San Benito County Municipal Code Art. III Storm Drainage Design Standards

(A) Storm frequency generally. The storm frequency to be used in drainage system design will be the storm frequency applicable for the design point under consideration. The following guidelines give a general rule for determining applicable design storm frequency.

(B) Frequency determined by Engineer. The actual storm frequency used will be specified at the discretion of the Engineer.

(1) Ten-year storm. The drainage system for the ten-year storm is to be designed to minimize inconvenience, protect against minor damage and reduce maintenance costs. Improvements to be designed for the ten-year storm shall generally include on-site and non-sump conditions and local drainage facilities for residential, commercial, office and industrial development. This will almost always include all on-site closed conduit design and minor channel sections.

(2) Twenty-five-year storm. Twenty-five- year storm is required for sump conditions in the public right-of-way.

(3) One hundred-year storm. The drainage system for the 100-year storm is to be designed to protect against loss of life or substantial property damage. Improvements requiring 100-year design capacity are channels, detention ponds and retention basins. Major channels and closed conduit systems shall also meet the requirements for the 100-year storm as specified in these standards.

(A) Rational formula.

(1) The rational formula shall be used to determine the peak flow rate for the design storm:

Q = CIA where Formula 2.1

(a) Q = peak rate of flow in cubic feet per second.

(b) C = coefficient of runoff having a value between 0.0 and 1.0 depending on surface characteristics (23.31.041(1)).

(c) I = the average intensity of rainfall in inches per hour for a duration equal to the critical time, usually the time of concentration.

(d) A = the tributary area in acres corresponding to the critical time above.

(2) The procedure for determining the values of C, A and I are given in the following sections.

(B) Runoff coefficient, C. Table 23.31.041(1) shows the basic coefficient, C, to be used for various types of surfaces. Where a tributary area contains more than one type of surface, the value of C shall be the weighted average of the respective values shown on Table 23.31.041(2) based on percentage of each surface area to the total area.

Table 23.31.041(1) Basic Runoff Coefficients

Table 23.31.041(2) Composite Runoff Coefficients & Minimum Inlet Times for Various Land Uses

Table 23.31.041(2) Composite Runoff Coefficients & Minimum Inlet Times for Various Land Uses

(C) Rainfall intensity, I. Runoff for the ten-year storm must be based on the rainfall zone map and the rainfall intensity - duration curve.

(D) Tributary area, A. The tributary area in acres for each point of computation shall be based on actual field reconnaissance or use of appropriately scaled maps that certainly depict the drainage boundaries. All of the area that will contribute runoff to the drainage system shall be considered, regardless of the limits of the particular development under consideration.

(E) Critical flow time.

(1) The critical flow time is the time that results in the maximum flow rate for a given point in a drainage system. Maximum flow occurs when the product of the intensity and the contributing area corresponding to the flow time is a maximum. The time required for water to flow from the most hydraulic remote point in the watershed to the point in question is called the time of concentration. Using the intensity corresponding to this time and the entire drainage area in the rational formula usually results in the maximum flow rate for the point.

(2) The nomograph shall be used to determine the time of concentration to the first inlet of the drainage system. If this time is less than the minimum inlet time, the values shown in the table shall be used.

(3) When any part of the storm waters are conveyed to the point in question by pipes or open channels, the flow time in these conveyances shall be added to the inlet time to compute the total flow time. In complex drainage situations more than one computation may be required to determine the combination of contributing area and flow time that results in the maximum flow rate.

(4) The rational method tends to result in more conservative values for peak flows as the time of concentration becomes quite large and when several branches of varying times of concentration are involved; therefore, the designer may consider using a hydrograph method for determining runoff when the drainage basin is larger than 100 acres.

(F) Off-site flows. Flows entering the proposed development from outside the property are off-site flows. The off-site storm runoff must be determined and included in the drainage system design. Available drainage reports for off-site developed areas affecting the property must be reviewed and considered in the drainage system planning and design. Runoff entering the site from off-site must be computed using runoff coefficients based upon existing development, or for undeveloped land, based on zoning, whichever is greater. Allowable discharge for the developed area shall be limited to the ten-year event pre-development discharge, or the channel capacity, whichever is the lesser.

(G) Figures. See figures on following pages.

