Tide gate layout and Implementation

Tide gate layout and Implementation
Background for this discussion Initial tidegate research and design was with the Coos Watershed Association Constructed tidegates side by side one with side mounted tidegate and the other with top mounted tidegate. Goal was to replace an existing tidegate and to give watershed association a site where they could monitor the difference between the two design types. Leo Kuntz from Nehalem Marine installed. We used a precast headwall system which was placed under wet conditions at low tide. Worked with Nehalem Marine to develop typical specifications for tidegates. Unique specifications required unlike culverts and bridges outside of sloughs Developed an excel program that was accepted by agencies for modeling tidegates Prepared plans and specifications for Nehalem Marine and Watershed Associations for tidegate structures often in combination with Channel restoration Engineering Considerations - Tidegate Design

Tidegate Technical Considerations
Tidegates are unique compared to most bridges and Culverts Located in areas of weak soils and soils where subsidence is normal Saltwater conditions at most sites requiring special materials Potential for seepage as dikes are miniature dams with dam characteristics. Need to be installed in clay soils similar to dikes in area Will often experience overtopping during peak flows Flows are a function of backwater area Forces are larger particularly water hammer, soils loads and buoyancy Tide gates have unique Technical Design considerations in comparisons with typical road culverts and bridges Tidegates are unique compared to most bridges and Culverts Located in areas of weak soils and soils where subsidence is normal Bearing pressure is in 500 to 1000 psi range whereas culverts are in 2000 to 5000 psi range. Passive Pressures must be adjusted in subsoil's for saturated conditions the result is sheet pilling depths and overturning concerns become critical Saltwater conditions at most sites requiring special materials Need to use materials that will resist corrosion such as Plastics, Newer culvert coatings , and concrete. Galvanized Steel is not a good option. Potential for seepage as dikes are miniature dams with dam characteristics. Use concrete sealed cutoff piling Maintain clay seal under structure Use sheet piling at inlet or outlet as seepage barrier Need to be installed in clay soils similar to dikes in area Difficult to compact under wet conditions Use of clay common material is strictly prevented in most roadway installations Will often experience overtopping during peak flows Slopes need to be armored to prevent overtopping erosion Slope stability during overtopping as material becomes saturated or rapid drawdown causes high pore pressure resulting in wing walls tipping, slope stability, and saturated fills Sizing is a function of numerous variables Forces are larger particularly water hammer, soils loads and buoyancy

Tidegate Layout and Implementation Permitting Considerations
5 Permits Tidegate ODFW- Fish passage at all flows within stream flow range ODFW-(4)c- Minimum size of a tidegate is 4 ft wide ODFW- Gate must allow fish passage 52% of tidal cycle ODFW-Inlet has adequate attraction flows ODFW-Velocities less than 2 feet per second for fish passage SLOPES V-Does not address tidegates accordingly must write a biological opinion for each site. Tide gates also have unique permitting requirements in comparisons with typical road culverts and bridges Culverts on Private lands are regulated under different Regulation than Federal or ODOT Lands. Oregon Dept of Fish and Wildlife Requirement –Designs on Private lands (4)(c) tide gates and associated fish passage structures shall be a minimum of 4 feet wide and shall meet the requirements of OAR (2) within the design stream flow range and for an average of at least 51% of tidal cycles, excluding periods when the channel is not passable under natural conditions. (2) Requirements for fish passage at dams and other artificial obstructions which create a discontinuity between upstream and downstream water surface or streambed elevations are: (a) Fish ways shall provide fish passage at all flows within the design stream flow range; (b) The fish way entrance shall be located and adequate attraction flow shall be provided at one or more points where fish can easily locate and enter the fish way; (c) Fish way water velocities shall: (A) Range between 1 and 2 feet per second in transport channels; (B) Average no greater than 5 feet per second in baffled-chute fish ways, including but not limited to Alaska steep passes and denils; and (C) Not exceed 8 feet per second in discrete fish way transitions between the fish way entrance, pools, and exit through which fish must swim to move upstream, including but not limited to slots, orifices, or weir crests; (d) At any point entering, within, or exiting the fish way where fish are required to jump to move upstream, the maximum difference between the upstream and downstream water surface elevations shall be 6 inches, except it shall be 12 inches if only salmon or steelhead adults require fish passage USACE SLOPES V- Private Lands The primary biological opinion used by the Corp of Engineers is Slope 5 transportation or Slopes 5 Restoration. These document specifies the sizes and shapes of culverts and bridges for replacement projects without the need for a separate biological opinion. Tidegates however are not included and a separate biological opinion is required for their installation at this time. In the future a nationwide opinion is being sought to speed up the approval process. Considerations on Nationwide Permits Sounds good. No, you would not need to request a variance to work outside of the in-water work window if the work would be confined to July 15 to September 30, But..one thing to keep in mind... The current 2012 Nationwide Permits are going to expire on March 17, They run on 5-year cycles. The next cycle is going to start March 18, 2017 and will have different terms and conditions. For those projects where we verified the project prior to the expiration date and you're ready to go to work, or contracted to go to work, the permittee gets a 1-year grace period. That's a good thing here and will cover the work if you're planning it for next summer. Best of luck on the project, Designs must document compliance with those requirements before a 404 permit will be issue. As part of that documentation alternatives are requested for review. In the end the agencies at this time select the culvert or bridge replacement size.

