Study Grant EPA funded grant, follow-up to a previous DWQ study on assessing isolated wetlands The study is multi-disciplinary Our role, in part was

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2 Study Grant EPA funded grant, follow-up to a previous DWQ study on assessing isolated wetlands The study is multi-disciplinary Our role, in part was to study hydrologic connectivity to navigable surface waters 2

3 The report citation is in the abstract and at the end of this presentation, but I just want to draw attention to the expertise associated with this project. 3

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5 Background how we are defining a geographically isolated wetland Hydric soil completely surrounded by non-hydric soil No surface water drainage Not ecological or hydrologic isolated (IWs have ground water connection) 5

6 Background wetland functions It is likely that isolated wetlands serve the same functions as those drained by surface water AND that their destruction will lead to the same problems associated with loss of other wetlands. One major difference is that isolated wetlands provide a habitat for amphibians that need fish free environments to reproduce. 6

7 Policy Significant because of Clean Water Act As a result of 2 Supreme Court decisions that removed IWs from CWA 7

8 In terms of policy, there is no national policy governing isolated wetlands, only state by state protections. North Carolina developed regulations beginning in 2001 There are size requirements for both reporting the presence of wetlands on a permit and for mitigating wetlands that are impacted by permitted development The 1 acre deal is for mitigation, a permit is still required for all wetlands of at least 0.1 acre in the Piedmont and 0.33 acre in the Coastal Plain. 8

9 The simplistic question is: are isolated wetlands connected to surface water via groundwater? The simple answer is yes, at least in the case of those studied here. The next question is: what is the pollution absorption capacity and the water quality and hydrologic function of these systems? Our goal is to characterize and document the degree and quality of this connection, to get a handle on how sensitive these systems are to hydrologic change. 9

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11 Study area Coastal Plain (actually some site in SC as well) Sites in both Bladen and Brunswick County 11

12 Study area NC lidar maps Bladen county Cape Fear River Floodplain Brunswick County ancient beach front 12

13 Aerial photo of Bladen County covered in Carolina Bays, including several of our sites Though we did not concentrate on Carolina Bays as a research question 13

14 No Carolina Bays but perhaps an ancient scarp and plenty of sinkholes (don t show up on map) 14

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16 Just to show the variety of the NC sites Recent clear cut Piney woods Forested Carolina Bay Tiny carolina bay Cedar growing in a sinkhole 16

17 We collected a ton of data I m making an assumption here that most of you are not hydrogeologists so I m going to go into more detail about some of the methods more than I usually would 17

18 First day was cold! 4 months, span freezing to 105 degrees. 18

19 Drilling rigs: The Geoprobe (white) was used for coring and installing 1 diameter monitoring wells Mounted on a big pickup truck Other ways to mount this type rig sometimes will see on a small tracked vehicle This is called push technology because the rods are basically pushed into the earth with a hydraulic hammer don t use this with rock It is not a rotating, cutting drill-head 19

20 Coring A core cut open for observation and logging Examples of sediment found in cores Sand sand with interbedded clay gravel, sand and wood Clay 20

21 Set wells from 12 to 40 feet deep Combination of shallow and deep wells We did catch at least one big rain event 21

22 At 3 sites installed a pumping well in order to perform an aquifer test downgradient of the wetland Upgradient of the receiving water body The CME (yellow) was used for augering holes for 4 diameter pumping wells Bigger rig Uses augers that screw into the ground Does have a rotating drill bit 22

23 water levels, monthly in all wells, continuously in about 25 wells 10 stream gages, upgradient and downgradient at most sites Especially at sites where we did aquifer tests 23

24 water quality sampling quarterly at 25 wells plus wetland and stream at all sites, if water present 24

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26 Cored in wetland 4 points surrounding it streamside 26

27 Installed a transect of monitoring wells from upland of the wetland, through the wetland, to the stream At 3 sites installed a pumping well to perform an aquifer test 27

28 Installed some sort of surface water monitoring at some sites, especially where we were doing aquifer tests 28

29 Installed automatic dataloggers in at least 3 wells wetland, upland, streamside In Situ Trolls OnSite hobos Staff gage in surface water 29