COUNTY OF SAN BENITO DEPARTMENT OF PUBLIC WORKS ISOHYETAL MAP - MEAN ANNUAL PRECIPITATION FIGURE 23.31.041(1)

[Figure]

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COUNTY OF SAN BENITO DEPARTMENT OF PUBLIC WORKS INTENSITY DURATION CHARTS FIGURE 23.31.041(2)

[Figure]

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COUNTY OF SAN BENITO DEPARTMENT OF PUBLIC WORKS TIME OF CONCENTRATION (RURAL WATERSHEDS) FIGURE 23.31.041(3)

[Figure]

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COUNTY OF SAN BENITO DEPARTMENT OF PUBLIC WORKS INLET TIME (SUBURBAN-URBAN) FIGURE 23.31.041(4)

[Figure]

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COUNTY OF SAN BENITO DEPARTMENT OF PUBLIC WORKS VOLUME FIGURE 23.31.041(5)

[Figure]

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(A) Manning Equation.

(1) The Manning Equation shall be used to determine the capacity of open channels and enclosed gravity conduits:

Q = AV = 1.486 R 2/3 S 1/2 A n

(a) Q is the flow rate in cubic feet per second.

(b) R is the hydraulic radius in feet.

(c) A is the cross sectional area of the flow in square feet.

(d) S is the slope in feet per foot

(e) V is the flow velocity in feet per second.

(f) n is the Manning coefficient

(2) Values of the Manning coefficient for various pipes and open channels are given in Table 23.31.042(1).

Table 23.31.042(1) Manning Coefficient

Table 23.31.042(1) Manning Coefficient

(B) Pipe flow criteria.

(1) Catch basin laterals shall be not less than 12 inches in diameter. All mains or trunk lines shall be not less than 18 inches in diameter.

(2) The minimum velocity in closed conduits shall be one fps when flowing full. Maximum velocity shall be ten fps.

(3) The hydraulic grade line (HGL) of the design storm flow must be computed for all storm drain systems and must be shown on the design profile when it is above the top of the pipe. The HGL shall be a minimum of one-half feet below the elevation of the inlet grates and manhole covers of all structures within the system.

(C) Open channel flow.

(1) Maximum velocities in open channels shall be as follows on Table 23.31.042(2).

Table 23.31.042(2)

Table 23.31.042(2)

(2) Freeboard requirements shall be set by the Engineer or the agency governing the proposed channel facilities.

(3) Channel flow shall be placed in closed conduits where the flow requires a concrete pipe of 48 inches diameter or less.

(D) Backwater effects. When obstructions, transitions, junctions, constrictions or other irregularities in an otherwise uniform channel system create backwater conditions in the system, the consulting engineer shall make computations to determining the effects of the backwater condition. The consulting engineer shall use careful consideration in determining when losses due to channel irregularities are small enough to neglect or when they are large enough to create considerable backwater effects.

(E) Detention basins.

(1) Detention basins other than those shown on the Master Storm Drainage Map may be used for revisions to the Master Plan or the staged development only upon approval of the Engineer.

(2) The volume of water to be stored shall be computed from the following basic formula with credit for outlet flow per division (E)(2)(d) below:

(a) V = the volume in acre-feet.

(b) C = the runoff coefficient (see Tables 23.31.041(1) or 23.31.041(2)).

(c) A = the contributing area in acres.

(d) R = the total rainfall in inches for the 24-hour storm period, using a 100-year storm frequency.

(3) The volume of detention basins shall be determined with no allowance for percolation.

(4) All detention basins shall have outlet facilities providing terminal drainage capable of emptying a full basin within 24 hours. Allowance for outlet facilities to reduce the total volume of the basin can be made only if the consulting engineer can demonstrate by routing computation that the basin will operate properly.

(5) The bottom of the basin shall be above the highest recorded groundwater elevation and shall also meet the requirement of the state’s Water Quality Control Board. It is the responsibility of the developer’s consulting engineer to coordinate with the state’s Water Quality Control Board and submit evidence of their approval to the Engineer.

(6) The design water surface elevation of basin shall be a minimum of one foot below all berm, and of roads, and/or top of curb elevations upstream from the basin.

(F) Retention ponds.

(1) Developments will be required to provide terminal drainage where developments are within one mile of a terminal drainage facility.

(2) When terminal drainage is not available, retention ponds utilizing percolation as a means for emptying the basin may be used only upon approval of the Engineer.

(3) Retention ponds that utilize percolation as a means of emptying the retention ponds shall not be permitted unless bottom elevation of the retention pond is two feet or more above the highest recorded groundwater elevation in the previous ten years.

