Low Impact Development Training

Module 3: Bioretention System Construction

Dennis Chestnut

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Sponsors

District Department of Transportation

U.S. Department of Transportation Federal Highway Administration

The Low Impact Development Center, Inc.

University of the District of Columbia

Funding for this project was provided through a grant from the Federal Highway Administration, U.S. Department of Transportation

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Contributors

The Low Impact Development Center, Inc.

John Shorb Landscaping, Inc.Logo

Groundwork Anacostia River, D.C.

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Copyright

Unless otherwise noted, Low Impact Development Training, funded by DDOT & DDOE, is licensed under a Creative Commons Attribution-NonCommerical-ShareAlike 3.0 Unported License.

Content provided by cited entities remains the property of those entities and may not be used without their explicit permission.

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Outline

• Doing Business in The District• Preparing bids for bioretention

construction• Estimating construction costs• Bioretention construction sequencing• Common construction errors

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Expected Outcomes

• Know what licenses and certifications are required to do business in The District

• Be able to prepare bids for construction of bioretention cells

• Know the proper construction sequence for bioretention cells

• Be able to anticipate and avoid common construction mistakes

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Doing Business in the District

• 30-minute lecture to be given by a guest speaker from DCRA

• Licenses• Certifications• Training

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Bioretention Costs and Bids

• Justification for costs (sources)• Lump sum or line item?

– Confirm certified sources (Agency schedule)– Bond costs– Means™– Recent bids

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Estimating Materials Costs

• Local sourced credits?• Seasonal• Availability and multiple sources• Damage/breakage/theft?• FOB?• Labor for handling• Access

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Estimating Crew and Equipment Costs

• Rental/lease/own• Labor certification• Training time for equipment• Down time• Weather • Scheduling• Subcontracting

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Preparing Contract Documents

• Terms • Work times• Location of contract disputes• Termination• Weather• Unknown/Unexpected conditions• Subcontracting and transferability• Liability• Punchlist• Closeout• Errors• Negotiations of extras

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Permitting

• Permits are needed to occupy and construct in the public ROW:– Occupancy permit

• Apply in TOPS (Transportation Online Permit System https://tops.ddot.dc.gov/ )

• Issued by the DDOT Public Space Permit Office  • If a DDOT contractor is doing maintenance or construction in

the ROW, the DDOT project manager can set up a contract record to facilitate a no-cost occupancy permit in TOPS.  

– Building permit• Issued by DCRA• Includes Soil Erosion and Sediment Control and Stormwater

Management Plans, if needed 

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Working with Site Plans

Plans Courtesy of the Low Impact Development Center, Inc.

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Interpreting a Legend

Plans Courtesy of the Low Impact Development Center, Inc.

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Understanding Scale in Plan View

Plans Courtesy of the Low Impact Development Center, Inc.

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Using an Engineering Scale

• Plans will specify the scale at which they are drawn

• An engineer’s scale can be used to measure distances

• Use the side of the scale corresponding to the specified drawing scale

• Markings on the scale show distances in feet• Caution: make sure you are using an

engineering scale, NOT an architecture scale!

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Reading Topographic Lines

Plans Courtesy of the Low Impact Development Center, Inc.

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Reading Topographic Markings

• Grading plans will show both existing and planned topography

• Elevations of contour lines are printed on the lines and are given in feet above sea level

• Elevations between contour lines remain between the elevations of the bounding contour lines

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Reading a landscape plan

Plans Courtesy of the Low Impact Development Center, Inc.

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Understanding plant schedules

Plans Courtesy of the Low Impact Development Center, Inc.

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Working with Specifications

• Material specifications for bioretention cells are specific and detailed

• They must be adhered to as closely as possible

• If substitutions are necessary, they should be cleared by an engineer

• Unapproved material substitutions are a common cause of bioretention failure

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Bioretention media

• Bioretention media used in DDOT projects should be mixed offsite by the soil supplier, NOT by the contractor

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Construction

• Notifications• Maintenance of Traffic• Coordination with Prime or other subs• Briefings and reporting• Inspection• Documentation• Closeout/Punchlist

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Notifications

• DDOE• Miss Utility / District One Call• DDOT if working in the right-of-way

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Inspections

• The approved SWMP will contain a construction inspection schedule, which specifies the stages of construction at which DDOE will conduct inspections

