local conditions-ne minnesota · 12 local conditions-ne minnesota special waters zlake superior...

11

Local Conditions-NE Minnesota

Identifying Regional StormwaterChallengesSelecting BMPs for our areaExperience & observations from MNDOT & MPCA BMPs that work / don’t work in NE Minnesota


Regional Construction StormwaterChallenges

Special WatersClayey soilsPoor quality topsoil Steep slopesShallow depth to bedrock

12


Special WatersLake SuperiorTrout Streams

Clayey SoilsVery common throughout region: Duluth, North Shore, North-central MN


Poor Quality TopsoilIn general, the forested region of MNParticularly the Canadian Shield terrain

Steep SlopesCommon throughout region: Duluth, North Shore

Shallow Depth to BedrockCanadian Shield

13


Shaded areas bedrock at surface or < 15 m (50’) BGSShallow depth to bedrockPoor quality topsoilSteep slopes along North ShoreSpecial Waters

Reproduced from Geology of Minnesota, Ojakangas, Matsch 1982 & Minnesota Geological Survey

Definitions

Erosion ControlPreventing (or minimizing) the dislodgment of soil particles

Sediment ControlControlling the movement of soil particles dislodged by failed erosion control practices

14

Definitions

StabilizedMulch, ECBs, sod, rip rap, aggregate surfacing, pavement or other materials that prevent erosion

Surface WaterStreams, rivers, lakes, ponds, wetlands, ditches, storm sewer systems (including curb & gutter)

BMPs for Northeast Minnesota

EROSION CONTROLUp-gradient runoff diversionTemporary slope drainsRapid Stabilization Methods

• Seed w/ oats (Spring, Summer)• Seed w/ winter wheat (Fall)• Straw, or ECBs

Temporary covering w/ geotextile, tarps, poly sheeting, etc.

15

MnDOT Rapid Stabilization Methods

Method 1 – Type 1 Mulch, Disc AnchorMethod 2 – Type 1 Mulch & tack w/HSSMethod 3 – Seed, Fert., Type 6 HSSMethod 4 – Seed, Fert., & cat. 3 ECBsMethod 5 – Geotextile & class II rip rap


SEDIMENT CONTROL BMPsPhased construction

• Construct sensitive areas first• Final grade & stabilize perimeter areas early• Disturb only what is needed for short-term

construction activities

16


SEDIMENT CONTROL BMPs (cont)Perimeter Sediment Control (Overland Sheet Flow)

• Silt Fence– Machine Sliced monofilament fabric– MNDOT Heavy Duty– Preassembled

• Biorolls / Compost tubes• Topsoil berms


SEDIMENT CONTROL BMPs (cont)Stormwater Conveyance Channels

• Riffle & Pool effect• Rock ditch checks/ Stone weepers/ gabions• Boirolls• Sod lined swales• Rip rap• Hay bales

17


SEDIMENT CONTROL BMPs (cont)Inlet Protection

• Inlet Weir• Pop-up retractable riser (Wimco) type• Dandy bag type• Rock snake, rock log (Sac Bag type)

Ponding• Sediment settling• Perf. Riser / monofilament geotextile /pea gravel• Chitosan treatment


SEDIMENT CONTROL BMPs (cont)Dewatering (pumping)

• Discharge to:– Flat surface energy diffuser (plate, plywood, etc.)– Natural basin– Vegetated area– Sanitary sewer (with approval)

• Longer discharge hose !!

18


Poor Quality TopsoilSalvage & re-use existing topsoilImport from adjacent projectsAmend topsoil with:

• Organic materials (black dirt, manure, etc.)• Wood chips from land clearing• Commercial fertilizer• compost


Steep SlopesFlow diversionSlope drainsRiffle & Pool effectTerracing, benchingCat tracking (aka horizontal slope grading)Rip Rap (well defined channel, geotextile)Drop structure

19


Shallow Depth to BedrockRiffle & Pool effectUtilize rock checks to slow runoffCommonly associated with significant elevation differences

MPCA Observations

Erosion control is far more effective than sediment controlProper installation of ECBs is more important than ECB selectionDon’t expect miracles from silt fenceSilt fence not trenched in = no silt fence

20

MPCA Observations

Every construction project should include:Knowledgeable person responsible for ESC workProject SWPPP (on NPDES permitted projects)Landscape rake & shovel Hand seeder, seed appropriate for the application, 10-0-10 commercial fertilizerStraw mulch and/or ECB’sMinimum 200’ of discharge hose for dewaterng

MPCA ObservationsThe root cause of nearly all ESC problem sites is a poor (or non-existent) erosion control effort.A great SWPPP is worthless if not followed in the field.Communication breakdown during construction phase Owner/Consultant should identify exactly what ESC work is required Make all ESC work pay items

21

MPCA Observations

Complying with NPDES permit requirements takes:

