HomeMy WebLinkAboutWPO202100021 Study 2021-05-12 1992 3.04
STD & SPEC 3.04
STRAW BALE BARRIER STB
Definition
A temporary sediment barrier consisting of a row of entrenched and anchored straw bales.
Purposes
1. To intercept and detain small amounts of sediment from disturbed areas of limited
extent in order to prevent sediment from leaving the construction site.
2. To decrease the velocity of sheet flows.
111
111111444
,., •$ E t ` a _
* • uag�**
•" w , ^r.. , "r
III - 14
1992 3.04
Conditions Where Practice Applies
1. Below disturbed areas subject to sheet and rill erosion.
2. Where the size of the drainage area is no greater than one-fourth of an acre per 100
feet of barrier length; the maximum slope length behind the barrier is 100 feet; and
the maximum slope gradient behind the barrier is 50 percent (2:1).
3. Where effectiveness is required for less than 3 months.
4. Under no circumstances should straw bale barriers be constructed in live streams or
in swales where there is the possibility of a washout.
5. The measure should not be used where water may concentrate in defined ditches and
minor swales.
6. Straw bale barriers shall not be used on areas where rock or another hard surface
prevents the full and uniform anchoring of the barrier.
Planning Considerations
Based on observations made in Virginia, Pennsylvania, Maryland and other parts of the
nation, straw bale barriers have not been as effective as many users had hoped they would
be - especially when used to slow down and filter concentrated flows. They should be used
judiciously and with caution as erosion control measures. There are three major reasons
for such ineffectiveness.
First, improper utilization of straw bale barriers has been a major problem. Straw bale
barriers have been used in streams and drainageways where high water depth and velocities
have destroyed or damaged the control. Secondly, improper placement and installation of
the barriers, such as staking the bales directly to the ground with no soil seal or
entrenchment, has allowed undercutting and end flow. This has resulted in additions of,
rather than removal of, sediment from runoff waters. Finally, inadequate maintenance
lowers the effectiveness of these barriers. Trapping efficiencies of carefully installed straw
bale barriers on one project in Virginia dropped from 57% to 16% in one month due to
lack of maintenance.
There are serious questions about the continued use of straw bale barriers as they are
presently installed and maintained. Averaging from $3 to $6 per linear foot, the thousands
of straw bale barriers used annually in Virginia represent such a considerable expense that
optimum installation procedures should be emphasized.
III - 15
•
1992 3.04
Design Criteria
A formal design is not required. However, an effort should be made to locate the straw
bale barrier, as well as other perimeter controls, at least 5 to 7 feet from the base of
disturbed slopes with grades greater than 7%. This will help prevent the measure from
being rendered useless following the initial movement of soil.
Construction Specifications
Sheet Flow Application
1. Bales shall be placed in a single row, lengthwise _on the contour, with ends of
adjacent bales tightly abutting one another.
2. All bales shall be either wire-bound or string-tied. Straw bales shall be installed so
that bindings are oriented around the sides rather than along the tops and bottoms •
of the bales in order to prevent deterioration of the bindings (see Plate 3.04-1).
3. The barrier shall be entrenched and backfilled. A trench shall be excavated the
width of a bale and the length of the proposed barrier to a minimum depth of 4
inches. After the bales are staked and chinked (gaps filled by wedging), the
excavated soil shall be backfilled against the barrier. Backfill soil shall conform to
the ground level on the downhill side and shall be built up to 4 inches against the
uphill side of the barrier (see Plate 3.04-1).
4. Each bale shall be securely anchored by at least two stakes (minimum dimensions
2 inches x 2 inches x 36 inches) or standard 'T' or "U" steel posts (minimum weight
of 1.33 pounds per linear foot) driven through the bale. The first stake or steel post
in each bale shall be driven toward the previously laid bale to force the bales
together. Stakes or steel pickets shall be driven a minimum 18 inches deep into the
ground to securely anchor the bales.
5. The gaps between bales shall be chinked (filled by wedging) with straw to prevent
water from escaping between the bales. Loose straw scattered over the area
immediately uphill from a straw bale barrier tends to increase barrier efficiency.
6. Inspection shall be frequent and repair or replacement shall be made promptly as
needed.
7. Straw bale barriers shall be removed when they have served their usefulness, but not
before the upslope areas have been permanently stabilized.
III - 16
1992 3.04
Maintenance
1. Straw bale barriers shall be inspected immediately after each rainfall and at least
daily during prolonged rainfall.
2. Close attention shall be paid to the repair of damaged bales, end runs and
undercutting beneath bales.
3. Necessary repairs to barriers or replacement of bales shall be accomplished promptly.
4. Sediment deposits should be removed after each rainfall. They must be removed
when the level of deposition reaches approximately one-half the height of the barrier.
5. Any sediment deposits remaining in place after the straw bale barrier is no longer
required shall be dressed to conform to the existing grade, prepared and seeded.
