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CayugaInletDredgeMaterial:Opportunities for Restoring Ecosystem Functions & Services

Fall 2011 Cornell University Restoration Ecology Class Report


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Introduction:

Executive Summary 4Ben Hedstrom

Project Introduction 5Tim Lynch

Watershed:

Southern Cayuga Lake Watershed 9Matthew Gonser

Dredge Material Analysis:Dredge Material 16Jamie Nassar & Hayden Stebbins

Dryden Site Plan Communities 26Becky Mikulay, Jamie Nassar & Hayden

Stebbins

Methane Analysis:

Methane Production in InletSediments: Spatial Variability andAlternatives for Mitigation 30Jack Mascharka, Rebecca Montross, NadiaPierrehumbert

Hydrilla verticillata:Managing Hydrilla verticillata for the

Cayuga Inlet 36Trinity Boisvert & Yong Seuk Peter KwonAlternatives & Reference

Sites:Introduction 44Gene Fifer

Industrial Products:Introduction 45Matthew Horvath

Synthetic Soils 46Becky Mikulay

Brick Production 47Amy McLean

Lightweight Aggregate 49Amy McLean

Cement Lock 50Amy McLean

Dry Sites:

Introduction 51Matthew Horvath

Cornell Lake Source Cooling Project:Dryden, NY 52Becky Mikulay

Times Beach: Bufalo, NY 53Andrew Miller

Cuyahoga River & Dike 14:Cleveland, OH 54Andrew Miller

Dredge Inll Project at Stewart Park:Ithaca, NY 56Becky Mikulay

TableofContents:

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Dredge Inll Project at Cass Park:Ithaca, NY 58Becky Mikulay

Wetland Sites:Introduction 59Gene Fifer

Manning and Cowett Proposal atStewart & Cass Park 60

Amy McLean

Poplar Island:Chesapeake Bay, MD 62Amy McLean

Living Shorelines:St. Michaels, MD 64Amy McLean

Montezuma National Wildlife Refuge:Seneca Falls, NY 65Gene Fifer

Catherine Creek Natural Area:Watkins Glen, NY 66Gene Fifer

Appendices:A: Landslide Susceptibility

Analysis Methods 67

B Soil Health Test Results 68

C: Dryden Site Species Curves 69

Acknowledgments: 72

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Our Restoration Ecology class(consisting of undergraduate and graduatestudents in the schools of Earth SystemsScience, Natural and EnvironmentalSystems, Landscape Architecture, and Cityand Regional Planning) spent the Fall 2011semester investigating the Cayuga InletDredging Project and the complicationsit has faced with the discovery of Hydrillaverticillata. Doctor Thomas Whitlow ofthe Cornell University Department of

Horticulture led this course.Our report includes ndings from

studies on local dredge material, Hydrilla,the southern Cayuga Lake watershed, andseveral case studies on successful projectsinvolving the productive reuse of dredgematerial.

Dredge Material At the Cornell Soil Health Lab, we

analyzed samples of local dredge material formany qualities including toxicity and poten-tial use as a plant growing or structural mate-rial. While restricted access to the inlet was alimitation to our study, our ndings concludethat this material is not generally hazardousand the existing nutrient levels are self-stabi-lizing. There do however appear to be localhotspots for lead so it is not a recommend-

ed medium for food production. With moreintensive testing, and mixing it with other

soil or compost, much of the material couldpotentially be used in this way.

Previous studies have indicated thatthe dredge material is a silty-clay, but wehave found it is actually more a sandy-loam.This material contains a higher percentage oforganic material than was expected and hasthe ability to support terrestrial plant spe-cies similar to those found on a 12-year olddredge disposal site in Dryden. The materialwe tested has low aggregate stability andwould make a poor structural material.

Additionally, we measured the dredgematerials potential to release methane intothe atmosphere. The overall anthropogenicimpact would be small compared to releasesfrom local dairy operations, even given thelargest scope of the dredging project.

Hydrilla verticillata Samples of Hydrilla verticillata weretested over a period of several weeks fordesiccation tolerance to understand the spe-cies survival ability in dewatered dredge ma-terial. Generally, our tests indicate that shortterm desiccation alone cannot kill Hydrilla.A management plan for Hydrilla eradicationshould absolutely be made in conjunction

to the plan to dredge the inlet. Given thatsome reports indicate Hydrilla can live for

up to ve years in dry material, the currentplan to store dewatering dredge materialfor one year with subsequent use across thelandscape has a great potential to proliferatethe infestation in waterways throughout thecounty. Solarization, a method of soil steril-ization beneath plastic sheeting, is potential-ly more eective at killing Hydrilla than meredrying.

Simultaneously, certain areas of theinlet should potentially be managed indi-vidually, namely Cascadilla Creek. Under theconditions encountered this October, ourlight extinction readings show that below2.5 feet, light intensity is below the lightcompensation point and would be unlikely tosupport vigorous stands of Hydrilla. Howev-er, since Cascadilla Creek and the small tribu-tary creek across the Inlet in Cass Park are

shallow and generally have clear water, theyare more prone to infestation and a separatemanagement plan should be created for anydredge material from these areas.

Our Local WatershedSedimentation in the inlet is a natural

geomorphologic process that has existedsince the end of the glacial retreat. Human

ExecutiveSummary:Ben Hedstrom

4Introduction


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activity has accelerated the pre-settlementcondition. Replacing our native ood plain

and wetland habitats at the outfalls oftributaries at the south end of the lake withpaved or turf surfaces, and stripping streamedges of bank-stabilizing vegetation for de-velopment over the past century decreasesfunctionality to the already accreting system.While our analysis of area forest cover levelsindicate that there may be slightly lower lev-els of sediment in the future due to decreas-ing levels of farming, history has shown thatsedimentation will continue to occur.

Dating back to the sand bar that wasremoved from the inlet at the beginning ofthe nineteenth century to allow boat trac,dredging has been a part of Ithacas historyand will remain so as long as humans need tonavigate the waterfront. Our recent tenden-cy to defer maintenance demonstrates thatperhaps a lack of action is the most signi-

cant eect of humans on the inlet.At this time, we have a chance and a

duty to make human actions that attempt torelieve this situation and instigate a plan thatworks with the evident natural process. Ourreport provides several practical and success-ful examples of productive dredge use andrestoration projects that collectively describeopportunities to:

Use the dredge material in ecologicallyand economically productive ways.

Dene an ecient plan for the future thatunderstands sedimentation in the inlet asa persistent issue.

Increase project innovation utilizing theexpertise of diverse agencies and levelsof government.

While we probably do not need to restorethe channel to its original conguration forthe maximum potentials of navigability,recreation, and ood-control, our legacy tothe Cayuga Inlet Dredging Project should aimto create a better situation than the one thathas materialized.

Potentially a wetland site, with smallcells that could easily be monitored andsolarized, with installation of a silt fence toretain Hydrilla from other parts of the lake,remains the most viable option. Similar to

Poplar Island, but on a much smaller scale,this plan has the highest ability to connethe material, while creating a new specieshabitat and still limiting the distance materialwould travel.

If we dont allow someone to try something

to see if it works, how will we move ahead?

5Introduction

Mark SudolUSACOE Regulatory Program ChiefScience Magazine, April 2008


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The City of Ithaca is in the planningand approval stage for a dredging projectthat will remove accumulated sediment fromthe inlet. The inlet consists of the CascadillaCreek, Cayuga Inlet and the Flood ControlWorks. These three entities perform a varietyof ecological, infrastructural, commercialand recreational functions. The Army Corpsof Engineers has estimated that a totalof 660,000 cubic yards of sediment haveaccumulated within the channels. The City

will be collaborating with multiple agenciesincluding the US Army Corps of Engineers(ACOE), New York State Department ofEnvironmental Conservation (NYSDEC)and the New York State Canal Corporation(NYSCC).

The city is currently planning a de-watering facility to be located on a 23-acreportion of city owned land behind Lowesand Wal-Mart known as the Southwest Site.

This Sediment Management Facility (SMF)

will use earthen berms to create multiplecells for the processing of dredge material

at dierent stages of dewatering. The DraftEnvironmental Impact Statement (DEIS) pre-pared for the City by Ecologic LLC estimatesthat the SMF would have an annual process-ing capacity of 80,000 cubic yards. The DEISproposes utilizing this material for a varietyof benecial re-uses including habitat resto-ration and being mixed with yard waste toproduce topsoil. The City does not currently

have a rm plan for the benecial re-use ofmaterial.The city plans to construct the SMF

beginning in the spring of 2012 and begin therst stage of the project with the dredging ofan estimated 25,000 cubic yards of sedimentfrom the Cascadilla Creek section of the Inlet.The DEIS submitted by the City of Ithaca inNovember of 2011 involves this initial stageof the larger planned project and the related

construction of the SMF.

ReportThis report was produced by Cornell

University students as part of a semesterlong study of the dredge project as part ofa Restoration Ecology (HORT 4400) classtaught by Professor Tom Whitlow. Thereport intends to summarize the ndings ofthe class research on this subject, to providethe Ithaca Community with information per-tinent to the dredge project, to investigatethe possible benecial uses of the dredgematerial and to add to the body of knowl-edge related to the aquatic invasive Hydrillaverticillata.

Regional Geologic History The processes of erosion and sedi-mentation have been an integral part ofthe natural history of the central NY region.Prior to the Ice Age, the Finger Lakes werenorth owing rivers that were fed by a series

of perpendicular streams. The rivers were

6Introduction

ProjectIntroduction:Tim Lynch

Our Class Visit to the Southwest Dewatering Site, September 2011


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deepened and widened by the glaciers andthe stream valleys were lled with glacial

debris. Since the retreat of the glaciers,these streams have been constantly movingthis debris into the lake and have formed thegorges unique to the area.

