CHAPTER 4mdotcf.state.mi.us/public/design/files/roadmanual/rdm04.pdf · 4.01.06 Drainage Considerations ... 4.05.13 Corrugated Structural Plate Pipe and Pipe Arches ... VOLUME 3 MICHIGAN

VOLUME 3 MICHIGAN DESIGN MANUALROAD DESIGN (SI)

CHAPTER 4

INDEX

DRAINAGE

4.01 GENERAL INFORMATION

4.01.01 References

4.01.02 Glossary

4.01.03 General Procedure

4.01.04 Legal Precedent to Discharge Surface Water

4.01.05 Types of Right-of-Way Easements or Conveyance for Drainage

4.01.06 Drainage ConsiderationsA. Drainage Conditions and Participation with Local Agencies/Private EntitiesB. Participation Agreements & CostsC. Intracounty and Intercounty Drainage Systems for State Trunkline Storm

WaterD. Relocation of Existing Drainage CourseE. Relocation of Field Tile DrainsF. Design Procedures for Unknown Field Tile Locations

4.02 STORM SEWER DESIGN

4.02.01 General

4.02.02 Storm Sewer Design Criteria and ProcedureA. Roadways with Enclosed DrainageB. Depressed RoadwaysC. Design VelocityD. Hydraulic Grade LineE. Rational Method

4.02.03 Deleted

4.02.04 Rainfall-Frequency Zones

4.02.05 Rainfall Intensity - Duration Tables

4.02.06 Solving Manning’s Formula

4.02.07 Design Factors for Storm Sewers


CHAPTER 4 DRAINAGE INDEX (continued)

4.02.08 Steps in the Design of Storm Sewers using Rational MethodA. Tabulation Sheet for Computing Storm SewersB. Hydraulic Elements of Channel Sections Chart

4.02.09 Deleted

4.02.10 Factors in Locating Catch Basins or Inlets

4.02.11 Factors in Locating Manholes

4.02.12 Numbering Drainage Structures

4.02.13 Access Manholes to Storm SewersA. TypesB. ConsiderationsC. Measurement and Payment

4.02.14 Deleted

4.02.15 Sewer Bulkheads

4.02.16 Deleted

4.02.17 Deleted

4.02.18 Storm Sewers Under Structures

4.02.19 Storm Sewer Pipe Classification and Usage Guidelines

4.02.20 Jacked-in-Place Sewers

4.02.21 Storm Sewer Soil Borings

4.02.22 Storm Sewer Pipe - Curved

4.03 DRAINAGE OUTLETS

4.03.01 Acceptable Drainage Outlets

4.03.02 Unacceptable Drainage Outlets

4.03.03 Retention/Detention Systems



4.03.04 Design Guidelines to Reduce Impacts of Nonpoint SourcePollution on Receiving Waters

A. Vegetative ControlsB. Detention BasinsC. Infiltration SystemsD. Wetland Treatments

4.03.05 Storm Water Runoff Detention Basin Design GuidelinesA. Design ConsiderationsB. Design Procedures

4.04 DITCHES

4.04.01 Roadway Drainage Ditches

4.04.02 Standard DitchesA. Round Bottom DitchB. Berm or Swamp DitchC. Independent DitchesD. Toe of Slope DitchE. Valley and No-Ditch Sections

4.05 DESIGN CRITERIA FOR ROADWAY CULVERTS

4.05.01 MDOT and FHWA Requirements

4.05.02 Culvert Pay Lengths

4.05.03 Roadway Culvert Size Determination

4.05.04 Culvert Pipe Class Designations

4.05.05 Culvert Usage Guidelines

4.05.06 Permit Requirements for Roadway CulvertsA. Culvert Drainage Areas Equal to or Greater Than Five Square Kilometers

(Two Square Miles)B. Culvert Drainage Areas Under Five Square Kilometers

(Two Square Miles)

4.05.07 Determining Culvert Sizes

4.05.08 Estimating Peak Flows for CulvertsA. MDNR’s Soil Conservation Service (SCS) MethodB. The Rational Method for Estimating Peak Flows for Culverts

4.05.09 Deleted



4.05.10 Hydraulic Analysis Data and Soil Borings on Plans

4.05.11 Culvert Extensions and ReplacementsA. Hydraulic Analysis RequirementsB. Reinforced Circular Concrete Pipe ExtensionsC. Extending Existing Box and Slab Culverts

4.05.12 Bedding and Filling Around Pipe CulvertsA. Trench InstallationB. Positive Projecting ConduitsC. Negative Projecting Embankment ConduitD. Induced Trench Conduit

4.05.13 Corrugated Structural Plate Pipe and Pipe Arches

4.05.14 End Treatment for CulvertsA. Culvert Sloped End SectionsB. Guidelines for Usage

4.05.15 C.S.P. to Concrete Culvert Adapter

4.05.16 Outlet Headwalls

4.05.17 Downspout Headers

4.05.18 Concrete Slab Culverts

4.05.19 Precast Concrete Box Culverts

4.05.20 Lining of Culverts

4.05.21 Drainage Marker Posts

4.06 UNDERDRAINS

4.06.01 Purpose of Underdrains

4.06.02 Bank Underdrains

4.06.03 Subgrade and Subbase Underdrains

4.06.04 Open-Graded Underdrains

4.06.05 Underdrain Outlets & Outlet Endings

4.06.06 Stone Baskets


CHAPTER 4

DRAINAGE

4.01

GENERAL INFORMATION

4.01.01 (revised 3-8-99)

References

A. Computing Flood Discharges for SmallUngaged Watersheds, MDNR, datedSeptember 1991

B Concrete Pipe Design Manual,American Concrete Pipe Association,(October 1987)

C. Concrete Pipe Handbook, AmericanConcrete Pipe Association, (January1988)

D. Drainage of Highway Pavements,Hydrologic Engineering Circular, No. 12,FHWA, March 1984

E. Eagle Point Storm Sewers User Manual,11-13-1992

F. Federal Aid Program Guide, Part 650,FHWA, dated September 30, 1992

G. Guidebook of Best ManagementPractices for Michigan Watersheds,MDEQ Surface Water Quality Division,reprinted October 1998

H. Handbook of Steel Drainage andHighway Construction Products,American Iron and Steel Institute, (1983)

4.01.01 (continued)

I. Highway Drainage Guidelines,AASHTO, 1992

J. Hydraulic Design of Highway Culverts,Hydraulic Engineering Design Series,No. 5, FHWA, dated September 1985

K. Hydrology, Section 4, NationalEngineering Handbook, Soil ConservationService

L. Model Drainage Manual, AASHTO, 1991

M. Modern Sewer Design, American Ironand Steel Institute, (1980)

N. Rainfall Frequency for Michigan,MDNR, September 1990

O. Storm Sewer Design, MDOT DesignDivision, April 1974

P. Stormwater Management Guidebook,MDNR, March 1992

Q. Urban Drainage Design Manual,HEC-22, FHWA, 1996

R. U.S. Weather Bureau Technical PaperNo. 25 and No. 40


4.01.02 (revised 2-18-2000)

Glossary

Auxiliary Spillway - A rock or vegetated earthwaterway around a dam, used to supplementthe principal spillway in conveying extremeamounts of runoff.

Average Rainfall Intensity, I - The averagerate of rainfall upon a watershed, usuallyexpressed in millimeters per hour.

Baffle - A structure built on the bed of a streamto deflect or disturb the flow. Also a deviceused in a culvert to facilitate fish passage.

Base flood - 100 year flood frequency.

Best Management Practice (BMP)- Structuraldevices or nonstructural practices that aredesigned to prevent pollutants from enteringinto storm water flows, to direct the flow ofstorm water or to treat polluted storm waterflows.

Bulkhead - Plugs installed in sewer pipesconstructed of concrete, brick, or masonry blockto prevent flow into or out of a conveyancesystem.

Conveyance - A measure, K, of the ability ofa stream, channel, or conduit to convey water.In Manning's formula K = (1/n)AR2/3.

cms - Abbreviation for cubic meters per second(m3/s). A unit of discharge or water flow.

Check Dams - A low structure, dam or weir,across a channel for the control of water stage,or velocity, or to control channel erosion.

Crown - The highest interior elevation of aculvert, sewer, drain pipe, or tunnel.

Culvert - A structure that is usually designedhydraulically to convey surface runoff throughan embankment. The span length is less than6 meters.

4.01.02 (continued)

Design Flood - A flood that does not exceedthe magnitude of the discharge for the designfrequency.

Design Flood Frequency - The return intervalor recurrence interval used as a basis for thedesign discharge.

Detention Basin - A basin or reservoirincorporated into the watershed whereby runoffis temporarily stored, thus attenuating the peakof the runoff hydrograph. Water is released andno permanent pool remains.

Discharge - The rate of the volume of flow of astream or drain per unit of time, usuallyexpressed in cms.

Drainage Area, A - The surface flow areadraining into a stream or drain at a given point.

Drainage Tap - Connection to a sewer systemthrough an existing drainage structure orjunction chamber.

End Section - A concrete or metal structureattached to the end of a culvert for purposes ofappearance, anchorage, retaining theembankment from spilling into the waterway,etc.

Energy Dissipation - The phenomenonwhereby kinetic energy is dissipated or used up.

Energy Grade Line - A line joining theelevation of energy heads; a line drawn abovethe hydraulic grade line a distance equivalent tothe velocity head of the flowing water at eachsection along a stream, channel or conduit.

Flood Frequency - The average time interval inyears in which a given storm or discharge ofwater in a stream will be exceeded.


4.01.02 (continued)

Glossary

Flood Plain - The alluvial land bordering astream, formed by stream processes, that issubject to inundation by floods.

Floodway - The channel of a river or streamand those portions of the flood plain adjoiningthe channel which are reasonably required tocarry and discharge a 100 year flood.

Flowline - The lowest physical surfaceelevation in a drainage system. For stormsewers, the flow line is the same as the invert.This may or may not be true with a culvert. SeeSection 4.05.

Freeboard - “The vertical distance between thelevel of the water surface, usuallycorresponding to design flow and a point ofinterest such as a low chord of a bridge beamor specific location on the roadway grade, forexample bottom of subbase grade.” (ModelDrainage Manual, AASHTO)

Gutter - That portion of the roadway sectionadjacent to the curb which is utilized to conveystorm runoff water.

Harmful Interference - Causing an unnaturallyhigh stage or unnatural direction of flow on ariver or stream that causes, or may cause,damage to property, a threat to life, a threat ofpersonal injury, or a threat to water resources.

Headwall - The structural appurtenance usuallyapplied to the end of a culvert to control anadjacent highway embankment and protect theculvert end.

Headwater (HW) - That depth of waterimpounded upstream of a culvert due to theinfluence of the culvert constriction, friction, andconfiguration.

Hydraulics - The characteristics of fluidmechanics involved with the flow of water in orthrough drainage facilities.

4.01.02 (continued)

Hydraulic Grade Line - A profile of thepiezometric level to which the water would risein piezometer line tubes along a pipe run. Inopen channel flow, it is the water surface.

Hydraulic Radius - A measure of the boundaryresistance to flow, computed as the quotient ofcross-sectional area of flow divided by thewetted perimeter. For wide shallow flow, thehydraulic radius can be approximated by theaverage depth.

Hydrology - The study of the occurrence,circulation, distribution, and properties of thewaters of the earth and its atmosphere.

Impervious - Impermeable to the movement ofwater.

Infiltration - That part of rainfall that enters thesoil. The passage of water through the soilsurface into the ground. Used interchangeablywith percolation.

Infiltration Basin - A detention basin thatdischarges stored water into the ground.

Infiltration Rate - The rate at which waterenters the soil under a given condition. Therate is usually expressed in millimeters perhour, meters per day, or cubic meters persecond.

Inflow - The rate of discharge arriving at a point(in a stream, structure, or reservoir).

Inlet - A structure for capturing concentratedsurface flow. May be located along theroadway, in a gutter, in the highway median, orin a field.

Invert - The lowest interior elevation of aculvert, sewer, or tunnel. Compared to crown.

Inverted Syphon - A structure used to conveywater under a road using pressure flow. Thehydraulic grade line is above the crown of thestructure.


4.01.02 (continued)

Glossary

Manning’s Coefficient “n” - A coefficient ofroughness, used in a formula for estimating thecapacity of a channel to convey water.Generally, “n” values are determined byengineering judgement based on inspection ofthe conveyance system.

Peak Flow - Maximum discharge rate on arunoff hydrograph.

Retention Basin - A basin or reservoir whereinwater is stored and regulates a flood. It has acontrolled outlet. The stored water isdischarged by either infiltration, injection or drywells, or by release to the downstream drainagesystem during and after a storm event. Therelease may be through a gate-controlledgravity system or by pumping. The basinmaintains a permanent pool elevation.

Riprap - Stones placed in a loose assemblagealong the banks and bed of a channel to inhibiterosion, stream instability, or scour.

Runoff - That part of the precipitation whichruns off the surface of a drainage area after allabstractions are accounted for.

Runoff Coefficient (C) - A factor representingthe portion of runoff resulting from a unit rainfalland is dependent on topography, land use andsoil conditions. A factor used in the RationalMethod.

Sewer Tap - Connection made to a sewerwithout the use of a drainage structure orjunction chamber.

Spread - The accumulated flow in and next tothe roadway gutter. This water often representsan interruption to traffic flow during rainstorms.The lateral distance, in meters, of roadwayponding from the curb.

Slotted Drain Inlets - Drainage inletscomposed of a continuous slot built into the topof a pipe which serves to intercept, collect andtransport the flow.

4.01.02 (continued)

Stream - A river, creek, or any other body ofwater that has definite banks, a bed, and visibleevidence of a continued flow or continuedoccurrence of water.

Time of Concentration, tc - The time it takeswater from the most distant point (hydraulically)to reach a discharge point.

Tributary - Branch of the watershed streamsystem.

Water Table - The upper surface of the zone ofsaturation, except where that surface is formedby an impermeable body (perched water table).

Wetted Perimeter - The boundary over whichwater flows in a channel or culvert, takennormal to flow.

Wetland - Land characterized by the presenceof water at a frequency and duration sufficientto support and that under normal circumstancesdoes support wetland vegetation or aquatic life.It is commonly referred to as a bog, swamp, ormarsh.

4.01.03 (revised 12-23-96)

General Procedures

At the time the line and grade of new roadwaysor the extent and limits of a widening orreconstruction project are determined, a carefulengineering study and design must be madeconcurrently for surface and subsurfacedrainage. Highway drainage design involvestwo basic operations: estimating peak flows ofrunoff and designing a conveyance system.

Detailed hydrologic and hydraulic designguidelines are presented in the draft MDOTDrainage Manual. For specific informationc o n t a c t t h e D e s i g n Eng inee r -Hydraulics/Hydrology.