Tidegate Layout and Implementation Typical MTR Tidegate photo
Circular Culvert with Tidegate and float controller Nehalem Marine De Boer Culvert in Washington Slide 3 Culvert Outlet Steam side Photo of Deboer Tidegate in Washington Attached are some finished pix of the project. It was great to meet you, this world needs more Leo’s! Thanks Gary F. Goodall RIver and Flood Engineer 322 N. Commercial, Suite 120 Bellingham WA 98225 Office (360) x6287 Cell (360) .wa.us Notes: Side mounted tidegate Erosion fabric and riprap on slopes Culvert is set 1’ below normal low water elevation for passage

Tidegate Layout and Implementation- Photo of Typical MTR Tidegate
Circular Culvert with Tidegate and float controller Nehalem Marine De Boer Culvert in Washington Slide Culvert Inlet field side Photo of Deboer Tidegate in Washington walkway to seasonally adjust floats Floats sized to operate gates on stream size Slope protection rock to top of roadway Overflow section of channel one side.

Tidegate Layout and Implementation- Typical MTR Tidegate
Circular Culvert with Tidegate and MRT float controller Slide 6

Tidegate Layout and Implementation- Typical Elevation View
Circular Culvert with Tidegate and MRT float controller Slide 6 Extra rock each side for buoyancy Trenchcoat culvert for salinity Rock Slopes full height for erosion protection during overtopping Culvert has 10’ Sleeve on inlet in specifications to resist buoyancy uplift of ends Outlet set 2’ below invert to improve debris concerns or obstructions to tidegate closing.

Circular Culvert with Tidegate and MRT float controller Slide 6 Typical culvert section showing anchor and bedding rock

Circular Culvert with Tidegate and MRT float controller Slide 6 McDonald Slough Box Culvert prior to backfill

Tidegate Layout and Implementation Technical Considerations- soft soils low strength and subsidance
Located in areas of weak soils and soils where subsidence is anticipated over time Concrete structures will need stabilized foundations to prevent cracking and tilting. Add Reinforced soil mat Add Tie Backs or Geogrids behind wing walls Consider bearing piles but must be aware of subsidence concerns and their resulting loads Bearing pressure is in 500 to 1000 psi range whereas culverts are in 2000 to 5000 psi range. Passive Pressures must be adjusted in subsoil's for saturated conditions the result is sheet pilling depths are deeper in addition to concerns with rotational failures of The wing walls and structures.

Tidegate Layout and Implementation Technical Considerations- Soft soils low strength
Bearing pressure is in 500 to 1000 psi range whereas culverts are in 2000 to 5000 psi range. Passive Pressures must be adjusted in subsoil's for saturated conditions the result is sheet pilling depths are deeper in addition to concerns with rotational failures of The wing walls and structures. Reinforced soil mat under concrete structure to bridge soft soils

Bearing pressure is in 500 to 1000 psi range whereas culverts are in 2000 to 5000 psi range.
Passive Pressures must be adjusted in subsoil's for saturated conditions the result is sheet pilling depths are deeper in addition to concerns with rotational failures of The wing walls and structures. Anchor rods at top of wing wall and sheet pile at front for low bearing pressure and low passive resistance to slope failures

Tidegate Layout and Implementation Technical Considerations- Salinity effects on materials and adjacent farm lands Saltwater flows into streams s requiring special materials and effects of flooding on farm lands Selection of materials for salinity Concerns Circular Culvert Weolite out of Canada Trenchcoat over Galvanized Steel from Pacific Corrugate Pipe in Eugene Box Culverts Precast modules or cast in place concrete Planning and permits: Show acres of land that will be affected by salt water intrusion for each alternative setting of MTR.

