data that can be downloaded to Excel and sent via email or FTP FieldBooks can be created to store notes recorded during field visits including forms to store calibration data which can be submitted from the WQData LIVE mobile app This eliminates the need for conventional field books while keeping critical project information in a single easy to access location Site photos can even be placed onto FieldBook pages or uploaded into the project s Media page The WQData LIVE report feature allows data to be shown both graphically and in a tabular format Report templates can be saved so that specific information can quickly be referenced Project alarms send email or text messages to project staff for immediate notification of critical conditions With this unique set of features WQData LIVE provides everything needed to effectively manage an environmental monitoring application FONDRIEST COM 15 PURCHASE OR RENT When managing a large or long term dredging project purchasing several turbidity monitor ing systems is often the most economical option However for short term dredging projects on a tight budget it may not be practical to purchase the necessary turbidity monitoring equipment In these situations it is much more prudent to rent real time monitoring systems With several lease duration and extension options available the flexibility of renting turbidity monitoring
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