4.01.04

Legal Precedent to Discharge Surface Water

The legal precedent concerning the drainage ofsurface waters was established by the MichiganSupreme Court in 1906 in Tower vs. Townshipof Somerset, 143 Mich. 195, 201:

"Highway commissioners have the right tohave the surface water, falling, or comingnaturally upon the highway through thenatural and usual channel upon and overthe lower lands, and may construct drainsor ditches for that purpose." ReferenceFarnham on Waters and Water Rights,p.969.

A. The owner of a lower or servient estate isobligated to receive surface water from theupper or dominant estate in its naturalflow.

B. The owner of the lower or servient estatemay not fill his lands in such a way as toretard the natural flow of surface water orcause it to impound upon the upperowner's land.

C. The owner of the dominant estate has noright to divert, concentrate, or increase thevelocity of the natural surface water.Public authorities do not have the right todivert surface water that would, in thenatural state, disperse over a large areaand cast such in concentrated form uponthe lands of the abutting owner to hisdamage without compensation to him.

4.01.05

Types of Right-of-Way Easements orConveyance for Drainage

See Right-of-Way Chapter, Section 5.08.

4.01.06 (revised 2-18-2000)

Drainage Considerations

Drainage of storm water, either to or from statetrunkline right-of-way, may involve the use ofpublic or private storm water conveyancesystems. Whenever a storm water conveyancesystem from a state trunkline project isconnected into an existing public or privatestorm water conveyance system outside ofMDOT right-of-way (not allowed in combinedsewers), a written agreement on the design,construction, and future operation andmaintenance of the storm water system must beobtained from the owner of the system.Projects that may impact intracounty andintercounty drainage districts (see 4.01.06C) theProject Manager must coordinate the work withthe MDOT Drainage Coordinator (UtilitiesDesign Supervising Engineer) and theRegion/TSC Drainage Coordinator(s). TheProject Manager is responsible for contactingthe Design Engineer - Governmental andRailroad Coordination for the development ofany agreements. Hydrologic and hydraulicanalyses are needed to determine the impact ofthe connection on the storm water system(s),and must be reviewed and approved by theDesign Engineer - Hydraulics/Hydrology.

A. Drainage Conditions and Participationwith Local Agencies/Private Entities

The Project Manager must be aware of thevarious drainage conditions that maynecessitate participation costs and agreementswith local agencies, county drain commissions,drainage boards and private entities. Whencooperative drainage projects with localagencies or private entities are found to bemore economical than separate projects for theparticipating parties, an equitable sharing ofcost must be agreed upon in a writtenagreement. In all cooperative drainageprojects, storm water conveyance systems shallbe designed according to the design guidelinesin the current Department Design Manuals orother mutually acceptable design procedures.


4.01.06A (continued)

Drainage Conditions and Participation withLocal Agencies/Private Entities

The following conditions may be encounteredby a project:

Condition #1

MDOT intends to build a new storm sewer thatwill not involve another owner’s storm waterconveyance system. MDOT shall securesufficient right-of-way to place, maintain, andprotect against unauthorized use, its owni n d e p e n d e n t o u t l e t s e w e r s o rretention/detention facilities.

Condition #2

MDOT intends to build a new storm waterconveyance system (i.e. storm sewer), and thelocal agency requests MDOT to increase theproposed pipe sizes to accommodate drainageareas not naturally contributing to the highwayright-of-way.

The local agency shall submit a resolutionrequesting additional capacity in the MDOTstorm water conveyance system. Theresolution must provide for the willingness toparticipate in the increased construction andfuture operation and maintenance costs to theMDOT storm water system. The local agencymust provide a plan showing the proposeddrainage area to be accommodated and thecomputations for the expected storm waterrunoff chargeable to them based upon currentMDOT criteria (see Section 4.01.06B).


Condition #3

A local agency, county drainage district ordrainage board, or private entity desires adrainage improvement in an area where MDOThas no scheduled plans for improvement andrequests MDOT to participate in the proposeddrainage improvement. MDOT will cooperateand give financial support to neededimprovements based on the costs outlined inSection 4.01.06B.

An analysis of the existing highway drainagewill be made by the Hydraulics/Hydrology Unit,Design Division to determine the need, if any,and extent of MDOT's participation in the costsof the improvement. This cost will apply wherethe storm sewer is a separate project (e.g. , anoutlet sewer that extends beyond the normalhighway construction limits). This cost will be inaddition to furnishing and placing the sewer andshall include all other expenses, such as utilityrelocation, tree removal, road replacement, andright-of-way.

Condition #4

When MDOT intends to replace or improve anexisting open or closed storm waterconveyance system, the Project Manager mustmake an analysis of the potential drainageimpacts from and to abutting properties. MDOTwill accept the existing contributing drainagefrom abutting property to the right-of-way.Provisions for increased runoff due tocommercial or industrial development ofabutting property or for inclusion of additionalrunoff from abutting property will be at theprivate party's or local agency's cost (seeSection 4.01.06B).


Recurrence Interval(years)

Factor

2 1.0

5 1.3

10 1.6

50 2.2

4.01.06B

B. Participation Agreements & Costs

Agreements-Terms governing the construction,operation and maintenance of all cooperativesewer projects will be outlined in an agreement.The Project Manager is responsible forcontacting the Design Engineer - Governmentaland Railroad Coordination for the developmentof any agreements.

Costs - For MDOT construction projects withlocal authority participation costs forconstruction of a storm water conveyancesystem, the Project Manager will obtain theparticipation costs according to either “flowshare” or “equivalent runoff acres” methodsoutlined below.

In cooperative drainage projects done byothers, the engineering and contingency costsshall be 25 percent of the estimated cost. Thisfigure is subject to adjustment on final billingbased on actual costs.

The actual cost is the expense of furnishing andplacing the trunk sewer, including manholes,and construction of open channel conveyancesystems. Incidental items not required for theroad project will be included in the total actualcost. Items such as tree removal, maintainingtraffic, and other incidentals, which would berequired because of the road project or theMDOT sewer construction, will not be included.

Flow Share -The total cost shall be dividedbetween MDOT and the local agency or aprivate entity in proportion to the amount ofwater each party is contributing to each sectionof storm sewer. The design flow conditionshall be based on the same storm frequency(See Sewer Participation Sketch on thefollowing page). If the local agency is a countydrainage district or drainage board establishedunder the Drain Code, the costs shared arebased on a pro rata share of storm water runoffper the promulgated rules established underSection 14a of Act 51, Public Acts of 1951 asamended (see Design Engineer -Hydraulics/Hydrology).

4.01.06B (continued)

The participation cost should be based on thesame frequency storm runoff quantities as usedin the Department`s design. If there is adifference in the frequencies used, the stormwater quantity from the local authority may bephysically restricted at the junction of the localand Department facility. An agreed runoff(cms) would be metered into the Department’sfacility by using structural controls such as, butnot limited to, retention basins, sewer size,orifices, etc..

If different storm frequencies are used by therespective storm water systems, the runoffquantity computed for the local authority may bemultiplied by a factor to equal the recurrenceinterval of the local authority and theDepartment, based on the following table:

Recurrence Interval Factors*

* Source: Rule 9 for Section 14a of Act 51,P.A. 1951.

For example: When a local authority's flow (Q)contribution to a storm drainage facility is basedon a 10-year storm frequency in conjunctionwith a Department storm frequency of 50 years,the local authority's flow would have to bemultiplied by 2.2/1.6 to determine constructioncosts from the comparative flows.



Participation Agreements & Costs

Sewer Participation Sketch

Equivalent Runoff Acres-The pro rata share ofstorm water runoff from the landowner, publiccorporation and roadway authority’s parcel ofland shall be determined for the contributingdrainage area based on the equivalent runoffacres. Compute the equivalent runoff acres (E)using the formula: E = CA, where, E =equivalent runoff acres; C = runoff coefficient;A = contributing drainage area.

Storm water runoff based on equivalent runoffacres shall be determined for the entirecontributing drainage area. Compute theaverage runoff coefficient for individual parcels.A range of runoff coefficients for various landsurfaces are provided in the table below.

Equivalent runoff acres (E) may be affected byt h e i n s t a l l a t i on o f s to rm wa te rdetention/retention facilities. Equivalent runoffacres would then be based on the existing, predevelopment, conditions. Cost of theconstruction of such facilities is based onsupplemental benefit (see explanation of“Supplemental Benefits” in this section).

Range of Runoff Coefficients for VariousLand Surface Types

Type of SurfaceRunoff

Coefficient

Concrete or Asphalt Pavement 0.8 - 0.9

Commercial and Industrial 0.7 - 0.9

Gravel Roadways and Shoulders 0.5 - 0.7

Residentialless than 0.2 hectare lots

0.5 - 0.7

Residentialgreater than or equal to0.2 hectare lots

0.3 - 0.5

Agricultural - cultivated fields 0.15 - 0.4

Meadow, Pasture, Forested Areas 0.1 - 0.4

Berms 0.1 - 0.3

Lower values should be selected for flat slopesand or permeable soils, whereas higher valuesshould be selected for steeper slopes and lesspermeable soils or surfaces.



Participation Agreements & Costs

Supplemental Benefits-Supplemental benefitsmay be derived from the installation of facilities,structures, or mechanical devices jointlydetermined to be necessary by the landowneror public corporation and MDOT. These costsof supplemental benefits are determinedseparately from the cost of the storm waterconveyance system and outlined in anagreement between MDOT and the localagency or private entity (see explanation of“Agreements” in this section).

C. Intracounty and Intercounty DrainageSystems for State Trunkline StormWater

When a project involves drainage to aintracounty or intercounty drain, it is theresponsibility of the Project Manager tocoordinate the submittal of plans (required bylaw under the Drain Code) to the County DrainCommissioner or Drainage Board, with theMDOT Drainage Coordinator (Utilities DesignSupervising Engineer), and the respectiveRegion/TSC Drainage Coordinator(s).Resolution of any drainage issues must beapproved by the MDOT Drainage Coordinator.

An intracounty or intercounty drainage district isa public corporation and as such has all thelegal aspects attributable to corporations.

Any project that may change the amount ofstorm water flow to a intracounty or intercountydrainage district storm water system will requirea hydrologic and hydraulic design analyses.Such a change may impact MDOTapportionment within the Drainage District, andmust be reviewed and approved by the DesignEngineer - Hydraulics/Hydrology.

4.01.06C (continued)

The Project Manager should be aware thatCounty Drain Commissioners are reluctant totransfer storm water from one drainage districtto another drainage district. Such a transfer willrequire an agreement between MDOT and theCounty Drain Commissioner or Drainage Board.If the situation arises whereby it is necessary totransfer storm water between drainage districts,the issue must be resolved with the CountyDrain Commissioner by the Region/TSCDrainage Coordinator and MDOT DrainageCoordinator as early in the design process aspossible.

Copies of all correspondence with County DrainCommissioners should be sent to both theMDOT Drainage Coordinator (Utilities DesignSupervising Engineer) and Region/TSCDrainage Coordinator(s).

D. Relocation of Existing Drainage Course

The relocation of an existing drainage coursefor highway construction should be avoided.Where it is necessary for construction and/oreconomic reasons, an existing drainage coursemay be relocated after mutual agreementsbetween the Department, the MichiganDepartment of Environmental Quality (MDEQ),and, if applicable, the local drain commissionoffice or property owner are reached. MDEQpermit(s) may be required. The relocation of adrainage course will require a detailed hydraulicanalysis. The Project Manager must coordinatew i t h t h e D e s i g n E n g i n e e r -Hydraulics/Hydrology for either conducting thisanalysis or review and approval of the analysis.The Design Engineer - Hydraulics/Hydrologywill coordinate review by MDEQ through theBureau of Planning.


4.01.06 (continued)


E. Relocation of Field Tile Drains

Field tiles, that would affect a constructionproject, must be identified early to reduceproblems that may originate in the design. Thefollowing steps should be used to provideconsistent treatment for disrupted tile systems.

The Bureau of Planning involvement early inthe project.

The Bureau of Planning will provide, as part ofits public meeting format, the Department'spolicy for treating drain tiles disrupted by theproposed MDOT project. By early identificationof these tile systems, many of the systems canbe addressed in preliminary design and can bemade a part of the right-of-way purchaseagreement.

Design's process for known field tiledisruptions.

The following procedural steps shall be used,when it has been determined that the proposedMDOT project will impact existing tile fields.

1. All existing tile fields identified during theearly planning process shall be plotted onbase plans. Any environmental impactdocument should be checked foridentifying any field tile location.

2. Base plans showing the knowninformation on field tile drain systemsshall be transmitted to the Region/TSCDrainage Coordinator for submittal to theCounty Drain Commissioner's office. TheRegion/TSC Drainage Coordinator willthen make a request for any additions orcorrections to the field tile drain that arerequired. This must be completed prior toTHE Plan Review Meeting.

4.01.06E (continued)

3. Plans shall be updated to include anyadditions or corrections of the existingfacilities provided by the county draincommissioner's office.

4. Provide Real Estate Division with aproposed option for correcting knowndrainage tile systems with the final R.O.W.submittal. The following is in order ofdesign preference. (See section 5.20)

a) Continue the drainage under theroadway with an appropriate sizereplacement pipe.

When the replacement pipe is underthe influence of the roadway, use thecurrent culvert and sewerspecifications. Manholes shall beplaced outside of the right-of-way forcleanout purposes. Individual tilesshall be collected in a header andconveyed across the right-of-way ata minimal number of locations.

b) Collect the flow from the existing fieldtile in a header and outlet it into thehighway ditch using a minimalnumber of outlet locations.




The Real Estate Division will include in itsappraisal the cost for reconstructing thedrainage located outside the right-of-way. Anoffer that excludes the work necessary withinthe right-of-way and the cleanout structures atthe right-of-way line will be presented to theparcel owner. The offer will include the right ofthe Department to enter the property (GradingPermit) to construct the manholes, outletheaders, and crossing pipe. The ideal situationoccurs when the horizontal and verticalinformation are known. However, wheninadequate information is available forproposing exact actions to correct drainageproblems, the Real Estate Division will thenhave an appraisal made based on the bestavailable information, see section 5.08.

The Design plans will include the header,crossing pipe, and drainage structures justoutside the right-of-way lines, and the crossingpipe within the right-of-way.


5. Every effort shall be made by the RealEstate Division to include the tile field in theright-of-way settlement. If the tile field workcannot be settled by the Real EstateDivision, the work will be included in theproject plans. The Real Estate Divisionmust, however, have secured a right ofentry to perform the work requiredoutside of the right-of-way.