Tidegate Layout and Implementation Technical Considerations- Seepage
Potential for seepage through structures In circular culverts minimize depth of bedding aggregate. In concrete box culvert use sheet piling for watertight barrier located at the ends or center of the structure. See photo next slide. In earthen dams a clay center is used to prevent seepage

Tidegate Layout and Implementation Technical Considerations- Seepage
In circular culverts minimize depth of bedding aggregate. In concrete box culvert use sheet piling for watertight barrier located at the ends or center of the structure. See photo next slide Potential for seepage through structures Learned a good trick for sealing my cutoff wall pic 005. (not in plans but I always do them) I took the underwater patching material we use for ODOT and mixed it pretty thin. Then I used a concrete vibe and ran it through the rock fill on both sides of the cut off wall. Really worked well and was rock solid by the next morning. Nice stuff, did not shrink at all. It took on quite a bit of it and it was obvious when it was saturated. Leo Kutz

Dikes and Levees constructed with clay soils
Tidegate Layout and Implementation Technical Considerations – clay backfill is normal Dikes and Levees constructed with clay soils Special project specifications were developed for these conditions. See typicals used on recent projects following slides

Special project specifications were developed for these conditions.
See typicals used on recent projects following slides Tidegate Layout and Implementation Technical Considerations – clay material in levees Dikes and Levees constructed with clay soils

During Peak Flows sites often experience overtopping
Tidegate Layout and Implementation Technical Considerations- High stream flow overtopping o f Levees During Peak Flows sites often experience overtopping Use saturated conditions with high ground water for assessing loadings on structures and overturning. Add Erosion protection riprap along entire slope on both sides of levee. Use an aggregate surfacing of Levee top that can resist erosive forces.

Additional Forces; water hammer, Buoyancy
Tidegate Layout and Implementation Technical Considerations – water/wave action Additional Forces; water hammer, Buoyancy Wave action by tidegate door opening and closing rapidly as wave develops will literally destroy a conventional culvert . Need to add venting area at front of culvert or a vented ceiling to culvert to protect structure.

Tidegate Layout and Implementation Technical Considerations – Buoyancy
Additional Forces; water hammer, Buoyancy With tidegate closed and empty on field side buoyancy forces will occur from hydraulic uplift at stream side. The culvert acts like a boat Need to add sufficient ballast rock to prevent uplift forces. On concrete structure may need to add extra footing widths under soil loads . Remember that in high water situation the rock weight must be reduced by the water weight in the calculations (submerged loading conditions). On circular culverts add a longer sleeve at the connection of the tidegate to the culvert. The sleeve will prevent the culvert from bending acting as a reinforcement beam as load is transferred into the higher fills at the end.

Culvert Invert Elevation and grade
Tidegate Layout and Implementation Technical Considerations- Culvert invert and grade Culvert Invert Elevation and grade The grades of tide gated structures are set at a level or zero percent grade. The Invert Elevation ideally is developed from flow data taken with data loggers. Set the invert elevation one foot below the lowest level of the tide change under that condition the culvert has a foot depth of flow at the lowest tides. This is a site specific judgment that considers variables such as debris flow, flushing of pipes during seasonal rains, etc.

Tidegate Layout and Implementation Permit Reporting requirements- Brief
Permit Analysis From modeled data and studies Hydrology of site Peak flow Fish Passage flow Stream Characteristics Long Profile upstream and Downstream with sections Active Channel and Bank full Channel Widths Rock gradation within stream Section views of channel Alternatives reviewed and Preferred Alternative Volume of cut and fill within channel areas Areas of cut and fill within channel areas Maps depicting all improvements, fill areas, waste areas, storage areas Compliance with water quality Model to show compliance with velocity and time constraints. Calculations for sizing Riprap and embedment if needed Plans and Specifications for proposed Improvements Calculations for sizing Large wood if part of project. Effects on farm fields from flooding – salinity and access to fields. Analysis Considerations Future Conditions: A tide gated culvert is sized for two conditions: Peak flow and Fish Passage criterion. Designs should also allow for effects of future stream improvements. Improvement included the increase in pond volumes from stream restoration projects in the future. One possible improvement would be to install the culvert without an MTR unit and add it later when funds become available. Peak Flow Design: Culverts are typically sized for a peak flow with a Headwater to Depth ratio of 1.0 or less to accommodate debris flow. Debris accumulation at the inlet creates a risk of water over topping the road. Salinity Concerns: Historically water ponds in the fields during higher tidal flows in the Coquille River until the river recedes or rainfall causes the field elevation to rise above the Coquille River elevation. An important note is that the ponded water is fresh and not saline. The stream is considered saline at this location and backwater into farm fields from the stream will affect the viability of the pasture lands for agricultural purposes.