III - 17
1992 3.04
STRAW BALE BARRIER
STAKED AND ENTRENCHED
BINDING WIRE / STRAW BALE
OR TWINE f!/
t COMPACTED SOIL TO
lr` + PREVENT PIPING
q
FILTERED RUNOFF SEDIMENT LADEN
RUNOFF
IIIE ►Hi ill - III I 1 I - -
PROPERLY INSTALLED STRAW BALE
(CROSS SECTION)
1. EXCAVATE THE TRENCH. 2. PLACE AND STAKE STRAW BALES.
ce, ANGLE FIRST STAI{E
TOWARD PREVIOUSLY
p saw y� _. LAID BALE
Nkirift146, \.-",k-"'---',...je ./..i...-
�- �/ a� � �= 1r�il `j III I
ry
FLOW -if- �/ 1► 'f� {1�
�- BALE
WIDTH
Illibli%,,i._ .,i5- i
‘IriStitll,*' -Cfl-:.1filig .**•;- '7- . ;:'..':'MI 41 en 1 P if a III7
AVieltilyglW ''-' ----- ,---- ____.,' ' - ' ,--''
-----� ___114 4. BACKFILL AND COMPACT THE
3. WEDGE LOOSE STRAW BETWEEN BALES. EXCAVATED SOIL.
CONSTRUCTION OF STRAW BALE BARRIER
Source: Va. DSWC Plate 3.04-1
III - 18
1992 3.32
STD & SPEC 3.32
C PERMANENT SEEDING PS
Definition
The establishment of perennial vegetative cover on disturbed areas by planting seed.
Purposes
1. To reduce erosion and decrease sediment yield from disturbed areas.
2. To permanently stabilize disturbed areas in a manner that is economical, adaptable
to site conditions, and allows selection of the most appropriate plant materials.
3. To improve wildlife habitat.
4. To enhance natural beauty. •
•
•
III -289
1992 3.32
Conditions Where Practice Applies
1. Disturbed areas where permanent, long-lived vegetative cover is needed to stabilize
the soil.
2. Rough-graded areas which will not be brought to final grade for a year or more.
Planning Considerations
Vegetation controls erosion by reducing the velocity and the volume of overland flow and
protecting the bare soil surface from raindrop impact.
Areas which must be stabilized after the land has been disturbed require vegetative cover.
The most common and economical means of establishing this cover is by seeding grasses and
legumes. Permanent vegetative covers must meet the requirements of Minimum Standard
#3.
Advantages of seeding over other means of establishing plants include the small initial
establishment cost,the wide variety of grasses and legumes available,low labor requirement,
and ease of establishment in difficult areas.
Disadvantages which must be dealt with are the potential for erosion during the
establishment stage, a need to reseed areas that fail to establish,limited periods during the
year suitable for seeding, the potential need for weed control during the establishment
phase, and a need for water and appropriate climatic conditions during germination.
There are so many variables in plant growth that an end product cannot be guaranteed.
Much can be done in the planning stages to increase the chances for successful seeding.
Selection of the right plant materials for the site, good seedbed preparation, and
conscientious maintenance are important.
SELECTING PLANT MATERIALS: The factors affecting plant growth are climate, soils,
and topography. In Virginia, there are three major physiographic regions that reflect
changes in soil and topography. In selecting appropriate plant materials, one should take
into account the characteristics of the physiographic region in which the project is located
(see Plate 3.32-1).
PHYSIOGRAPHIC REGIONS:
Coastal Plain - Soils on the Coastal Plain are deeply weathered, stratified deposits
of sand and clay. They are generally acidic and low in plant nutrients. The sandy
soils are hot and droughty in summer. This region receives more rain and is warmer
than the other regions of the state. The land is fairly level, and many areas are
poorly drained. Warm season grasses traditionally perform well in these areas.
III - 290
0
n N
. C
P
d
cn
n
'yyttk.
. ,,‘,;,,-‘ : -' -;;;40.4tm"
ihlt \if
• • , . .,.7••• 34,4,r4,,, A.>4.*77)111111/4%
X.:`:: ‘'• . -.A.Yerea...„4,4wate wafi,‘,., 6...
, ),,,,,.3. ),, , , , ev.a.,04,..a.,,,,tor..., imilitskilit
i, ,,,,- -e„ 4 i-or....,,t11440,...452.2r.r'4.-.7,-,4 it
ti tits �. Y[40, I �.
C Njt
„.-., ' • . -.,--;--.•••.,,. ,-„,••.,,':At,,,pg.i.,,c,#row•:iry k.,41 Fiwa,,,, iiiit
,,,,, ,,, ,,, . ,:...... .....,,, ,
,,,.........,„,,......41.,?iff,g....avimp .o.,,, ..,,,;„. ...211,
,,,,„.,:.,:s.,... .. . , , , .,\',' •, • , ‘; .5.,,,N....47„ ..,...;:i
,,
,„ao......, .:, 1 „,....,A1.,
....:: .,..„..,.. ,,,,. ... .,,, ..,...:,,,. .,..„,‘ .,.:,...i.„....,„,,,,..ve ,... ..,.... ..
G.Vcti15t ��C:• R?�'.•5Y>�r .. b ..,,Li- ia i:}T...
APPALACHIAN' PIEDMONT COASTAL PLAIN
b PHYSIO GRAPHIC PROVINCES IN VIRGINIA
w
w
w _ W
N
- w
N
1992 3.32
Piedmont - Soils on the Piedmont plateau are highly variable. They tend to be
shallow, with clayey subsoils. Piedmont soils are low in phosphorus. Soils derived
from mica schist are highly erodible. Topography is rolling and hilly. The southern
Piedmont has much the same climate as the Coastal Plain. Often referred to as the
"transition zone" in planting. Contains areas that will support both warm or cool
season grasses.
Appalachian and Blue Ridge Region - This region is divided into plateaus,
mountains, and narrow valleys. Soils tend to be shallow and acid, and may erode
rapidly on steep slopes. Shaley slopes are often unstable and droughty. This area
is colder and drier than the rest of the State. The rugged topography makes plant
establishment difficult. Cool season grasses are normally specified in this region.