F. Design Procedures for UnknownField Tile Locations

Design will provide, on the note sheet,miscellaneous quantities of drainage structures,drainage structure covers, and 200 mm,250 mm, and 300 mm diameter pipe for usewhen tile fields are encountered duringconstruction that had not been identified in theplans. Written permission must be obtained bythe Construction and Technology Division fromthe property owner prior to any alteration of thetile field system on private property.


4.02

STORM SEWER DESIGN

4.02.01 (revised 12-23-96)

General

In the design of an enclosed drainage system,it is necessary to have complete and accurateinformation regarding the existing drainagesystem. Before an existing storm sewer can beused to drain a new roadway or improvement,its size, location, structural condition, andcapability to accept any additional flow must becarefully scrutinized. Occasionally, the originalsurvey needs to be supplemented withadditional drainage information. In order toexpedite and complete the design, the DesignUnit leader should, as soon as possible, orderadditional survey information.

The most desirable location for new sewers isoutside the influence of the pavement area.Locating the sewer outside the pavementsurface eliminates manhole covers andaccessing points from the driving surface.When unable to locate a new sewer outside thepavement area due to trees, utilities, or otherobstructions, the next choice would be in thecenter of a parking lane, and the last choicewould be in the center of a driving lane.

All new sewers on freeway projects shall belocated outside the pavement area.

All cross leads under the existing or proposedpavement should have a minimum diameter of300 millimeters.

4.02.02 (revised 2-18-2000)

Storm Sewer Design Criteria and Procedure

A. Roadways with Enclosed Drainage

The computed runoff for a roadway with curband gutter shall be based on a 10-year stormfrequency. The sewer should be designed toflow full, i.e., with a hydraulic grade line at ornear the top of pipe. See figure in 4.02.02D.

B. Depressed Roadways

The method for designing storm sewers fordepressed roadways is the same as for aroadway with enclosed drainage, except thatrunoff shall be computed using a 50-yearfrequency and the hydraulic grade line may bea minimum of 300 mm below the gutter gradeline of the roadway (pressure flow). Adepressed roadway will require a pumpingstation when a gravity drainage system cannotbe used to drain the low points. Frequently, theDepartment must provide a trunk sewer and anadequate and properly designed independentoutlet. An existing municipal sewer may onlybe used by agreement. See section 4.01.06.Con tac t t he Des ign Eng inee r -Hydraulics/Hydrology for assistance orguidance.


z1 �

p1w

z1�v 21

2g�

p1w� z2�

v 22

2g�

p2w

where g � 9.81m/sec2

4.02.02 (continued)


C. Design Velocity

Velocity is determined either by the slope of thepipe or the slope of the hydraulic grade line(greater than full flow condition). A minimumvelocity should be maintained, which isestablished by the minimum practicalconstruction grade. (See table "Pipe-SelfCleaning Velocities" 4.02.02D.)

Sewers will be designed with a limitingmaximum velocity of 3.7 meters per second(m/s). If sharp sediments, such as sand, arenot anticipated, the design may be based on amaximum velocity of 4.6 m/s. Velocities greaterthan 1.8 m/s may require the design andinstallation of energy dissipation structures atthe outlet of the storm sewer.

D. Hydraulic Grade Line

The Hydraulic Grade Line is the plot of pointsrepresented in Bernoulli's Equation as

and is the level that water will rise in a manhole.

Bernoulli Equation

w � 9810 N/m 3

v � Velocity of Flow in m/sec.z � Distance above Chosen Datum,

referred to as Elevation Headp � Pressure of fluid in Pa(N/m 2)

4.02.02D (continued)

∆g � Slope of Gutterso � Slope of Storm Sewer Pipe

HYDRAULIC AND ENERGY GRADE LINES


Pipe Self-Cleaning Velocities

Pipe Size(mm)

Grade % Pipe Size(mm)

Grade %

300 0.48 1350 0.09

375 0.36 1500 0.09

450 0.28 1650 0.08

600 0.17 1950 0.08

750 0.15 2250 0.07

900 0.12 2550 0.06

1050 0.12 2700 0.06

1200 0.10 3000 0.06

4.02.02D (continued)


The physical grade of the sewer should besufficient to ensure a reasonable self-cleaningvelocity at flows less than the design storm.

The table below lists the minimum practicalconstruction grades to be used for various sizesof circular concrete, plastic, or spiral rib pipewith a 0.013 Manning "n" value.

E. Rational Method

When designing storm sewers, use the rationalmethod to determine peak flows for each outlethaving a drainage area less than or equal toeight hectares. For drainage areas greater thaneight hectares, contact the Design Engineer -Hydraulics/Hydrology for alternate methods ofdesign. The rational method uses the formula"Q = 0.003CIA" to translate rainfall into peakrunoff flow rates. "Q" is the maximum rate ofrunoff expressed in cubic meters per second(cms).


"C" is the runoff coefficient. The values usedfor "C" are an estimate of the ratio of themaximum rate of runoff over the average rate ofrainfall on the area during the time ofconcentration. As the rational method uses theaverage rainfall intensity prevailing over thetime of concentration, the use of average "C"values has proven to be an acceptable tool insewer design. The following table lists suggested "C" valuesfor the land surface types commonly found inthe design of highway drainage systems.These values are given as a guide. Becausethis coefficient does not exhibit any relation toslope, type of surface or storm patterns, the "C"values must be carefully chosen.

Type of Surface “C”Value

Pavement &BituminousShoulder

0.8 to 0.9

1:2 Slopes & GravelShoulder 0.6

Flat UnpavedAreas-Heavy Soils 0.28

Flat Unpaved Areas- Sandy Soils. 0.10

Residential Areas 0.3 to 0.5

Commercial Areas 0.7 to 0.9




It is recommended that a weighted "C" value beused for an area with several types of surfaces.The following example demonstrates atechnique used to develop the weighted "C"value as applied to a typical highway crosssection:

ROW Width 30 m

Pavement 18 m

Sidewalks 3 m

Flat Grassed Area (Clay Soil) 15 m

18 (Pavement Area) x 0.80 = 14.43 (Sidewalk Area) x 0.80 = 2.4

15 (Grassed Area) x 0.28 = 4.2

36 (Weighted "C") = 21.021 ÷ 36 = 0.58

For the 36 meter width, a 0.58weighted "C" value is recommended.

"I" is the average rainfall intensity, in millimetersper hour, for the period of maximum rainfallhaving a duration equal to the time ofconcentration.

Rainfall Intensity - Duration tables wereoriginally developed from U.S. WeatherBureau Technical Paper Nos. 25 and 40.These tables were updated to 1990 data byusing rainfall curves calculated by the MDNR(Rainfall Frequency for Michigan September1990). The Rainfall Intensity - Duration tablesfor return periods of 10 and 50 years areprovided in section 4.02.05.


The time required for the maximum rate ofrunoff to develop is known as the "time ofconcentration". Generally, it is the timerequired for a drop of water to flow from themost remote part of the drainage area to thepoint under design. It consists of two parts: theinitial or inlet time and the time of flow in thesewer. The time of flow in the sewer can beclosely estimated from the hydraulic propertiesof the sewer. Flowing-full velocities aredetermined based on the slope of the hydraulicgrade line. The flowing-full velocity is to beused for determining the time of concentration.

The initial or inlet time must be estimated by thedesigner. Past practice has indicated a15-minute initial or inlet time to be adequate forthe design of most highway sewers. However,the steep grades associated with single sagdepressions tend to produce more rapid runoff.If construction of a pumphouse iscontemplated, at such a location, the use ofa 10-minute initial time is warranted.

"A" is the drainage area, in hectares, tributary tothe point where it will be collected by theconveyance system. The drainage areatributary to each collection point underconsideration in a storm sewer system must bedetermined. It is the only factor of the rationalformula capable to precise determination.

The Department's storm sewers shall bedesigned to accommodate the runoff fromhighway right-of-way and the surface drainageof those areas outside the right-of-way whichslope naturally toward the roadway. TheDesigner should review with the localjurisdictional authority, i.e. County DrainCommissioner, Local Planning Commission (onproposed zoning) on the future developmentneeds of the community. The Designer shouldnegotiate an agreement with the local authorityper 4.01.06.


4.02.04�(revised 12-23-96)

Rainfall-Frequency Zones


4.02.05�(revised 12-23-96)

Rainfall Intensity - Duration Tables

RAINFALL INTENSITY - DURATION TABLE

TIME INTERVAL ON THIS SHEET = 0.1 MINUTESRainfall Intensity given in mm per hour.

Time inMinutes

Zone 1 Zone 2 Zone 3 Zone 4

10 year 50 year 10 year 50 year 10 year 50 year 10 year 50 year

10.010.110.210.310.4

134133133132132

180179178178177

142141140140139

196195194194193

118117117116116

156156155154154

162161161160159

225224223222221

10.510.610.710.810.9

131131130130129

176176175174173

139138138137137

192191191190189

115115114114114

153153152152151

159158157157156

220219218218217

11.011.111.211.311.4

129128128127126

173172171171170

136136135135134

188188187186185

113113112112111

150150149149148

155155154154153

216215214214213

11.511.611.711.811.9

126125125124124

170169168168167

134133133132131

185184184183182

111110110109109

148147147146145

152152151151150

212211211210209

12.012.112.212.312.4

124123123122122

167166165165164

131131130130129

182181180180179

109108108107107

145144144144143

150149148148147

208207207206205

12.512.612.712.812.9

121121120120120

164163163162162

129128128127127

178178177177176

107106106106105

142142141141140

147146146145145

204204203203202

13.013.113.213.313.4

119119118118118

161160160159159

126126125125125

176175174173173

105104104104103

140139139138138

144144143143142

201200200199198

13.513.613.713.813.9

117117116116116

158158157157156

124124123123122

172172171171170

103103102102102

138137137136136

142141141140140

198197197196195


4.02.05 (continued)Rainfall Intensity - Duration Tables



Time inMinutes



14.014.114.214.314.4

115115115114114

156155155154154

122122121121121

170169169168168

101101101100100

135135135134134

139139139138138

195194193193193

14.514.614.714.814.9

113113113112112

153153152152151

120120120119119

167167166166165

100 99 99 99 99

133133133132132

137137136136136

192191191190189

15.015.115.215.315.4

112111111110110

151151150150149

118118118117117

165164164163163

98 98 98 97 97

132131131130130

135135134134133

189188188187187

15.515.615.715.815.9

110109109109109

149148148148147

117116116116115

162162161161160

97 96 96 96 96

130129129128128

133133132132132

186185185184184

16.016.116.216.316.4

108108108107107

147146146146145

115115114114113

160160159159158

95 95 95 94 94

128127127127126

131131130130129

184183182182181

16.516.616.716.816.9

107106106106105

145144144144143

113113113112112

158157157156156

94 93 93 93 93

126125125125124

129129129128128

181180180179179

17.017.117.217.317.4

105105105104104

143142142141141

112111111111110

156155155154154

92 92 92 92 91

124124123123123

127127127126126

179178178177177

17.517.617.717.817.9

104103103103103

141140140140139

110109109109109

153153153152152

91 91 91 90 90

122122122122121

125125125124124

176176175175174





Time inMinutes



18.018.118.218.318.4

102102102102101

139139139138138

108108108108107

151151151151150

90 90 89 89 89

121121121120120

124123123123123

174 174 173 173 172

18.518.618.718.818.9

101101100100100

137137137136136

107107106106106

150150149149148

8988888888

120119119119118

122122121121121

172171171170170

19.019.119.219.319.4

100 99 99 99 99

136135135135134

106105105105104

148148147147147

8887878787

118118118117117

120120120120119

170169169169168

19.519.619.719.819.9

98 98 98 98 97

134134133133133

104104104103103

146146145145145

8686868686

117116116116116

119119118118118

168167167166166

20.020.120.220.320.4

97 97 97 97 96

133132132132131

103103102102102

145144144144143

8585858585

115115115115114

117117117117117

166165165165164

20.520.620.720.820.9

96 96 96 95 95

131131130130130

102102101101101

142142142142141

8484848484

114114113113113

116116116115115

164163163163162

21.021.121.221.321.4

95 94 94 94 94

129129129128128

100100100100100

141140140140139

8383838383

113112112112111

115114114114114

162161161160160

21.521.621.721.821.9

9493939393

128127127127126

9999999998

139139138138138

8282828282

111111110110110

113113113113112

160159159159158


4.02.05 (continued)




Time inMinutes



22.022.122.222.322.4

9292929292

126126126125125

9898989897

138137137136136

8181818181

110110109109109

112112112111111

158157157156156

22.522.622.722.822.9

9191919191

125124124124124

9797979696

136136135135135

8080808080

108108108108108

111110110110110

156156155155155

23.023.123.223.323.4

9090909090

123123123123122

9696969595

135134134134133

8079797979

107107107107106

109109109109108

154154154153153

23.523.623.723.823.9

8989898989

122122122121121

9594949494

133133133132132

7878787878

106106106106105

108108108108107

153152152152151

24.024.124.224.324.4

8888888888

121121120120120

9494939393

132132131131131

7878777777

105105105105104

107107107106106

151151151150150

24.524.624.724.824.9

8887878787

120119119119119

9393929292

130130130130129

7777767676

104104104103103

106106105105105

150149149149148

25.025.125.225.325.4

8786868686

118118118118117

9291919191

129129129128128

7676767675

103103103102102

105104104104104

148148147147147

25.525.625.725.825.9

86 86 85 85 85

117117117117116

9191909090

128127127127127

7575757575

102102101101101

104104103103103

146146146146146





Time inMinutes



26.026.126.226.326.4

8585858484

116116116115115

9090908989

126126126126125

7574747474

101101101100100

103102102102102

145145145144144

26.526.626.726.826.9

8484848483

115115115114114

8989898988

125125125125124

7474737373

100100100100 99

102101101101101

144143143143142

27.027.127.227.327.4

8383838383

114114113113113

8888888888

124124123123123

7373737373

99 99 99 98 98

101101100100100

142142142141141

27.527.627.727.827.9

8282828282

113113112112112

8787878787

123123122122122

7272727272

98 98 98 98 97

100 99 99 99 99

141141140140140

28.028.128.228.328.4

8281818181

112112111111111

8686868686

122122121121121

7271717171

97 97 97 97 96

99 98 98 98 98

140139139139138

28.528.628.728.828.9

8181818080

110110110110110

8685858585

120120120120120

7171717170

96 96 96 96 96

98 98 98 97 97

138138138137137

29.029.129.229.329.4

8080808079

110109109109109

8585858484

120119119119119

7070707070

96 95 95 95 94

97 97 97 96 96

137137137136136

29.529.629.729.829.9

7979797979

109108108108108

8484848484

119118118118117

7069696969

94 94 94 94 94

96 96 96 95 95

136 136 135 135 135


4.02.05 (continued)