Inlet History and FloodingDuring the nineteenth and early-

twentieth centuries the inlet experienced

a massive amount of man-made altera-tions. Signicant de-forestation of the arealed to soil destabilization and subsequenterosion within the watershed as well to asan increase in ood occurrence and dam-age. At the same time, development of theoodplain continued into Renwick Marsh,now known as Tompkins Park. At the turn ofthe twentieth-century, the marsh consisted

of large areas of cattails and other aquaticplants. Decades of lling, bulwark construc-

tion and channelization created the inlet inits current form.

Dredging HistoryOver the last two centuries the inlet

has been dredged and re-congured as partof dierent projects that aimed to improvenavigability and in attempt to control thecommon occurrence of ooding. Between1860 and 1900 the inlet was dredged on sev-eral occasions to maintain a depth of sevenfeet. Between 1910 and 1965 the inlet wasdredged every 20-25 years. The severe oodof 1935 set in motion the plans for the Flood

Control Channel that was begun 30 yearslater in 1965 and completed in 1970. A major

dredge in 1982 removed over 200,000 yardsof material that was used to create the HogsHole Natural Wildlife Area in Allen H. Tre-man Marine Park. In 1999 the ACOE removed75,000 CY from the ood control channel.

Dredging ProcessThe current plan for the inlet dredg-

ing is to use a hydraulic dredge rather thanthe mechanical dredge method used for theLake Source Project. Hydraulic dredging is avacuum process that mixes water with thematerial to create a slurry mix that has theability to be pumped. There are cost ad-vantages to this method and it reduces theimmediate trucking of material. The primarydisadvantage is that it requires an extendedperiod of time and a large site for the dewa-tering process.

Lake Source Cooling Precedent ProjectAlso in 1999, Cornell University

dredged 3,000 CY of material from thesoutheast of Cayuga Lake as part of the LakeSource Cooling project. This project used aclamshell dredge to mechanically removematerial. This allowed the dewatering to oc-cur within hours on shore in containers. The

7Introduction

Renwick Marsh, 1906 (Ithaca Historical Society)Dredge in Cayuga Inlet near Cascadilla Creek, early 1900s(Ithaca Historical Society)


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material was then truck transported to a sitein Dryden.

Dredge MaterialThe class was able to use the Dryden

site to test the dierent properties of thedredge material using the existing materialas a control subject. Samples collected fromthe Six Mile Creek Reservoir and the inletitself were also tested. Testing included ana-lyzing plant species at the two Dryden plotsas well as numerous testing on all samplesto analyze physical, biological and chemicalproperties of materials from dierent dredgesites. These experiments sought to deter-mine the ability of these dierent dredgematerials as plant growth mediums.

MethaneThe dredging project will be remov-

ing anaerobic sediments from the inlet.

These sediments contain methane and thedisturbance has the potential to release thisgreenhouse gas into the atmosphere. Usingsediment samples collected from variouslocations in the inlet the class conducted ex-periments to determine the level of potentialmethane release and looked at the feasibilityof potential mitigation methods.

Hydrilla verticillata

The recent discovery of the aquatic

invasive Hydrilla verticillata proposes ad-ditional challenges to the Ithaca Inlet. Thehighly invasive species has to potential tocreate major disruption to the ecology of theinlet and Cayuga Lake and to have a negativeimpact on the recreational industry in thearea. Hydrilla spreads easily and has the abil-ity to regenerate from small plant fragments.The potential for dredging to spread Hydrillafrom its current locations is a cause forconcern. Following the August discovery ofhydrilla in multiple locations in the Inlet, theCity put together a task force to deal withthis issue. The locations were mapped andbeginning in September the inlet was closedto boat trac. In October the aquatic herbi-cide Aquathol K was applied in the aectedareas. Over the next several months the Citywill continue monitor the known stands of

Hydrilla.

This report will summarize the studiesinto the reproduction, survivability and thepossible management of Hydrilla within theinlet.

ReferencesArmstrong, Victoria. A Cultural History Sur-

vey of the Cayuga Waterfront. Print.

Ithaca Dredging Project Website. EcoLogicLLC. EcoLogic LLC, Nov. 2011. Web. 11 Dec.2011. .

Ithaca, NY - Parks. Ocial Website ofIthaca, NY. City of Ithaca. Web. 11 Dec. 2011..

Lawyer, Liz. Hydrilla Treatment Starts inCayuga Inlet. Ithaca Journal [Ithaca, NY] 11Oct. 2011. Print.

New York State Geology - Page 4. Museumof the Earth. Paleontological Research Insti-tution. Web. 11 Dec. 2011.

.

Wiedorn, William S. The Plans for the Develop-ment of Stewart Park. Ithaca: CornellUniversity, NY. Print. Thesis

8Introduction


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To understand the process of sedimentation in theCayuga Inlet system it is necessary to step back,look upstream and consider what the contributorsto the system are. Through a watershed approachit is possible to qualify what the hydrologic andmaterial inputs are and ask whether it is possible

to prevent the sediments from entering thesystem, thus reducing the need for dredgingmaintenance. As found through this investigationsedimentation in the inlet is the legacy of geologicand glacial processes, with contributions fromhuman activity in recent history. These eects areobserved today and the ability to inuence and/orreduce them is unlikely.

KEYNOTES:

(1) The Lake is an accreting system

a. In-stream and channel erosion andsedimentation is the result of large-scalegeomorphologicprocesses, a geologic legacy of glaciationsb. Human land use practices have historicallyaggravated upland soil erosion contributingto sediments in the hydrologic system, aprocess known as legacy sedimentdevelopment

(2) Accretion is a natural process (modied by humanactivity) and unlikely mitigated

(3) Continuous sedimentation creates a maintenanceissue

(4) Sediment in the inlet is a resource: SPOILS SOILS

South Cayuga Lake Inlet Complex

Watersheds operate at several scales(Figure 2.1.a-c), from large bodies of waterand their surrounding environments (1), thewaterways that ow through them (2), andthe geologic matrix that composes the edgesand bottoms of the hydrologic channels (3).A watershed is the upslope area that drainsto a specic point, typically the outlet of astream, river, or lake or the point where a lowerorder stream meets a higher order stream

(Hollingshead, Anderson, and Haith, 2008.). TheSouth Cayuga Lake Inlet Complex is fed by four(4) subwatersheds: Cayuga Inlet, Buttermilk

Creek, Six Mile Creek, and Cascadilla Creek(Figure 2.2 The four subwatersheds that feed

the South Cayuga Lake Inlet Complex (hillshadevertical exaggeration 5x)). Cayuga Inlet is thesecond-largest in area, receives ows fromTreman State Park and outlets through the FloodControl Channel. Buttermilk Creek is the smallestin area, ows through Buttermilk Falls State Park,and outlets into the Flood Control Channel. SixMile Creek is the largest in area, provides thecitys drinking water supply, and is channelizedthrough its lower reaches through South Ithaca.Cascadilla Creek is the second smallest in area,runs through Collegetown, Downtown, andoutlets into the inlet at the Farmers Market.

SouthernCayugaLakeWatershedMatthew Gonser

9Watershed

Figure 2.1 a Figure 2.1 b Figure 2.1 c


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Sedimentation Contributors to theSouth Cayuga Lake Inlet Complex

The proximate cause of sedimentation inthe inlet system is erosion. Erosion is the processby which soils are worn away by wind, water,

and other natural agents; human activity canaggravate this process. However, the ultimatecause of sedimentation in the inlet system isthe geologic legacy of glaciations and a periodof legacy sediment development in the recenthistory of European settlement in the area (ca.1790).

The Cayuga Lake Watershed Restorationand Protection Plan (2001) and the Cayuga InletDredging Project Site Reconnaissance Report

(2010) identied sediment (erosion of streambeds and banks, and not current land usepractices) as the most-signication non-pointsource (NPS) pollutant aecting Cayuga Lake andits tributary streams. Sediment, as a pollutant,has several impacts on water resources (Table2.1):

The concept of legacy sedimentsidenties sediment eroded from upland areasafter and during centuries of intensive landuses. Deposited in valley bottoms along streamcorridors, legacy sediments bury pre-settlementstreams, oodplains, wetlands, and valley

Pollutant Impact

Sediment:- From Natural erosion of stream channels, construction,urban runo, gravel operations, agriculture, logging,hydromodication

On Fisheries: - Decreases transmission of light, which aects plant production

(food and cover), behavioral activities (nesting, feeding, mating),respiration, digestion, reproduction- Increases surface water temperature, which decreases dissolvedoxygen concentration in water- Decreases spawning habitat (lls pools and nest sites)- Transports absorbed contaminants

On Water Supply:- Damages water treatment pumps, equipment- Increases treatment costs- Reduces reservoir volume- Toxic substances may adhere to sediment- Nutrients increase, which stimulates algae growth

- Decreases river bottom inltration, which reduces well y ieldOn Wetlands: - Reduces ood storage

- Increases peak discharge- Alters habitat

On Recreation:- Decreases clarity of water (public health and safety)- Reduces aesthetic and recreational value- Reduces sport shing populations

bottoms(Figure 2.3 Diagram of legacy sediment devel-opment (Maryland piedmont oodplain develop-ment model. Jacobson, B.D. and Colemen, D.R.1986. Figure 7: 635)). They alter and continue toimpair the hydrologic, biologic, aquatic, riparian,and water quality functions of pre-settlementand modern environments (Hartranft, n.d.).

