Category:805 Seeding

Design Guidance for Sec 805

805.1.1 Description

MoDOT is obligated to stabilize disturbed areas with permanent building materials or perennial vegetative cover to minimize erosion and sedimentation of disturbed areas as outlined in the current Missouri State Operating Permit for land disturbance. Vegetative cover helps slow down sheet flow runoff and promote infiltration, reduce pollutant loading of runoff, and stabilize slopes to improve the integratory of the roadway template.

805.1.2 Seed Mixes

As outlined in Sec 805, it is MoDOT’s intention to plant cool season and warm season grasses within the right-of-way. Cool season grasses provide a dense stand of grasses in a reduced time over warm season grasses. Cool season mixes grow better in the early spring and late fall when soil and air temperatures are cooler. Warm season grasses take a bit longer to establish growth, but they provide deep root systems that require less moisture, fertilizer, and pesticides.

Job special provisions will no longer be required for seeding mixes. Standard seed mixes, fertilizer, and lime rates have been developed and can be found in the Standard Plans based on soil type regions throughout the state. Projects shall be developed following the standard seed mixes, fertilizer, and lime rates shown in the standard plan. When designing large corridor projects, the Roadside Management Specialist, Maintenance, (573) 751-8647, should be contacted for consideration to refine fertilizer and lime rates as well as if any changes to the standard seed mixes are necessary.

805.1.3 Planned Quantities

When developing quantities for cool and warm season grasses, the intended objective is to provide a landscape that supports MoDOT’s mowing policy. MoDOT Roadside Vegetative Management policy can be found in EPG 822 Roadside Vegetation Management.

Seeding quantities for major road shall be computed based on the following:

• Cool season mixes shall be planted in the first 30 feet from the travel way;
• Medians narrower than 60 feet shall be planted in cool season grasses.
• Warm season grasses shall be planted beyond 30 feet from the travel way;
• Medians wider than 60 feet shall be planted with cool season grasses 20 feet from the travel way and warm season grasses within the remaining median.

Seeding quantities for minor roads shall be computed based on the following:

• Cool season grasses shall be placed from the edge of pavement or shoulder to the back of the ditch.
• Warm season grasses shall be placed in backslope areas to the right-of-way.

Maintenance Roadside Management Specialist shall be consulted if alternate seeding configurations are considered.

Temporary seeding should be set up for all grading projects as outlined in EPG 806.1.7 Temporary Seeding.

805.1.4 Design Considerations for Seeding

Seeding operations are typically the last operation a contractor completes on a project. The critical component of opening a road to traffic as quickly as possible is still desirable but final project closeout requires the project to obtain final stabilization among other obligations. When native grasses will be placed on a project, completion dates need to take in to account the warm season grass planting season outlined in Sec 805. The specifications include a provision for projects that will not be able to complete seeding within the contract completion date due to the planting season, but accounting for seeding when setting completion dates will eliminate potential risk for the contractor that may be reflected in the bid. Relying on the exception in the specifications should not be a default approach to addressing seeding and mulch operations and completion dates but an exception to extenuating circumstances within the project.

805.2 Construction Inspection Guidance for Sec 805

805.2.1 Description (Sec 805.1)

This work shall consist of furnishing and sowing seed as specified in the contract. Areas to be seeded include earth shoulders, medians, and the entire roadway outside of the roadbed limits, excluding sodded areas, surfaced areas, solid rock, and rock fill slopes consisting primarily of broken rock. The standard plans specify the seeding mixture and the rate of application. The areas to be seeded will be shown in the plans in acres. The seeding item includes the cost for fertilizing and liming. Mulch will be paid for by the acre in accordance with Sec 802.

805.2.2 Material (Sec 805.2)

Seeds shall be grown and processed in the United States or Canada and must comply with requirements of Missouri state laws. These laws require that each container of agricultural seeds bear a plainly written or printed label, or tag, giving certain information which includes lot number, percent pure seed, percent germination, percent hard seed, etc. Local ecotype native seeds adaptive to grow in Missouri should be used when available. Planting with local ecotypes varieties increases the likelihood that plants will survive and thrive in the local climate. When local ecotypes are not available, this should be documented by the contractor and submitted to the RE with a recommended alternative variety.

The contractor shall provide a certification with the lot number, percent pure seed, percent germination, percent hard seed, etc. prior to applying seed on the project. Certification should carry a statement to the following effect, "This seed is certified to meet all requirements of the Missouri Standard Specifications for Highway Construction." If the seed for the project is mixed prior to arriving on the project, the contractor shall certify the seed mix proportions comply with contract requirements and shall present the required documentation for the inspector in the field.