Time inMinutes



30.030.230.430.630.8

7878787877

108107107106106

8383838282

117117117116116

6969696868

9493939392

9595949494

135134134133133

31.031.231.431.631.8

7777767676

106105105105104

8281818181

115115115114114

6867676767

9292919191

9393929292

132132132131131

32.032.232.432.632.8

7675757575

104104103103103

8080808079

113113113112112

6766666666

9090908989

9291919190

130130129129128

33.033.233.433.633.8

7474747473

102102102101101

7979787878

112111111110110

6665656565

8989888888

9090898989

128127127127126

34.034.234.434.634.8

7373737272

101100100100 99

7777777776

110109109108108

6464646464

8887878786

8888888887

126125125124124

35.035.235.435.635.8

7272717171

99 99 98 98 98

7676767675

108107107107107

6363636362

8686868585

8787868686

124123123123122

36.036.236.436.636.8

7171707070

98 97 97 97 96

7575757474

106106105105105

6262626261

8584848484

8685858585

122121121121120

37.037.237.437.637.8

7069696969

9696959595

7473737373

105104104104103

6161616160

8483838383

8484848483

120 120 119 119 118





Time inMinutes



38.038.5

6968

9494

7372

103102

6060

8282

8382

118117

39.039.5

6867

9392

7271

102101

5959

8181

8281

117116

40.040.5

6766

9291

7170

100 99

5858

8079

8180

115114

41.041.5

6665

9090

6969

99 98

5857

7978

7979

113113

42.042.5

6564

8989

6868

97 97

5756

7777

7878

112111

43.043.5

6463

8887

6867

96 95

5656

7676

7776

110109

44.044.5

6362

8786

6766

95 94

5555

7675

7676

109108

45.045.5

6261

8685

6665

93 93

5454

7474

7574

107106

46.046.5

6161

8584

6564

92 92

5453

7473

7473

106105

47.047.5

6060

8383

6464

91 90

5353

7272

7373

104104

48.048.5

5959

8282

6363

90 89

5252

7271

7272

103102

49.049.5

5958

8181

6262

89 88

5251

7170

7171

102101

50.050.5

5858

8080

6161

87 87

5151

7069

7070

100100

51.051.5

5757

7979

6160

86 86

5050

6969

6969

99 99

52.052.5

5756

7878

6059

86 85

5049

6868

6968

98 98

53.053.5

5656

7777

5959

84 84

4949

6767

6867

97 96

54.054.5

5555

7676

5858

83 83

4948

6766

6766

96 95

55.055.5

5554

7675

5857

83 82

4848

6666

6666

95 94

56.056.5

5454

7574

5757

81 81

4747

6565

6565

93 93

57.057.5

5353

7473

5756

81 80

4746

6464

6564

92 92


4.02.05 (continued)




Time inMinutes



5859

5352

7372

5655

8079

4646

6463

6463

9190

6061626364

5251505049

7271706969

5554535352

7877767675

4545444443

6262616060

6261616060

9089888786

6566676869

4948484747

6867676665

5251515050

7473737271

4342424141

5958585757

5958585757

8584838281

7071727374

4646454544

6564636362

4949484847

7070696868

4140404039

5655555554

5655555454

8180797877

7576777879

4444434342

6161606059

4646464545

6767666565

3938383837

5453525252

5353525251

7776757574

8081828384

4242414141

5958585757

4444444343

6464636262

3737363636

5151505049

5150505049

7373727171

8586878889

4040393939

5656555554

4242424141

6161605959

3535353434

4949484847

4948484747

7070696868

9091929394

3838383837

5453535252

4140404039

5958585757

3434333333

4746464545

4646464545

6767666665

95969798

37373636

52515150

39393938

56565555

32323232

45444444

44444444

65 64 64 63


4.02.05 (continued)




Time inMinutes



100102104106108

3635343433

5049484746

3837363635

5453525251

3130303029

4342424140

4342414140

6261605958

110112114116118

3332323231

4645444443

3534343333

5049494847

2928282827

4039393838

4039383838

5757565554

120122124126128

3030302929

4342414140

3232323131

4646454444

2727262625

3737363635

3737363535

5353525151

130132134136138

2828282727

4039393838

3030292929

4343424241

2525242424

3534343333

3534343333

5049494847

140142144146148

2726262625

3737363635

2828282727

4140403939

2323232322

3332323131

3232323131

4746454544

150152154156158

2525242424

3535343433

2726262625

3838373736

2222212121

3030302929

3030292929

4443434242

160162164166168

2423232323

3333323231

2525242424

3636353534

2121202020

2828282827

2928282827

414140 40 39


4.02.05 (continued)



TIME INTERVAL ON THIS SHEET = 2.0 MINUTESRainfall Intensity given in mm per hour

Time inMinutes



170172174176178

2222222221

3130303029

2423232323

3433333332

2019191919

2726262626

2727262626

3938383837

180182184186188

2121212120

2929282828

2222222222

3232313130

1918181818

2525252524

2525252525

3736363535

190192194196198

2020201919

2827272726

2121212121

3030292929

1818171717

2424232323

2424242323

3534343333

200202204206208

1919191918

2626252525

2020202019

2828282727

1717161616

2323222222

2323222222

3333323231

210212214216218

1818181818

2524242424

1919191919

2727262626

1616161515

2121212121

2222222121

3130303029

220222224226228

1717171717

2323232322

1818181818

2525252524

1515151514

2020202020

2121212020

2929292828

230232234236238

1716161616

2222222221

1817171717

2424242423

1414141414

1919191919

2020201919

28 28 272727

240 16 21 17 23 14 18 19 26


Where Q ' DischargeA ' Areav ' Velocityk ' Conveyance Factorn ' Manning roughness coefficientr ' Hydraulic Radius ' (A/wp)S ' Slopewp ' wetted perimeter

Q ' k × S

v 'QA

k '1nr 2/3 A

4.02.06 (revised 3–8-99)

Solving Manning’s Formula

TABLE FOR SOLVING MANNING’S FORMULA FOR STORM SEWERS FLOWING FULLA “n = 0.013" is applied to concrete, plastic and spiral-ribbed pipeA “n = 0.024" is applied to corrugated metal pipe

Nominal Actual A (m2) r (m) n = 0.013 n = 0.024

300 305 0.073 0.076 1.009 0.546

375 381 0.114 0.095 1.829 0.991

450 457 0.164 0.114 2.974

600 610 0.292 0.152 6.405

750 762 0.456 0.191 11.613

900 914 0.657 0.229 18.885

1050 1067 0.894 0.267 28.487

1200 1219 1.167 0.305 40.671

1350 1372 1.478 0.343 55.725

1500 1524 1.824 0.381 73.743

1650 1676 2.207 0.419 95.083

1800 1829 2.627 0.457 119.915

1950 1981 3.083 0.495 148.447

2100 2134 3.575 0.533 180.884

2250 2286 4.104 0.572 217.421

2400 2438 4.670 0.610 258.254

2550 2591 5.272 0.648 303.569

2700 2743 5.910 0.686 353.553

2850 2896 6.585 0.724 408.387

3000 3048 7.297 0.762 468.248


4.02.07 (revised 7-17-98)

Design Factors for Storm Sewers

1. Contributing drainage area.

2. Slope of ground.

3. Type of soil.

4. Ground cover and land use as it relatesto the determination of the runoffcoefficient "C".

5. Choice of average rainfall intensity curve- design frequency and zone.

6. Risk associated with possible overload ofsewer.

7. The elevation difference of the hydraulicgrade line and gutter line for stormsewers.

8. Future development and localordinances.

9. Participation of municipality if sewer is toaccommodate more than the needs ofthe highway.

10. Location of catch basins and inlets.

11. Location of trunk sewer - horizontally andvertically.

12. Location, flow lines, and availablecapacity of any existing sewers.

13. Flow lines and contributing area of anyconnecting sewers.

14. Existing or proposed undergroundutilities.

15. Elevation, location, and adequacy ofoutlets.

16. Velocity (See 4.02.02C and 4.02.02D.)

17. Ease and economics of constructingsewer.

18. Discharge water quality controls perNational Pollution Discharge EliminationSystem general permit. See section4.03.03.

19. Pipe material.

4.02.08 (revised 3-8-99)

Steps in the Design of Storm Sewers usingRational Method

The following procedure is used to design astorm sewer system. Steps 1-7 must be donemanually. Steps 8-16 can be done by acomputer program or by hand calculation. Thecomputer program computes runoff, sewersizes, and grades and is the recommendedmethod of designing sewers. The computerprocedure is described in the manual titledEagle Point Storm Sewers Users Manualdated 11-13-92. This program can design anew system or analyze an existing system. (Atthis time this computer program uses onlyEnglish units. An updated metric version isbeing acquired. The designer should convertfinal pipe sizes to metric equivalents.)

1. Obtain a set of prints covering the areathat is contributing runoff to the proposedsewer, i.e., contributing drainage area.Sources of information are: USGSquadrangle maps, photogrammetry 0.5meter contours, aerial photographs,county drain maps, plan/profile sheets,etc.. Include drainage areas outside ofthe R.O.W.

2. Identify outlets for storm sewer system toexisting available conveyance systemssuch as watercourses, public drains, andstorm sewers (reference 4.01.06 C).

3. Locate the catch basins and inlets onthese prints. Consideration must begiven to the capacity of the inlet. Refer tosection 4.02.10.

4. Locate the trunk sewer and manholes onthe plan portion. Number the manholesbeginning at the upper end of the line.Refer to section 4.02.12.

5. Sketch a tentative grade on the profile forthe trunk sewer. Note any conflicts withexisting utilities. See step 17 regardingdepth of cover.


k 'Q

S.

4.02.08 (continued)

Steps in the Design of Storm Sewers usingRational Method

6. Mark the boundaries of the areascontributing to each manhole (catchbasin or inlet, where applicable). Divideand color portions of these areas to showth e d i f f e ren t pe rcen tage o fimperviousness.

7. Compute and label the area in hectares;also, indicate the runoff coefficient for thedifferent percentages of imperviousness.Refer to section 4.02.02E.

8. Determine a weighted runoff coefficient"C" value for the first inlet on the trunksewer. Refer to section 4.02.02E. Whenusing the Storm Sewer Program, 4different "C" values can be entered (4sub-areas of drainage).

9. Determine proper zone, frequency, andthe initial time of concentration (10 to 15minutes) using the Rainfall-FrequencyZone map and Rainfall Intensity DurationChart.

10. Using Q = 0.003 (CIA), compute "Q" forthe first sewer run and enter it in the"Tabulation Sheet for Computing StormSewers".

11. After computing the "Q" and selecting atentative sewer grade, the designer thencalculates the conveyance factor "k",using the formula:

By knowing the Manning "n", thediameter of sewer pipe can bedetermined by using the chart in section4.02.06. For example: when theconveyance factor equals 3, either a600 mm corrugated steel pipe (C.S.P.)with an n = 0.024, or a 450 mmreinforced concrete pipe (R.C.P.) with ann = 0.013 will be required.

4.02.08 (continued)

12. Compute velocity "V" for this pipe. If thepipe is not full, use the “HydraulicElements of Channel Sections” chart. Besure that the minimum velocity (1 m/sec)is exceeded. Enter "V" into the sewertabulation chart.

13. Using this velocity, compute the timerequired for the water to reach the nextmanhole. Add this time to the initial timeto get the time of concentration for thesecond manhole.

14. Add the new areas of the secondmanhole to the areas of the first manholeaccording to their runoff coefficients andcompute a new weighted "C" value.

15. Using the new time of concentration,area, intensity, and weighted "C" value,compute the runoff and pipe size asbefore.

16. Repeat this procedure throughout thelength of the sewer.

17. After computing the sewer sizes, put thesize and percent grade on the profilesheet. The sewer sizes and grades maybe altered to give the most economicalsewer in terms of pipe size and depth ofsewer or because of conflicts withexisting or proposed undergroundutilities. The depth of sewer shouldprovide a minimum of 900 mm of cover.


TAB

ULA

TIO

N S

HEE

T FO

R D

ESIG

N O

F ST

OR

M S

EWER

S

Rou

te

C

ontr

ol S

ectio

n

Zone

Job

Num

ber

C

ompu

ted

by:

D

ate

Stat

ion

to S

tatio

n

10

Yea

r

50 Y

ear

Che

cked

by:

Dat

e

n

valu

e

CB

or

MH

Stat

ion

New

Hec

tare

Adde

d

Wei

ghte

dC

Accu

m.

Hec

tare

Accu

m.

Wei

ghte

dC

Tim

e(m

in.)

Inte

nsity

(mm

/hr)

"Q"

(m3 /s

)Ac

cum

.

Gra

de(m

/m)

kSi

ze(m

m)

Velo

city

(m/s

)Le

ngth

(m)

Trav

elTi

me

(min

.)

4.02.08 (continued)

A. Tabulation Sheet for Computing Storm Sewers


EXAM

PLE

TAB

ULA

TIO

N S

HEE

T FO

R D

ESIG

N O

F ST

OR

M S

EWER

S

Rou

te

C

ontr

ol S

ectio

n

1

Zone

Job

Num

ber

C

ompu

ted

by:

D

ate

Stat

ion

1+67

1 to

Sta

tion

1+96

5

x

10 Y

ear

5

0 Ye

arC

heck

ed b

y:

D

ate

n va

lue

0.0

13

CB

or

MH

Stat

ion

New

Hec

tare

Adde

d

Wei

ghte

dC

Accu

m.

Hec

tare

Accu

m.

Wei

ghte

dC

Tim

e(m

in.)

Inte

nsity

(mm

/hr)

"Q"

(m3 /s

)Ac

cum

.

Gra

de(m

/m)

kSi

ze(m

m)

Velo

city

(m/s

)Le

ngth

(m)

Trav

elTi

me

(min

.)

A1+

671

0.65

0.52

0.65

0.52

15.0

112

0.11

0.00

481.

5937

51.

381

1.0

B1+

752

0.74

0.52

1.39

0.52

16.0

108

0.23

0.00

284.

3560

01.

385

1.1

C1+

837

0.76

0.52

2.15

0.52

17.1

105

0.35

0.00

227.

4675

01.

367

0.9

D1+

904

0.58

0.58

2.73

0.53

18.0

102

0.44

0.00

268.

6375

01.