SOILS: On the whole, soils in Virginia always require some nitrogen (N) fertilization to
establish plants. Phosphorus (P) and potassium (K) are usually needed. Except for some
small pockets of shallow limestone soils, lime is universally needed.
Soils can be modified with lime and fertilizer, but climate cannot be controlled. For this
reason, the State has been divided into two major climatic regions, referred to as the
Northern Piedmont and Mountain Region and the Southern Piedmont and Coastal Plain
Region, for grass and legume selection (see map, Plate 3.32-2):
Microclimate, or localized climate conditions,can affect plant growth. A south-facing slope
is drier and hotter than a north-facing slope, and may require drought-tolerant plants. ;.
Shaded areas require shade-tolerant plants; the windward side of a ridge will be drier than
the leeward, etc.
•
LAND USE: A prime consideration in selecting which plants to establish is the intended
use of the land. All of these uses-residential,industrial,commercial,recreational- can be
separated into two major categories: high-maintenance and low-maintenance.
High-maintenance areas will be mowed frequently, limed and fertilized regularly, and will
either receive intense use (e.g., athletics) or require maintaining to an aesthetic standard
(home lawns). Grasses used for these situations must be fine-leaved and attractive in
appearance,able to form tight sod,and be long-lived perennials. They must be well-adapted
to the geographic area where they are planted, because constant mowing puts turf under
great stress. Sites where high-maintenance vegetative cover is desirable include homes,
industrial parks, schools, churches, athletic playing surfaces as well as some recreational
areas.
Low-maintenance areas will be mowed infrequently or not at all;lime and fertilizer may not
be applied on a regular basis; the areas will not be subjected to intense use, nor required
to have a uniform appearance. These plants must be able to persist with little maintenance
over long periods of time. Grass and legume mixtures are favored for these sites because
legumes are capable of fixing nitrogen from the air for their own use, and the use of the
plants around them. Such mixed stands are better able to withstand adverse conditions.
III - 292
1992 3.32
Sites that would be suitable for low-maintenance vegetation include steep slopes, stream or
channel banks, some commercial properties, and "utility turf' areas such as roadbanks.
Seedbed Preparation-The soil on a disturbed site must be modified to provide an optimum
environment for seed germination and seedling growth. The surface soil must be loose
enough for water infiltration and root penetration. The pH (acidity and alkalinity) of the
soil must be such that it is not toxic and nutrients are available,usually between pH 6.0-7.0.
Sufficient nutrients (added as fertilizer) must be present. After seed is in place, it must be
protected with a mulch to hold moisture and modify temperature extremes, and to prevent
erosion while seedlings are growing.
The addition of lime is equally as important as applying fertilizer. Lime is best known as
a pH, or acidity, modifier, but it also supplies calcium and magnesium which are plant
nutrients. Its effect on pH makes other nutrients more available to the plant. It can also
prevent aluminum toxicity by making aluminum less soluble in the soil. Many soils in
Virginia are high in aluminum, which stunts the growth of plant roots.
MAINTENANCE: Even with careful, well-planned seeding operations, failures can occur.
When it is clear that plants have.not germinated on an area or have died, these areas must
be reseeded immediately to prevent erosion damage. However, it is extremely important
to determine for what reason germination did not take place and make any corrective action
necessary prior to reseeding the area. Healthy vegetation is the most effective erosion
control available.
Specifications
Selection of Plant Materials
1. Selection of plant materials is based on climate, topography, soils, land use, and
planting season. To determine which plant materials are best adapted to a specific
site, use Tables 3.32-A and 3.22-B which describe plant characteristics and list
recommended varieties.
2. Appropriate seeding mixtures for various site conditions in Virginia are given in
Tables 3.32-C, 3.32-D and 3.32-E. These mixtures are designed for general use, and
are known to perform well on the sites described. Check Tables 3.32-A and 3.32-B
for recommended varieties.
3. A more extensive description of plant materials (grasses and legumes), their usage
and pictorial representation can be found in Appendix 3.32-c.
4. When using some varieties of turfgrasses,the Virginia Crop Improvement Association
(VCIA) recommended turfgrass mixtures may also-be used. Consumer protection
programs have been devised to identify quality seed of the varieties recommended
by the Virginia Cooperative Extension Service. These will bear a label indicating
III -293
o `;
1.1 G N
a
a
w
b
CD
a
< kS : ,,,Ate\\
,*. x:0 `��:ifi
�.\`•..� Cif' 'd. �>...;�'_�`.c:;.
�' \ \ �> >`. Low Mean Annual
C7 s`` s f�, ? Temperature
'''''',7:','';':,:i.41,
F or
,a\?r \\ ��`�y` Higher
CD
414116
1111119i ' I
''"' go
Low Mean Annual �>' «:...-:' a::� �` : 8
Temperature �,` �ar:;. \?�y;` }a
Lower .,<": •;w.; :x;, }„•' : :
r.;.,..2,Y.:,,s,... :;•:-..-.,,,,,,s..:' 10111111101e1 if
4411160
Nar
,.0 -.:-. ......s.,•.„ ,,,,...--,..1,,o,:-....,7,,,,<.,..,-,..„, s.,,,- .4./,,:„. - qr.
sic\.' ., . •:\c ,`,5�'`':y:y •� `•�; sari
liplippollti,
: :: oli
.� a -:�z:a� `d ,S�r°<ta'ca?aa>a�a":< l
NORTHERN PIEDMONT - SOUTHERN PIEDMONT -
MOUNTAIN REGION COASTAL PLAIN REGION
PLANT HARDINESS ZONES IN VIRGINIA FOR GRASSES AND LEGUMES
b
CD
w (-)'
N N
N
1992 3.32
that they are approved by the Association. Mixtures may be designed for a specific
physiographic region or based on intended use. Special consideration is given to
plant characteristics, performance, etc.
