Overview
This section involves the re-establishment of vegetation in order to reduce erosion. It is also important to restore yards and parkways for beautification proposes.
Contract Documents
The first task is to learn the specifications for the project being inspected - whether the specifications are APWA, MoDOT, or project specific. The Inspector shall become knowledgeable on the specifications and contract documents prior to seeding or sodding.
Review the plans to become familiar with the scope of work. Verify quantities to ensure consistency between the plans and bid tabs.
Review the Measurement & Payment Section of Division 1 General Requirements to determine how the item is to be paid and to determine the work included in this pay item.
Review the Specifications, Codes and Standards Section of Division 1 General
Requirements to determine the specifications that govern this work.
Review the Technical Specifications, Project Special Provisions and Addendums to confirm that current contract requirements are being adhered-to.
Submittals
Contact Testing Lab – locate and notify a soil testing lab to set-up soil testing if the contract so states or if soils are questionable.
Review Submittals and Certifications – submittals and certifications are typically required for seed, mulch, plants and sod. Obtain seed, mulch, plant, and sod certifications; verify the certifications are legitimate and accurate. Tickets for seed, mulch, plants, and sod shall be collected. Get a letter from the seed, mulch, plant, and sod supplier verifying the seed, mulch, plants, and sod delivered to the project are per specifications. Verify the accuracy of pertinent submittals and certifications.
Field Observations
Verify installation and materials; document work in field book - verify and document proper seeding procedures. A guide for seeding protocol follows.
Collect all seed bag tickets and fertilizer tickets to both check for content as well as quantity to verify actual amounts of product per measured area.
Mulch shall also have a delivery ticket to insure the tons per acre amounts. Specifications typically require straw, not hay, as hay has undesirable weed seed and clover. Prohibit the use of hay as mulch.
Seeding
Seed Bed Preparation - prior to seeding, consult with a qualified professional to determine or verify the correctness of the prescribed plant materials (seed mix) and seeding rates. On Capital Improvement Project (CIP) sites, use plant materials and seeding rates contained in the specifications and contract documents. On development sites, refer to site plans. Consult with a qualified design professional if design specifications for seed mix, seeding dates, or mulching can’t be met. Use substitutions when required, per the professional’s recommendations. If specifications or plans do not specify dates or seasons for the prescribed seeding system(s), consult with a qualified professional. If the seeding system is prohibited in the present season, choose a species or mixture from the Design and Construction Manual Sections 2153 or 2400
To ensure vigorous and continual growth, add lime and fertilizer amendments to the soil. Successful vegetation is directly dependent on nutrients contained in the soil. Take soil tests to determine lime and fertilizer rates. For the soil tests, collect soil samples from the top 6 inches of each area to be seeded. Submit soil samples to a soil testing lab for liming and fertilizer recommendations. Add lime when pH is less than 5.3. Subsoil will likely require added nutrients to ensure growth. Refer to the soil test for guidance for the amount and types of fertilizer to apply for optimum plant growth.
A general recommendation for temporary seeding is to broadcast 90 lbs. of actual N-P-K per acre for areas receiving > 30 inches of annual precipitation, and 50# of N-P-K in areas receiving < 30 in.
For permanent seeding, apply a complete fertilizer at rates recommended by soil tests or as specified in the design plan. In the absence of soil tests, use the following as a guide:
Cool Season Grasses:
Apply 90-90-90 N-P-K if rainfall exceeds 30 inches per year.
Apply 50-50-50 N-P-K if rainfall is less than 30 inches per year.
Cool Season Grass/Legume Mixtures:
Apply 60-90-90 N-P-K.
Warm Season Grasses:
Apply 0-60-30 N-P-K
Cool/Warm Season Grass Mixtures:
Apply 30-60-30 N-P-K
Fertilizer can be blended to meet exact fertilizer recommendations. Take soil test recommendations to local fertilizer dealer for bulk fertilizer blends. This may be more economical than bagged fertilizer.
Incorporate fertilizer and lime 3 to 6 inches into the soil.
Loosen soil to a depth of three inches for broadcast seeding or drilling. If compacted, loosen soils for no till drilling. Avoid seeding in excessively wet soil. For no-till drilling, the surface does not need to be loosened unless the surface is too compact. Use a disk, ripper, chisel, harrow, or other till equipment to loosen the surface.
Grade soil to a smooth firm surface to enhance rooting of seedlings and to reduce erosion.
Ensure seed quality – use certified seed, tested within the past nine months. Use high quality seed. If uncertified seed is used, use the highest recommended seeding rate.
Refer to the Design and Construction Manual Section 2153 or 2400 to determine plant species and application rates. If plant species and application rates are specified in approved plans, follow the approved plans. On CIP projects, refer to construction specifications and plans.
Apply seed evenly with a broadcast seeder, drill, cultipacker seeder, or hydroseeder. Plant small grains no more than 1.5 inches deep. Plant grasses and legumes no more than 0.5 inches deep.
After seeding and prior to mulching, incorporate the seed into the seed bed to ensure germination. To accomplish this, use a harrow, or rake, or drag the surface with a section of chain-link fence. On bare soils, firm lightly with a roller or cultipacker.
After seeding, verify the entire ground surface has been covered with mulching materials. Maximum depth for mulch is 2 inches. Mulching is necessary to conserve moisture and prevent erosion. Evenly cover the ground surface with mulch material. Use the material specified in the specifications and contract documents (CIP) or site plans (development projects). If a type of mulch material has not been specified, refer to Design and Construction Manual Sections 2153.6 and 5103.5. Which states the timely placement of erosion resistant cover reduces erosion on areas where grading has ceased. Approved nonliving cover is effective immediately. Seeded areas need protection during the establishment period. Mulches provide immediate erosion protection and a hospitable micro-environment for seed germination. If the slopes are long, then seeded areas need devices that will interrupt and redistribute the flow across the slope.