561

0.7

E1+

965

4.02.08 (continued)

A. Tabulation Sheet for Computing Storm Sewers


4.02.08 (continued)

B. Hydraulic Elements of Channel Sections Chart

“Q”Accum.(m3/s)

“Q”Full

(m3/s)

“Q”Accum.“Q”Full

(%)

VelocityFull

(m/s)

VelocityVelocity Full

(%)

Velocity(m/s)

0.11 0.13 85 1.18 114 1.3


4.02.10 (revised 3-8-99)

Factors in Locating Catch Basins or Inlets

The following items should be considered whenlocating and spacing catch basins. Please referto FHWA’s Drainage of Highway PavementsHydrologic Engineering Circular, No. 12 forspecific design problems such as spread andneed for additional catch basins. MDOTgeneral design guidelines for the placement ofcatch basins are as follows:

1. At all low points in gutter grades.

2. At points either side of the low point thatare 60 mm higher than the low point or amaximum of 23 m either side of the lowpoint. Other alternatives, such as slotteddrain, may be considered in lieu ofadditional catch basins. This applies inlong sags.

3. Ahead of drives, where possible.

4. For concrete pavements, catch basinsshould not be placed at spring points ofstreet intersections as they interfere withthe construction of the expansion joint atthat location. They should be placed 3meters either side of the spring line or atthe midpoint of the arc if detailed gradesindicate that location as the low spot inthe grade. Water should be interceptedbefore it crosses any areas used bypedestrians, especially in commercial orbusiness areas.

5. On both sides of cross streets that draintoward the roadway. Water should neverbe carried across intersections in valleygutters or troughs.

6. Behind shoulders or back of sidewalks todrain low spots.

4.02.10 (continued)

7. On the low side of superelevated or tiltedpavement sections.

8. Provide a sufficient number of catchbasins on the high side of superelevatedor tilted pavement sections to preventgutter flow from crossing the pavement.

9. At any location where there will be aheavy concentration of water. Thedesigner should use the maximumspacing guidelines shown in FHWA’sDrainage of Highway PavementsHydrologic Engineering Circular, No. 12.

10. The use of 600 mm diameter catchbasins should be limited to upstreamends of sewer runs where the run to thenext drainage structure is 20 m or less,and where the structure depth does notexceed 2.4 m. Use 1200 mm diameterdrainage structures for catch basins in allother locations.

11. Do not locate drainage structures in linewith a sidewalk ramp. Except whereexisting structures are being used, thelocation of the ramp takes precedenceover the location of the drainagestructures.

12. Where flat grades or multi-lanes occur,consider placing a larger cover, such asa Cover V, or double catch basins.


4.02.11

Factors in Locating Manholes

General design guidelines for the location andspacing of manholes to be used by MDOTdesigners are as follows:

1. For trunk sewers 750 mm diameter andunder, space approximately 90 m apartto facilitate maintenance.

2. For trunk sewers 900 mm diameter andover, space approximately 100 pipediameters apart.

3. At angles in the main sewer.

4. At points where the size of the sewerchanges.

5. At points where the grade of the sewerchanges.

6. At the junction of sewer lines.

7. At street intersections or other pointssuch as connecting lines to catch basinsor inlets.

8. Access manholes for sewer inspection onlarge tunnel sewers shall be spaced atapproximately 365 m centers.

9. Trunkline Sewer Location

4.02.12 (revised 12-23-96)

Numbering Drainage Structures

A system of numbering drainage structures onprojects has proven to be valuable to fieldpersonnel, especially on complex urbanprojects. Therefore, drainage structures will benumbered consecutively on plans. Thecorresponding number for each drainagestructure should also be shown on the profilesor any other place on the plans where it wouldappear. Culverts need not be numbered.

4.02.13 (revised 2-18-2000)

Access Manholes to Storm Sewers

A. Types

Access manholes to storm sewers are detailedon the following standard plans.

1. Standard Plan R-1-Series shows themanhole structure for sewers 1200 mm &under.

2. Standard Plan R-2-Series, Manhole BaseType 1 may be used as an intermediatemanhole between junctures on existingsewers.

3. Standard Plan R-3-Series shows precastmanhole tees and risers for use onsewers 1050 mm through 2700 mm.Precast manhole tees provide access tolarge sewers. Manhole tees may beused as an intermediate manhole on newsewers between sewer junctures.

4. Standard Plan R-4-Series, Manhole BaseType 2 should be used at sewerjunctions of sewers 1200 mm through2700 mm.


4.02.13 (continued)

Access Manholes to Storm Sewers

B. Considerations

If there is a considerable deflection in thesewer, or if the inlet and outlet inverts are atsubstantially different elevations at theStructure, Manhole Base Type 2 cannot beused, and a special manhole or junction boxmust be detailed instead. Care must beexercised in not introducing too many sewerleads into conventional manholes (StandardPlan R-1-Series) at or near the same elevationor having large sewers, such as a 900 mm anda 1050 mm entering or leaving at the sameelevation. In these cases the structural integrityis seriously weakened and either a largemanhole or a special design should be used.Follow the guidelines below for selecting thesize of drainage structures where the inlet andoutlet pipes deflection is between 135 and 180degrees:

Drainage Structuresize, mm

Sewer Size, mm

1200 600 & under

1500 750 to 900

1800 1050 to 1200

Contact the Design Engineer - MunicipalUtilities to request a special design.

C. Measurement and Payment

The current standard specifications classifyAccess Manholes as Drainage Structures.Payment for additional depth will be in metersto tenths of a meter. The riser above aManhole Tee or Manhole Base will be paid forseparately in meters to tenths of a meter.

4.02.15 (revised 3-8-99)

Sewer Bulkheads

Only sewer bulkheads larger than 300 mm indiameter will be measured for payment. Thecost of placing sewer bulkheads 300 mm indiameter and less will not be paid for separatelybut payment for the work will be considered ashaving been included in the contract unit pricesbid for other contract items. The sewerbulkhead location should be shown on theplans.

4.02.18 (revised 10-30-97)

Storm Sewers Under Structures

Storm sewers within the stress influence of thefootings shall be protected by concreteencasement or other approved methods. If thedesigner has any question about which thestress influence lines in a particular structure,he should contact the Geotechnical ServicesUnit of the Construction and TechnologyDivision.


4.02.19 (revised 10-30-97)

Storm Sewer Pipe Classification and UsageGuidelines

The Design Unit should follow the procedureslisted below:

A. Select the appropriate class of seweraccording to the current MDOT StandardSpecifications. The design life for sewerswill be 70 years.

B. In some applications a specific materialfor a sewer pipe may be requiredexclusively or a specific material may bedetermined inappropriate for a specificlocation. The required material shouldbe specified in the pay item. Theprohibited material should be identifiedby note on the plans. When a specificmaterial is prohibited and its exclusion isnot covered in the Standard Specificationfor Construction, a note to the file mustbe written to describe the basis forexclusion. This information should alsobe forwarded to the field. The exceptionis when extending an existing systemwith a like material.

Example:

When a specific location has an existingcorrugated metal pipe that has failedprematurely due to corrosion, exclusionof that material may be warranted. Ifconcern exists that the environment maybe aggressive to a corrugated metal pipe,collected pH and resistivity datasupporting the concern would justify anexclusion of that product.

4.02.19 (continued)

C. The following examples are to be usedas a guide when calling for sewers onplans:

Sewer, Class 1, 450 mm, Tr Det A 30 m

Sewer, Cl C76M III, 450 mm, Tr Det A30 m

Sewer, Cl C76M IV, 1050 mm, Jacked inPlace - 30 m

D. Sewers of the chosen class shouldextend between structures rather thanbeing broken in the middle of a section;however, the trench detail can change.

E. In a given section of sewer, the entiresection should meet the requirements forthe most critical point in the section.


4.02.20 (revised 10-30-97)

Jacked-in-Place Sewers

At times it may be necessary to install sewerpipe by jacking or tunneling methods. A sewerinstalled by jacking or tunneling may beconsidered a special design, therefore arequest to determine the design of the pipeshould be made to the Design Engineer -Municipal Utilities. However, some generaljacking information for designers is listed below.

1. The smallest practical pipe size that canbe jacked is 900 mm in diameter.However, a smaller size pipe may beinserted inside a jacked casing and thevoid outside the sewer filled with aflowable fill.

2. Concrete pipe is to be specified whenjacking a storm sewer.

3. If circumstances require jacking a pipesmaller than 900 mm, a C76 Wall Class5 pipe shall be specified.

4. Jacking a storm sewer will normally bemore economical than an open trenchinstallation when either the fill heightexceeds approximately 5 meters ormaintaining traffic is beneficial. Thesituation should be reviewed at THE PlanReview Meeting and a recommendationprovided to the designer.

5. Jacking will usually continue on a24-hour-per-day operation due to thepipe’s tendency to set up if the jackingoperation is interrupted for more than afew hours.

6. Jacking is usually done from the low sideup grade to allow water to drain outduring the jacking operation. However, itmay also be done by jacking down grade,which allows for better control of the pipegrade due to the weight of the pipe.

4.02.20 (continued)

7. Pipe that is being jacked is subjected tovertical loads from the weight of earthand horizontal loads from the jackingpressure. The resultant vertical earthload on a horizontal plane at the top ofthe bore is a function of the weight ofearth above the bore minus the upwardfriction forces, minus the cohesion of thesoil along the limits of the prism abovethe bore.

a. The vertical load from the weight ofearth and possible live load willdetermine the class of pipe to bespecified.

b. The cross-sectional area of theconcrete pipe is adequate to resistaxial compression from jacking,and unless unusual circumstancesexist, little or no gain isaccomplished in increasingcrushing resistance by specifying ahigher class of concrete pipe thanrequired for vertical loads .

4.02.21 (revised 10-30-97)

Storm Sewer Soil Borings

The plans and specifications do notautomatically provide for the additional workrequired to install sewers through areas ofunstable soils. Therefore, soil borings must beobtained and shown on the plans to identifywhere remedial treatment is necessary.Corrective treatment usually meansundercutting and backfilling. Also, in areashaving a high water table, a well point systemmay sometimes be considered. The designershould use the following procedures.


4.02.21 (continued)

Storm Sewer Soil Borings

1. The need for soil borings should bediscussed at the scope verificationmeeting. The Project Manager shouldprovide the Region/TSC Soils Engineerwith any necessary information forlocating proposed sewer lines. TheRegion/TSC Soils Engineer will thenprovide the Project Manager withp e r t i n e n t s o i l s d a t a a n drecommendations.

2. Follow up requests to be sure soilborings are received. The completeboring data shall be made part of theplans and proposal. The data report willinclude the log of borings, the completeshear report, the weight and moisturereport, as well as a plot of the shearstrength. The report by the GeotechnicalServices Unit, Construction andTechnology Division can be reproducedon a plan sheet.

3. When unstable soils are encountered,the Designer and the GeotechnicalServices Unit, Construction andTechnology Division engineers shouldconfer to determine the best method ofcorrection.

4. Estimated quantities for the correctionshould be included in the plans.

5. Where unstable soil conditions, orobstructions other than rock, requireexcavation of the sewer trench below theelevation shown on the plans, suchexcavation shall be made to thedimensions authorized by the Engineer.The pay item "Trench Undercut andBackfill" is used to pay for this excavatingand backfilling of the trench with aspecified aggregate up to the bottom ofthe trench elevation on the plans. Manyjobs will include short runs of relativelyshallow depth sewers where undercuttingis unnecessary, therefore, the designerwill have to make some judgement whenrequesting soil borings.

4.02.22 (revised 3-8-99)

Storm Sewer Pipe - Curved

For sewer sizes 900 mm diameter and over, thenumber of manholes may be reduced bycurving the sewer pipe (tapered sections). Theradius of the pipe should meet the minimumrequirements of the Concrete Pipe Handbookor the Concrete Pipe Design Manual. Goodjudgment should be used in selecting locationswhen this method is considered. The DesignEngineer - Municipal Utilities should review theproposed sewer.

Curved concrete pipe will not be paid forseparately. It will be measured and paid for asthe same contract pay item specified for theadjacent linear pipe.

7½° SEGMENT

See chart on next page for sizes.


L D

762 mm 152 mm

1524 mm 305 mm

2286 mm 457 mm

4.02.22 (continued)

Storm Sewer Pipe - CurvedChart for 7½° SEGMENT

I.D. 900 mm 1050 mm 1200 mm 1350 mm 1500 mm 1650 mm 1800 mm 1950 mm 2100 mm

RADIUS 2.845 m 2.921 m 3.023 m 3.099 m 3.200 m 3.277 m 3.429 m 3.434 m 3.556 m

LAYINGLENGTH

379 mm 391 mm 400 mm 413 mm 425 mm 438 mm 451 mm 460 mm 476 mm

A 305 mm 305 mm 305 mm 305 mm 305 mm 305 mm 305 mm 305 mm 305 mm

I.D. 2250 mm 2400 mm 2550 mm 2700 mm 2850 mm 3000 mm 3150 mm 3300 mm 3600 mm

RADIUS 3.632 m 3.708 m 3.785 m 3.886 m 7.925 m 8.128 m 8.230 m 8.337 m 8.839 m

LAYINGLENGTH

483 mm 495 mm 505 mm 514 mm 832 mm 845 mm 854 mm 867 mm 893 mm

A 305 mm 305 mm 305 mm 305 mm 610 mm 610 mm 610 mm 610 mm 610 mm

INCREASER-REDUCER

TYPICAL LAYOUT

NOTES:

1. 7 1/2° SEGMENT AVAILABLE WITH MODIFIED GROOVETONGUE (M.G.T.)

2. FOR SEGMENTS 750 mm DIAMETER AND SMALLERSECTIONS MANUFACTURED ON REQUEST.

3. ALL SECTIONS MANUFACTURED TO ASTM C-76SPECIFICATIONS.

4. ALL SIZES HAVE STANDARD WALL THICKNESS.


4.03

DRAINAGE OUTLETS

4.03.01 (revised 10-30-97)

Acceptable Drainage Outlets

The following drainage outlets may beconsidered acceptable:

1. Natural watercourses. For highwaypurposes a natural watercourse isdefined as one that has not beenartificially altered.

2. County drains.

3. Storm sewers or ditches owned by otherthan MDOT. Approval to use thesefacilities must be obtained from theowner. When considering a sewerowned by others, (see 4.01.06) MDOTwill also evaluate future maintenancecosts, outlet costs, and future capacity.

4.03.02 (revised 12-23-96)

Unacceptable Drainage Outlets

The following drainage outlets are consideredunacceptable: natural depressions, vacant land,farm tiles, sanitary sewers, small sags on theprofile, or a previously diked drainage courseunless drainage rights are purchased.

4.03.03 (revised 3-8-99)

Retention/Detention Systems

When an existing outlet lacks size and cannotbe economically increased, the discharge maystill be adequately handled by designing aretention system that will meter out thedischarge at a predetermined rate. Outflowsare regulated either by local agencyrequirements or existing flow conditions.Contact Design Engineer - Hydraulics/Hydrology Unit for assistance in the design of aretention system.