•
•
•
•
•
•
111 - 295
1992 3.32
TABLE 3.32-D
SITE SPECIFIC SEEDING MIXTURES FOR PIEDMONT AREA
Total Lbs.
Per Acre
Minimum_care Lawn
- Commercial or Residential 175-200 lbs.
- Kentucky 31 or Turf-Type Tall Fescue 95-100%
- Improved Perennial Ryegrass 0-5%
- Kentucky Bluegrass 0-5%
High-Maintenance Lawn 200-250 lbs.
- Kentucky 31 or Turf-Type Tall Fescue 100%
General Slope (3:1 or less)
- Kentucky 31 Fescue 128 lbs.
- Red Top Grass 2 lbs.
- Seasonal Nurse Crop * 20 lbs.
• 150 lbs.
Low-Maintenance Slope (Steeper than 3:1)
- Kentucky 31 Fescue 108 lbs.
- Red Top Grass 2 lbs.
- Seasonal Nurse Crop * 20 lbs.
- Crownvetch ** 20 lbs.
150 lbs.
* Use seasonal nurse crop in accordance with seeding dates as stated below:
February 16th through April Annual Rye
May 1st through August 15th Foxtail Millet
August 16th through October Annual Rye
November through February 15th Winter Rye
** Substitute Sericea lespedeza for Crownvetch east of Farmville, Va. (May
through September use hulled Sericea, all other periods, use unhulled Sericea).
If Flatpea is used in lieu of Crownvetch, increase rate to 30 lbs./acre. All legume
seed must be properly inoculated. Weeping Lovegrass may be added to any slope
or low-maintenance mix during warmer seeding periods; add 10-20 lbs./acre in
mixes.
III - 303
1992 3.32
Seedbed Requirements
Vegetation should not be established on slopes that are unsuitable due to inappropriate soil
texture, poor internal structure or internal drainage, volume of overland flow, or excessive
steepness, until measures have been taken to correct these problems.
To maintain a good stand of vegetation, the soil must meet certain minimum requirements
as a growth medium. The existing soil must have these characteristics:
1. Enough fine-grained material to maintain adequate moisture and nutrient supply.
2. Sufficient pore space to permit root penetration. A bulk density of 1.2 to 1.5
indicates that sufficient pore space is present. A fine granular or crumb-like
structure is also favorable.
3. Sufficient depth of soil to provide an adequate root zone. The depth to rock or
impermeable layers such as hardpans shall be 12 inches or more, except on slopes
steeper than 2:1 where the addition of soil is not feasible.
4. A favorable pH range for plant growth. If the soil is so acidic that a pH range of
6.0-7.0 cannot be attained by addition of pH-modifying materials, then the soil is
considered an unsuitable environment for plant roots and further soil modification
would be required.
5. Freedom from toxic amounts of materials harmful to plant growth.
6. Freedom from excessive quantities of roots, branches, large stones, large clods of
earth, or trash of any kind. Clods and stones may be left on slopes steeper than 3:1
if they do not significantly impede good seed soil contact.
If any of the above criteria cannot be met, i.e., if the existing soil is too coarse, dense,
shallow, acidic, or contaminated to foster vegetation, then topsoil shall be applied in
accordance with TOPSOILING, Std. & Spec. 3.30.
Necessary structural erosion and sediment control practices will be installed prior to seeding.
Grading will be carried out according to the approved plan.
Surfaces will be roughened in accordance with SURFACE ROUGHENING, Std. & Spec.
3.29.
Soil Conditioners
•
In order to modify the texture, structure, or drainage characteristics of a soil, the following
materials may be added to the soil:
III - 305
1992 3.32
1. Peat is a very costly conditioner,but works well.If added, it shall be sphagnum moss
peat, hypnum moss peat, reed-sedge peat or peat humus, from fresh-water sources.
Peat shall be shredded and conditioned in storage piles for at least six months after
excavation.
2. Sand shall be clean and free of toxic materials. Sand modification is ineffective
unless you are adding 80 to 90% sand on a volume basis. This is extremely difficult
to do on-site. If this practice is considered, consult a professional authority to ensure
that it is done properly.
3. Vermiculite shall be horticultural grade and free of toxic substances. It is an
impractical modifier for larger acreage due to expense.
4. Raw manure is more commonly used in agricultural applications. However, when
stored properly and allowed to compost, it will stabilize nitrogen and other nutrients.
Manure, in its composted form, is a viable soil conditioner; however, its use should
be based on site-specific recommendations offered by a professional in this field.
5. Thoroughly rotted sawdust shall have 6 pounds of nitrogen added to each cubic yard
and shall be free of stones, sticks, and toxic substances.
6. The use of treated sewage sludge has benefitted from continuing advancements in
its applications in the agricultural community. When composted, it offers an
alternative soil amendment. Limitations include a potentially undesirable pH
(because of lime added during the treatment process) and the possible presence of
heavy metals. This practice should be thoroughly evaluated by a professional and be
used in accordance with any local, state, and federal regulations.