The period of greatest legacy sedimentdevelopment in Tompkins County occurredbetween 1790 (i.e., approximate period of majorEuropean settlement) and 1900. From a 1790baseline gure for forest cover of nearly 100%,

10Watershed

Figure 2.2 - The Four Watersheds that Feed South Cayuga Lake Inlet

Table 2.1 - Sediments potential impact on water resources (adapted: G/FLRPC and EcoLogic, 2001a, Table 3.1.1, p.3-2)


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11

forest cover dropped to 19% by 1900 (Smith,Marks, and Gardescu, 1993). However, thispercentage increased to 28% in 1938 and 50% by1980 (Figure 2.4 Canopy cover of the SouthCayuga Lake area). This fact indicates that themajority of forests in Tompkins County today arepost-agricultural, and of these reforested areas

it is predominantly on the steeper lakeside andstreamside slopes rather than the atter uplands(Smith et al., 1993). Yet, the impacts of thehistorical forest clearance are being felt today,as legacy sediments are transferred downstreamincluding the inlet complex, and are mostlyirremediable.

Two other major contributors areroadbanks and streambanks (Figure 2.5.a-b

Streambank and roadbank erosion followingTropical Storm Lee, Banks Rd., Six Mile Creek,Ithaca NY (30 September 2011 Photo: M.Gonser)) . Roadside ditches are sources ofsedimentation and erosion. Generally, thecloser they are to the lake the more erosion isoccurring mainly due to steep gradients from theupland portions of the watershed down to thelake (G/FLRPC and EcoLogic, 2001a, p.14). Withthe exception of the Buttermilk and Cascadilla

Watershed

Figure 2.3 - Diagram of legacy sediment development2011 Cover

1940 Cover

Figure 2.4 - Canopy cover of South Cayuga Lake area

Figure 2.5 a - Roadbank erosion

Figure 2.5 b - Streambank erosion


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Creek watersheds, the southern subwatershedshave numerous road ditches classied as verysevere. Six Mile Creek roadbanks are areas ofconcern, with numerous sites documented asmoderately eroded or severely eroded. CayugaInlet appears to have serious roadbank erosion.G/FLRPC and Ecologic (2001a) found a number ofroad ditches documented as having moderate orsevere erosion problems, and a few very severesites.

In the southern tributaries of CayugaLake, the primary source of sediment appears

to be streambank erosion, not runo fromconstruction sites or cultivated elds (G/FLRPCand EcoLogic, LLC. 2001a, p.2). The southernportions of Tompkins County are generallysteeper and less amenable to agriculture. TheCayuga Inlet is characterized as very severe andcontains some of the highest stream ranks in thewatershed (Figure 2.6 Erosion classicationby subwatershed: Streambank Inventory andAverage Stream Rank (G/FLRPC and Ecologic,2001a, Map 3.4.3)). Though qualitatively ranked,is it possible to quantify the material owsthrough the South Cayuga Lake Inlet Complex?

Soil Mass Loading/Wasting

The Cayuga Lake Generalized WatershedLoading Function Geospatial Database (GWLF)(Haith and Shoemaker, 1987) was designedto quantify factors associated with non-pointsource (NPS) pollutants in the Cayuga Lakewatershed at the landscape scale. The databasecontains information on land use, land cover,soil characteristics, climate, sewer and septicsystems, impervious surfaces, and topographyfor the entire Cayuga Lake watershed. Focusingthe model on the four (4) subwatersheds of theCayuga Inlet system we can extract the followingsediment yield estimates (Table 2.2):

12Watershed

Figure 2.6 - Erosion classication by subwatershed

Subwatershed Sediment Yield Estimates (kg/ha/yr) Area (ha)

Buttermilk CreekCascadilla CreekCayuga Inlet

Six Mile Creek

Totals

494091

54

234

29423451

10,336

13,306

30,035 7,028,190 kg/yr

Table 2.2 - Sediment yield estimates per subwatershed generated by the GWLF (Haith and Shoemaker, 1987)


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These numbers, though not necessarily equatingto sedimentation in the inlet itself, are useful

when considering maintenance and managementregimes in light of the current issue of deferredmaintenance, and this and future dredgingprojects. That is, this model can be applied to anapproximate mass balance of the inlet system,quantifying the inputs and outputs againstsome time component (i.e., number of years ofdredging project or frequency of maintenancedredging).

With known erosion classicationsand sedimentation estimates for the four (4)

subwatersheds the next question is are certainplaces more susceptible and is it possible tointervene? One measure of such soil masswasting events is landslide susceptibility. Ingeneral, a landslide is the downward movementof a slope and materials under the forceof gravity. As may be expected with thetopography of the local gorge channel systemsthere is potential for stream bank and wallfailures resulting in greater-than-normal erosion.

The team conducted a landslidesusceptibility analysis adapted from a USGS/NYSGS preliminary landslide analysis algorithm(NYS Division of Homeland Security andEmergency Services, 2007). The two inputsinto the model are slope and soil conditions,from which six (6) weighted factors are derivedand used to determine a hazard range. Thefactors are derived from two (2) data sources:digital elevation models (DEMs) (1) slope;

USDA SSURGO Digital Soil Survey (2) AmericanAssociation of State Highway and Transportation

Ocials (AASHTO) soil classication, (3) liquidlimit, (4) hydrologic group, (5) physical soilproperties (as % silt and clay), and (6) hazardof erosion (see Appendix X for an abridgedmethodology). The resultant output (Figure2.7 Landslide susceptibility for the four (4)South Cayuga Lake subwatersheds (hillshadeexaggeration 5x)) illustrates that the areashighest hazard zones are along gorge channelsand stream banks. As previously noted, thesefragile systems undergo a natural erosion

process that is unlikely to be inuenced throughhuman intervention.

However, this model is merely a depictedof the susceptibility of land to mass wasting and

is not a determination of occurrence. Thoughthe landslide susceptibility analysis is useful inidentifying areas of concern, eld checks arenecessary for validation. Current canopy cover(estimated at 55-60%), which suggests slopestability, qualitatively appears to correspondwith the areas of higher landslide susceptibilityindicating that land cover and use is an importantadditional factor to consider, and is a conditionthat is perhaps improving (Figure 2.8 Currentcanopy cover within the four (4) South Cayuga

Lake subwatersheds with hydrography).

13Watershed

Figure 2.7 - Landslide susceptibility for the four (4) SouthCayuga Lake subwatersheds (hillshade exaggeration 5x)

Figure 2.8 - Current canopy cover within the four (4) SouthCayuga Lake subwatersheds with hydrography


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Mass Balance Maintenance andManagement Regime

The issue surrounding the inlet systemis an extended period of deferred maintenance.As a naturally accreting system, the inletexperiences annual sediment inputs that eitherfall out of solution in the inlet or are transportedto the lake (Figure 2.9 Sediment plume in SouthCayuga Lake, 1993 (G/FLRPC and Ecologic, 2001a,Figure 4.2.8)). This sedimentation necessitatesdredging of the material to ensure the ecosystemservices of navigation and recreation within theinlet. So, what does this all mean? What has

been learned from the investigation of sedimentinputs and the specications of the Cayuga Inlet

Dredging Project?The GWLF estimates 7,028,190 kg/yr of

sediments move through the South Cayuga LakeInlet Complex. This equates to approximately4,167 yd3 annually. Though this volume is notall deposited in the inlet complex, it provides aconservative number to conduct a mass balanceof the inputs versus the outputs over someperiod of time.

The high-end estimate for materialneeded to be dredged is 660,000 yd3. Given that

the decided upon dewatering site at SouthwestPark has a capacity to process 80,000 yd3/yr,if conducted on a continuous schedule, thedredging project will take over 8 years. Duringthat time the inlet will accumulate additionalmaterial (though not the total estimate of 4,167yd3/yr ). That means the net removal of materialwill not actually be 80,000 yd3/yr, thus extendingthe timeframe of the dredging project. Theserough calculations demonstrate the limitations

of the dewatering facility and suggest thatalternative processing methods in conjunctionwith the site at Southwest Park should beinvestigated accelerating the extraction ofmaterial and potentially demonstrating otherbenecial re-uses of dredged material. Theultimate challenge is to develop a continuedmaintenance and management regime fordredging and the dredged material.

Conclusions and Lessons Learned

This section posed the questions ofwhat the hydrologic and material inputs tothe inlet system are. Additionally, it soughtto articulate whether anything could be doneabout preventing sediments from reaching theSouth Cayuga Lake Inlet Complex. From thendings presented above, there are four (4) mainconclusions:

(1) The Lake is an accreting systema. In-stream and channel erosion and

sedimentation is the result of large-scale geomorphologic processes, ageologic legacy of glaciations

b. Human land use practices havehistorically aggravated uplandsoil erosion contributing to sedimentsin the hydrologic system, a processknown as legacy sedimentdevelopment

(2) Accretion is a natural process (modied

by human activity) and unlikely mitigated(3) Continuous sedimentation creates a

maintenance issue(4) Sediment in the inlet is a resource:

SPOILS SOILS

Acknowledging that the sediment will continueto move to and/or through the system and thatinterventions in the landscape are not likely tohalt the process should not be discouraging.

14Watershed

Figure 2.9 - Sediment plume in South Cayuga Lake, 1993(G/FLRPC and Ecologic, 2001a, Figure 4.2.8)


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Once dredged, the material should be viewedas a resource, as parent material or soil in the

making. This stresses that this is a maintenanceand management issue and opportunity forconsidering alternative benecial re-uses of thematerial, changing the mind-set that this materialis a waste product (spoil), but is in fact a resource(soil).

To better understand the potentials ofthe dredged material as a resource, the teamconducted numerous physical, biological, andchemical tests on samples from the watershed,as well as other reference projects and disposal

sites.

References

EcoLogic, LLC. 2010. Site Reconnaissance Report:Southern Tributaries to Cayuga Lake DredgingProject

Genesee/Finger Lakes Regional PlanningCouncil and EcoLogic, LLC. 2000. Cayuga

Lake Watershed Preliminary WatershedCharacterization (http://www.cayugawatershed.org/characterization/#pwc_index).

Genesee/Finger Lakes Regional Planning Counciland EcoLogic, LLC. 2001a. Cayuga Lake WatershedRestoration and Protection Plan (http://www.cayugawatershed.org/Cayuga%20Lake/RPP/cayindex3.htm).

