Lake Worth Lagoon Hydrographic Survey Report

C-51 Canal Sediment Trap Lake Worth Lagoon Hydrographic Survey Report July 11, 2013 South Florida Water Management District 3301 Gun Club Road West Palm Beach, Florida 33406

Table of Contents Background... 3 Location Map... 4 Methodology... 5 Surveyor s Notes... 5 Field Work... 6 Data Processing... 7 Results... 8 Conclusion... 11 Certification... 11 Appendix... 12 Photos... 13 References: Sea Diversified, Inc. surveys done in 2007, 2008, 2009, and 2010 (provided by Palm Beach County) Sea Diversified, Inc. report completed April 25, 2011 SFWMD survey completed July 8, 2013 CD Includes: Report Copy Survey Drawing AutoCAD etransmit file Field Notes Photographs South Florida Water Management District 2

Background The C-51 Canal Sediment Management Project began in January of 2006, a collaboration between the South Florida Water Management District (SFWMD), Palm Beach County Department of Environmental Resources Management (PBC), and the City of West Palm Beach, to construct and monitor a sediment trap on a yearly basis. Construction was completed in July 2007. Sea Diversified, Inc. (SDI) was contracted by PBC to perform hydrographic surveys from 2007-2010. The original survey conducted in 2007 reached from Forest Hill Blvd. to the S-155 Water Control Structure. In 2008 this area was extended from Congress Ave. to S-155. This extension was requested to obtain a better awareness of erosion and accretion occurring in the sediment trap. By conducting these surveys on a yearly basis PBC and SFWMD would like to define if maintenance for the sediment trap is required. Hydrographic surveys done by SDI: 2007 Original baseline survey between Forest Hill Blvd. and S-155 2008 Project extended to be between Congress Ave. and S-155 2009 Congress Ave. to S-155 2010 Congress Ave. to S-155 SDI performed an in-depth analysis comparing the surveys to the 2007/2008 baseline. Part of SDI s investigation includes examining if there was a correlation between the amount of discharge at S-155 to erosion and accretion along C-51. By examining DBHYDRO data SDI determined that erosion and accretion could have a connection to the amount of water being discharged from S-155. SDI recommended that monitoring surveys continue to help in understanding the movement of sediments through the C-51 Canal. No surveys were performed in 2011 or 2012 for this project. In May 2013 PBC approached SFWMD to continue the monitoring of the sediment trap. It is understood that not having surveys for 2011/2012 will make it impossible to correlate any erosion or accretion to any particular rain event or dry period. This will however, be able to aid in showing if a maintenance dredging schedule should be done for the sediment trap or if the trap does not accumulate enough sediment to warrant a maintenance cycle. South Florida Water Management District 3

Location Map For the 2007 survey, the area only encompassed from Forest Hill Blvd. to S-155. Starting in 2008 the survey area covers the east side of Congress Ave. to the west side of S-155 to evaluate possible sediment sources. To maintain consistency with the report done by SDI the project is broken into four segments. Reach A: Congress Ave. Summit Blvd. Reach B: Summit Blvd. Forest Hill Blvd. Reach C: Forest Hill Blvd. Interstate 95 Reach D: Interstate 95 S-155 Structure A Congress Ave. B Summit Blvd. N C D South Florida Water Management District 4

Methodology The hydrographic survey meets the applicable minimum technical standards for surveys in Florida Administrative Code 5J-17.051 set forth by the Florida Board of Surveyors and Mappers pursuant to section 472.027 Florida State Statutes. Surveyor s Notes 1. The purpose of this hydrographic survey is to establish elevations of C-51 Canal from Congress Ave. to S-155 located in Sections 4, 5, 8, 9, 15, 16, & 17, Township 44 South, Range 43 East; Palm Beach County, Florida. 2. All measurements herein are in U.S. Survey Feet and decimal thereof, unless otherwise specified. 3. The bottom depths were collected using an Odom HydroTrac echo sounder in conjunction with a 200 KHz transducer and a laptop computer operating HyPack 2013. 4. This survey report is not valid without the signature and the original raised seal of a Florida Licensed Surveyor and Mapper. 5. Additions or deletions to this survey report by any other than the signing party (or parties) is prohibited without written consent of the signing party (or parties). 6. Date of last field work: June 27, 2013. 7. The coordinates, bearings, and distances refer to the Florida State Coordinate System, Transverse Mercator Projection, Florida East Zone, North American Datum of 1983 (NAD 83). Coordinates were obtained with a Trimble SPS351 DGPS Receiver providing sub-meter precision. 8. Elevations shown hereon refer to the North American Vertical Datum of 1988 (NAVD88). To convert to NGVD29 add +1.52. Conversion calculated using CORPSCON Ver. 6.0.1 9. The vertical control points are as follows: FCE3521 USACOE brass disk set in top of a 10 round concrete cylinder, from the Southwest corner of the fence surrounding the parking lot of the S-155 building on the North side of the S-155 structure, go North along the West fence line 25 feet ±, thence West 5 feet ± to bench mark, stamped FCE3521 1971. Elevation (NAVD88) = 15.030 SUMMIT 10 Palm Beach County aluminum disk set in the Northwest corner of a concrete bridge over C-51 Canal at Summit Blvd., stamped SUM 10 Elevation (NAVD88) = 16.901 10. No boundary survey was performed as part of this survey. South Florida Water Management District 5