Tack down the mulch.
Inspect seeded areas two weeks after seeding for vegetation establishment. Stands of vegetation should be uniform and dense. Fertilize, reseed and mulch bare and sparse areas immediately.
Problems:
Inadequate seedbed preparation - causes poor seedling emergence and growth – repair gullies, prepare seedbed, fertilize, lime (if necessary), mulch and re-seed.
Unsuitable choice of plant materials; resulting in poor germination or inadequate stand (less than 70% of ground surface covered) – choose plant materials appropriate for season, prepare seedbed and replant.
Inadequate mulching - resulting in poor or spotty stands – cover area evenly and tack or tie down mulch properly, especially critical on slopes, ridges and in channels.
Lack of nitrogen; causes poor plant vigor, lack of color and short height – add 50# of nitrogen fertilizer per acre. Do not apply over the top of existing plants from June 1 to Aug. 15 or on frozen ground.
Drying plants - usually caused by soil compaction that limits root growth and water availability to plants – loosen soil if reseeding is necessary or before seeding permanent vegetation.
Sodding
A guide for Sodding protocol follows.
Prior to start of installation, plant materials and amendments should be specified by a qualified professional. Plans and specifications should be referred to by the inspector and other field personnel throughout the installation process.
Use high quality, healthy, moist, fresh sod.
Soil supplied nutrients are critical to sod establishment and continued plant growth. Test soil for nutrients and pH. Soil testing can be done at University extension offices and private labs.
Apply amendments according to soil test recommendations. In the absence of a soil analysis, apply fertilizer amendments at the following maximum rates:
Fertilizer:
90-90-90 N-P-K per acre, or consult a sod expert
Apply ground agricultural limestone unless a soil test shows a pH of 6.0 or greater. If soil test recommendations are not available and soil pH is < 6.0, use:
Ground agricultural limestone: 20 lbs Equivalent Neutralizing Material (ENM)/1000 sq. ft., or 800 lbs ENM/acre
Incorporate amendments to depth of 4 to 6 inches with a disk or chisel plow.
Rake or harrow to achieve a smooth final grade on which to lay the sod. Surface should be loose, and free of plants, trash, and other debris.
Do not lay sod on frozen ground.
During high temperatures, moisten the soil immediately prior to laying sod. This cools the soil and reduces root burning and dieback.
Lay the first row of sod in a straight line with subsequent rows placed parallel to and butting tightly against each other. Stagger joints to create a brick-like pattern and to promote more uniform growth and strength. Ensure that sod is not stretched or overlapped and that all joints are butted tight to prevent spaces which would cause drying of the roots.
On slopes 3:1 or steeper, or wherever erosion may be a problem, lay sod with staggered joints and secure by stapling or pegging. Install sod with the length perpendicular to the water flow (on the contour).
Immediately after laying the sod, roll or tamp it to provide firm contact between the roots and soil, then irrigate sod deeply so that the underside of the sod pad and the soil 4 inches below the sod is thoroughly wet.
Until a good root system develops, water sod during dry periods as often as necessary to maintain moist soil to a depth of at least 4 inches.
Wait until the sod is firmly rooted before mowing for the first time, usually 2 to 3 weeks. Not more than 1/3 of the grass leaf should be removed at any one cutting.
Sodded Waterways
Sod provides quicker protection than seeding and may reduce the risk of early washout unless fiber blankets are used.
When installing sod in waterways, use the type of sod specified in the channel design.
Lay sod strips perpendicular to the direction of water flow, and staggered in a brick-like pattern.
Staple firmly at the corners and middle of each strip. Jute or synthetic netting may be pegged over the sod for further protection against washout during establishment.
Check materials and installation for compliance with specifications.
Consult with a qualified design professional if variations in topography on site indicate the sodding materials will not function as intended; changes in plan may be needed.
Consult with a qualified design professional if design specifications for sod variety cannot be met or irrigation is not possible; substitution or seeding may be required. Unapproved substitutions could result in erosion or sod failure.
Maintenance
Keep sod moist until it is fully rooted.
Mow to a height of 2 to 3 inches after sod is well-rooted. Do not remove more than 1/3 of the leaf blade in any mowing.
Permanent, fine turf areas require yearly fertilization. Fertilize warm-season grass in late spring to early summer; cool-season grass in late winter and again in early fall.
Documentation
Collect seed bag tickets and fertilizer bag tickets to check for content as well as quantity and to verify actual amounts of product per measured area.
Delivery tickets for seed, mulch, plants, and sod shall be collected.
Obtain seed, mulch, plant, and sod certifications; verify those certifications are legitimate and accurate.
Get a letter from the seed, mulch, plant, and sod suppliers. The letter shall verify the seed, mulch, plants, and sod meet project specifications.
Measure seed, mulch, and sod by wheel or cross section to document areas that have been restored.
Count plants and identify plants - verify quantity and species are correct. Verify locations for plants are correct.
Write down dates and times of watering sod. Get meter readings from the contractor as they meter the water used. Record the amount of water used.
Common Problems:
Sod laid on poorly prepared soil or unsuitable surface; grass dies because it is unable to root – remove dead sod, prepare surface and re-sod.
Sod not adequately irrigated after installation; may cause root die-back or grass does not root rapidly and is subject to drying out – irrigate sod and underlying soil to a depth of 4 inches and keep moist until roots are established.
Sod not anchored properly; may be loosened by runoff – replace damaged areas and anchor sod.
Slow growth due to lack of nitrogen; may cause yellowing of leaf blades – re-fertilize sod, but avoid fertilizing cool season grasses from late May through July.