In addition to requirements of Missouri Seed Law, the specifications list minimum percentages of purity and germination, which govern unless otherwise permitted by the engineer. Intent of this specification is that seed will not be furnished with less than the percent purity and/ or germination required. Standard seed mixes have been developed with permissible additional seed species that may be added to the standard mix at the option of the contractor for no additional pay. Requests may be received to modify the standard seed mixes, in such cases, the resident engineer should consult with the Roadside Management Specialist, Maintenance, (573) 751-8647, for approval and revised application rates. Additional consideration may be necessary if requests are submitted for permission to apply increased quantities of seed deficient in purity and/or germination to compensate for deviation from the specification. The Roadside Management Specialist should be consulted for approval and revised application rates. This procedure will not normally be allowed as it is intended that the contractor furnish seed of specified quality. If approval is granted, the revised rate will not give credit for any excess purity and/or germination that may exist.

Under no condition is approval to be given to reduce specified amounts of seed per acre even if certification and test results indicate purity and/or germination greater than minimums specified.

Stored seed should be protected from moisture, heat, and rodents.

805.2.3 Construction Requirements (Sec 805.3)

The seedbed shall be prepared in accordance with Sec 801. The seeding operation follows after lime and fertilizer has been applied to the soil. Before lime, fertilizer, and seed application, the seedbed should be inspected to determine that soil conditions conform to intent of the specifications. Seed should not be applied to eroded, dry, crusted, or frozen soil. Soil with high silt or clay content may crust over following a light shower and deter proper seed application. Soil should be firm, but uncompacted, with a relatively fine texture. Ground preparation when soil is so wet that it clings to equipment is not only impractical but unsatisfactory because soil is not being broken down into fine particles. Preparation when soil is frozen is undesirable for the same reason.

Sowing

Grass mixes, fertilizer, and lime rates shall be based on the zone indicated in the standard plan for seeding (Std. Plan 805.00) in which the project falls. It is the contractor’s responsibility to ensure vegetative growth. Projects that fall in multiple zones should follow the recommended fertilizer and lime rates for that zone.

Cool Season Grasses – The preferred time to seed cool season grasses is outlined in Sec 805.3. Full seeding periods include the months of December through May, August, and September. During these months, all lime, fertilizer, seed, and mulch shall be applied. When seeding of cool season grasses occurs during the months of June, July, October, or November, partial fertilizer and seed shall be applied at the rates specified in Sec 805.3. Overseeding, to include the specified rates of seed and fertilizer, shall be applied during the months of August, September, December, January, or February. Lime will be applied at the full rate during the initial installation and will not require additional application at the time of overseeding. Likewise, additional mulch will not be required for overseeding, unless there are bare spots that require correction, as directed by the engineer. No additional payment for mulch will be made for any areas of correction.

Warm Season Grasses – Seeding of warm season grasses shall only occur during the period of October 15 through April 15 both dates inclusive. Temporary stabilization efforts necessary to comply with the statewide operating permit for land disturbance from April 16 through October 14 shall be done with temporary seeding in accordance with Sec 806.50 and 100 percent of the necessary lime for the permanent seed application. The temporary seeded areas shall be overseeded with warm season grasses during the next October through April seeding period at the full rate specified for seed and fertilizer in the standard plans. It is not necessary that additional lime be applied. Mulching will not be required in overseeded areas unless areas lack temporary vegetation or original mulch is no longer adequately covering the ground.

This is a performance-based specification; therefore, it is the contractor's responsibility to furnish materials in quantities according to areas and rates specified. The seeding is to be applied at no less than the rates specified in the contract. The inspector's count of number and weight of bags of seed used is part of the inspector's record for approving partial payment for areas completed. The inspector must document when an area is seeded as acceptance is made within 60 days of seeding.

It is usually necessary to mix seed on the project in proportions to provide the proper amount of each seed per acre. The inspector should carefully observe mixing operations to be sure a thorough blend is obtained.

Various methods of sowing are available to the contractor. Each has their advantages and disadvantages. The inspector should note the method used in a diary or daily work report.

Dry Seeding

Broadcast distribution of dry seed is affected by winds. Drills may be used without regard to wind. Normally, a drill operating in one direction produces satisfactory distribution of seeds. Drills have a tendency to place seed too deep. Mechanical seeders should produce satisfactory coverage when operated in one direction only. When seeding is by hand or by mechanical hand seeder, in order to obtain desirable seed distribution, it should be done in two directions, at right angles to each other. Raking, or other approved method, covers the seed to a desirable depth. Care should be taken to preserve proper seed distribution. Seed may also be sufficiently covered by dragging brush, chain, or timber over the seeded area if soil is loose and easily pulverized at the surface, particularly if fine seeds have been sown.

Hydraulic Seeding

Hydraulic application is done by what is frequently called the "slurry method". On slopes steeper than 2 to 1 fertilizer and seed may be mixed with water and sprayed on the area in one application. On other slopes seed and fertilizer are applied separately. No seed should be applied which has been mixed with water for more than 4 hours as germination may be effected.

Application Rate

Minimum application rates are required by the standard plans and applicable JSPs in the contract, based on the location of the project. Rate of seeding should be checked as soon as possible after beginning operations, and frequently thereafter by comparing areas seeded with the measured quantity of seed used. Area dimensions, type of seed, and quantities applied should be recorded in the diary or daily work report.