KnowledgeSense of PlanningResourcesAttitude

MPCA Observations

Erosion Control is far more effective than Sediment ControlSediment Control

Think “riffle & pool” affect• Sheet flow and concentrated flow runoff• Micro and macro scale

22

MnDOT’sMnDOT’s experienceexperience

Todd Campbell, P.E. Todd Campbell, P.E. District Hydraulics Engineer District Hydraulics Engineer –– MnDOTMnDOTDistrict 1District 1

Wood chip mulch & rock checks

23

Rock gutter check

Rock Sock flow diversion

24

Divert flow around erosive soils

Temporary sediment basin

25

Temporary Stabilization

Wood Chip Entrance

26

Fortified Rock Ditch Check

Bioroll on Ledge Rock

27

ECB installation

Bonded Fiber Matrix

28

Ditch check types

Machine Sliced Mono Silt Fence

29

Vegetated Swale / Rock Checks

Floatation silt curtain – low flow stream

30

Properly stabilized slope

Compost log perimeter sediment control

31

Combination of correct BMPs

Protect trout streams!

32

Stabilizing a difficult site

Questions?

33


Riffle & Pool EffectSheet flow, micro scaleRiffle & Pool

Affect

(Sheet Flow,Micro scale)

Typical grading practice

Dozer travels parallel to contourMini-rills develop from dozer pad imprints

34

Common result of grading on the contour

Sheet flow transforming to rill erosion

Rock CheckSumpStabilized DitchStabilized Grading

35

Failed Erosion & Sediment Control


36



37



38

Construction Practices to Avoid

Successful Erosion Control Practices

39

Successful Sediment Control Practices

Successful Sediment Control PracticesSuccessful Sediment Control Practices

Excavate with Excavate with teeth of bucket teeth of bucket traveling parallel traveling parallel to contourto contourRiffle & PoolRiffle & PoolLoosened, Loosened, roughened roughened subgradesubgrade

40



41



42

Successful Dewatering Practices


43


Successful Construction PracticesSuccessful Construction Practices

Perimeter Control Perimeter Control Erosion ProtectionErosion ProtectionSand Bag Diversion Sand Bag Diversion BermBermPump, Long Discharge Pump, Long Discharge HoseHose

44


Successful Perimeter Sediment ControlSuccessful Perimeter Sediment Control

Silt Fence properly installedSilt Fence properly installed

45

Successful Perimeter Sediment ControlSuccessful Perimeter Sediment Control

Straw Wattle / Straw Wattle / BiorollBioroll

Successful Perimeter Sediment Control

46

Sequencing Construction…Sequencing Construction…

Establish Final Grade Establish Final Grade Early at Sensitive & Early at Sensitive & Perimeter AreasPerimeter Areas

Sequencing Construction…Sequencing Construction…

Timely Timely Stabilization w/ Stabilization w/ Appropriate Appropriate BMPsBMPs

47

Sequencing ConstructionSequencing Construction

Relax & Watch Relax & Watch Your Risks Your Risks DiminishDiminish

Successful Construction PracticesSuccessful Construction Practices

Vegetated Strip Between Vegetated Strip Between Disturbed areas and Silt Fence Disturbed areas and Silt Fence

48

Successful Perimeter Sediment Control

Water Quality Benefits

Erosion controlErosion controlSediment Sediment removalremovalNutrient & Nutrient & pollutant pollutant removalremovalFlow retentionFlow retentionRunoff coolingRunoff cooling

49

Local Support for NPDES Permit – NE Minnesota

MPCA internet site @ http://www.pca.state.mn.us/water/stormwater/stormwater-c.html

General informationNPDES Permit requirementsPermit formsSpecial waters search

50


http://www.pca.state.mn.us/water/stormwater/stormwater-c.html (cont)

Fact Sheets & Guidance ToolsTraining OpportunitiesMPCA staff contacts


Permit and Program Formspermit applicationPermit Transfer/ModificationSubdivision RegistrationNotice of TerminationInspection checklist

51


Special WatersSpecial Waters listSpecial Waters Search Tool

Fact Sheets and Guidance ToolsOverview of NPDES PermitE & S Control for New HomeownersStormwater Compliance Tool Kit for Small Construction OperatorsConstruction SWPPP Template


Additional Training OpportunitiesMECA

• Annual Conference• E & S control lab at Rice Lake, WI

MNDOT/ U of MN• Inspector/Installer• Site Manager• Design

Resource Professionals Alliance• January 19-21, 2005 - Minneapolis, MN

52


MPCA Staff ContactsNE Minnesota (Aitkin, Carlton, Itasca, Koochiching, St. Louis, Lake, Cook Counties)

Jim Dexter MPCA Northeast Regional Office 525 S. Lake Avenue, Suite 400 Duluth, MN 55802 218-529-6253 [email protected]

local conditions-ne minnesota · 12 local conditions-ne minnesota special waters zlake superior...

Documents