Genesee/Finger Lakes Regional Planning Counciland EcoLogic, LLC. 2001b. Cayuga Lake Watershed

Wetlands Management Project (http://www.cayugawatershed.org/Cayuga%20Lake/wetland/Final%20Report.pdf).

Hartranft, J. n.d. Big Spring Run NaturalFloodplain, Stream and Riparian WetlandRestoration Research Project, Lancaster, PA.

Hollingshead, N., Anderson, S., and Haith, D.2008. The Cayuga Lake Watershed GeneralizedWatershed Loading Function, Department of

Biological and Environmental Engineering, CornellUniversity, Ithaca, New York.

International Association of Dredging Companies(IADC). n.d. (http://www.iadc-dredging.com).

Jacobson, R.B. And Coleman, D.J. 1986.Stratigraphy and Recent evolution of MarylandPiedmont ood plains,American Journal ofScience, 286(8): 617-37.

Karig, D., Miller, T., Hackett, K., and Johnston,R. 2007. Six Mile Creek: A Status Report. Six MileCreek Partners.

New York State Division of Homeland Securityand Emergency Services. 2007. New York StateHazard Mitigation Plan, Section 3.13 LandslideHazard Prole: 3-3623-391 (http://www.semo.state.ny.us/programs/planning/CEMP_Final/S3.J_

Landslide_Hazard_Prole.pdf).

Pennsylvania Department of EnvironmentalProtection. 2006. Chesapeake Bay TributaryStrategy Steering Committee Meetings(March 27). Legacy Sediment WorkgroupMeeting (http://les.dep.state.pa.us/Water/Chesapeake%20Bay%20Program/lib/chesapeake/pdfs/legacy_sediment_denitions.pdf).

Smith, B.E., Marks, P.L., and Gardescu, S. 1993.Two hundred years of forest cover changesin Tompkins County, New York, Bulletin of the

Torrey Botanical Club, 120(3): 229-47.

Acknowledgements

Thanks to Todd Walter andRebecca Marjerison in the Department ofBiological & Environmental Engineering atCornell University.

15Watershed


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Introduction

The purpose of performing tests on

dredge material was to nd out what qualitydredge in the Cayuga Inlet is so that wecould recommend potential benecial usesfor it. The goal was to establish if the dredgematerial is able to sustain plant life and ifthere are any limitations with potentiallyusing the dredge material for variousproductive uses.

Sample Sites

Six Mile Creek ReservoirThe original plan was to collect

samples from the Cayuga Inlet, but the Inletwas closed once Hydrilla verticillata wasdiscovered. We made the decision to usethe Six Mile Creek Reservoir as a samplesite because dredging is already planned toincrease the depth of the reservoir, and it is

very similar as it is simply upstream. It is alsoused by the City of Ithaca as a reservoir fordrinking water, so it would provide a usefuldata set. A total of 16 samples were gath-ered. 10 samples were tested; 3 from the lefttransect, 4 from the center, and 3 from theright [Fig 3.1].

Cayuga Inlet and Flood Control ChannelOnce the inlet was reopened, this

sample site was selected because it is thelocation of the dredging project. Thesesamples were intended to provide a betterunderstanding of what the dredge materialconsists of and what it could be used for.Three samples were tested throughout theInlet and Channel, as denoted by the red tagsin the photo below [Fig 3.2].

16DredgeMaterial

DredgeMaterialAnalysisJamie Nassar & Hayden Stebbins

KEYNOTES:

(1) Nutrients found in dredge material are self

stabilizing based on its chemical characteristics.

(2) Dredge material is low in Organic Matter andcontains High pH levels.

(3) Previous testing indicated that inlet sediment wasmostly clay, based on our ndings inlet sediment is asandy loam.

(4) Dredge material has the ability to sustain plant life.

(5) Aggregate Stability of Dredge material

demonstrates a low quality for structural material.

Figure 3.1 - Location of sample sites in Six Mile Creek Reservoir Figure 3.2 - Location of sample sites in Cayuga Inlet


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Lake Source Cooling Dredge Disposal Site,Dryden, NY(Intersection of Hanshaw Rd. & Niemi Rd.)

This sample site was chosen as areference site to assess what happens to

dredge that is left on a eld and treated witha zero-order restoration approach. This wasthe site where Cornell spread dredge mate-rial from the Lake Source Cooling project onCayuga Lake in 2000. Dredge material wasspread onto an old corneld and left undis-turbed. Six samples were taken from thedredge material and six samples were takenfrom the eld directly adjacent [Fig 3.3].

Three samples from each side were tested.Species diversity was also studied and com-

pared between the dredge eld and the non-dredge eld. This site provided an oppor-tunity to test whether there are persistent,long-term dierences in soil characteristicsand plant community composition betweendredge and non-dredge material.

Materials and Methods The Materials and Methods sectionfor soil analysis has been adapted from theCornell Soil Health Assessment TrainingManual, since the tests were carried out inthe Cornell Soil Health Lab. The samples fromthe Inlet and the Reservoir were taken usingan Eckman dredge dropped from a canoeonto the substrate [Fig 3.4]. The samples at

the Dryden site were taken by digging up soilsamples.

Cornell Soil Health LabsThe Cornell Soil Health Test was

performed on the samples from the Dryden,Inlet, and Six Mile Creek sample sites withthe help and guidance of Extension AssociateBob Schindelbeck. Tests were performed onthe physical, biological, and chemical char-acteristics of the soil samples. The physicaltests included testing rapid soil texture, wetaggregate stability, available water capac-ity, and eld penetration. Biological testsincluded an active carbon test, potentiallyminerizable nitrogen, and root health rating.Chemical tests included organic matter andnutrient analysis.

17DredgeMaterial

Figure 3.3 - Dredge and Non-dredge sample sites

Figure 3.4 - Students harvesting dredge material from inlet


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Soil Texture

PurposeSoil particles are the building blocks

of the soil skeleton. Most of a soils particlesare a mixture of variously sized minerals thatdene its texture. A soils textural classsuch as clay, clay loam, loam, sandy loam,or sandis perhaps its most fundamental

inherent characteristics. It aects many ofthe important physical, biological, and chemi-cal processes in a soil and changes little overtime. The textural class is dened by the rela-tive amounts of sand (0.05 to 2 mm particlesize), silt (0.002 to 0.05 mm), and clay (lessthan 0.002 mm), as seen in the textural tri-angle. Particles that are larger than 2 mm arerock fragments (pebbles, cobbles, stones,

and boulders), which are not considered inthe textural class because they are relatively

inert.

Methods A portion of the soil sample is oven-driedat 60 C and sieved past 2mm. About 14g (+/- 0.1g) of sieved soil is addedto a 50ml centrifuge tube containing 42ml of3% soap (sodium hexametaphosphate) solu-tion. Shake vigorously on reciprocating shakerfor 2 hours to fully disperse soil into suspen-sion. Entire contents of centrifuge tube arewashed onto a 0.053mm soil sieve assembly.Sieve assembly consists of 0.053mm sieve ontop of a plastic funnel above a 600ml beaker.

18DredgeMaterial

Figure 3.6 - Critical tests performed on the dredge material

Figure 3.7 - Students performing Soil Texture test


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Rinse all material through the sieve using n-gers or rubber policeman. Sand captured on

top of the sieve is washed into a tarred metalcan and set aside. Silt and clay particles collected in the600ml beaker are re-suspended by stirringand allowed to settle for 2 hours. The clayin suspension is then carefully decanted.The settled silt at the bottom of the beakeris washed into a second tarred can. Bothtarred cans (one containing the sand frac-tion and the other the silt fraction) are driedovernight at 105 C to constant weight beforeweighing. Calculate percent sand, silt clay from:Sand (%) = dry wt. sand (g) / dry wt. (g) soiladded to centrifuge tubeSilt (%) = dry wt. silt (g) / dry wt. (g) soiladded to centrifuge tubeClay (%) = 100% - Sand (%) - Silt (%)

ConclusionAnother preconceived notion aboutthe dredge material was that it would bepredominantly clay and ne particle material.However, our testing found that the CayugaInlet is a sandy loam, which contains verylittle clay (only 6.82%) [Table 3.1].

Aggregate Stability

PurposeThis tests the soils physical quality

with regard to its capacity to sustain its struc-ture during most impacting conditions: a

heavy rainstorm after surface drying weath-er. Soils with low aggregate stability tend toform surface crusts, which can reduce bothwater inltration and air exchange. This poorsoil aggregation also makes the soil moredicult to manage, and reduces its ability todry o quickly. In heavy soils, enhanced fri-ability and crumbliness from good aggrega-tion makes the soil seem lighter.

MethodsA portion of the soil is oven-dried at 40 oC.Using stacked sieves of 2.0 mm and 0.25

mm with a catch pan, the dried soil is shakenfor 10 seconds on a Tyler Coarse Sieve Shakerto separate it into varied size fractions; small(0.25 - 2.0 mm) and large (2.0 - 8.0 mm).A single layer of small aggregates (0.25 -2.0 mm) is spread on a 0.25 mm sieve (sievediameter is 200 mm (8 inches)) (A).Sieves are placed at a distance of 500 mm(20 inches) below a rainfall simulator, which

19DredgeMaterial

Table 3.1 - Soil Texture Triangle with Inlet, Dryden, and Res-ervoir soil range in red.

Table 3.2 - Graph of Aggregate Stability results between thereservoir and Dryden samples.


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delivers individual drops of 4.0 mm diameter(B).