(4) Retention ponds that utilize percolation as a means of emptying the retention pond shall conform to the following design criteria:

(a) The retention pond design shall be the responsibility of the developer’s engineer and subject to review by the county.

(b) Permeability and differential head available must be considered for the life of the project, not just present values.

(c) Earth material and groundwater condition evaluations shall be made on a site-specific basis by a qualified Geotechnical Engineer and include project-specific subsurface data and tests, all subject to review by the county.

(d) The volume of storage required shall be 100% of the computed volume of storage for the 100-year storm.

(e) Retention ponds shall be designed to empty 100% of the required volume of storage within ten calendar days.

(f) Levees shall be discouraged around retention ponds.

(G) Culvert criteria.

(1) Culverts shall be designed per CALTRANS standards. Maximum headwater depth at inlets shall not exceed one and one-half times the pipe diameter without approval of the Engineer.

(2) The constants Ke = 0.25 and Ko = 0.75 shall be used for concrete pipes and box culverts. For corrugated pipes, Ke = 0.50 and Ko = 1.0 shall be used.

(3) Cross culvert conduits and box structures shall be designed to pass the peak flow from the ten-year storm without damage to the roadway and shall be checked on the basis of the ten-year runoff plus 50% to determine that no serious damage will be incurred upstream as a result of the higher design storm.

(4) Cross culvert profile will be determined by an examination of the overall profile of the channel for a minimum distance of 500 feet each side of the installation.

(5) Outlet velocities of all culverts must be checked. When outlet velocity exceeds the maximum permissible channel velocity listed on Table 23.31.042(2), energy dissipaters must be provided to minimize potential erosion at the outlet.

(H) Inlet criteria.

(1) Inlets shall be spaced so that the flow capacity of the inlet is not exceeded by the design storm flow rate or so that the length of gutter flow does not exceed 700 feet, whichever is less. The maximum flow capacity of a single standard storm: Drain Inlet No. 1 at a sag point is 2.0 cfs. On a continuous grade greater than 0.5%, the maximum capacity is approximately one cfs, and 0.50 cfs on grades less than 0.5%. Larger Basin No. 2 may be used in industrial or commercial areas or when approved by the Engineer. Industrial/commercial catch basins shall conform to county standards, and will have capacities approximately 50% greater than the Standard Drain inlet No. 1.

(2) Drainage in a sump area must be provided with a secondary outlet for flows greater than the ten-year design capacity of the drain inlet. This outlet must be provided as overland, street or

other above ground means of carrying flow, unless it can be shown that a secondary drain inlet to the underground system, along with that underground system can convey the 100-year storm without flooding beyond the limits shown in division (I) below.

(3) Eighteen inch storm drain inlets may be used at sag point only as approved by the Engineer. Capacity of this inlet is dependent on maximum allowable submergence and will be reviewed on a case by case basis.

(I) Surface flow in street and allowable inundation of 100-year storm.

(1) The primary use of roads is for traffic. The allowable depth of flow in streets shall be limited to the following:

Table 23.31.042(3)

(J) On-site drainage.

(1) Minimum pipe size shall be 12 inches or as approved by the Engineer.

(2) Maximum area to be drained to a single inlet is two acres.

(A) Alignment of drainage facilities.

(1) The diversion of natural drainage will be allowed only within the limits of the proposed improvement. All natural drainage must enter and leave the improved area at its original horizontal and vertical alignment unless an agreement, approved by the Engineer, has been executed with the adjoining property owners.

(2) Alignment of drainage facilities must coordinate with other utilities and street designs.

(3) Closed conduit must usually be placed straight between manholes. Long radius curves are permitted for pipe 24 inches and larger. The radius of curvature must not be less than 100 feet or the manufacturers recommendation for curved alignment, whichever is greater. Curves, radii and length of pipe joints must be shown on the improvement plans.

(B) Easements. Easements for drainage facilities shall meet the requirements of the county improvement standards and the following design standards:

(1) Closed conduit. Easements for closed conduits shall meet the following requirements:

(a) For pipes 24 inches in diameter and less with trench depth less than or equal to five feet, the minimum width of the easement shall be ten feet with the centerline of the pipe at quarter point; pipe may reverse sides at angle points.

(b) Temporary access and working easements must be obtained for work outside of the easement.