11. Underground utilities were not located as part of this survey. 12. The aerial imagery shown hereon is the 2011 Palm Beach County quarter foot pixel resolution. It is shown for informational purposes only and is not part of this survey. 13. The C-51 Canal centerline stationing, created by SFWMD, is for reference only. 14. Surveys done by Sea Diversified, Inc. (2007, 2008, 2009, and 2010) in NGVD 29 were converted to NAVD 88 by using the conversion factor in Note 8. Field Work This hydrographic survey was performed by SFWMD surveyors on June 17-20, 27, 2013. Field notes are located in the field book MISC FB 6R. For this survey the water surface elevations were established by placing a hub at a known elevation in the canal by using the benchmarks described in Note 9. The hubs were placed at the intersection of C-51 and Summit Blvd. as well as at S-155 and were checked throughout the day to maintain an accurate value for the change in water surface elevation. Hub placed at Summit Blvd. Depths were collected using a side mounted 200 KHz transducer connected to an Odom HydroTrac echo sounder. The echo sounder was calibrated using a check sounding at the beginning and end of each work day. To do this calibration a 25 fiberglass rod was used to determine the water depth and then the echo sounder was adjusted to verify the soundings were correct. Horizontal location was obtained using a Trimble SPS351 DGPS Receiver which provided sub-meter precision, ideal for marine surveying. The GPS and echo sounder were connected to a laptop running HYPACK 2013. Odom HydroTrac during cross sections South Florida Water Management District 6

To maintain similarities with the surveys completed by Sea Diversified Inc. the cross section work was located at approximately fifty (50) feet, along lines previously run by SDI and were obtained as close to the bank as feasible. Obstacles such as aquatic vegetation, docks, and irrigation pipes effected the extents of many of the cross sections. Three (3) profile lines were also acquired to benefit the survey, with the addition of two (2) more located inside of the sediment trap to increase coverage in the wider segment of C-51. Typical data collection lines shown in HYPACK (color by depth) Data Processing Before loading the files into AutoCAD, the raw data files were processed using standard SFWMD techniques. Tide files were created for each day to change the depths into NAVD 88 elevations. Each raw file was then examined to remove any errant data collection points. Once each raw file was edited using HYPACK s Single Beam Editor, a sorted file was created selecting an edited sounding every five (5) feet. The five (5) feet distance is the typical SFWMD sorted distance used to create surfaces in CAD. The sorted data files were then exported into an YXZ file. The surveys done by Sea Diversified, Inc. were obtained in a XYZ NGVD 29 format and were converted into NAVD 88 using the value shown in Note 8; no other editing was done to SDI s data. Typical cross section before editing South Florida Water Management District 7

Results The sediment trap was constructed to minimize the amount of material flowing into the Lake Worth Lagoon. The purpose of surveying this area on a yearly basis was to determine if a maintenance schedule needed to be implemented to aid the sediment trap process. Sea Diversified, Inc. conducted surveys from 2007 to 2010 and determined the volumetric change (Erosion / Accretion) by conducting surface-to-surface comparisons in AutoCAD. With the SFWMD data collected in June of 2013 it was then possible to compare the elevation change over the project period. Cross sections were placed at approximately 500 feet intervals (or where appropriate) along C-51. The intervals were shortened to 100 feet inside of the sediment trap to convey a better representation of variations between the five (5) years. The extents of the project were expanded in 2008 to include more of the C-51 Canal (north from sediment trap) to discover where any material was originating. From Congress Ave. to the northern extents of the sediment trap and from I-95 to S-155 the cross sectional data showed slight change in elevation over the project duration (left figure). This is illustrated on the cross section sheets of the survey accompanying this report C-51 CANAL SEDIMENT TRAP. The sediment trap, unlike the rest of the project, showed significant increase in material from 2007 to 2013 (right figure). South Florida Water Management District 8