Tidegate Layout and Implementation Modeling Structures and Permitting
Model flow to determine compliance with permit requirements Percent of cycle tidegate is open > 51 % Maximum Velocity < 2 fps by % for each alternative. Alternatives Evaluated Type of structures Costs of structures Size of structures Volume of material removed or placed Levels and areas of backwater allowed for each alternative Effects of Increase backwater on downstream and upstream flows and elevations. Information needed for Evaluation of Tidegate Alternatives using modeling program. Area of Drainage for peak flow analysis Topographic area of backwatered drainage for determining the volume per foot of backwater behind tidegate. Lydar data supplemented with GPS topographic data for accuracy Topographic area of stream at site to determine minimum level of flows at site. Typically we set tidegates at minimum elevation of 0.00 which may be below the stream level. Topographic map of site for design and permit quantities. Tidal Data at site for selected months of the year. Should be within a reach of the stream adjacent to site. Using the tidal records we can than correlated to the NOAA tidal charts to see if muted relationship exists. Elevation of site needs to be to same tidal datum as NOAA charts. GPS equipment gives an accurate value for each site. Calculate Design stream flow range- Hydrology of site compared to adjacent streams with gaged data. Determine active channel of stream – Field measurements

Tidegate Layout and Implementation Modeling - output requirements
Information needed to model tidegate velocities, areas, and flows Percent of cycle tidegate is open > 51 % Maximum Velocity < 2 fps by % for each alternative. Alternatives Evaluated Type of structures Costs of structures Size of structures Volume of material removed or placed Levels and areas of backwater allowed for each alternative Effects of Increase backwater on downstream and upstream flows and elevations. Information needed for Evaluation of Tidegate Alternatives using modeling program. Area of Drainage for peak flow analysis Topographic area of backwatered drainage for determining the volume per foot of backwater behind tidegate. Lydar data supplemented with GPS topographic data for accuracy Topographic area of stream at site to determine minimum level of flows at site. Typically we set tidegates at minimum elevation of 0.00 which may be below the stream level. Topographic map of site for design and permit quantities. Tidal Data at site for selected months of the year. Should be within a reach of the stream adjacent to site. Using the tidal records we can than correlated to the NOAA tidal charts to see if muted relationship exists. Elevation of site needs to be to same tidal datum as NOAA charts. GPS equipment gives an accurate value for each site. Calculate Design stream flow range- Hydrology of site compared to adjacent streams with gaged data. Determine active channel of stream – Field measurements

Tidegate Layout and Implementation- Modeling of flows
Topography Inundation Area Storage Using topographic maps such as lydar in conjunction with field sections create a relationship table of the area of the inundation area by elevation. This lookup table is used to determine the incremental storage available during the rise and fall of the tide. Tide Flow. The flow of water thought the structure from the tide flow is controlled by either weir flow equations or the volume of water per available storage volume in the inundation area less the flow from runoff and rainfall. The Tail water (TW) or H2 is the calculated height of the water in the inundation area after each incremental change in the tide. The Headwater HI is the height of the water in the stream which is the height of the tide. Rainfall Adjustments For a given rainfall the height of the storage area will rise based on the available volume of storage per foot at the inundations area level. Accordingly in the model we add the rainfall affects to the level of the backwater at the beginning of the increment calculations. Muted Tidal Regulators (MTR) A MTR system is proposed that uses floats to keep the side mounted tide gates open during an incoming tide to a pre established height. Without the MTR system, the door would close when the HW height in the main stream is greater than the TW height on the field side.

Tidegate Layout and Implementation- Inundation area Modeling of flows
Topography Inundation Area Storage Using topographic maps such as lydar in conjunction with field sections create a relationship table of the area of the inundation area by elevation. This lookup table is used to determine the incremental storage available during the rise and fall of the tide. Tide Flow. The flow of water thought the structure from the tide flow is controlled by either weir flow equations or the volume of water per available storage volume in the inundation area less the flow from runoff and rainfall. The Tail water (TW) or H2 is the calculated height of the water in the inundation area after each incremental change in the tide. The Headwater HI is the height of the water in the stream which is the height of the tide. Rainfall Adjustments For a given rainfall the height of the storage area will rise based on the available volume of storage per foot at the inundations area level. Accordingly in the model we add the rainfall affects to the level of the backwater at the beginning of the increment calculations. Muted Tidal Regulators (MTR) A MTR system is proposed that uses floats to keep the side mounted tide gates open during an incoming tide to a pre established height. Without the MTR system, the door would close when the HW height in the main stream is greater than the TW height on the field side.