(c) For pipes exceeding 24 inches in diameter or trenches greater than five feet deep, the easement shall have additional width to provide ample working space as required by the Engineer.

(2) Open channels. Easements for open channels shall have sufficient width to contain the open channel with side slopes, fencing where required, and a 15-foot service road when required by the Engineer. Suitable ramps must be provided for access to the bottom when bottom is used for maintenance access.

(C) Closed conduit design.

(1) Closed conduits shall be either cast-in-place concrete pipe, precast reinforced concrete pipe, non-reinforced concrete pipe, corrugated steel pipe or corrugated aluminum pipe, or other type approved by the County Engineer.

(2) The specified type of pipe or alternate pipes must be shown on the plans. Revised plans must be submitted to the county for approval if use of pipe not shown on the plans is desired.

(3) Cover requirements shall be as shown on standard drawings. Where the minimum cover requirement cannot be provided, the conduit shall be encased in concrete or provided with a concrete cover or other method of pipe protection approved by the Engineer. These charts are based on Type I bedding and backfill per standard drawing. Type I bedding and backfill shall be used for storm drain conduit unless otherwise specified by the Engineer. Other trench requirements can be found in the standard specifications sections.

(4) Where different size pipes meet at a junction, the pipe crown elevations shall be matched unless otherwise approved by the Engineer.

(D) Manholes and junction boxes.

(1) Standard precast concrete or saddle type manholes per Standard Drawings D-1 and D-2 shall be used where feasible. For cases where special manholes or junction boxes are necessary, the design must be approved by the Engineer. In no case shall manholes or junction boxes be allowed that are smaller than 24 inches inside dimensions. All manholes and junction boxes other than inlets shall have standard manhole covers per standard drawings. Slotted manhole may be used when approved by the Engineer to back up minor drainage in non-traffic areas. These covers will not be allowed in gutters, pedestrian, bicycle or vehicle access areas.

(2) Manhole shall be constructed at junction points, angle points greater than 15, changes in grade and changes in pipe size. On curved pipes manholes must be located at the B.C. and E.C. of the curve. Where approved by the Engineer, inlet pipe with diameter 20% or less in size than the main line may not require a manhole at the connection. Manholes located in major intersections shall be avoided wherever possible.

(3) Maximum spacing of manholes shall be as follows:

(a) For pipe sizes 24 inches or less in diameter the maximum spacing of manholes shall be 500 feet.

(b) For pipes greater than 24 inches in diameter the maximum spacing may be up to 600 feet.

(c) For curved pipe with radii less than 400 feet, maximum spacing shall be 300 feet.

(d) For curved pipe of radii 400 feet or greater, the maximum spacing shall be 400 feet for pipe 24 inches or less in diameter and 500 feet for pipe greater than 24 inches in diameter.

(E) Inlets.

(1) Drain inlets shall be constructed per standard drawings. Deviations from the standard inlets must be approved by the Engineer.

(2) A drain inlet must be placed at all gutter sag points. Inlets located within street crosswalks shall be avoided whenever possible. Spacing of inlets shall meet the hydraulic criteria as set in these standards.

(F) Open channels.

(1) Natural channels. Natural or grass lined channels shall have a minimum side slope of two to one. For locations of unstable soils, the minimum side slope may be three to one at the discretion of the Engineer. The minimum bottom width shall be six feet with no shrubs or trees within the flow limits of the channel.

(2) Concrete lined channels.

(a) Concrete lined channels may be constructed if a natural channel is not feasible and one or more of the following conditions are met:

• 1. The capacity of a 66 inch pipe is exceeded;
• 2. The cover requirements for buried pipe cannot be met;
• 3. The required pipe or natural channel grade cannot be maintained; or
• 4. Slope lining is required to maintain the desired channel side slope.

(b) Rectangular concrete channels must be structurally designed to retain resultant earth pressures. Calculations must be submitted to the county.

(c) Trapezoidal concrete sections shall be designed per the standard drawings. The minimum bottom width shall be six feet. A ten-foot wide access road will be required on either bank and will be provided with adequate ramping per standard drawings for access of maintenance equipment to the channel bottom. At the discretion of the Engineer, a bank side road may not be required where channel bottom width is greater than or equal to ten feet and vehicular access to the channel bottom is included.

(d) All concrete lined channels shall be enclosed by a minimum six-foot high chain link fence.