The test is run for 5 minutes and delivers12.5 mm depth of water (approximately 0.5inches) as drops to each sieve. This is equiva-lent to a heavy thunderstorm. See soils start-ing to wet in (C). A total of 0.74 J of energythus impact each sieve over this 5-minuterainfall period. Since 0.164 mJ of energy isdelivered for each 4.0 mm diameter, it can becalculated that 15 drops per second impacteach sieve.The slaked soil material that fell throughthe during the simulated rainfall event, andany stones remaining on the sieve are col-lected, dried and weighed, and the fractionof stable soil aggregates is calculated usingthe following equation:WSA = Wstable / W total, whereWstable = Wtotal - (Wslaked +Wstones)where W = weight (g) of stable soil aggre-

gates (stable), total aggregates tested (to-tal), aggregates slaked out of sieve (slaked),and stones retained in sieve after test(stones). Corrections are made for stones.

ConclusionAggregate Stability of the Reservoir

was much lower than the control site, 8.91%compared to 87.33%. This means that the

dredge material will probably have a veryweak ability to sustain its physical structure.

This can be attributed to many things, butmainly its low organic matter content. Or-ganic matter helps soils maintain physicalstructure, so adding organic matter to thedredge material, which will be discussed inthe Alternatives section, could amelioratethis (Refer to appendix B for charted re-sults).

Available Water Capacity (AWC)

PurposeWater storage in soil is important for

plant growth. Water is stored in soil poresand in organic matter. In the eld, the moistend of water storage begins when gravitydrainage ceases (eld capacity). The dry endof the storage range is that the permanentwilting point. Water held in soils that is

unavailable to plants is called hygroscopicwater. Clay soils tend to hold more waterthan sandy soils. Sandy soils tend to losemore water to gravity than clay soils

MethodsSoil is placed on ceramic plates that areinserted into high-pressure chambers to ex-tract the water at eld capacity (10 kPa) and

at the permanent wilting point (1500 kPa) (Aand B).

After the sample equilibrates at the targetpressure; the sample is weighed and thenoven-dried at 105oC overnight (C).The sample dry weight is then determinedand soil water content at each pressure iscalculated. The available water capacity isthe soil water loss between the 10 and 1500kPa pressures.)

Conclusion

In the end the results showed thatthe dredge material that was taken from thereservoir had a higher AWC than that of thedredge material that was tested on from theDryden site. The samples that had the high-est AWC were the ones from the control sitein Dryden. Several factors could be contrib-uted to the results but one should look at thesoil texture to understand the numbers. The

fact that the non-dredge material has thehighest percentage of clay in the soil wouldconrm that this soil has the highest AWCrating. Next the dredge material in Drydenhas the highest percentage of sand, whichwould allow the water to ow through thesoil prole, thus lower the AWC. (Refer to ap-pendix B for charted results)

20DredgeMaterial


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Organic Matter

PurposeOrganic matter is any material that

is derived from living organisms, includingplants and soil fauna. Total soil organic mat-ter consists of both living and dead material,including well-decomposed humus. The per-cent organic matter is determined by loss onignition, based on the change in weight aftera soil is exposed to approximately 950F ina furnace. Organic matter content is often

provided by soil analysis laboratories in con-junction with the analysis of major and minornutrients.

MethodsThe Cornell Nutrient Analysis Laboratorymeasures the percent organic matter usingloss on ignition.A sample is dried at 105C to remove all

water.The sample is then ashed for two hoursat 500C and the percent of weight lost iscalculated.The % loss on ignition (LOI) is converted to% organic matter (OM) using the followingequation:% OM = (% LOI * 0.7) - 0.23

ConclusionOriginally, it was thought that there

would be no organic matter in the dredgematerial, however we found that there was2.2% organic matter in the Reservoir sitesamples. This is not a very high amount, butaround a 5% OM content is recommendedfor agricultural uses, and it is much higherthan the expected content of 0%. [Table 3.3](Refer to appendix B for charted results)

Active Carbon

PurposeActive carbon is an indicator of the

fraction of soil organic matter that is readilyavailable as a carbon and energy source forthe soil microbial community (i.e., food forthe soil food web). The soil is mixed with po-tassium permanganate (deep purple in color)and as it oxidizes, the active carbon the colorchanges (becomes less purple), which canbe observed visually, but is very accurately

measured with a spectrophotometer.

MethodsFrom the larger thoroughly mixed com-posite bulk soil, a subsample is collected andallowed to air dry. The soil is ground andsieved to 2 mm.A 2.5 g sample of air-dried soil is placed ina 50 ml centrifuge tube lled with 20 ml of a

0.02 M potassium permanganate (KMnO4)solution, which is deep purple in colorThe soil and KMnO4 are shaken for exactly2 minutes to oxidize the active carbon inthe sample. The purple color becomes lighteras a result of this oxidation.The sample is centrifuged for 5 minutes,and the supernatant is diluted with distilledwater and measured for absorbance at 550nm.

21DredgeMaterial

Table 3.3 - Graph of Organic Matter results between thereservoir and Dryden samples.


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soil microbial community to convert (min-eralize) nitrogen tied up in complex organic

residues into the plant available form ofammonium. Soil samples are incubated for7 days and the amount of ammonium pro-duced in that period reects the capacity fornitrogen mineralization.

MethodsAs soon as possible after sampling, themixed composite bulk soil sample (stored at40F) is sieved and two 8-g soil samples are

removed and placed into 50 ml centrifugetubes.40 ml of 2.0 M potassium chloride (KCl)is added to one of the tubes, shaken on amechanical shaker for 1 hour, centrifuged for10 minutes, and then 20 ml of the superna-tant is collected and analyzed for ammoniumconcentration (time 0 measurement).10 ml of distilled water is added to the sec-

ond tube, it is hand shaken and stored (incu-bated) for 7 days at 30C (86F).After the 7 day anaerobic incubation, 30ml of 2.67 M KCl is added to the secondtube (creating a 2.0 M solution), the tube isshaken on a mechanical shaker for 1 hour,centrifuged for 10 minutes, and then 20 mlof the supernatant is collected and analyzedfor ammonium concentration (time 7 days

The absorbance of a standard dilutionseries of the KMnO4 is also measured to cre-

ate a calibration curve for interpreting thesample absorbance data.A simple formula is used to convert sampleabsorbance value to active C in units of mgcarbon per kg of soil.

ConclusionActive Carbon was low in both the

reservoir and the Dryden dredge material;the non-dredge material was in range of

a healthy level according the Cornell SoilHealth Test. This could be expected by look-ing back at the levels of the organic matterand aggregate stability in the soil, which isan indicator of Active Carbon levels in a soil,the lower the levels of organic matter thelower levels of active carbon. The fact thatthe dredge material has lower levels of activecarbon would result in prolong periods of

management to increase the organic mattercontent (Refer to Appendix B for chartedresults).

Potentially Mineralizable Nitrogen

PurposePotentially Mineralizable Nitrogen

(PMN) is an indicator of the capacity of the

measurement).The dierence between the time 0 and

time 7-day ammonium concentration is therate at which the soil microbes are able tomineralize organic nitrogen in the soil sam-ple. Results are reported in units of micro-grams nitrogen mineralized per gram dryweight of soil per week.

ConclusionThe PMN results were unforeseen

due to the fact every other test has been in

line with conventional wisdom, which wouldlead you to think that since the reservoirmaterial is low in organic matter, aggregatestability and active carbon it would have alow PMN. So when the results showed thatthe reservoir had almost double the amountof PMN compared to that of the non-dredgematerial it seemed like an anomaly. This highscore tells us that the reservoir has a higher

amount nitrogen rich organic matter, as aresult an abundant amount of soil microbes.Further tests would be needed to

conrm these ndings since they are not inline with conventions (Refer to appendix Bfor charted results).

22DredgeMaterial


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Root Health Assessment

PurposeRoot health assessment is a mea-

sure of the quality and function of the rootsas indicated by size, color, texture and theabsence of symptoms and damage by rootpathogens including the fungi Fusarium,Pythium, Rhizoctonia, Thielaviopsis, and

plant-parasitic nematodes such as northernroot-knot. For vegetable production sys-tems, a soil bioassay with beans was shownto be highly eective in assessing root healthas a component of overall soil health. Beansare susceptible to the major pathogensthat impact vegetable, legume, and foragecrops grown in New York and the Northeastregion, thus their suitability as an indicator

plant. The selection of other indicator plantsmight be needed for the proper assessment

of root health of soils under dierent produc-tion systems.

MethodsA sub-sample from the composited bulk soilsample is thoroughly mixed.Approximately 200 cubic cm of soil isplaced in each of 7 cone-tubes (A), whichhave a light cotton ball, paper towel, or smallrock placed in the bottom to prevent soil loss

through the drainage holes.Each tube is planted with one snap beanseed such as cv. Hystyle or others. Theseeds are treated with a combination of fun-gicides to prevent seed decay and seedlingdiseases (B). The helium (curved side) of theseed is placed at/horizontally to encouragesuccessful seed germination and emergence(straight vertical shoots).

The plants are maintained in a greenhouseunder supplemental light or in a screenhouse and watered regularly for 4 weeks (C).The plants are removed from their contain-ers and the roots washed under runningwater and rated for root health on a scale of1 to 9. For example:1 = white and coarse textured hypocotyl androots; healthy (D);

3 = light discoloration and lesions coveringup to a maximum of 10% of

Hypocotyl and root tissues (E);5 = approximately 25% of hypocotyl and roottissue have lesions, but the tissues remainrm. There is little decay or damage to theroot system (F);7 to 9 = 50 to 75% of hypocotyl and roots se-verely symptomatic and at advanced stagesof decay (G).

Conclusion

Root Health Assessment is measuredon a scale of 1 -9, with 1 being the most and9 being the least functional. All three-samplesites (reservoir, Dryden dredge and Drydennon-dredge) fell with in the 5-6 ranges withthe Dryden dredge being the lowest at 5.1and the Dryden non-dredge being the high-est at 5.9. The results show us that all threeof these soil fall within the average, which

was a little unexpected at least for theDryden non dredge material (Refer to Ap-pendix B for charted results).