Lime and Fertilizer
Lime and fertilizer needs should be determined by soil tests. Soil tests may be performed
by the Cooperative Extension Service Soil Testing Laboratory at VPI&SU,or by a reputable
commercial laboratory.Information concerning the State Soil Testing Laboratory is available
from county extension agents. Reference Appendix 3.32-d for liming applications (in lbs.)
needed to correct undesirable pH for various soil types.
Under unusual conditions where it is not possible to obtain a soil test, the following soil
amendments will be applied:
Lime
Coastal Plain: 2 tons/acre pulverized agricultural grade limestone (90
lbs./1000 ft.2).
Piedmont and Appalachian Region: 2 tons/acre pulverized agricultural grade
limestone (90 lbs./1000 ft.2).
III - 306
1992 3.32
Note: An agricultural grade of limestone should always be used.
Fertilizer
Mixed grasses and legumes: 1000 lbs./acre 10-20-10 or equivalent nutrients
(23 lbs./1000 ft.2).
Legume stands only: 1000 lbs./acre 5-20-10 (23 lbs./ 1000 ft.2) is preferred;
however, 1000 lbs./acre of 10-20-10 or equivalent may
be used.
Grass stands only: 1000 lbs./acre 10-20-10 or equivalent nutrients, (23 lbs./1000
ft.2).
Other fertilizer formulations, including slow-release sources of nitrogen (preferred
from a water quality standpoint), may be used provided they can supply the same
amounts and proportions of plant nutrients.
Incorporation - Lime and fertilizer shall be incorporated into the top 4-6 inches of the soil
by discing or other means whenever possible. For erosion control,when applying lime and
fertilizer with a hydroseeder, apply to a rough, loose surface.
Seeding
1. Certified seed will be used for all permanent seeding whenever possible. Certified
seed is inspected by the Virginia Crop Improvement Association or the certifying
agency in other states. The seed must meet published state standards and bear an
official "Certified Seed" label (see Appendix 3.32-a).
Kentucky Bluegrass Seed Mixtures Kentucky Bluegrass Seed Blends
MARYLAND - VIRGINIA VIRGINIA- MARYLAND
RECOMMENDED RECOMMENDED
•
•FINE TEXT < „ KENTUCKY B ISEED
i....
ci4i^ '"':;�.'� rnB ri s wmpo idn• W a r:tit n
This seed is r 4, b aurrenty�aoannwn• < Nb• s k and
oa�� aytho r q attic es on
.sit skr's u. L< aw. a en on.
Arag.:•.. � a� a _�s•Boerd^oYAtK3ifbiia �F��4'�s �a� �� . .. •: A
Department of•A9 die•
•Recommended Area is Shaded. V 33505 V 25004
III - 307
•
•
1992 3.32
2. Legume seed should be inoculated with the inoculant appropriate to the species.
Seed of the Lespedezas, the Clovers and Crownvetch should be-scarified to promote
uniform germination.
3. Apply seed uniformly with a broadcast seeder, drill, culti-packer seeder, or
hydroseeder on a firm, friable seedbed. Seeding depth should be 1/4 to 1/2 inch.
4. To avoid poor germination rates as a result of seed damage during hydroseeding, it
is recommended that if a machinery breakdown of 30 minutes to 2 hours occurs,50%
more seed be added to the tank, based on the proportion of the slurry remaining in
the tank. Beyond 2 hours, a full rate of new seed may be necessary.
Often hydroseeding contractors prefer not to apply lime in their rigs as it is abrasive.
In inaccessible areas, lime may have to be applied separately in pelletized or liquid
form. Surface roughening is particularly important when hydroseeding, as a
roughened slope will provide some natural coverage of lime, fertilizer and seed.
Legume inoculants should be applied at five times the recommended rate when ,
inoculant is included in the hydroseeder slurry.
Mulching
All permanent seeding must be mulched immediately upon completion of seed
application. Refer to MULCHING, Std. & Spec. 3.35.
Maintenance of New Seedings
In general, a stand of vegetation cannot be determined to be fully established until
it has been maintained for one full year after planting.
Irrigation: New seedings should be supplied with adequate moisture. Supply water
as needed, especially late in the season, in abnormally hot or dry weather, or on
adverse sites. Water application rates should be controlled to prevent excessive
runoff. Inadequate amounts of water may be more harmful than no water.
Re-seeding: Inspect seeded areas for failure and make necessary repairs and re-
seedings within the same season, if possible.
•
a. If vegetative cover is inadequate to prevent rill erosion, over-seed and fertilize
in accordance with soil test results.
b. If a stand has less than 40% cover, re-evaluate choice of plant materials and
quantities of lime and fertilizer. The soil must be tested to determine if
acidity or nutrient imbalances are responsible. Re-establish the stand
following seedbed preparation and seeding recommendations.
III - 308
1992 3.32
Fertilization: Cool season grasses should begin to be fertilized 90 days after planting
to ensure proper stand and density. Warm season fertilization should begin at 30
days after planting.
Apply maintenance levels of fertilizer as determined by soil test. In the absence of
a soil test, fertilization should be as follows:
Cool Season Grasses
4 lbs. nitrogen (N)
1 lb. phosphorus (P) \ Per 1000 ft.2 per year
2 lbs. potash (K)
Seventy-five percent of the total requirements should be applied between September
1 and December 31st. The balance should be applied during the remainder of the
year. More than 1 lb. of soluble nitrogen per 1000 ft.2 should not be applied at any
one time,
Warm Season Grasses
Apply 4-5 lbs. nitrogen (N) between May 1 and August 15th per 1000 ft.2 per
year.