(3) Rock lined channel. Rock lined channels may be constructed in lieu of concrete channels, but must maintain a minimum two to one side slope and must conform to standards and specifications of the California Department of Transportation.

(4) Inlet and outlet structures.

(a) Inlets from channels to pipes shall be designed per approved standard drawing. A trash rack will be required in instances where the Engineer deems that significant amounts of debris may occur at the inlet. Trash racks will be designed per approved standard drawing.

(b) Outlets from pipes to natural or grass lined channels shall include erosion control provisions per standard drawings.

(G) Culverts.

(1) The U.S. Bureau of Public Roads nomograph shall be used to compute the capacity of all cross culverts that are not to become a part of a closed conduit system.

(2) All headwalls, wingwalls and endwalls shall be considered individually and shall be, in general, designed in accordance with the Standards and Specifications of the California Department of Transportation.

(H) Detention and retention systems.

(1) General.

(a) The maximum side slope for retention ponds or detention basis shall be two to one where adequate side slope stability can be demonstrated. All ponds or basins with depth of 18 inches and with side slopes steeper than five to one shall be completely enclosed by a six-foot high chain link fence. Ponds or basins with slopes five to one or flatter will have no fencing requirements. Where side slopes are steeper than five to one, a vehicular access ramp shall be included into the pond.

(b) Vegetation other than trees or landscape shrubs on side slopes and banks of basins and ponds must be mowed, burned or treated with herbicide so as to not reach a height greater than six inches during the non rainy season (March 15 to November 15).

(2) Detention basins.

(a) Detention basins may be constructed to facilitate other public uses where possible.

(b) Detention basins shall be designed with gravity in-flow and gravity out-flow whenever possible. (i.e., large pipe in/smaller pipe out, or overflow in/flap gated outlet). Detention systems requiring pumping facilities must meet the requirements of these standards and must be approved by the Engineer.

(c) The bottom of a detention basin shall be sloped at a minimum of 1% towards the outlet works. Whenever possible, a low flow channel or pipe through the basin shall be incorporated into the design.

(3) Retention ponds. Retention ponds shall be constructed per standard drawings. Deviation from this design must be approved by the Engineer. The number and depth of percolation pits necessary will be based on recommendations of a certified soil or geotechnical engineer.

(I) Pump stations.

(1) General.

(a) The use of drainage pumps shall be avoided whenever possible and used only with the specific approval of the Engineer.

(b) If the use of drainage pumps is permitted, the drainage system shall be so designed as to provide for gravity outfall during the summer months and other periods of low water stages. If a low stage gravity outfall is impossible or impractical, an alternate pump of smaller capacity for low stage flow shall be provided.

(c) Pumping installations shall be so designed to accommodate a design storm as specified in these standards. When a station contains gravity discharge, discharge capacity must be equal to the allowable outflow. When the station does not have a gravity discharge, pumping units must be designed to furnish 100% of allowable outflow with any one pump out. Any deviation from this criteria must receive the specific approval of the Engineer.

(d) Each pumping installation shall require approval for each of the following items: electrical system, piping system, pumps, housing installation and other miscellaneous design features.

(e) For facilities to be maintained by the county, a multi-pump system shall be provided and a pump house shall be required for the electrical control equipment conforming to the improvement standard drawings.

(2) Design.

(a) Pumping plant sites shall be fenced with a six-foot high chain link fence with three strand barbed wire and a ten-foot minimum width gate. The site shall also be provided with a paved access road. Unpaved areas within the fence boundary shall be sterilized with a soil sterilant.

(b) Adequate access shall be provided for cleaning the pump sump.

(c) Trash racks shall be provided upstream from the pumping plant. Provisions shall be made for easy cleaning of the trash racks.

(d) Hatch covers, where used, shall be of raised pattern aluminum floor plate, or other approved lightweight cover. Dissimilar metals shall be insulated from each other when necessary.

(e) Ladder rungs, where used, shall be of a non-slip variety.

(J) Temporary drainage diversion.

(1) Temporary drainage diversions, such as dams and pipe plugs, shall be located and constructed in such a fashion as to permit their removal during adverse weather.

(2) Locations and removal procedures for temporary drainage installations shall be approved by the Engineer, and these installations shall be removed when necessary to prevent damage to adjoining property.

(K) Fence requirements.

(1) Where required.

(a) Improved channels, detention basins and retention ponds in developed areas exceeding one and one half feet in depth and with side slopes steeper than five to one shall be fenced with six-foot chain link fence. In all other areas, fencing shall be placed only upon the recommendation of the Engineer.