Tidegate Modeling of flows
Given the data from the sheets above the program calculates the flows through the culvert adjusting for rainfall, volume of water tail water elevations ,etc.  Using Tide data calculates the beginning flow for first increment  Calculates H1 and H2  Adjusts for rainfall by raising the level of the water in the basin by the amount of rain for the time increment using topography and rainfall data  For the adjusted H2 for rainfall, calculates the weir flow into the culvert using culvert characteristics data sheet.  Adjusts Weir flow and tail water into culvert to account for the available water in the basin that can or cannot move from basin for the change in elevation of the water for that time increment. o If basin is less volume than the flow that could move based on weir flow the flows are reduced . The height of the tail water going into the next iteration is equal to the tide change. o If basin is larger than the flows that could move based on weir flow than the flows are controlled by the weir flows . The tail water elevation is adjusted leaving a larger head (H1-H2) going into the next iteration.  Calculates the velocity of flow based on Velocity= Flow/area. The area is determined from the culvert tables for the height of the water flowing through the culvert  Using counters records the times that flow moves through the culvert  Using counters records the times that flow exceeds target velocities

Box Culvert(s) Option Coos County Culvert at Mile Post Pierce Lands Reference tide Charleston Station NAVD Storm Flow 0.00 CFS Length of Culvert 60.00 feet Rise of Culvert 8.00 Span of Culvert Type of Culvert box Number of Culverts 1.00 each MTR setting at datam elevation of 5.00 Foot Invert Elevationsof Culvert:Tidegates culverts are set level Mannings Roughness per table 4.6 0.0120 Per FHWA PROGRAM Velocity of flow- Box Culvert Flow Velocity Comparisons as percentage of incoming tide, outgoing tide and total tide Velocity Below Target Velocity Value in ft/sec incoming tide minutes above target outgoing tide minutes above target Total Tide Cycle Percent above target value Total Tide cycle Percent Under target value 2 0.0% 100.0% 3 4 Percentage of time Gate is Open Percent shown is the percent of total tide cycle including times when gate is closed and water level is below invert. Category of tidal flow minutes open total Minutes in category Percent of category- open Percent of Tide Cycle - open Tide Cycle- incoming and outgoing 54% incoming tide 47% 25% Outgoing Tide 62% 29% Water Level Depth Summary Elevation of field water in feet (NAVD 1998) Depth of flow above culvert invert total minutes Percentage of tide cycle water level exceeds field elevation Acres of flooding -1 -1.0 0.0 1 1.0 91.1% 0.01 2.0 82.7% 0.07 3.0 71.5% 0.15 4.0 59.9% 0.44

Tidegate Modeling of flows graph of percent of time velocity exceeds 2%. Differs with each alternative and condition Models displays the percent of time velocity exceeds the 2fps target Velocity

Tidegate Modeling of flows- Sample MTR Management Plan
February 1st to June 1st: Set Floats on _____, (this is a critical period for ramping up agricultural production and drainage is critical for early grass production.) 2. June 1st to July 1st: Set Floats on MTR between _____.0 to ______ depending on weather conditions. Drier periods would allow more inundation while wetter conditions would dictate lower. 3. July 1st to Approximately Late September (depending on the beginning of the rain season), set floats on MTR to ______. 4. Late September (depending on conditions) through January 30, Set floats on MTR at elevation____. Notes: between elevations ____ & ____ water breaks into low agricultural areas 5. A review team should evaluate the settings annually. The team will typically include the Land Owners of the drainage and roads and permitting agencies such as the ODFW. This relationship needs to be clarified by all parties as part of the permitting process.

Tidegate Modeling of flows- Establishing Management Plan
Muted Tide System Operation & Maintenance Plan The following is a format for a sample management for setting the elevations of the MTR. Float. The settings should balance the following concerns. 1. The highest level water can rise before salinity affects agricultural uses of the lands. 2. The highest water level before agriculture uses of property will be delayed or prevented. EG. Grassing, field fertilization and herbicide applications, soil tilling that affects stream sedimentation, etc. 3. Minimum levels desired for habitat and wildlife restoration values. The following is a sample management plan proposed for setting the elevations of the MTR floats.

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