30 This is what an aquifer pumping test looks like cables everywhere lots of clipboards the idea is to measure water levels in as many observation wells as possible as you pump water out of the aquifer as hard as you can. Pump the water off site don t want to re-introduce it into the system a day to set up, ½ day to break down lots of people to record by hand for the first and last few hours lots of time to hang around for the other 40+ hours, checking levels periodically Minimum of two people on-site 30

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32 Coring data allows us to draw geologic cross-sections. Use these to determine where to set wells This is the simplest site 25 feet of undifferentiated sand overlying a hard dark gray clay Often a gravel bed and wood chuncks at the base of the sand 32

33 In all cases found that groundwater is flowing through the wetland from some higher elevation to the stream in seemingly unimpeded flow 33

34 This is automated datalogger data from 3 shallow observation wells, the stream and precipitation Water flows from the wetland to the stream Indicate that all wells respond in a similar fashion Recharge follows rain very quickly seems to be within a day Response to gravity gradient toward stream Sufficient permeability to allow drainage This is base flow Suggests seasonal variability 34

35 Aquifer tests help understand how the stratigraphy affects the hydrology At this site there are no impediments to flow We re not sure what the jumps in the line indicate 35

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38 That was all the set-up and types of monitoring we did and the sorts of results we were seeing. What does it all mean to a hydrogeologist? We found there were some commonalities and also each site had some unique findings. 38

39 Our initial assumption was that IW s were perched water tables essentially clay bowls Hydrologic regime controlled by precipitation and evapotranspiration. They do exist. Not the case at any of the sites we studied -The next 5 slides show the wide variety of stratigraphies we found beneath IW s 39

40 BL 7 We found an IW in sand Water in isolated wetland when water table was up Dry when the water table is down If you walk thru when its dry you might not recognize it as a wetland unless you recognize that wetland species are present 40

41 BL 1 We found an IW in sand including bodies of silt Created a perched water table 41

42 BL 6 We found an IW lying atop a silt body But the silt body pinches out 42

43 GS 1 We found an IW where there is a layer of sand and a layer of interbedded clay/silt sand

44 BL 9 We found an IW with a ring of organic cemented sand around it approximately 6 below the ground surface. DOES exert hydrologic control - perching 44

45 Also found a paleochannel, drilled to 42 feet hit clay in one but not the other Coastal Carolina University ran GPR around this site 45

46 We found that the hydrology of IW s varies widely -the next 6 slides show horizontal and vertical water flow found at the sites 46

47 Flow Direction BL 7 -creek, wells Location of wetland Might expect radial flow in or out In fact, preferred flowpath like this What u d expect if u relied on topography 47

48 Flow Direction BL 17 Wetland, wells, creek Topography not much help Radial out of the IW There is a predominant horizontal flow direction through the IW We didn t install wells all the way round the IW to do a complete hydrologic site assessment. Our goal was primarily to determine if wetlands were connected to surface water. Placing wells to also partially determine flow direction is a perk. 48

49 Vertical Gradient Upward -we also determined vertical water flow at the IW s by collecting water levels from deep and shallow wells - in some wetlands, water generally discharged up into the wetland (water flow was up) 49

50 Vertical Gradient Downward - others generally recharged groundwater (water flow was down) 50

51 Vertical Gradient No Vertical Gradient -in others it flowed neither up nor down but rather passed horizontally through 51

52 Vertical Gradient Changes with conditions -In others, we continuously monitored water levels and raingages and found that water flowed generally upward during baseflow conditions but switched to downward (recharge) for a short time after rainfall 52

53 Look at C:\B_Projects\Presentations\2012_WRRI presentation And C:\B_Projects\Presentations\2012_SWS-IsoWet Aquifer test from GS1 here 53

54 Remember the stratigraphy at BL7 Stratigraphy - pretty simple, 20 feet of sand over clay Groundwater is flowing from the wetland to the stream the entire system responds simultaneously and instantly to precipitation, and there is some topographic control to horizontal flow. 54

55 Aquifer tests BL7 Data indicate no significant barriers to horizontal groundwater flow The curves all have similar shapes Even the shaking is at the same times. We don t know what caused this if you have any ideas find one of us later!! Not all sites were this simple let s look at the not so simple sites 55