(b) The fence shall be located six inches within the required drainage easement lines.

(2) Access. Double panel access gates shall be required for all vehicular access. The minimum width shall be ten feet and shall be based on the specific application.

(A) Required. For subdivisions larger than two acres, a drainage report shall be submitted with the submittal of the improvement plans. Subdivisions less than two acres will be checked on a case by case basis with requirements determined by the Engineer.

(B) Format. The following format shall be followed in preparation of the drainage calculations:

(1) Title page.

(a) Type of calculations (preliminary or final);

(b) Project name;

(c) Preparer’s name, firm and date; and

(d) Stamp and signature of engineer who prepared the calculations.

(2) Introduction.

(a) Site location:

1. City, county, street grid; and

2. Adjacent development.

(b) Site description:

1. Existing topography, land use and the like; and

2. Existing drainage facilities.

(c) Proposed project description; and

(d) Reference to flood hazard reports or other related drainage reports or flood insurance rate maps (FIRMs).

(3) Existing drainage system.

(a) Basin drainage characteristics;

(b) Existing drainage patterns; and

(c) Off-site flows and effects of historic flows or adjacent properties.

(4) Proposed drainage system.

(a) Discussion of criteria:

• 1. Basin and sub-basin sizes;
• 2. Hydrologic method;
• 3. Storm frequencies analyzed;
• 4. Proposed flow patterns; and
• 5. Hydraulic controls for terminal drainage outfall.

(b) Major facilities:

1. Discuss location, size and configuration of major trunk lines, open channels, culverts and the like and relate to existing or proposed terminal drainage facilities; and

2. Discuss need for and sizes of detention or retention facilities and means of releasing stored runoff.

(5) Conclusions. Discuss impacts of improvements:

1. Benefits - Does the improvement reduce existing drainage problems; and

2. Adverse impacts with solutions to mitigate impact.

(6) Appendices containing hydrologic and hydraulic computations.

(a) Runoff calculations:

1. On-site map shall be a reproducible watershed map, which includes:

a. Sub-area acreage;

b. Sub-area design flow rates;

c. Sub-area runoff rates; and

d. Plan view of improvements with respective design flow rates.

2. Off-site watershed shall be shown on USGS quad map and shall indicate:

a. Watershed acreage;

b. Design flow rate and location of discharge;

c. Flow patterns; and

d. Runoff coefficients used.

3. Table of runoff for each sub-area showing acres, runoff coefficient, time of concentration and intensity used.

(b) 1. Hydraulic calculations:

a. Main line pipe and channels; and

b. Calculation sheets shall include:

(i) Contributory drainage areas;

(ii) CFS in each pipe or channel reach;

(iii) Invert elevations of each pipe or channel reach;

(iv) Hydraulic grade line control;

(v) Hydraulic gradient;

(vi) Hydraulic grade line elevations;

(vii) Pipe sizes, lengths and slopes; and

(viii) Channel dimensions and water surface profile computations. The standard storm drain design sheet shall be per standard drawings.

2. Detention or retention ponds. Calculations must include:

a. Volume or routing computations for ten-year storm;

b. Ponding elevations;

c. Discharge rates to show that ponds will regain adequate capacity; and

d. Ponds with no outlets for retention shall include soil information and percolation rates from a certified geotechnical engineer showing that the necessary volume will be regained in the specified time.

3. Pump stations:

a. Pump sizing calculations;

b. Sump sizing criteria; and

c. Sketch of station layout.

(A) A plan and profile shall be shown for all drainage facilities that carry natural drainage that originate upstream of or within the limits of the development.

(B) The plan view shall show all pipelines, pipe sizes, flow directions, manhole locations, inlets, channels, culverts, centerlines, stationing and curve data on centerline or as an offset from another construction centerline. Catch basin and connector pipe invert elevations will also be shown on the plan view.

(C) The profile shall show pipe length, slope, size and construction material used for each mainline pipe or channel section. Manhole locations, inverts and stationing shall also be shown.

(D) Channel profiles will include the channel flowline and existing ground elevation along the channel centerline. Invert elevations will be shown at the grade changes.

(E) The hydraulic grade line of the design storm shall be shown on all channel profiles and the 100-year as required by the Engineer for major channels. In closed conduit, the hydraulic grade line shall be shown when it is above the soffit of the pipe.