Phosphorus (P) and Potash (K) should only be applied according to soil test.
Note:. The use of slow-release fertilizer formulations for maintenance of turf is
encouraged to reduce the number of applications and the impact on groundwater.
Additional Information on the Successful Establishment of Grasses and Legumes
See Appendix 3.32-b for "helpful hints" in achieving high success rates in grass or legume
plantings.
III - 309
1992 3.32
APPENDIX 3.32-a
SEED QUALITY CRITERIA
Where certified seed is not available, the minimum requirements for grass and legume seed
used in vegetative establishment are as follows:
a. All tags on containers of seed shall be labeled to meet the requirements of the State
Seed Law.
b. All seed shall be subject to re-testing by a recognized seed laboratory that employs
a registered seed technologist or by a state seed lab.
c. All seed used shall have been tested within twelve (12) months.
d. Inoculant- the inoculant added to legume seed in the seed mixtures shall be a pure
culture of nitrogen-fixing bacteria prepared for the species. Inoculants shall not be
used later than the date indicated on the container. Twice the supplier's
recommended rate of inoculant will be used on dry seedings; five times the
recommended rate if hydroseeded.
e. The quality of the seed used shall be shown on the bag tags to conform to the
guidelines in Table 3.32-E.
•
•
•
III - 310
1992 3.32
APPENDIX 3.32-b
• KEYS TO SUCCESSFUL ESTABLISHMENT OF GRASSES AND LEGUMES
PIanning
Where feasible, grading operations should be planned around optimal seeding dates for the
particular region. The most effective times for establishing perennial grass in Virginia
generally extend from March through May and from August through October. Outside
• these dates, the probability of failure is much higher. If the time of year is not suitable for
seeding a permanent cover (perennial species), a temporary cover crop should be planted.
Temporary seeding of annual species (small grains, ryegrasses or millets) often succeeds
during periods of the year that are unsuitable for seeding permanent (perennial) species.
Variations in weather and local site conditions can modify the effects of regional climate on
seeding success. For this reason,mixtures including both cool and warm season species are
preferred for low-maintenance cover, particularly in the Coastal Plain. Such mixtures
• promote cover which can adapt to a range of conditions. Many of these mixtures are not
desirable, however, for high quality lawns, where variation in texture of the turf is
inappropriate. It is important to note that in Virginia the establishment of 100% warm
season grasses in a high quality lawn is limited to the extreme eastern portions of the
Coastal Plain.
Selection,
Species selection should be considered early in the process of preparing an erosion and
sediment control plan. A variety of vegetation can be established in Virginia due to the
diversity in both soils and climate. However, for practical, economical stabilization and
long-term protection of disturbed sites, species selection should be made judiciously.
Seasonality must be considered when selecting species. Grasses and legumes are usually
classified as warm or cool season in reference to their season of growth. Cool season plants
• realize most of their growth during the spring and fall and are relatively inactive or dormant
during the hot summer months. Therefore, fall is the most favorable time to plant them.
Warm season plants "green-up" late in the spring, grow most actively during the summer,
and go dormant at the time of the first frost in fall. Spring and early summer are preferred
planting times for warm season plants.
Seed Mixtures
As previously noted, the establishment of high quality turf frequently involves planting one
single species. However, in seedings for erosion control purposes, the inclusion of more
than one species should always be considered. Mixtures need not be excessive in poundage
or seed count. The addition of a quick-growing annual provides early protection and •
facilitates establishment of one or two perennials in a mix. More complex mixtures might
include a quick-growing annual, one or two legumes and more than one perennial grass.
III - 312
y �
1992 3.32
The addition of a "nurse" crop (quick-growing annuals added to permanent mixtures) is a
sound practice for soil stabilization, particularly on difficult sites - those with steep slopes;
poor, rocky,erosive soils; those seeded out the optimum seeding periods; or in any situation
where the development of permanent cover is likely to be slow. The nurse crop germinates
and grows rapidly, holding the soil until the slower-growing perennial seedlings become
established.
III - 313
1992 3.35
STD & SPEC 3.35
4, ® MULCHINGCO
Definition
Application of plant residues or other suitable materials to the soil surface.
Purposes
1. To prevent erosion by protecting the soil surface from raindrop impact and reducing
the velocity of overland flow.
2. To foster the growth of vegetation by increasing available moisture and providing
insulation against extreme heat and cold.
Conditions Where Practice Applies
1. Areas which have been permanently seeded (see Std. & Spec. 3.32, PERMANENT
SEEDING) should be mulched immediately following seeding.
$:, 4 fit f
+ y
y, a ♦.* i .i ss
._ .. .re iT-� i,..,- :,. ♦«fie-., J}�;re
w
k F
J :
l'
III - 349
1992 3.35
2. Areas which cannot be seeded because of the season should be mulched to provide
some protection to the soil surface. An organic mulch should be used, and the area
then seeded as soon weather or seasonal conditions permit. It is not recommended
that fiber mulch be used alone for this practice; at normal application rates it just
simply does not provide the protection that is achieved using other types of mulch.
3. Mulch may be used together with plantings of trees, shrubs, or certain ground covers
which do not provide adequate soil stabilization by themselves.
4. Mulch shall be used in conjunction with temporary seeding operations as specified
in TEMPORARY SEEDING, Std. & Spec. 3.31.
Planning Considerations
Mulches are applied to the soil surface to conserve a desirable soil property or to promote
plant growth. A surface mulch is one of the most effective means of controlling runoff and
erosion on disturbed land.