A volume calculation was done for the sediment trap only because of the minor changes in the cross section elevations for the remainder of the C-51 Canal survey. The comparison can be clearly seen on the 2007 AND 2013 VOLUME CALCULATIONS page of the survey. As shown in the surface comparison and cross section views, the majority of material build up is located along the West and South of the sediment trap. The amount of erosion/accretion is shown in the following table: Erosion Cubic Yards Volume Summary Accretion Cubic Yards Net Cubic Yards 4,257 29,779 25,522 DBHYDRO data was compiled to decide if the flow rate throughout C-51 had any effect on the amount of material build up in the sediment trap. By doing so it could be possible to attribute erosion and accretion to the flow rate of S-155 over the years. For the SFWMD survey there are two (2) years where no survey was completed. As shown in the table below, the flow rate during 2011 and 2012 were at complete opposite ends of the spectrum. During 2011 the lowest amount of cubic feet per second (cfs) was discharged over the study period, while 2012 had an active hurricane season and with the amount of water brought by storms such as Tropical Storm Isaac, S-155 saw greatly increased flow rates. (A larger graph appears in the appendix.) Spike attributed to Tropical Storm Isaac South Florida Water Management District 9

With the gap in data collection it cannot be shown how a dry or rainy season directly affects the sediment trap. By examining the cross sections it appears to show a constant increase in material build up, regardless of the flow rate of S-155. Excluding the change from 2007-2008, which saw the greatest increase in sediment, there seems to be a trend of increased material at approximately 1 foot per year inside the sediment trap. In Reach C the first year saw an increase of 10,478 cubic yards of accretion and an increase of 2,800 3,200 cubic yards per year from 2008 2013. 3 year gap Cross section showing elevation trend Average Accretion for Reach C Years 2007 2008 2008 2010 2010 2013 Total (CY) 10,478 6,401 8,643 Average / Year 10,478 3,200 2,881 South Florida Water Management District 10

Conclusion The purpose of this survey was to determine if a maintenance schedule needed to be implemented to maintain the effectiveness of the sediment trap. An attempt was also made to correlate the flow rate of S-155 to material build up. By comparing the results from multiple surveys this shows that the sediment trap is indeed collecting sediment brought through C-51. This build up appears to increase, regardless of the cfs being discharged through S-155, at a pace of approximately 1 foot in elevation change or 2,800 3,200 cubic yards of accretion per year. Certification This survey report was prepared for: Rod Braun Principal Scientist South Florida Water Management District 3301 Gun Club Road West Palm Beach, FL 33406 Unless it bears the signature and the original raised seal of the Florida Licensed Surveyor and Mapper, this report is for informational purposes only and is not valid. I hereby certify that this hydrographic survey was made under my responsible charge and meets the applicable minimum technical standards for surveys as set forth by the Florida Board of Land Surveyors in Chapter 5J-17.051, Florida Administrative Code, pursuant to Section 472.027, Florida State Statues. Richard E Barnes, Jr. Professional Surveyor and Mapper Florida Certificate No. 5173 Date South Florida Water Management District 11

South Florida Water Management District 12 0 Jan-08 Feb-08 Mar-08 Apr-08 May-08 Jun-08 Jul-08 Aug-08 Sep-08 Oct-08 Nov-08 Dec-08 Jan-09 Feb-09 Mar-09 Apr-09 May-09 Jun-09 Jul-09 Aug-09 Sep-09 Oct-09 Nov-09 Dec-09 Jan-10 Feb-10 Mar-10 Apr-10 May-10 Jun-10 Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Dec-10 Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 Mar-12 Apr-12 May-12 Jun-12 Jul-12 Aug-12 Sep -12 Oct-12 Nov-12 Dec-12 Jan-13 Jan-13 Mar-13 Apr-13 May-13 May-13 Jun-13... 0 8 "' 0 8 ~ 8 ~ 8 C-51 Canal Sediment Trap July 11, 2013 Appendix S-155 Flow Rate

Photos Discharge from S-155 Aquatic vegetation and tree overhang South Florida Water Management District 13

Aquatic vegetation C-51 (looking south to Forest Hill Blvd.) South Florida Water Management District 14

Debris along Reach D S-155 headwater South Florida Water Management District 15