4.03.03 (continued)

In order to meet the National PollutionDischarge Elimination System (NPDES) permitrequirements in municipalities, a detentionbasin may be necessary. Guidelines for thedesign of such a system are discussed in4.03.04 and 4.03.05. Contact the DesignEngineer - Hydraulics/Hydrology for designassistance.

The designer should refer to section 7.06.10 forfencing requirements.

4.03.04 (revised 2-18-2000)

Design Guidelines to Reduce Impacts ofNonpoint Source Pollution on ReceivingWaters

Regulatory legislation and policies havenecessitated that the Department reevaluatethe design practices used to control thepollutants contained in storm water runoff fromstate highways. MDEQ, EPA, or FHWA mayrequire the inclusion of storm water runoffcontrol measures as a precondition forobtaining state and federal environmentalclearance. Environmental regulations haveincreased emphasis on water quality andnonpoint source pollution. Storm water BestManagement Practices (BMP) will be greatlyexpanded and required on future projects. Forexample, as part of the National PollutantDischarge Elimination System (NPDES) Permitapplications required from the Water Quality Actof 1988, it will be necessary to provide locationsof soil erosion control measures on the designplans. The design engineers must providecopies of the plans with site specific controlmeasures along with other NPDES constructionpermit application information to the Grading /Drainage and Consultant Contracting Engineer(GDCC), Construction and Technology Division.Please reference sections 2.05 and 10.04.04B.

The Designer should contact the EnvironmentalSection of the Project Planning Division forstatus of environmental clearance on stormwater.


4.03.04 (continued)


The following general guidelines for controlling thepollution contained in storm water runoff areapplicable to virtually all highway situations.There are a number of low-cost drainage designprinciples and practices that have significantpotential for reducing pollutant loads from highwaystorm water runoff. These relatively low-costprinciples and practices can be incorporated intoexisting highway design procedures. They areintended to be used wherever practicable andwithout the necessity of identifying a specifichighway runoff contaminant problem. Theprincipal concepts that should be consideredwhen designing highway systems include:

1. Reduce direct discharges - Avoid directdischarges of highway storm water runoffto receiving waters (includinggroundwater) wherever practicable.Highway storm water runoff should berouted through one or a combination ofeffective storm water managementmeasures including: vegetation,detention, infiltration, or wetland systemsprior to discharge to receiving waters.

When possible, drains along bridgedecks over open water should beeliminated.

2. Reduce runoff velocity - Reducing therunoff velocity to a non-erosive leveldecreases the transport of sediment andencourages sedimentation, especiallybedload. The bedload contains largersoil particles that slide, roll or bouncealong the channel bottom. The methodsfor reducing the runoff velocity includereducing gradients, installing velocityreduction devices (such as: check dams,drop structures, baffles, sediment basinsand diversions), and by using vegetativecontrols (grassed waterways, overlandsheet flow etc.).

4.03.04 (continued)

Typically, the sediment pollutant load istransported along the pavement, curbs, andshoulders, as suspended solids or absorbed tosuspended solids in storm water runoff.Therefore, pollutant reduction measures areusually intended to reduce the volume ofparticulates available for transport by runoff orto filter and settle out suspended solids.

Storm water Best Management Practices (BMP)may be needed when the ADT is greater than30,000, or when required by the EnvironmentalImpact Statement, Environmental AgencyPermit requirements or Local Storm WaterOrdinances. The following BMP’s may berequired:

A. Vegetative Controls

Vegetative controls that include grassedchannels, vegetated waterways, filter strips, andoverland flow, work by reducing the velocity ofthe surface flow or channel flow allowingsediment and suspended solids to settle out.Since many of the sediments contain absorbedpollutants, these pollutants in the runoff may bereduced substantially prior to entering adjacentwaterways, if the velocity of runoff is slowedover an adequate length of vegetation. Thesesystems also take advantage of soil absorptioncapabilities.

Vegetated controls can be applied whereversuitable land area is available. Vegetativecontrols are adaptable to a variety of siteconditions, are flexible in design and layout,and are the least costly managementprocedure. Vegetative controls can be used assole management measures or in conjunctionwith secondary measures (detention basins,infiltration systems).




Drainage design should include provisions formaximum use of vegetative controls. A lengthof approximately 60 meters has been shown tobe very effective in pollutant removal; however,any length is helpful. Pollutant removal usingvegetative control is consistently high,particularly for suspended solids and heavymetals. The vegetation acts to reduce runoffvelocity, enhancing sedimentation and filtrationof suspended solids, increasing infiltration, andallowing a greater opportunity for absorptionand uptake by plants.

B. Detention Basins

Detention basins are those basins without apermanent pool to receive runoff inflow and apositive outflow structure. Settling ofsuspended materials is the primary pollutantremoval action, although some biologicalremoval of nutrients also occurs. The conceptof temporarily storing storm water runoff is afundamental approach to storm watermanagement and may be used to achieve bothflood control and pollutant reduction benefits.

Detention basins can be utilized in areas:

1. where suitable depressions occur or canbe constructed, and where acceptableinflow and outflow conditions can beachieved. Also from a cost standpoint,the basin should be placed where theleast amount of earth moving is requiredand still obtain the necessary basinvolume;

2. where soils are able to provide a stableembankment;

3. where storage and the required surfacearea of detention basins for pollutionabatement area are adequate to retainthe runoff from a specified storm event(i.e., 10 year, 25 year, etc.) of thecontributing drainage area.


Potentially, detention basins can be highlyeffective in pollutant removals. Differences inbasin performances are attributed to the size ofthe basin relative to the connected drainagearea and local storm characteristics. Results ofthe Nationwide Urban Runoff Program (NURP,EPA 1982) research indicated that biologicalprocesses in the permanent pool producedsignificant reductions in soluble nutrients, inaddition to the physical settling of particles.See Section 4.03.05.

C. Infiltration Systems

Infiltration systems are a method in whichsurface runoff is temporarily contained andallowed to infiltrate or percolate in the soil,utilizing the sediment layers as mechanism tofilter out pollutants. Infiltration systems involvesystems which infiltrate runoff after it has beencollected (infiltration basins, drainage wells,deep infiltration wells, shallow infiltration wells,shallow infiltration pits and trenches).

Infiltration systems can easily be adapted to fitthe requirements of highway, railroad andairport, systems, i.e., shaped into deep-sidedlinear basins, constructed in borrow areas, orlinked in a series of small basins. Infiltrationsystems are primarily applied in cases wherebyright-of-way is a limiting factor, and where thesoil is relatively permeable and the groundwatertable is not too close to the point of discharge.

Little data are available concerning pollutantremoval efficiencies of infiltration systems.Theoretically, since there is no outflow unlessthe storage capacity is exceeded, pollutantremoval efficiencies, in terms of storm waterrunoff approaches 100 percent. True pollutantremoval efficiencies however, depends onspecific requirements. Designers mustconsider the following:




1. soil/subsoils that are moderately to highlypermeable. A percolation test and/orgradation may be needed. Contact theRegion/TSC Soils Engineer forassistance.

2. groundwater table is approximately 3 mbelow the bottom of the storage area.The location of the ground water tablemay be provided by the Region/TSCSoils Engineer.

3. runoff inflow is relatively free ofsuspended solids. Designers can useeither a two cell system or a vegetatedditch with a minimum length of 60 m.

4. there is sufficient storage for the runoffduring infiltration period (see DesignEngineer - Hydraulics/Hydrology).

D. Wetland Treatments

Wetlands systems, man-made or natural, canbe used as a runoff pollutant-removalmechanism through sediment retention andvegetation uptake. Due to the variation inhighway quality and each wetland’s ability towithstand impacts, treatment capacity andeffectiveness is best evaluated on a site-by-sitebasis and coordinated with the Project PlanningDivision.

Overall pollutant removal effectiveness isdependent on type of wetland, geographiclocation, climate, and hydrologic parameters.However, the literature indicates wetlands canprovide a highly effective managementmeasure and studies have shown that removalof nutrients, moderate amounts of suspendedsolids, Biochemical Oxygen Demand (BOD),and heavy metals were consistently high.These systems are limited, in that heavyamounts of sediments in the runoff water canadversely affect detention and pollution removalcharacteristics, and therefore wetland systemsare not recommended solely for soil erosionand sedimentation control practices.

4.03.05 (revised 3-8-99)

Storm Water Runoff Detention Basin DesignGuidelines

These design guidelines are proposed to meetthe criteria for detention basins discussed insection 4.03.04. The purpose of the detentionbasins is to provide a process to removepollutants from highway runoff. Detentionbasins are effective if sufficient detention timeis provided to settle out suspended and bedloadparticles in the storm water runoff. Final designshou ld be coord ina ted w i th theHydraulics/Hydrology Unit. Detention basindesigns differ from "retention" in that retentionbasins are designed to reduce new peak flowsto flows that do not exceed existing conditions.If retention is required, contact Design Engineer- Hydraulics/Hydrology.

A. Design Considerations

The following design considerations were takenfrom FHWA’s "Retention, Detention, andOverland Flow for Pollutant Removal FromHighway Storm Water Runoff: InterimGuidelines for Management Measures" datedMarch 1988, and the Michigan Department ofNatural Resource’s Stormwater ManagementGuidebook, dated March 1992. Application ofthese published guidelines to the statetrunklines are highlighted in these designguidelines. The design of a detention basinmust consider the following:

1. Storage volume and surface area availablefor detention must be determined.Additional ROW may be required.

2. Stability of the detention basinembankments and natural slopes requiresthe following:

a. Soil boring(s) for embankment basinarea and outlet structure

b. Determination of groundwater elevation

c. Embankment slopes at 1:3 or flatter

d. Grassed slopes (maintained)



Storm Water Runoff Detention Basin DesignGuidelines

3. Maximize the travel time from inlet(discharge from storm drainage system) tooutlet structure of the basin. Can beaccomplished by:

a. Use of baffles or islands

b. Irregular shoreline

c. Elongated or narrow basin

4. Release of the stored volume of runoff inthe basin should be discharged over aminimum 24 hour period as recommendedby the Michigan Department ofEnvironmental Quality.

5. Outlet system can be either a mechanicalspillway (CSP riser and outlet tube) orpermanent steel sheet piling weir(preferred based on constructability,maintenance, and safety considerations.)

6. Highway Safety and Aesthetics

a. AASHTO recommends protectivetreatments when a body of water, morethan 0.6 meter deep, is located in theclear zone. See Section 7.06.10.

b. Public safety, i.e. fencing to denyaccess; gentle slopes for access;measures to prevent access to outletstructures. Local zoning requirementsmay ex ist for storm waterdetention/retention facilities andfencing.

c. Shallow impoundments are unattractiveand the need for visual screeningand/or landscaping is needed. Onemeter permanent water depth mayalleviate problems with odor, weedsand vectors.

4.03.05 (continued)

B. Design Procedures

A basic assumption is that the storage capacityis sized to control minor storms (less than the2-year or 50 percent chance flood event) asopposed to major flood-producing events.Therefore, the concept of "first flush" is used."First flush" refers to the large percentage ofstorm pollutant loading that is produced by arelatively small percentage of the runoff volumeduring the initial stages of the runoff. Thestorage volume required will be based oncontrolling the first 13 mm (unpaved area) to25 mm (paved area) of runoff volume from thedrainage area. The following equation can beused to design estimated runoff volume:

Vs = (0.025) x Ap + (0.013) x Auwhere:

Vs = Volume of storage in hectare-meter

Ap = Area of impervious pavement inhectares.

Au = Unpaved Area in hectarescontributing to the highwaydrainage

The flood elevation of the receiving waters,whether an open channel or enclosed system,must be evaluated for impacts on the outletstructure and basin.

Conceptual designs for discharge from adetention basin to either an "Open ChannelOutlet" or an "Enclosed Outlet System" areavailable from the Design Engineer -Hydraulics/Hydrology.


4.04

DITCHES

4.04.01 (revised 1-8-98)

Roadway Drainage Ditches

Open ditches for drainage areas within MDOT’sR.O.W. shall be designed for a 50-year storm.The effects of a 100-year storm should bechecked for possible harmful interference toadjacent properties. Normally, the standardditch section will be adequate for a 50-yearstorm, unless the ditch is unusually long or hasditches from outside the R.O.W. that inlet into it.The ditch should be designed to have the watersurface elevation either outside the clear zoneor the depth should not exceed 0.6 meter.

There are both permanent and temporaryerosion control measures in relation to drainageditches. The road designer should design thepermanent erosion control measures to beapplied in the establishment of ditches. TheRegion Soils and Materials Engineer will designthe temporary erosion control measures for theditches during construction activity, see Section2.05 and Standard Plan R-96-Series.

Below are guidelines for permanent stabilizationtreatments for various ditch grades. Thedesignated treatment for all situations shouldinclude installation in the ditch bottom and1.5 m up both slopes. The soil type should beconsidered for borderline situations. The lessertreatment can be used for cohesive soils, whilethe higher level treatment should be used forcohesionless soils. If questions arise regardingsoil suitability for a particular ditch flow orunusual conditions, further guidance can besought from the Region Soils and MaterialsEngineer, the Environmental Section of theProject Planning Division, or the GeotechnicalServices Unit of the Construction andTechnology Division.

4.04.01 (continued)

PERMANENT STABILIZATIONTREATMENTS FOR VARIOUS DITCH

GRADES

Ditch BottomTreatment Ditch Grades

Seed & Mulch ** * 0.1% to 0.5%

Standard Mulch Blanket ** 0.5% to 1.5%

High VelocityMulch Blanketor Sod **

1.5% to 3.0%

Turf ReinforcementMat or Cobble Ditch 3.0% to 6.0%

Specific DesignRequired *** 6.0% +

* Minimum ditch grade 0.1% with 0.3%desirable minimum.

** When within 60 m of a stream, thepermanent ditch treatment will be mulchblanket for ditch grades of 0.5% or lessand sod for ditch grades between 0.5%and 3.0%. The designer should set up amiscellaneous quantity of mulch blanket (ifnot already set up) and high velocity mulchblanket to use in case sod is notimmediately available or it is outside ofseasonal sodding limits.

*** Downspouts see Standard PlanR-32-Series; paved ditches see StandardPlan R-46-Series; for spillways consult witht h e D e s i g n E n g i n e e r -Hydraulics/Hydrology.


4.04.02 (revised 10-30-97)

Standard Ditches

The ditch types discussed here are as shownon Standard Plan R-105-Series, "GradingCross-Sections". The type, width, depth, andbackslope of the ditch to be used in any givenlocation depends upon many factors, includingsoil, depth of subbase, surface drainage,built-up conditions along the roadside,excavation requirements, and snow conditions.Any variation from the standard-type ditchesmust be covered by note or sketch on thetypical cross-section.