Mulches can increase the infiltration rate of the soil, reduce soil moisture loss by
evaporation, prevent crusting and sealing of the soil surface, modify soil temperatures, and
provide a suitable microclimate for seed germination.
Organic mulch materials, such as straw,wood chips, bark, and fiber mulch have been found
to be the most effective.
Chemical soil stabilizers or soil binders should not be used alone for mulch. These
materials are useful to bind organic mulches together to prevent displacement.
A variety of manufactured SOIL STABILIZATION BLANKETS AND MATTING(see Std.
& Spec. 3.36) have been developed for erosion control in recent years. Some of these
products can be used as mulches, particularly in critical areas such as waterways. They also
may be used to hold other mulches to the soil surface.
The choice of materials for mulching will be based on the type of soil to be protected, site
conditions, season and economics. It is especially important to mulch liberally in mid-
summer and prior to winter, and on cut slopes and southern slope exposures.
Organic Mulches
Straw - The mulch most commonly used in conjunction with seeding. The straw should
come from wheat or oats (free of troublesome weed seeds) and may be spread by hand or
machine. Straw can be windblown and must be anchored down by an acceptable method.
III - 350
1992 3.35
Hay - May be used in lieu of straw where volunteers will not present a problem, and may
be spread by hand or machine. Hay can be windblown and must also be anchored or tacked
down.
Corn Stalks - These should be shredded into 4- to 6-inch lengths. Stalks decompose slowly
and are resistant to displacement.
Wood Chips - Suitable for areas that will not be closely mowed, and around ornamental
plantings. Chips decompose slowly and do not require tacking. They must be treated with
12 pounds of nitrogen per ton to prevent nutrient deficiency in plants; however, can be a
very inexpensive mulch if chips are obtained from trees cleared on the site.
Bark Chips. Shredded Bark- These are by-products of timber processing which are used in
landscaped plantings. Bark is also a suitable mulch for areas planted to grasses and not
closely mowed. It may be applied by hand or mechanically and is not usually toxic to
grasses or legumes; additional nitrogen fertilizer is not required.
Fiber Mulch - Used in hydroseeding operations and applied as part of the slurry. It creates
the best seed-soil contact when applied over top of(as a separate operation) newly seeded
areas. These fibers do not require tacking, although tacking agents or binders are
sometimes used in conjunction with the application of fiber mulch. This form of mulch does
not provide sufficient protection to highly erodible soils. Additionally, fiber mulch will not
be considered adequate mulch when used during the dry summer months or when used for
late fall mulch cover. Use straw mulch during these periods. Fiber mulch may be used to
tack (anchor) straw mulch. This treatment is well suited for steep slopes, critical areas, and
areas susceptible to displacement.
There are other organic materials which make excellent mulches but are only available
locally or seasonally. Creative use of these materials can reduce costs.
Chemical Mulches and Soil Binders
A wide range of synthetic, spray-on materials are marketed to stabilize and protect the soil
surface. These are emulsions or dispersions of vinyl compounds, rubber or other substances
which are mixed with water and applied to the soil. They may be used alone in some cases
as temporary stabilizers, or in conjunction with fiber mulches or straw.
When used alone, chemical mulches do not have the capability to insulate the soil or retain
soil moisture that organic mulches have. This soil protection is also easily damaged by
traffic. Application of these mulches is usually more expensive than organic mulching, and
the mulches decompose in 60-90 days.
Blankets and Matting
Field experience has shown that plastic netting, when used alone, does not retain soil
moisture or modify soil temperature. In some cases it may stabilize the soil surface while
III - 351
•
1992 3.35
grasses are being established, but is primarily used in grassed waterways and on slopes JQ
hold straw or similar mulch in place.
Jute mesh and other soil stabilization blankets are good choices for mulching on difficult
slopes and in minor drainage swales. Most of the soil stabilization mattings (used to create
a permanent matrix for root growth within the soil) must receive mulching in order to
properly stabilize an area. Notably,some manufacturers have recently developed permanent
mattings which include self-contained, temporary mulching materials; however, these
measures will have to meet the requirements noted in Std. & Spec. 3.36, SOIL
STABILIZATION BLANKETS AND MATTING,before they can be recommended for use
on steep slopes and in channel flow situations.
The most critical aspect of installing blankets and mats is obtaining firm, continuous contact
between the material and the soil. Without such contact, the material may fail and thereby
allow erosion to occur. It is important to use an adequate number of staples and make sure
the material is installed properly in order to maximize soil protection. These products are
discussed in more detail in Std. & Spec. 3.36, SOIL STABIIJZATION BLANKETS &
MATTING.
Specifications
Organic.Mulches
Organic mulches may be used in any area where mulch is required, subject to the
restrictions noted in Table 3.35-A.
Materials: Select mulch material based on site requirements, availability of materials, and
availability of labor and equipment. Table 3.35-A lists the most commonly used organic
mulches. Other materials, such as peanut hulls and cotton burs, may be used with the
permission of the local Plan-Approving Authority.
Prior to mulching: Complete the required grading and install needed sediment control
practices.
Lime and fertilizer should be incorporated and surface roughening accomplished as needed.
Seed should be applied prior to mulching except in the following cases:
a. Where seed is to be applied as part of a hydroseeder slurry containing fiber
mulch.
b. Where seed is to be applied following a straw mulch spread during winter
months.