• Work cannot proceed past the stage of construction triggering an inspection until DDOE has inspected and approved the work done

• Section 5.2 of the Guidebook contains detailed instructions for scheduling and conducting inspections

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Inspections

• In general, inspections are usually required:– Before construction begins– During infiltration tests– After construction of temporary sediment

controls and drainage– After excavation to subgrade– During installation of underdrains and

standpipes– After construction is completed

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Crew and Equipment Selection

• Level of supervision• Skillset and overlap of skills• Equipment malfunctions/substitutes• Location and availability of equipment• Mobilization

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Crew Training

• Safety• Reporting and documentation• Sequencing• Observation/inspection• Interaction with public and client

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Mobilization and Storage

• Hazardous materials• Storage requirements and location (e.g.

watering, covering..)• Mobilization area• Work times• Coordination with other contractors• Utility notification

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Construction Sequencing

• Pre-construction inspection and documentation

• Utility coordination• Notifications• Mobilization• Construction and inspection• Punch list• Closeout

Slide 31Photos Courtesy of The Low Impact Development Center

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Step 1

• Stabilize the entire contributing drainage area, preferably with vegetation

• Have utilities mark locations of existing lines

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District One Call (Miss Utility)

• http://www.missutility.net/washingtondc/ or call 811

• Allow 2 business days for utilities to be marked

• Hand digging required within 18 inches of marked utilities

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Understanding Utility Markings

• There is a uniform color code for marking underground utility lines, which is consistent across the country

Proposed Excavation

Temporary Survey Markings

Electric Power Lines, Cables, Conduit and Lighting Cables

Gas, Oil, Steam, Petroleum or Gaseous Materials

Communication, Alarm or Signal Lines, Cables or Conduit

Potable Water

Reclaimed Water, Irrigation and Slurry Lines

Sewer and Drain Lines

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Step 2

• Pre-construction meeting– Designer, installer, and DDOE inspector– DDOE inspector with check that the

boundaries of the drainage area and inlet elevations conform to the original design

– Submit material certifications for aggregate, soil media, and geotextiles

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Step 3

• Install temporary erosion and sediment controls to divert stormwater during construction

Photo Courtesy of DDOT

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Maintenance of Traffic

• Identify a qualified safety officer• Determine need for permits• Traffic Control Devices• Personnel needs – trained Flagger• Call Miss Utility• Notify DDOT 48 hours before work is to

begin

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Maintenance of Traffic

• Notify neighbors of parking restrictions• Repair any damage that occurs during

operations at the site• Refer to the DDOT Work Zone Temporary

Traffic Control Manual for detailed information

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Maintenance of Traffic

• Traffic is to be guided clearly and safely around the work zone

• Traffic includes vehicles, bicycles and pedestrians

• Review the “Daily Checklist for Temporary Traffic Control” found in the DDOT manual

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Maintenance of Traffic

• The safety officer is responsible for ensuring the safety of the area

• The safety officer is authorized to halt work should a problem or deficiency occur

• All traffic control devices must be removed once work is complete

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Maintenance of Traffic

• Pedestrian safety includes:– Signs and other devices to guide pedestrians

around the work area– Notify neighboring properties in advance– Maintain access to businesses– Maintain access for handicapped individuals– Pedestrians are to be protected

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Step 4

• Excavate pretreatment cells, if applicable

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Step 5

• Excavate the bioretention cell• Work from the sides; do not allow heavy

equipment within the bioretention cell

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Step 6

• Rip bottom soils to 6-12 inch depth if necessary

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Step 7

• Place filter fabric, if specified, on sides of bioretention cell. Overlap sides by 6 inches.

• Place stone for storage layer, perforated underdrain pipe, stone diaphragm, choking layer, and permeable geotextile layers as specified.

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Step 8

• Place approved bioretention media• Apply in 12-inch lifts to desired top

elevation• Allow media to settle for a few days, then

add media as needed

• Add media in 12” lifts

• Thoroughly wet and allow soil to drain

• Make sure the media is at specified height below overflow

Bioretention: Media Placement

Photo Courtesy of the Low Impact Development Center, Inc.