A. Round Bottom Ditch

In rural areas, the standard ditch is a roundbottom ditch 1.22 m below plan grade, 1.83 min width, and a 1:6 front and backslope. R.O.W.restrictions may require the backslope to besteeper and the ditch width reduced to 1.22 m.

B. Berm or Swamp Ditch

A berm or swamp ditch is called for when thenormal round bottom ditch would be too deep,such as in areas of low fill and the ditchcenterline is a specified distance from the edgeof pavement.

4.04.02 (continued)

C. Independent Ditches

Independent ditches are called for when it isnecessary to crest the ditch at a differentlocation from plan grade. Independent ditchesshould not be called for if ditches are adverse tosteep road grades. The grade for ditches,independent or dependent, is 0.1% minimumand 0.3% desirable minimum. Ditches in thetransition section of superelevated curves mustbe designed to avoid flat spots or pocketscreated by combinations of relatively flat gradesand the superelevation transition .

D. Toe of Slope Ditch

A toe of slope ditch is a type of independentditch that is placed at the slope stake line wherethe grade is too high for a standard road ditchand the volume of water too small to justify aswamp ditch. They are used only in agriculturaland similar areas to prevent drainage fromrunning over the adjacent land.

E. Valley and No-Ditch Sections

In sandy soils or in semi-urban areas, wherespace is limited, valley type ditches or no-ditchsections may be used. An underdrain may berequired to drain the subbase in conjunctionwith these ditches where subbase is used.


4.05

DESIGN CRITERIA FORROADWAY CULVERTS

4.05.01 (revised 10-30-97)

MDOT and FHWA Requirements

FHWA’s Federal Aid Program Guide (FAPG)Part 650 for federal-aid projects and state lawrequires that at each location where thehighway will encroach on the flood plain, theplans will show the following: magnitude,frequency, and water surface elevations for thedesign flood (50-year) and base flood(100-year). Floodplain data can be obtainedf r o m t h e D e s i g n E n g i n e e r -Hydraulics/Hydrology.

All highways that encroach on the floodplain,either transversely or longitudinally, shallrequire a hydraulic analysis and be designed topermit conveyance of the 100-year flood withoutcausing an adverse impact on natural andbeneficial flood plain levels, damage toproperty, or a significant increase in potentialfor interruption or termination of emergencyservice or emergency evacuation routes.

Where the size of the waterway opening iscontrolled by factors other than hydraulics,FHWA requests that they be advised of theseconsiderations, when the plans are submittedfor their review. FHWA and MDOT reviewrequires early submittal of this data. Data mustbe included prior to THE Plan Review Meeting.

4.05.02 (12-23-96)

Culvert Pay Lengths

Concrete pipe 600 mm diameter and above isavailable in commercial lengths of 2.44 m. Inthe upper peninsula concrete pipe is availablein 1.22 m, 1.83 m and 2.44 m commerciallengths for 450 mm and 600 mm diameters.Therefore, when installing new culverts orextending existing culverts, the length quantitiesshould be based on available commerciallengths.

4.05.03 (revised 12-23-96)

Roadway Culvert Size Determination

1. The determination of the appropriate sizeand type of culvert for a proposed roadwaycrossing of a waterway requires ahydraulic analysis that will enable thedesigner to select the size of culvert whichwill allow the design discharge to passwithout exceeding the allowable headwaterdepth at the inlet. The accepted designprocedure for the selection of culvert sizeis presented in the Hydraulic Design ofHighway Culverts, Hydraulic EngineeringDesign Series, No. 5, prepared by theFederal Highway Administration, datedSeptember 1985.

2. The hydraulic capacity and height ofheadwater is normally controlled by theconditions at either the inlet or the outlet ofthe culvert. Inlet control as described inHydraulic Design of Highway Culverts,Hydraulic Engineering Design Series,No. 5 means that the discharge capacity ofa culvert is controlled by the entrancegeometry and by the depth of headwater(HW) at the entrance. Outlet control isdependent on downstream conditions.Losses for a culvert flowing under outletcontrol would include expansion (at outlet),friction (culvert length and material type),and contraction (at entrance). Fordetermining the allowable headwater for aparticular culvert, refer to Section 4.05.06.

3. For culverts not requiring a permit and withflows that are normally low or intermittent,the designer may use the simplifiedmethod of determining culvert sizedescribed in Hydraulic Design ofHighway Culverts Hydraulic EngineeringDesign Series, No. 5.


4.05.04 (revised 12-23-96)

Culvert Pipe Class Designations

Culvert pipe classes are used to designate thepipe's strength and its load carrying properties.Culvert pipes are designated Class 1 (lowest)through Class 6 (highest), with the allowablepipe alternates shown in the current specifica-tions. The height of fill over the top of culvertpipe determines the class pipe to be used. Seethe current specifications for requirements.

4.05.05 (revised 2-18-2000)

Culvert Usage Guidelines

All pipe culverts will be specified by class anddiameter; e.g., Culv, Cl 2, 600 mm. The designlife for culverts will be 50 years, exceptdriveway culverts will be 25 years.

For pipe culverts equal to or greater than750 mm, the material type, i.e. the Manning’sroughness coefficient, must be accounted for inthe hydraulic analysis. The designer must do ahydraulic analysis for all available pipematerials in the class (See Section 4.05.03).Alternative pay items must be called for on theplans and in the proposal. They may beentered into the Trns`port program in theCategory Alternate Bid Code field (seeTrns`port newsletter Vol.2, No. 1 forinstructions). Contact the Design Engineer -Hydraulics/Hydrology for assistance.

In some applications a specific material for aculvert pipe may be required exclusively or aspecific material may be determinedinappropriate for a specific location. Therequired material should be specified in the payitem. Specify the pipe culvert by class,material, and diameter, e.g., Culv, Cl 2, Conc,1050 mm. The prohibited material should beidentified by note on the plans. When aspecific material is prohibited and its exclusionis not covered in the

4.05.05 (continued)

Standard Specifications, a note to the file mustbe written to describe the basis for exclusion.This information should also be forwarded tothe field. The exception is when extending anexisting system with like material.

4.05.06 (revised 2-18-2000)

Permit Requirements for Roadway Culverts

All Michigan Department of EnvironmentalQuality (MDEQ) permit applications are to bereviewed and coordinated by MDOT's ProjectPlanning Services Division (PPD). PPD willensure compliance with current MDEQ andCorps permit application requirements.Assistance in preparing appropriate permitapplications is available from the DesignEngineer - Hydraulics/ Hydrology.

1. Part 301 Inland Lakes and Streams of theNatural Resource and Environmental Act451 of Public Acts of 1994 requires anInland Lakes and Streams Permit from theMDEQ for construction over or adjacent toinland lakes or streams. An inland streamis defined as a watercourse with definitebanks, a bed, and visible evidence of acontinued flow or continued occurrence ofwater. These watercourses can beidentified on the USGS quadrangle maps.

2. Part 31 Water Resources Protection of theNatural Resource and Environmental Act451 of Public Acts of 1994, as amended,requires a Floodplain Permit from theMDEQ for construction over or adjacent tostreams that have drainage areas inexcess of five square kilometers (twosquare miles) upstream of the crossing. Inaddition MDOT must comply with theGovernor's State Executive Order 1977-4,"State Flood Hazard Management Plan"since it establishes flood standards anddesign requirements.


4.05.06 (continued)

Permit Requirements for Roadway Culverts

3. The MDEQ coordinates under joint permitthe Corps of Engineers 404 Permit. TheWater Pollution Control Act's 404 Permit isrequired for watercourses with a flowgreater than 0.14 m3/sec or adjacentwetlands, as currently listed in the Corps ofEngineers Jurisdiction maps.

4. Part 303 Wetland Protection of the NaturalResource and Environmental Act 451 ofPublic Acts of 1994 requires a StateWetland Permit from the MDEQ forconstruction in wetland areas. Wetlandmitigation plans are to be coordinated withthe Environmental Engineer in the ProjectDevelopment Section.

5. Culverts carrying county drains must besubmitted to the County DrainCommissioner or Drainage Board. SeeSection 4.01.06C.

A. Culvert Drainage Areas Equal to orGreater Than Five Square Kilometers(Two Square Miles)

All drainage areas equal to or greater than fivesquare kilometers (two square miles) willrequire a detailed hydraulic analysis andapproval for a permit from the MichiganDepartment of Environmental Quality (MDEQ).A request for a hydraulic analysis must besubmitted to the Design Engineer -Hydraulics/Hydrology (see section 4.05.08).The waterway crossing shall be designed topass a 100-year flood without producing aharmful interference. (for definition of harmfulinterference, see 4.01.02).

1. Inundation of the roadway will be allowedas part of the flood flow, when theinundation does not interrupt or terminateemergency service or the roadway is notpart of an emergency evacuation route.Interstate lanes shall be designed to bekept dry for a 50-year storm.


2. The flood stage level may be increased ifno adverse impact results to the highwayor properties within the natural flood plain.A certification on the hydraulic capacitymust accompany the permit application.

B. Culvert Drainage Areas Under FiveSquare Kilometers (Two Square Miles)

When a culvert drains an area less than fivesquare kilometers (two square miles),determine the existing and proposed hydraulicconditions for the 50-year and 100-year floodevents. The proposed design shall be basedon passing the 50-year storm through theculvert while keeping the roadway dry, andbased on the 100-year flood event producing noharmful interference to the highway or adjacentproperty.


4.05.07 (revised 2-18-2000)

Determining Culvert Sizes

Culverts should meet all design constraints ateach individual site and their size determinedby using the culvert’s maximum possiblecapacity.

1. Normal procedure is to design circularculverts for flowing 0.9 full.

2. The allowable freeboard to the bottom ofsubbase grade is 0.5 meter for the50-year flow.

3. Outlet velocities shall not exceed existingstream velocities that would causeerosion without erosion control treatment.Outlet velocities less than 1.83 m/sec willgenerally not require special treatment ifa headwall or end section is used. Outletvelocities in excess of 1.83 m/sec willrequire provisions for erosion controltreatment and possible energydissipation structures. Contact theDesign Engineer - Hydraulics/Hydrologyfor recommendations.

4. The invert of a circular culvert will beburied below the stream or ditch flow linea minimum of 0.1 x dia. or 150 mm,whichever is less. However, thehydraulic analysis should assume thatthe full waterway area is available fordesign discharge.

4.05.08 (revised 2-18-2000)

Estimating Peak Flows for Culverts

If the drainage area exceeds five squarekilometers (2 square miles), a permit from theMichigan Department of Environmental Quality(MDEQ) is required. A request for hydrologicand hydraulic analyses is to be made to theDesign Engineer Hydraulics/Hydrology. TheHydraulics/ Hydrology Unit will prepare thehydraulic analysis and submit a report to theMDEQ.

A. MDNR's Soil Conservation Service(SCS) Method

The hydrologic analysis required for culvertscan use either the method described in theMichigan Department of Natural Resourcespaper entitled Computing Flood DischargesFor Small Ungaged Watersheds datedSeptember 1991, referred to as MDNR SCSMethod, or The Rational Method. All crossculverts must be designed for the 50-year flowand checked against the 100-year flood flow.

The MDNR SCS Method is based on Section 4Hydrology from the SCS National EngineeringHandbook. It is an acceptable method to beused for small drainage areas of less than 52square kilometers.

B. The Rational Method for EstimatingPeak Flows for Culverts

If the area is less than 8 hectares and the flowto the culvert crossing is low or intermittent, themore simplified Rational Method (see section4.02.02E) may be used for design. Assistanceon determining estimated peak flows can beobtained from Design Engineer - Hydraulics/Hydrology.


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4.05.10 (revised 3-8-99)

Hydraulic Analysis Data and Soil Borings onPlans

If either the size or location of the culvert arechanged, the Road Design Unit must obtainnew approval from the Design Engineer -Hydraulics/ Hydrology. A plan sheet should beincluded in all projects showing the projectdrainage (see section 1.02.03). All drainagestructures should be accompanied by atabulation of drainage data shown on theDrainage Map. For drainage areas equal to orgreater than five square kilometers (two squaremiles), or design discharge in excess of14 m3/sec, the tabular form illustrated below isrequired and can be obtained from the DesignEngineer - Hydraulics/Hydrology. For all otherculverts, the tabulation must include the designflood frequency discharge and the drainagearea.

Soil borings must be requested from theGeotechnical Services Unit for any new orextended culverts that have the following sizesor equivalent area:

a. Pipe culverts equal to or greater than1500 mm diameter

b. Box and slab culverts equal to or greaterthan 1200 mm X 1200 mm

For culverts smaller than these sizes, the soilborings must be requested from theRegion/TSC Soils and Materials Engineer.(Reference Section 14.24 of draft Chapter14). All soil borings and related informationmust be shown on the plans.

4.05.10 (continued)


4.05.11 (revised 2-18-2000)

Culvert Extensions and Replacements

For MDEQ permit application and hydraulicanalysis, the length of a culvert extension isdefined as: the length of the extension on bothends of the pipe and the length of both slopedend sections.

A. Hydraulic Analysis Requirements

Culvert extensions and replacements with adrainage area equal to or greater than fivesquare kilometers (2 square miles) will requirea detailed hydraulic analysis. The DesignEngineer - Hydraulics/ Hydrology will preparethe hydraulic analysis and submit a report to theMDEQ.

Culvert extensions and replacements with adrainage area less than five square kilometers(2 square miles) requires an analysis to bedone by the Road Design Unit. Culvertextensions and replacements must beevaluated for both existing and proposedconditions. The results of the analyses mustshow no "harmful interference" to adjacentriparians (See 4.01.02).

B. Reinforced Circular Concrete PipeExtensions

It is often necessary to extend circular culvertson upgrading projects. The concrete industryhas changed its joint design over the years, andwhen old culverts are extended with new pipe,which is presently designed to be adaptable togasketed joints, this may result in poorly fittedjoints. In order to ensure tight joints and toforewarn contractors of possible extra workrequired on applicable projects, the followingGeneral Plan Note should be placed on thenote sheet:


Circular Culvert Extensions

The extension of existing circular concreteculverts on this project may require extrawork to obtain a tight seal at the jointconnecting new culvert pipe to existingculvert pipe. The joint between the existingand new pipes shall be completely filled withmortar to form a tight seal. Any extra workrequired to obtain tight joints will not be paidfor separately but will be included incompensation for extending culverts.

C. Extending Existing Box and SlabCulverts

The extension of existing box or slab culvertsless than 1200 mm X 1200 mm may be with aconcrete circular pipe, with a reinforcedconcrete connecting collar, of sufficient size tohave a hydraulic capacity equal to or greaterthan existing conditions. The following table isprovided as a guide for the Scope preparationand initial cost estimating by the designer untila hydraulic analysis is completed:

Existing Size(mm)

Concrete CircularPipe Size

(mm)600 x 600 750750 x 750 900900 x 900 12001200 x 900 1500

1200 x 1200 Use precastconcrete box

For box culverts equal to or greater than1200 mm X 1200 mm, the extension must be aprecast concrete box with the appropriateconnecting collar. Design of the extension canbe obtained from the Design Engineer -Municipal Utilities.