III - 352
1992 3.35
TABLE 3.35-A
ORGANIC MULCH MATERIALS AND APPLICATION RATES
RATES:
1 MULCHES: Per Acre Per 1000 sq. ft. NOTES:
Straw or Hay 1 1 - 2 tons 70 - 90 lbs. Free from weeds and coarse
(Minimum 2 matter. Must be anchored.
tons for Spread with mulch blower
winter cover) or by hand.
Fiber Mulch Minimum 35 lbs. Do not use as mulch for
1500 lbs. winter cover or during hot,
dry periods.* Apply as
slurry.
Corn Stalks 4 - 6 tons 185 - 275 lbs. Cut or shredded in 4-6"
lengths. Air-dried. Do not
use in fine turf areas. Apply
with mulch blower or by
hand.
Wood Chips 4 - 6 tons 185 - 275 lbs. Free of coarse matter. Air-
dried. Treat with 12 lbs
nitrogen per ton. Do not
use in fine turf areas. Apply
with mulch blower, chip
handler, or by hand.
Bark Chips 50 - 70 cu. 1-2 cu. yds. Free of coarse matter. Air-
or yds. dried. Do not use in fine
Shredded turf areas. Apply with
Bark mulch blower, chip handler,
or by hand.
* When fiber mulch is the only available mulch during periods when straw
should be used, apply at a minimum rate of 2000 lbs./ac. or 45 lbs./1000 sq. ft.
Source: Va. DSWC
III - 353
1992 3.35
Application: Mulch materials shall be spread uniformly, by hand or machine.
When spreading straw mulch by hand, divide the area to be mulched into approximately
1,000 sq.ft. sections and place 70-90 lbs. (1; to 2 bales) of straw in each section to facilitate
uniform distribution.
Mulch Anchoring: Straw mulch must be anchored immediately after spreading to prevent
displacement. Other organic mulches listed in Table 3.35-A do not require anchoring. The
following methods of anchoring straw may be used:
1. Mulch anchoring tool (often referred to as a Krimper or Krimper Tool): This is a
tractor-drawn implement designed to punch mulch into the soil surface. This method
provides good erosion control with straw. It is limited to use on slopes no steeper
than 3:1, where equipment can operate safely. Machinery shall be operated on the
contour.
2. Fiber Mulch: A very common practice with widespread use today. Apply fiber
mulch by means of a hydroseeder at a rate of 500-750 lbs./acre over top of straw
mulch or hay. It has an added benefit of providing additional mulch to the newly
seeded area.
3. Liquid mulch binders: Application of liquid mulch binders and tackifiers should be
heaviest at edges of areas and at crests of ridges and banks, to prevent displacement.
The remainder of the area should have binder applied uniformly. Binders may be
applied after mulch is spread or may be sprayed into the mulch as it is being blown
onto the soil.
The following types of binders may be used:
a. Synthetic binders - Formulated binders or organically formulated
products may be used as recommended by the manufacturer to anchor
mulch.
* b. Asphalt - Any type of asphalt thin enough to be blown from spray
equipment is satisfactory. Recommended for use are rapid curing
(RC-70, RC-250, RC-800), medium curing (MC-250, MC-800) and
emulsified asphalt(SS-1,CSS-1,CMS-2,MS-2,RS-1,RS-2,CRS-1, and
CRS-2).
Apply asphalt at 0.10 gallon per square yard (10 gal./1000 sq. ft. or 430
gal./acre). Do not use heavier applications as it may cause the straw
to "perch" over rills. All asphalt designations are from the Asphalt
Institute Specifications.
* Note: This particular method is not used as commonly today as it once was in the
past. The development of hydraulic seeding equipment promoted the industry
III - 354
1992 3.35
to turn to synthetic or organically based binders and tackifiers. When this
method is used, environmental concerns should be addressed to ensure that
petroleum-based products do not enter valuable water supplies. Avoid
applications into waterways or channels.
4. Mulch nettings: Lightweight plastic, cotton, or paper nets may be stapled over the
mulch according to manufacturer's recommendations.
5. Peg and twine: Because it is labor-intensive, this method is feasible only in small
areas where other methods cannot be used. Drive 8- to 10-inch wooden pegs to
within 3 inches of the soil surface, every 4 feet in all directions. Stakes may be
driven before or after straw is spread. Secure mulch by stretching twine between
pegs in a criss-cross-within-a square pattern. Turn twine 2 or more times around
each peg.
Chemical Mulches
Chemical mulches* may be used alone only in the following situations:
a. Where no other mulching material is available.
b. In conjunction with temporary seeding during the times when mulch is not
required for that practice.
c. From March 15 to May 1 and August 15 to September 30, provided that they
are used on areas with slopes no steeper than 4:1,which have been roughened
in accordance with SURFACE ROUGHENING, Std. & Spec. 3.29. If rill
erosion occurs, another mulch material shall be applied immediately.
* Note: Chemical mulches may be used to bind other mulches or with fiber mulch in
a hydroseeded slurry at any time. Manufacturer's recommendations for
application of chemical mulches shall be followed.
Maintenance
All mulches and soil coverings should be inspected periodically (particularly after
rainstorms) to check for erosion. Where erosion is observed in mulched areas, additional
mulch should be applied. Nets and mats should be inspected after rainstorms for dislocation
or failure. If washouts or breakage occur, re-install netting or matting as necessary after
repairing damage to the slope or ditch. Inspections should take place up until grasses are
firmly established. Where mulch is used in conjunction with ornamental plantings, inspect
periodically throughout the year to determine if mulch is maintaining coverage of the soil
surface; repair as needed.
III - 355