23DredgeMaterial


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Zinc also found in the samples, as shown inTable 3.5.

Calcium and Magnesium were alsofound in high levels, however Calcium acts asa buer to the uptake of Magnesium, so theyshouldnt be of concern. The dredge materialis suitable for plant growth, but should bemade more stable by adding organic matterif it is to be used for planting medium.

Metals According to the Ecologic LLC report,several hotspots were found for Lead, Cop-per, PAHs, and PCBs, qualifying the dredgematerial from Cayuga Inlet as Class B [Fig3.9/3.10]. However, the majority of thesamples tested at Class A levels, and when

Chemical Analysis

PurposeThe chemical analysis as part of the

Cornell Soil Health Test is a traditional soilfertility test analysis package that measureslevels of pH and plant macro- and micronutri-ents. Measured levels are interpreted in theframework of suciency and excess but arenot crop specic.

Conclusion

Nutrients (see appendix C)pH was also found to be high in the

Reservoir samples. Luckily, this acts as abuer to the uptake of unusually high levelsof Manganese, Aluminum, Iron, Copper, and

the Inlet is dredged, these hotspots will bedispersed.

Also, if the dredge material is mixedwith organic material such as compost, theconcentrations of these toxins will be dilutedand the organic matter could make much ofit biologically unavailable, according to Mur-ray McBride. The high pH level also meanscopper will not be very biologically available[Fig. 3.9].

24DredgeMaterial

Plant Available Nutrients:

Extractable phosphorsExtractable potassiumMagnesiumIronManganeseZinc

pH

The available nutrients are extracted with Morgans solution, a sodiumacetate/acetic acid solution, well buered at pH 4.8. Activated carbonis added to the extraction to aid in the removal of o rganic matter andto help decolorize the extraction solution. After shaking, the extractionslurry is ltered and analyzed for K, Ca, Mg, Fe, Al, Mn, and Zn on the ICP(Jyobin Yvon). The plant available PO4-P is measured using an Alpkem

Automated rapid ow analyzer.

The pH of a suspension of one part water to one part soil is determinedeither manually, using standard pH meter and electrodes, orautomatically using a Fisher CATTM titrimeter.

Chemical Analysis Methods

Figure 3.8 - pH Nutrient Chart


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25DredgeMaterial

Table 3.5 - Nutrient Levels of site samples

Figure 3.10 - Location of samples on Cayuga Inlet byECOLOGIC for metals testing

Figure 3.9 - EcoLogics Metal Test Results: Analytes detected in Cayuga Inlet sediments exceeding TOGS5.1.9 Class A Sediment Quality Threshold values (Courtesy

Measurements Reservoir Dryden Dredge Site Dryden Control Site

Phosphorus(P)(lbs./A) 10.2 5.3 11.3

Potassium (K)(lbs./A) 473.5 401.7 446.7

Magnesium(Mg)(lbs./A) 1107.5 498.3 570.0

Iron(Fe)(lbs./A) 116.9 16.0 14.7

Manganese(Mn)(lbs./A) 1048.3 108.0 68.3

Zinc (Zn)(lbs./A) 8.1 5.0 2.6

Calcium (Ca)(lbs./A) 84597.0 12846.7 4363.3

Aluminum(Al)(lbs./A) 90.1 34.0 135.3


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Purpose

This study was performed at theDryden dredge disposal site. The studyof plant communities looks at one of thepressing questions when analyzing thedredge material: can dredge materialsustain plant growth with out any additionalmanagement practices? The answer to thisquestion could have a direct inuence onhow the dredge material can be used in the

future. We tested to see what plants wouldbe found in the dredge material comparedto the non-dredge material, and which plantwould be shared between the two sites.

MethodsThe rarefaction method was used in settingboundaries for establishing the respectiveplant communities for the dredge and non-dredge material.A location was selected at each siteStarting with a .25 meter square quadrant,the quadrant were progressively enlargedaccording to the chart [Fig 4.2]Species in each quadrat were recorded andcollected in the eldSpecies collected from each quadrat werekeyed out to the most precise taxonomicname possible

ConclusionsIt was found that dredge material

left untouched to a zero order managementpractice does have the ability to sustain plant

growth on its own. The dredge sedimentwas found to have roughly 20 identiableplant species with 12 of those species be-ing exclusive to the dredge material. Out ofthe 12 species half of them were non-nativeplants. The non-dredge or Old Field Site had25 total plant species with 17 species beingexclusive to the non-dredge material. Out ofthose 17 species 7 of them were non-native.

26DredgeMaterial

DrydenSitePlantCommunitiesJamie Nassar & Hayden Stebbins

Combined between the two sites there wasa total of 37 identiable species with 8 of thespecies shared between the two sites and atotal of 17 species being non-native [Fig 4.1].

Looking closer at the plant commu-nities, there is a dierence not just in the

numbers, but in the actual plants that werefound with the site. The dredge material hasa dierent plant community that the non-dredge, which could be due to the fact thatdredge material has dierent parent materialand possibly carried some seeds with it whenit was removed from the lake. No confor-mation was gained into weather or not thedredge material contains a seed bank.

Figure 4.1 - Dryden Site Species Area Curve

Figure 4.2 - Nested Quadrant


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27DredgeMaterial

Figure 4.3 - Dryden Plant Communities

Aster larvisAster novae-angliaeCornus spp.Daucus pusillusDipsacus sylvestrusFragaria virginianaFraxinus pensylvanicaHieracium spp.Lonicera tataricaOnoclea sensibilisOxalis spp.Phleum pratenvse

Polygonum pensylvanicumPotentilla indicaRanunculus bulbosusRhamnus catharticaSolidago canadensisUnknown Aster 1Viburnum dentatumVitis spp.

Aster simplex

ChrysanthemumleucanthemumConvolvulus arvensis

Fragaria chiloensisGeranium maculatumHieracium longipilumLonicera involucrata

Lotus corniculatusPenstemon digitalisPenstemon hirsutusPontentilla simplex

Salix albaUnknown Aster 2Unknown Grass 2Unknown Grass 4Unknown Rush 2

Viburnum var. cassinoides

Aster lateriforus

Cirsium vulgareGalium mollugoPrunella vilgarisSolidego rugosa

Solidego tenuifolia

Stellaria mediaTrifolium repensUnknown Grass 1Unknown Grass 3Unknown Rush 1

Veronica Spp.Vicia spp.

Ambrosia artemisiifoliaAsclepias syriaca

Gentianposis crinitaPhalaris arundinacea

A - Old Field Soil

B - Sediment Soil

A/B - Both Soils

C - Outside Sample Area


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28DredgeMaterial

Figure 4.4 - Dryden Plant Communities


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29DredgeMaterial

ReferencesDelhaize, Emmanuel and Peter R. Ryan.Alu-minum Toxicity and Tolerance in Plants. PlantPhysiology. Vol. 107, No. 2 (Feb., 1995), pp.315-321

EcoLogic, LLC. 2010. Site ReconnaissanceReport: Southern Tributaries to Cayuga LakeDredging Project Genesee/Finger LakesRegional Planning Council and EcoLogic, LLC.2000. Cayuga Lake Watershed PreliminaryWatershed Characterization (http://www.ca-

yugawatershed.org/characterization/#pwc_index).

Environmental Enhancement through Recy-cling of Natural Materials. Minnesota Mulchand Soil, 2010. Print.(http://www.mnmulchandsoil.com/up-loads/3/7/7/4/3774799/dredged_pp.pdf)

Schulte, E.E., and K.A. Kelling. Soil Calcium

to Magnesium Ratios-Should You Be Con-cerned. University of Wisconsin Extension(1993). Print.(http://www.soils.wisc.edu/extension/pubs/A2986.Pdf)

Gugino, Beth K., George S. Abawi, OmololuJ. Idowu, Robert R. Schindelbeck, Larissa L.Smith, Janice E. Thies, David W. Wolfe, and EsHarold M. Van. Cornell Soil Health AssessmentTraining Manual. Geneva, NY: Cornell Univer-sity College of Agriculture and Life Sciences,2009. Print. {http://soilhealth.cals.cornell.edu/extension/manual.htm}

Thompson, Louis Milton. Soils and Soil Fertil-ity. New York: McGraw-Hill, 1973. Print.

http://organicgarden.org.uk/gardening/soil/soil-chemistryCalcium

AcknowledgementsMurray McBride and Bob Schindelbeck, Cropand Soil Science, College of Agriculture and

Life Sciences, Cornell University

Students Identifying Plant Samples from the Dryden Site


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Introduction

Methane (CH4) is one of themost signicant greenhouse gasses aftercarbon dioxide. Since pre-industrial times,atmospheric methane concentrations haveincreased from approximately 715 parts per

billion (ppb) to 1774 ppb in 2005 as a resultof human activity. This has contributeda radiative forcing of 0.48 W/m

2, nearly a

third the radiative forcing of carbon dioxidedespite methanes much lower atmosphericconcentration (IPCC 2007). Thus, the releaseof even a small amount of methane is ofconcern for global climate change.

Dredging the Cayuga Inlet has the

potential to release methane into the atmo-sphere. Low-oxygen sediments are home

to a community of methanogenic archea,microorganisms which produce methane asthe nal step of fermenting organic matter inanaerobic respiration. This sort of methanebiogenesis constitutes most of the recentmethane production (Reeburgh 1996).

Inlet sediments, like most sedi-ments at the bottoms at lakes, are likely tobe anaerobic, or low in oxygen, and thushome to methanogens. How much methane

production can we expect from the dredg-ing of the Cayuga Inlet? Is this productionuniform, or are there hotspots of particularconcern? To nd out, we collected sedimentsamples from a variety of locations and mea-sured their total methane production over amonth.