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Step 9

• Install trees and shrubs• Follow the planting plan!• Install temporary irrigation, if used

Slide 49

• Follow the landscaping plan

• Incorporate the plan into maintenance

• Modify plan when plants are added, replaced, or removed

Landscaping Plan

Graphic Courtesy of the Low Impact Development Center, Inc.

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Step 10

• Install surface cover– Mulch to 3” depth– River stone at inlet, if specified

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Step 11

• Install herbaceous plant materials• Follow the planting plan!• Water as needed for the first two months

of establishment

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Step 12

• Once drainage area and side slopes have good vegetative cover, unblock any blocked curb cuts or inlets, and remove erosion controls

Keep Erosion Controls in Place Until Drainage Area is Stabilized

Irving St Images

P5240081 &

P4260061

Photos Courtesy of the Low Impact Development Center, Inc.

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Step 13

• Conduct final construction inspection• Provide as-built certification to DDOE• Submit GPS coordinates for each

bioretention facility to DDOE for entry into their maintenance tracking database

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Photo Courtesy of NC Cooperative Extension, NC State University

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Photo Courtesy of NC Cooperative Extension, NC State University

57Photo Courtesy of NC Cooperative Extension, NC State University

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Photo Courtesy of NC Cooperative Extension, NC State University

59Photo Courtesy of NC State BAE Stormwater Engineering Group

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Photo Courtesy of NC State BAE Stormwater Engineering Group

61Photo Courtesy of NC Cooperative Extension, NC State University

62Photo Courtesy of NC Cooperative Extension, NC State University

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Photo Courtesy of NC Cooperative Extension, NC State University

64Photo Courtesy of NC Cooperative Extension, NC State University

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Photo Courtesy of NC Cooperative Extension, NC State University

66Photo Courtesy of NC Cooperative Extension, NC State University

9,000 ft2 Drainage Area

Rain Garden(1,500 ft2)

Photo Courtesy of NC Cooperative Extension, NC State University

68Photo Courtesy of NC Cooperative Extension, NC State University

69Photo Courtesy of NC Cooperative Extension, NC State University

70Photo Courtesy of NC Cooperative Extension, NC State University

71Photo Courtesy of NC Cooperative Extension, NC State University

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Principal (Mrs. Greene)

Photo Courtesy of NC Cooperative Extension, NC State University

73Photo Courtesy of NC Cooperative Extension, NC State University

74Photo Courtesy of NC Cooperative Extension, NC State University

Common Construction Errors

Inadequate Erosion Control or Protection of BMP Areas

Photo Courtesy of the Low Impact Development Center, Inc.

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Keep Erosion Controls in Place Until Drainage Area is Stabilized

Irving St Images

P5240081 &

P4260061

Photos Courtesy of the Low Impact Development Center, Inc.

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Unapproved Material Substitutions

Photo Courtesy of the Low Impact Development Center, Inc.

Plant Density

Plant Location

Photos Courtesy of the Low Impact Development Center, Inc. 79

80Photo Courtesy of the Low Impact Development Center, Inc.

81Photos Courtesy of the Low Impact Development Center, Inc.

Improper Pooling Depth & Drainage

Photos Courtesy of the Low Impact Development Center, Inc. 82

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Incorrect grading

• Lack of curb cuts• Compaction sequencing and

documentation• “Rogue” materials• Incorrect slopes• Incorrect equiptment

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Resolving Issues and Challenges

• Contract terms• Document, Document, Document• Scheduling Impacts• Adjustments

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Demobilization

• Timing of equipment removal and labor• Punch lists• Documentation• Closeout procedures• Suggest follow up visit and notification

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Reporting and Records

• Materials receipts and certifications• Procedures for omissions and

substitutions• Organization of pictures, as-builts, and

logs• Labor use and timesheets• Subcontractors

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Review

• There is no such thing as to much documentation

• Create a checklist for each project• Conduct basic training project overview for

each crew• Document any potential conflict or problem• Follow up with client and make

recommendations on how to improve projects

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Resources

• Miss Utility Damage Prevention Guide http://www.missutility.net/pdfs/2011DamagePreventionGuide.pdf

• Low Impact Development (LID) Construction and Maintenance Guidance Manual, Version 1.0. DDOE. 2009. (http://ddoe.dc.gov/riversmarthomes)

• 2013 District of Columbia Stormwater Management Guidebook (http://ddoe.dc.gov/swregs)