56 Site BL1 Silt Bodies This site is an example of why this level of stratigraphic analysis is important. In one core there was a 4 thick layer of silt in between two 15 layers of sand. We did not know what the effect of this silt was on the hydrology how much of a barrier did it form? There was a zone of groundwater perched on the silt But according to hydrographs, the site-wide water table was independent of (not affected by) the silt body. 56

57 Site BL1 Aquifer Test The perched water at MW6S was not affected by pumping from the deep well (PW1). 57

58 Remember site BL6 where we had a large silt body I m not presenting all the supporting data, but that is in the report My point here is that using the water level data we had we were able to show that the silt body large enough to create a locally confined aquifer But the system is really one connected aquifer I wish we could have done an aquifer test at this site! 58

59 What happens where there is a layer throughout the site? The connected wetland here is connected to navigable waters, one of our criteria for site selection, so that s our receiving water body, not a stream. Then the coring data becomes critical. We call this site the Sinkholes site, because the land surface here is covered in hollows. Something beneath the surface just collapsed and the entire section did not collapse in on itself, it just sank several feet. The coring data bear this out. Notice the thickness of each layer stays the same while the elevation changes. Sand Interbedded sand and clay. At two sites this was a 4 thick silt layer Sand Bottom unknown here but in Bladen county the bottom is the hard gray clay

60 Have a look at the triangles indicating water level - You can see that the water levels are all pretty close to each other - not exact Deep not quite the same as shallow, but close The sinkholes don t seem to matter topography is not controlling the water table that s the next slide. Also notice the arrangement of the wells and that the pump is in a deep well. During the aquifer test we pump from the bottom and watch how water levels in the upper levels respond

61 When we plot the water levels on a graph, the shallow distinguish themselves from the deep 0.8 difference Dashed lines are from deeper wells Solid are shalow it is one surficial aquifer with water moving horizontally and vertically, but with a leaky confining unit that lowers hydraulic conductivity -just slower in one part of the aquifer (learned this through aquifer test) 61

62 During the aquifer test we pump from the bottom and watch how water levels in the upper levels respond Deep monitoring wells responded quickly Shallow wells took longer - but they did respond Tells us two things Shallow and deep ARE hydraulically connected AND the interbedded sand and clay layer is semi-confining, causing the shallow wells to take longer to respond 62

63 analyzed by Dan Tufford, USC We don t have a lot to report but we were working in pretty pristine areas 63

64 Water Quality Nitrogen - Mostly organic N - highest org N conc in IW (surface water), drops significantly in upland, high org N conc again in stream/surface water from other inputs -we found what you d expect to find, but concs are low in the pristine environments - trends varied between sites (-at other sites there was evidence of some mineralization of nitrate to ammonium) Org N may be produced in IW, not tranported, is a sink 64

65 Water Quality Organic Carbon -this slide shows general trends of concentrations of organic carbon in wetlands, wells and the stream. - similar pattern -there simply isn t much organic material below the top 6 inches or so Wetlands may produce more organic carbon, not transported through the system IW is a carbon sink 65

66 Soil Analysis -Done by Dan Tufford -In general, soils in the IW hold more organic components and are more acidic and the upland soils are more sandy, basic and have less OM. - The results are typical of soils on the Coastal Plain. 66

67 The Iws in this study are hydrologically connected to downstream surface water IWs are hydraulically connected to SW Stratigraphy and hydrology may vary There may be local, discontinuous confining layers, but they do not affect overall connectivity. Stratigraphy affects hydrology 67

68 IW s occur where the water table rises above the land surface for periods long enough to produce hydric soil 68

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70 We owe a lot to these folks for giving us access to some beautiful land 70

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72 The hydrologic connectivity project was a follow-up to earlier work, Assessing Geographically Isolated Wetlands in North and South Carolina the Southeast Isolated Wetlands Assessment (SEIWA) - Final Report and these are the best contact people for that work 72

73 Major parts of this study were the biology and ecology, and questions about those portions should be directed to Ginny and Dan. 73