805.2.4 Acceptance (Sec 805.4)

Acceptance of permanent seeding is based on the final stabilization requirements as specified in the current state operating permit for land disturbance. The current permit requires that vegetative cover to be at least 70% perennial plant density over 100% of the disturbed area.

In order to obtain the permanent vegetation desired, job seed mixtures are tailored for the region. Standard seed mixes, fertilizer, and lime rates have been developed and can be found in the Standard Plans based on soil type regions throughout the state. Initial plant growth typically will be from the annual seeds included in the mix. Competition from annual cover crop species can affect the success of permanent vegetative establishment. For this reason, the contractor should not be allowed to increase the percentage of the annual cover crop seeds in the mix above what is allowed in the seed mixes. The contractor shall only use acceptable additional seed species unless approved by the engineer and the Maintenance Roadside Manager.

Inspection for acceptance is dependent on when the seeding occurred (see EPG 805.2.9 Basis of Payment for when an evaluation for acceptance should be made). Careful examination is critical to ensure that the vegetative cover is from the permanent seeding mix and not a temporary cover crop or other foreign plant. It may be necessary to ask for assistance from Roadside Management staff in the Maintenance Division if there is a question regarding plant species present. The seed species picture guide is available to assist with general inspection and acceptance of vegetative covers allowed by specification. Documentation of final acceptance should be made for all seeded areas.

Seed acceptance shall be by certification. Certification shall state that seed meets Sec 805 and seed mixture complies with contract requirements and shall be presented to the inspector on the project, prior to application.

Please refer to the example for acceptable form of certification.

805.2.5 Report (Records)

Seed shall be reported through AASHTOWARE Project (AWP). A copy of the certification for the seed is to be retained as part of the project files. The report is to show a Status of Accepted/Complete or Rejected/Fail. Appropriate remarks, as described in EPG 106.20 Reporting, are to be included in the report to clarify conditions of acceptance or rejection. Free form report should be attached to the AWP record with any additional information. The AWP record shall be the responsibility of the project inspection personnel upon incorporation into the project.

Acceptance of sufficient seed growth, shall be noted in AWP in a daily work report. Final seed growth may be listed as an exception on the semi-final inspection.

805.2.6 Time Extension (Sec 805.5)

When seeding operations cannot be completed within the specified contract timeframe due to seeding period limitations, an extension of time can be requested by the contractor. The request shall include a proposed work schedule showing final seeding operations being completed promptly during the next available seeding period. The request must document why the delay is at no fault of the contractor. The extension shall not apply to any other uncompleted work. If approved, time extensions are to be granted without assessment of liquidated damages.

805.2.7 Corrective Action (Sec 805.7)

If an area has not been accepted for seeding and erosion exists due to the lack of ground cover, the contractor will be responsible for the repair. Cost to repair erosion from sheet and rill flow is the contractor’s responsibility. In the event gulley erosion results from linear flow drainage from outside the construction area, the resident engineer should authorize payment to the contractor to make the necessary repairs.

805.2.8 Method of Measurement (Sec 805.8)

Follow the specification.

805.2.9 Basis of Payment (Sec 805.9)

After full seeding has been applied on a properly prepared seed bed, and all applicable material certifications have been received (for example, certifications for seed, lime, fertilizer, etc.), a partial payment of 80% should be made unless additional withholding is justified. If cool season seeding is applied during the partial seeding period, where 50% of the specified rate is applied to the seeded area, a partial payment of 40% should be made. An additional 40% shall be paid upon overseeding of those areas. The balance of the payment due should be withheld until final stabilization has been achieved in accordance with the state operating permit for land disturbance, and as follows:

For cool season grasses applied during the full seeding period from March 1 through May 31 and August 1 through September 30, the engineer’s initial evaluation for acceptance should occur between 45 and 60 days from the date the seed was applied, but no later than 60 days. A notification of the results of the evaluation shall be promptly submitted to the contractor so that any re-seeding work can be scheduled.

For cool season grasses applied during the partial seeding period from June 1 through July 31 and October 1 through November 30, the engineer’s initial evaluation for acceptance shall not be made until overseeding during the specified timeframe is performed. Evaluation for acceptance shall be based on the time period of the overseeding, not the partial seeding.

For all warm season grasses and cool season grasses applied during the full seeding periods applied between December 1 and February 28, the engineer’s initial evaluation for acceptance should occur on or shortly after May 1 (for example, May 1-7). A notification of the results of the evaluation shall be promptly submitted to the contractor so that any re-seeding work can be scheduled.

Evaluation of any re-seeding work should be based on the time period of the re-seeding and not the time period of the original seeding.

Where temporary seeding is used for vegetative stabilization in areas where warm season grasses will be placed and 100% of the lime is provided in accordance with Sec 806.50, the contractor may request an initial compensation payment of 10% of the warm season grass bid to compensate the contractor for lime placed.

Repairs

When the engineer waives contractor responsibility for damaged areas, payment for repairing the seedbed and reseeding shall be made as provided in Sec 109.4 of the Standard Specifications.