Methods

Sediment samples were collectedfrom above the 60-foot dam at the Six MileCreek Reservoir (Fig. 5.1) and the Cayuga In-let (Fig. 5.2) using canoes and a small Ekmandredge. Initial plans called for sample col-lection only from the inlet, but the presenceof Hydrilla verticillata in the inlet postponedsample collection, so samples were rst col-lected from the reservoir. Sediment sampleswere placed in mason jars and the headspace

lled with water, following standard Fahey-Yavitt lab procedures. Samples were left torest and settle in a dark cabinet for approxi-

30MethaneAnalysis

mately a week after collection.After a week of rest, samples were

stirred to free any methane produced andbriey left to settle again before the waterlling the headspace was drained. Then themason jars were sealed and all air evacuatedto create an anoxic environment. Approxi-mately every week (for reservoir samples) ortwice a week (for inlet samples) for a monthfollowing, a 20 milliliter gas sample wasdrawn through a septum in the lid of each jarusing a syringe. Each gas sample was then

MethaneProductioninInletSediments:SpatialVariabilityandAlternativesforMitigationJack Mascharka, Rebecca Montross, & Nadia PierrehumbertKEYNOTES:

(1) Methane-producing microorganisms inhabitanaerobic (low-oxygen) sediments, such as those inthe Cayuga Inlet

(2) Laboratory tests indicate that if anaerobicconditions in sediment persist after dredging, upto 30,300 kg of methane could be released into theatmosphere

(3) A number of methane mitigation measures, suchas promoting aerobic conditions during dewateringor capturing any methane produced, could be

incorporated into the dewatering process to preventthe release of this greenhouse gas.

Figure 5.1 - Sediment collection sites, Six Mile Creek Reservoir


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injected into a gas chromatograph to mea-sure methane concentration.

Samples of lab air and standard 2000parts per million methane were also mea-sured to test for anomalous conditions in thelab and establish proper calibration, respec-tively.

Parts per million of methane wereconverted to micromoles and standardizedto the amount of sediment in each sample,thus returning results in micromoles of meth-ane production per liter of sediment over

time.

ResultsReservoir samples

Because methane production in theinlet, not the reservoir, was the primaryconcern, reservoir samples were used totest and rene methods. Methane produc-tion in all reservoir samples increased sub-stantially over the testing period (Table 5.1),conrming the presence of methanogensand organic carbon in the samples. Becausejar headspace was not recorded for reservoirsamples, meaningful comparisons betweensamples was not possible; however, allsamples showed signicant methane produc-tion over the testing period.

Taking into account the reservoir sam-ple results, methods were altered as follows:

sample testing increased in frequency, fromonce to twice per week; the sensitivity of thegas chromatograph was adjusted to be ablemeasure higher expected methane concen-

trations; future sediment samples were col-lected in larger jars, to facilitate drawing ogas samples; and headspace in the jars wasmeasured to allow conversion from parts permillion to moles.

Inlet samplesMost inlet samples produced meth-

ane over the testing period, with the only ex-

31MethaneAnalysis

Figure 5.2 - Sediment collection sites, Cayuga Inlet

Table 5.1 - Methane production in Reservoir samples, partsper million

Sample ID

R1 83094 max maxR2 1175 4081 8756

R3 1221 11871 38779

R4 55942 91305 max

R5 2139 13358 41613

R6 4418 17011 47511

C1 106537 max max

C2 21986 58476 104395

C3 3752 22871 57598

C4 52594 114861 max

C5 23330 69842 max

C6 8283 38066 82299

L1 20677 59468 100834L2 6675 31150 59371

L3 6795 23605 20551

L4 2979 22868 53980

Concentration[ppm]10.14.2011




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ception being sample 1W (Table 5.2). Meth-ane production in inlet samples sorted into

three groups and two anomalous samples.The rst group, consisting of samples 1C, 2C,3C, 4C, and 6C, produced very little meth-ane throughout the experiment, with totalmethane production remaining below 200umol per liter of wet sediment. The secondgroup, comprising samples 1E and 2E, pro-duced very little methane initially, but slowlyincreased production to 500-1000 umol/Lwet sediment over the course of the month.

The third group, samples 5W and from theadjoining culvert, produced methane rapidlyduring the rst week before tapering o toa nal production between 1000 and 2000umol/L wet sediment. Sample 1W appears to

have reached its peak methane productionbefore testing even began and methane con-

centration in the jar declined for unknownreasons over the month. Finally, sample 5Cproduced methane in substantial quantitiesthroughout the month, peaking at about4,700 umol/L wet sediment at the end of thetesting period with no denite signs of taper-ing o.

With the exception of 5C, centersamples showed very low methane produc-tion (Fig. 5.3). Samples showing appreciable

methane production (Fig. 5.4) were generallylocated near the east and west banks of thechannel. In addition, higher methane pro-duction is concentrated in certain hotspots,such as the narrow Six Mile Creek inlet, while

lower methane production is scattered inthe center of the wider ood control channel

(Fig. 5.5).

Discussion and conclusionsThe results suggest several alterations tothe procedure for future studies of methaneproduction in the Cayuga inlet.

The peculiar pattern of methaneproduction over time in inlet sample 1W,which peaked before testing started andapparently consumed methane throughout

the testing period, suggests that methaneconcentrations should be measured soonerthan a week after samples are prepared; infact, establishing a baseline methane concen-tration immediately after evacuating the airin the jar might be a good idea. In addition, amore thorough study would continue mea-surements of methane concentration untilall samples had ceased production, unlikesample 5C, whose methane concentrationwas still increasing when the experiment wasended.

The non-uniform spatial distributionof methane production also suggest that amore thorough survey is necessary to accu-rately estimate potential methane produc-tion from inlet sediments. In particular, thehotspot of methane production in Six MileCreek is also the only source of sample from

32MethaneAnalysis

Table 5.2 -Methane production in Inlet samples, umol methane per liter of wet sediment

Sample ID 11-Nov-11 15-Nov-11 18-Nov-11 22-Nov-11 29-Nov-11 2-Dec-11

1E 117.94 25.08 191.35 404.38 675.49 850.74

1C 15.20 46.54 63.65 57.06 48.82 55.85

1W 429.78 50.42 64.45 7.07 0 4.3

2E 60.95 89.95 311.11 454.02 607.89 602.642C 118.54 105.9 68.1 3.59 2.87 2.03

3C 96.66 63.7 7.82 2.81 72.35 126.26

4C 30.17 26.24 32.85 50.44 174.68 151.56

5C 729.42 1764.37 2726.77 3699.59 4761.17 4733.22

5W 408.34 963.74 1357.89 1532.43 1498.98 1708.33

6C 105.94 68.25 15.59 1.09 1

Culvert 251.57 692.45 1109.23 1229.57 1311.65 1267.82


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Six Mile Creek; most samples were takenfrom the Flood Control Channel, which the

city of Ithaca is not responsible for dredg-ing. Are methane production values in thehotspot typical of the Six Mile Creek channel?Does methane production further down-stream in the Inlet more closely resemblethat in the Flood Control Channel or in SixMile Creek channel? To be able to accuratelyassess the methane output of the dredgingproject, these questions must be addressed,

and more thorough sampling throughout theinlet would do so.

Input of organic matter may contrib-ute to the observed geographical distribu-tion of hotspots of methane production (Fig.5.5). The only hotspot in the ood controlchannel occurs near the west bank; the SixMile Creek hotspot, near the Bualo StreetBridge, is in a narrow channel. Both theselocations will receive a higher input of or-ganic matter than the center of the broad

ood control channel, thus providing morefood for the methanogens. In addition, the

Six Mile Creek hotspot is downstream of awooded area with overhanging vegetation,which will also contribute substantial quanti-ties of organic matter to the channel sedi-ments. This stands in contrast to the oodcontrol channel, whose rip-rapped banks andgrassy verge can contribute relatively littleorganic matter for decomposition.

Several possible approaches to pre-

33MethaneAnalysis

8-Nov 13-Nov 18-Nov 23-Nov 28-Nov 3-Dec 8-Dec

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

3500.00

4000.00

4500.00

5000.00

Methane Evolution of Inlet Samples over Time

1C

2C

3C

4C

5C

6C

Date

umolCH4

perLwetsediment

8-Nov 13-Nov 18-Nov 23-Nov 28-Nov 3-Dec 8-Dec

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

3500.00

4000.00

4500.00

5000.00

Methane Evolution of Inlet Samples over Time

1E

1W

2E

5C

5W

Culvert

Date

umolCH4

perLwetsediment

Figure 5.3 -Total methane production in center Inlet samples over time Figure 5.4 - Total methane production in higher-range Inlet samples over time


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venting or mitigating methane release fromdredging might be incorporated into the

sediment dewatering and reuse plans. Therst option is to articially hasten the onsetof aerobic, rather than anaerobic, conditionsin the sediment. This would shift the micro-bial community from methanogens to CO2-producing bacteria. Three possibilities forpromoting the diusion of oxygen into thesediment are turbation, aeration, and spread-ing the sediment thinly. Periodic turbation,or mixing, of the sediment would incorpo-

rate oxygen further down into the sedimentcolumn, thus promoting aerobic conditions.Aeration could be done either mechanicallyor biologically, using pipes, roots, or burrow-ing worms to let oxygen penetrate furtherdown. However, dense vegetation growingon the sediment is likely to decrease oxygendiusion. Finally, since the most anaerobicconditions are deep in the sediment andoxygen diusion is highest near the surface,simply spreading the sediment thinly wouldincrease oxygen concentration and preventanaerobic conditions.