Extension of an existing slab culvert with areinforced concrete box culvert or circular piperequires the area between the footings shall bepoured with concrete and sufficient steelreinforcement doweled into the footings.



Extending Existing Box and Slab Culverts

The designer is cautioned that total culvertextensions equal to or greater up to 7.2 meters,including the end section, will require hydrauliccertification for the MDEQ permit application.The hydraulic certification must be submittedand approved by the Design Engineer -Hydraulics/Hydrology and then provided toProject Planning Division for submission withthe MDEQ permit application. For assistance inthe hydraulic analyses and hydrauliccertification contact the Design Engineer -Hydraulics/Hydrology."

4.05.12

Bedding and Filling Around Pipe Culverts

The bedding and filling around pipe culverts isdone according to Standard Plan R-82-Seriesupon which the Culvert Class-Depth-UsageTable is based. This type of installation isreferred to as a "Positive ProjectingEmbankment Conduit" for a concrete pipe. Thefollowing information describes other types ofinstallations for concrete pipe. However, whenspecial designs or installations are required, adesign request should be made to the BridgeDesign Section.

A. Trench Installation

When the culvert pipe is placed in a narrowtrench and covered with earth, the backfill willtend to settle downward. This downwardmovement or tendency for movement of thebackfill within the trench above the conduit isretarded by frictional forces along the sides ofthe trench that act upward and help support thebackfill. As this type of installation appliesnormally to a sewer-type installation and ourstandard plans and specifications do not restrictthe trench width for a culvert, this type ofinstallation is not normally considered in design.

4.05.12 (continued)

B. Positive Projecting Conduits

Positive projecting pipes are installed in shallowbedding with the top of the conduit projectingabove the surface of the natural ground orcompacted fill at the time of installation andthen covered with earth fill. Culverts placed inwide trenches also are included with thisclassification. This classification is the basis forour Standard Plan R-82-Series.

C. Negative Projecting EmbankmentConduit

Negative projecting embankment culvert pipesare installed in relatively shallow trenches ofsuch depth that the top of the pipe is below thelevel of the natural ground surface orcompacted fill at the time of installation andthen covered by earth fill, the height of fill beinggreater than the depth of trench. As with atrench installation, the load on the pipe isreduced by frictional forces along the sides ofthe trench. This may reduce the ASTM class ofconcrete pipe required; however, a request toBridge Design for a design will be requiredbefore reducing pipe class.

D. Induced Trench Conduit

The induced or imperfect trench installation isused when it is necessary to relieve or reducethe load on a concrete pipe under a high fill.The culvert is initially installed as a positiveprojecting pipe. When the embankment fill hasbeen placed to an elevation of two to threetimes the diameter of the culvert above naturalground, a trench is excavated over the culvertand backfilled with compressible materialsimulating a negative projecting installation . Asthis is a special design, the design and detailsfor this type of construction are to be requestedfrom Bridge Design.


4.05.13

Corrugated Structural Plate Pipe andPipe Arches

Structural plate pipe and structural plate pipearches are field-assembled pipes from curvedsections with 150 mm x 50 mm corrugations.

Whenever corrugated structural plate pipe orcorrugated structural plate pipe arches areused, the following information is required onthe plans:

1. Span and rise (or diameter).

2. Pay length (bottom length) .

3. Nominal thickness of metal.

4. Angle with centerline.

5. Cutoff height.

The following is an example of how the itemsmentioned in 1, 2, and 3 above should beshown on plans:

Corrugated Steel Structural Plate Pipe Arch2800 mm x 1950 mm, (3.51 mm Thick)17.68 m.

Item 4 and 5 shall be detailed on plans.

4.05.14 (revised 2-18-2000)

End Treatment for Culverts

A. Culvert Sloped End Sections

Culvert sloped end sections can be installed onthe ends of culverts and fitted into 1:4 or 1:6slopes. They are designed to be used for crossor parallel drainage. Standard PlanR-95-Series details the various cross andlongitudinal tubes needed for each situationalong with the connection details of the culvertsloped end section to the various culvert pipematerials and sizes.

The culvert sizes that can be fitted with theculvert sloped end sections are as follows:

1. Circular pipe culverts sizes375 mm to 1500 mm.

2. Arch pipes 530 mm x 380 mm through2100 mm x 1450 mm.

3. Elliptical pipes 365 mm x 575 mmthrough 1220 mm x 1920 mm.


4.05.14 (continued)

B. Guidelines for Usage

Guidelines for Culvert End Treatments Within the Clear Zone

TransverseCulverts

Circular450 mm and smaller

Existing End Section Leave in place, no grate required.

Existing Headwall Remove headwall, extend if needed to meetslope, fit with standard end section

New culvert, orcurrent end section needs adjustment.

Design / extend to meet slope, fit withstandard end section.

Circular 525 mm to 1500 mm

Arch 530 mm x 380 mm

to2100 mm x 1450 mm

Elliptical 365 mm x 575 mm

to 1220 mm x 1920 mm

Existing End Section Leave in place, but grate required. Alternative: fit with culvert sloped end section

Existing Headwall Remove headwall, extend if needed to meetslope, fit with culvert sloped end section.

New culvert, orcurrent end sectionneeds adjustment

Design / extend to meet slope, fit with culvertsloped end section

Slab and Boxculverts and

All pipes larger thanlisted above

Shield with guardrail or extend beyond clear zone.

LongitudinalCulverts

(approachend)

Freeway

Circular300 mm

Standard end section.Alternative: use 375 mm pipe, culvert slopedend section

Circular375 mm and larger Culvert sloped end section.

Non-Freeway

Postedspeed

64 km/h(40 mph)or greater

Circular300 mm

and 375 mm

Standard end section.Alternative: use 375 mm pipe, culvert slopedend section

Circular450 mm and larger Culvert sloped end section.

Postedspeed

56 km/h(35 mph)

or less

Generally, no grates or sloped end sections required. Crash analysisand recommendations from Traffic and Safety Division may indicate aneed to shield culvert ends in unique locations.

CulvertsOutside theClear Zone

Engineering judgment should be used to provide improved roadside safety, when a smallincrease in cost is involved. Examples might include extending small culverts beyond the clearzone or placing a culvert sloped end section outside the clear zone in a gore area.

1:3 slopes should be free of fixed objects or discontinuities that might interfere with an otherwiseclear run out distance. See sections 7.01.11 A and 7.01.30 for more information on clear zonecriteria and guardrail at embankments.


4.05.15

C.S.P. to Concrete Culvert Adapter

C.S.P. to Concrete Culvert Adapters, currentlyshown on Standard Plan R-92-Series, aresometimes used to extend an existing concreteculvert with a steel culvert or vice versa. Its useensures a proper connection between thepipes. The current policy of using culvertsloped end sections and its adapter reduces itsneed, except for its possible use on large sizeculverts that need to be extended outside theclear zone.

4.05.16 (revised 2-18-2000)

Outlet Headwalls

Outlet headwalls, shown on Standard PlanR-85-Series, should not be used where they willbe exposed to traffic in the clear zone,regardless of which way they face, unless theyare in an area protected by guardrail. Outletheadwalls with a baffle must be considered forthe lower ends of steep culverts (10% orsteeper) with large areas of runoff, with ditcheslonger than 120 m and/or with large cut slopes.

4.05.17 (revised 12-23-96)

Downspout Headers

Standard Plan R-32-Series shows details ofbridge approach curb and gutter which includesdownspout headers. The accepted designprocedure for placement of downspout headerscan be found in the Drainage of HighwayPavements, Hydraulic Engineering CircularNo. 12 -, prepared by FHWA. Contact theDesign Engineer - Hydraulics and Hydrology forassistance. Downspout headers are designedto fit between the 1905 mm guardrail postspacing, therefore the spacing betweendownspout header must be in 1905 mmintervals, but not necessarily every 1905 mm.They should be located to prevent erosion ofthe approach shoulders as well as to interceptthe highest concentration of runoff as ispossible.

4.05.18 (2-18-2000)

Concrete Slab Culverts

Precast slab culverts are commonly used andare specified by a special provision. Contactthe Hydraulics/Hydrology Unit for assistance.

Details for cast-in-place reinforced concreteslab culverts are available from the DesignStandards Unit. These details are forconstructing new or extending existing slabculverts and were designed for HS20 loading.

When extending an existing slab culvert,adhesive anchored bolts shall be used to tie thenew construction to the existing.

The top of footing shall be a minimum of450 mm below the average stream flow linewithin the culvert.


4.05.19 (revised 2-18-2000)

Precast Concrete Box Culverts

Precast box culverts are available in numeroussizes state-wide. The designer should contacta local supplier to verify that a particular size isavailable. The supplier, in some instances,may be willing to furnish a larger size if hisavailable forms do not match the required size.Precast box culverts offer the advantage ofrapid installation and are competitively pricedwith cast-in-place box culverts for newconstruction or culvert extensions.

Precast concrete box culverts are called for byASTM specification and size. The depth ofcover dictates which pay item to use. ASTMC789M is called for when the depth of cover isto be greater than or equal to 600 mm. ASTMC 850M is used when the depth of cover is lessthan 600 mm. In either case it should be notedon the plans that the box culvert shall meet thespecified ASTM requirements for MS18 (HS20)loading. If the culvert is located under arailroad crossing, consult the Design Engineer -Municipal Utilities. When the culvert requiresheadwalls, details must be obtained from theDesign Engineer - Municipal Utilities.

When extending box culverts, adhesiveanchored bolts shall be used to tie the newconstruction to the existing.

The invert elevation of a box culvert is to be set150 mm below the normal flow line. Thiselevation is to be referred to as the invertelevation on the details to avoid confusion withthe flow line of the waterway that appears onthe profile.

4.05.20 (added 2-18-2000)

Lining Culverts

When a culvert has structural deterioration, itmay be possible to line the culvert instead ofreplacing it. Caution must be used by thedesigner and a hydraulic analysis should bedone to determine the potential hydraulicimpacts of inserting the liner. The analysisshould cover the range of flows passed by theculvert.

Lining may be in the form of inserting plasticpipe and grouting the annulus or insertion of aresin-impregnated flexible liner. Installation iscovered by appropriate Special Provision, e.g.“In Place Culvert Rehabilitation, Liner.” Theinstallation of a liner may be allowed for thefollowing conditions:

1. The culvert is a cross culvert that acts asan equalizer between two bodies of water(e.g. between two wetlands).

2. A driveway culvert that is only carryingditch flow generated from MDOT ROW.For the range of design flows, the watersurface elevation upstream of the culvertis contained within the ROW.

3. The culvert is a CMP that will notexperience inlet control over the range ofdesign flows.

Any questions regarding the hydraulic analysisor potential impacts should be directed to theDesign Engineer - Hydraulics/Hydrology.

4.05.21 (revised 12-23-96)

Drainage Marker Posts

Drainage marker posts are installed to helpmaintenance personnel locate end sections orheadwalls of transverse culverts 900 mmdiameter or less. Drainage marker posts are tobe placed outside the shoulder hinge lines andshould not be used in medians except onspread roadways. Drainage marker posts shallbe at least 2 m long and shall conform to thedelineator or steel line posts that are specifiedin the current standard specifications.


4.06

UNDERDRAINS

4.06.01

Purpose of Underdrains

Current methods of installing underdrains areshown on Standard Plan R-80-Series. In orderto protect a roadway surface from earlydeterioration, a stable base must be built for theroadway. Water in subbase materials weakensthe foundation soils, therefore a good roadwayrequires good drainage. Underdrains interceptand remove seepage from the subbase,eliminating springy or bad subsoil conditions.Underdrains are used on both enclosed anddaylighted drainage systems.

The various underdrains either captures anddrains the water trapped below the pavementsurface or intercepts seepage water before itenters the space below the pavement and thenconveys the seepage to either an outlet ditch ora storm sewer system.

4.06.02

Bank Underdrains

Bank underdrains are sometimes placed in theback slopes to intercept seepage planes beforethey reach the roadway to minimize erosion orsloughing. Two basic methods of installingbank underdrains are shown on the standardplan. One method backfills the trench with agranular material and wraps the underdrainpipe with a geotextile. The other methodenvelopes both the open-graded material andthe underdrain pipe by lining the trench with ageotextile.

4.06.03

Subgrade and Subbase Underdrains

Subgrade underdrains are meant to drain boththe subbase and subgrade under the pavement.Currently, two methods of constructingsubgrade underdrains are shown on thestandard plan. One method lines the trenchwith a geotextile that envelopes both theopen-graded material and the underdrain pipe.The other method uses granular material andwraps the underdrain pipe with a geotextile.

The subbase underdrain is meant to drain onlythe subbase. The flow line of the underdrain isnormally a maximum of 250 mm below the topof the subgrade. The underdrain pipe iswrapped with a geotextile.

4.06.04 (revised 3-8-99)

Open-Graded Underdrains

Four methods of installing open-gradedunderdrains are shown on the standard plan.All four have an open-graded materialimmediately below the pavement surfacing.Their purpose is to drain quickly any water thatenters through joints or cracks in the pavementand to minimize the amount of water enteringthe subbase material. Two of the methods useunderdrain pipe and two use the PrefabricatedDrainage System (PDS).


4.06.05

Underdrain Outlets & Outlet Endings

Underdrain outlets are used to connectunderdrains to the outlet endings. To resistcrushing from heavy construction andmaintenance vehicles and to insure positiveflow, rigid PVC or corrugated steel pipe shall beused for underdrain outlets.

Currently three approved outlet endings areshown on Standard Plan R-80-Series. Otherdesigns may be used when approved by theEngineer.

4.06.06 (revised 3-8-99)

Stone Baskets

Stone baskets are used to drain springs thatoccur below the roadway. The stone basket isconstructed by making an excavation at thespring head 1.2 m in diameter andapproximately 1.5 m below the bottom ofembankment. A geotextile shall be placed inthe excavated hole and backfilled with 38 mmto 150 mm stone or masonry, and a 300 mmthick layer of 6A stone. A 150 mm diameterunderdrain is used to dissipate water from thestone basket. The location of the stone basketshould be shown on the typical cross sectionand the following sketch detailed in theconstruction plans.

TYPICAL STONE BASKET SECTION

Documents

CHAPTER 4mdotcf.state.mi.us/public/design/files/roadmanual/rdm04.pdf · 4.01.06 Drainage Considerations ... 4.05.13 Corrugated Structural Plate Pipe and Pipe Arches ... VOLUME 3 MICHIGAN