Methane capture has been used onlandlls (Bracmort et al, 2009). This ap-proach sees methane production as a re-source rather than a liability. The dewateringsite would be capped and methane col-lected as it rose. The methane could then be

34MethaneAnalysis

Figure 5.5 - Geographical distribution of methane production

Peak Methane Productionof Inlet Samples

Key

1E = 0091C = 0071W= 0112E = 0122C = 013

3C = 014.54C = 0155C = 0055W=0066C = 017

Culvert = 014

2000-4000 umolCH4 per uL Air





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burned as biofuel. However, since methaneproduction in most samples was relatively

low and ceased after approximately twoweeks, methane capture might not be eco-nomically viable.

In fact, methane production may below enough to consider methane mitigationas only a secondary concern in sediment de-watering and processing, taking a back seatto more pressing concerns such as Hydrillatreatment. If the low methane productionof the samples taken from the center of the

ood control channel are typical, then dredg-ing would produce approximately 100 or700 kg of methane for 100,000 and 670,000cubic yards of sediment, respectively. Even ifall the sediment dredged produced methaneat a high rate comparable to 5C, methaneproduction would be approximately 4,500kg, for the lower dredging volume, or 30,300for the higher. Especially considering thatdredging will be spread over several years,this may not be enough production to justifyincorporating elaborate mitigation strategiesinto dewatering. However, if methane miti-gation can easily be incorporated into someother aspect of the project, such as Hydrillatreatment, then it might be worth taking intoaccount.

ReferencesBracmort, Kelsi et al. Methane Capture: Op-

tions for Greenhouse Gas Emission REduc-tionL R40813. Congressional Research Ser-vice: Report; 9/17/2009, p6-25

IPCC, 2007: Summary for Policymakers. In:Climate Change 2007: The Physical ScienceBasis. Contribution of Working Group I to theFourth Assessment Report of the Intergovern-mental Panel on Climate Change [Solomon,S., D. Qin, M. Manning, Z. Chen, M. Marquis,

K.B. Averyt, M.Tignor and H.L. Miller(eds.)]. Cambridge University Press, Cam-bridge, United Kingdom and New York, NY,USA.

Reeburgh, W.S. Soft spots in the globalmethane budget. In Eighth InternationalSymposium on Microbial Growth in C1 Com-pounds, pp. 334-342. Edited by M.E. Lindstom& F.R. Tabita. Dordrecht: Kluwer, 1996.

Acknowledgements Thanks to Alexis Heinz and the Fahey/Yavitt lab at Cornell University.

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Introduction

Hydrilla verticillatais an aggressiveaquatic invasive from Eastern Asia, which hastaken over much of the Southeastern and someWestern US watersheds. Known to grow inalmost any freshwater body and in only 1% of fullsunlight, Hydrilla is an invasive capable of out-competing most native species in areas where itcolonizes. Its cold-tolerant, monoecious biotypewas discovered in the Cayuga Inlet of Ithaca,NY in early August. Initial identier R. Johnson

derived its population to be less than two

years old as of 2011 (Menninger 2011). Hydrillapopulations were limited to the immediate inlet

area as of August 2011.However, additional colonies of Hydrillahave been discovered further upstream in theinlet channel as well as channelized portionsof Cascadilla creek since the initial Augustrecording. This demonstrates Hydrillas capabilityto spread relatively quickly, emphasizing theimportance of a well-maintained quarantine anderadication protocol. Its high potential for spreadusing waterways as vectors is a critical hindrancein utilizing dredge material from the Cayuga Inlet

in aquatic settings.Monoecious Hydrilla verticillatautilizes

its subterranean tubers, growing up to 1/2 incheslong, to overwinter and re-sprout in the spring.Hydrilla produces turions, or overwintering buds,which will sink to lake bottoms during winterand sprout again when spring arrives. Finally,external force, like traveling boats, fragmentHydrilla stems deeper into waterways. Thesefragments will attach to boat exteriors or enterballast water and will potentially spread to otherwaterways, where the individual nodes (areaswhere leaves are attached) on a fragment arecapable of taking root. In order to execute aproper management protocol it is necessary tocreate a plan that will simultaneously accountfor fragments, turions, and tubers as negligenceof one or more of these items will increaseprobability of Hydrilla introduction to any givenwater body.

36Hydrillaverticillata

ManagingHydrillaverticillatafortheCayugaInletTrinity Boisvert & Yong Seuk Peter Kwon

Figure 5.2 - Turion growth from Hydrilla verticillata

Figure 5.1 - Cayuga Inlet Hydrilla distribution (August 29,2011). Open white circles indicate dense infestations andpurple circles indicate presence of rooted fragments.Image from Dr. Holly Menninger

KEYNOTES:

(1) Hydrilla verticillata is an invasive aquatic plant

species.(2) Dessication alone cannot kill fragments.(3) Additional treatment will be needed.(4) Not all existing turions will sprout after drying

and natural recreation attraction.(5) To ensure proper control, we require a monitoring-

management plan


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Materials and Methods

Hydrilla is present at the site to bedredged, so fragments of Hydrilla stems, turions,and tubers will also be present in the dredgematerial. If the Hydrilla in the dredge material isstill viable, Hydrilla could be spread during thedredging process, at the dewatering site, whenthe dredged material is trucked, or when it isreused. The presence of Hydrilla verticillatais thevery reason the DEC wants the dredge materialkept away from water bodies. However, ifdesiccation itself could eectively kill the Hydrilla,

then no such restriction would be necessary. Totest this, we performed three quasi-experiments.

We collected Hydrilla verticillatafrom theFarmers Market dock at the beginning of thesemester by hand and shovel. Two buckets ofsoil were also collected at the docks. The Hydrillawere then kept in a greenhouse kept at 70 F in alarge bucket full of water. All Hydrilla used in thefollowing experiments were from this collection.

Stem Fragment Experiment

For the fragments of the plant itself, we wanted

to test whether the length of the plant, thedepth it was buried, and how completely it wasburied aected its ability to re-grow. To testthis, we created 12 samples with 20 fragmentseach buried in soil material collected from theFarmers Market dock. We lined four plastic atswith fabric, so that the contents would drain,

but would not fall out of the at, and lled theats with three samples each. The fragmentshad either 5 or 10 nodes (aka the point wherethe leaves formed a swirl). The fragments wereburied 5 centimeters deep, which was nearly thebottom of the tray, 2.5 cm deep, or placed on thesurface. They were either buried horizontally, sothey would be completely covered, or vertically,so some of the Hydrilla fragments would beexposed to air. The ats were left undisturbed in

the greenhouse for one week.At the end of the week, the Hydrilla

verticillatafragments were carefully dug up. The

soil material did not dry evenly. The surface wasalmost completely dried out, grey, and caked,but at lower levels the soil was darker, granular,and slightly damp. Parts of the Hydrilla thatwere left exposed appeared dried out and greyor yellow, while the segments that were buried

still appeared green. The fragments were almostcompletely recovered; some nodes and leaveswere lost digging them up.

Each sample was placed in a mason jarhalf-full of water. It was left to rehydrate for twoweeks. To act as a control, two samples eachof twenty 5 and 10 node Hydrilla that had been

37

Figure 5.3 - Hydrilla verticillatain ats - picture 1



Hydrillaverticillata


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brown. They were also called alive if there wasnew growth or a turion o the original fragment.

New growths and turions were alsocollected if they were not connected to afragment. Each jar was rinsed out and relledwith water and a squirt of fertilizer. The livingsamples were put back in their respective jars.The process was repeated the next week, but nofertilizer was added. The following graphs showthe results by treatment, depth, and number ofnodes.

We observed the fragments for anadditional week. No new growths formed.

However, one sample decomposed, one turionsprouted, and one node grew further. TheControls continued to grow as well.

Our results showed that the driedHydrilla did not survive as well as the controls(Fig 5.7, 5.8, & 5.9 on the following page). Thenumber of life signs increased with the depthof the sample, presumably because moisturecontent increased. This would also explain whythe samples that were buried completely didbetter than those that were vertically plantedand partially exposed to air. The Hydrillafragments that were longer survived better thanthe ve-node Hydrilla. This might be because thelonger fragments have more matter in them, sothey can retain turgor and have enough storageto create new growths.

The second experiment involved onlyturions. These turions grew in the bucketof Hydrilla over several weeks. Ninety-eight

sitting in the bucket were put in half-full masonjars as well. At the end of those two weeks,algae was growing in most of jars. The sampleswere removed and placed in shallow dishes.

Each sample was visually dividedinto living and dead. Hydrilla fragments wereclassied as living if they retained shape out ofwater or were green, versus becoming limp and

turions were used in this experiment. Somewere completely free-oating, some were stillattached to short stems, and some were still fullyattached to Hydrilla plants. The turions weredivided equally between two ats lined withfabric. One at was left to dry for a week, theother was left out to dry for two weeks. Afterthe drying period was complete, the turionswere placed in jars full of water. The free-oatingturions were divided between two jars, theturions with some stem were placed in one jar,and the turions attached to plants were dividedbetween two jars as well. After drying, the

turions seemed bleached, but were still green.The leaves were very distinct. However, none ofthe turions sprouted.

This is interesting when contrasted withour rst experiment, where one of the turionsdid sprout. The sprouted turion grew after thefragment had been dried. This suggests theremight be a stress response.

We found one tuber in the dredgematerial. It was dried for one week during thestem fragment experiment at about 2.5 cm. Itwas then rehydrated in its own mason jar. Itsprouted. This agrees with the literature, whichsuggests drying induces growth in tubers.

Our results are not concrete. All ourHydrilla were only dried for one or two weeks. Itwill take at least a year for the dredge materialto dewater. Considering that the dredge will notdry evenly, further studies should consider thewater content of the soil the Hydrilla is drying

38

Figure 5.5 - Hydrilla verticillatafragment in a mason jar

Figure 5.6 - Mason jars containing Hydrilla verticillata

Hydrillaverticillata


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in. Re-growth, while easy to measure, is also nota concrete measure of survivability, especiallyfor turions and tubers. The l iterature suggeststubers can remain dormant for up to ve years.Dewatering can induce

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