Section 672-15-04 - Construction Techniques(Refer to Handbook, Section 6)
1. During road construction, reasonable measures should be undertaken to control water runoff and erosion in order to avoid sedimentation of water bodies.2. Drainage ditches should be provided whenever necessary to effectively control water entering and leaving the road area.3. Cut and fill sections and road banks should be effectively stabilized so as to prevent erosion or slumping.4. In order to prevent road surface drainage from directly entering water bodies, roads and their associated drainage ditches, should be located, constructed and maintained so as to leave an unscarified filter strip, of at least the width indicated in the following table, between the exposed mineral soil of the road and the normal high water mark of the surface waterbody or water course: Average Slope of Land Between Exposed Mineral Soil and Normal High Water Mark (Percent) | Width of Strip Between Exposed Mineral Soil and Normal High Water Mark (Feet Along Surface of the Ground) |
0 | 25 |
10 | 45 |
20 | 65 |
30 | 85 |
40 | 105 |
50 | 125 |
60 | 145 |
70 | 165 |
This guideline shall not apply to road approaches to water crossings.
5. Drainage ditches for roads approaching a water crossing should be designed, constructed, and maintained to empty into an unscarified filter strip, of at least the width indicated in the table set forth in Subsection 4 above, between the outflow point of the ditch and the normal high water mark of the waterbody. Where such filter strip is impracticable, other appropriate techniques should be used to reasonably avoid sedimentation of the waterbody. Such techniques may include the installation of sump holes or settling basins, and/or the effective use of additional ditch relief culverts and ditch water turnouts placed so as to reasonably avoid sedimentation of the waterbody.6. Cross drainage culverts or drainage dips should be installed to get drainage water from the uphill side of the road to the downhill side before the flow in drainage ditches or roads gains sufficient volume or head to cause erosion and water sedimentation. Drainage water on the downhill side of the road should be diverted from the road ditch into vegetated areas by installation of water turnouts spaced so as to prevent the flow in the ditch from gaining sufficient volume or head to cause erosion and water sedimentation.
Such water diversion structures should be located and constructed as follows:
a. Drainage dips should be used in place of ditch relief culverts only where the road grade is 10 percent or less. Such dips should be constructed so that the road slope is reversed, the base of the dip drains to the outslope, and the surface of the dip is graveled.b. On roads having slopes greater than 10%, ditch relief culverts should be placed across the road at approximately a 30 degree angle downslope from a line perpendicular to the center line of the road.c. Culverts and drainage dips should also be installed so as to direct drainage water onto a unscarified filter strip.d. Inlet end of culverts should extend into side ditches to intercept ditch flows and should be adequately stabilized by riprap or other suitable means to reasonably avoid erosion of material around the culvert.e. Culverts, drainage dips, and water turnouts should be spaced along the road at intervals which are sufficient to prevent the water flow in drainage ditches or roads from gaining sufficient volume or head to cause erosion and water sedimentation. As a general guide, culverts, dips and water turnouts should be space as follows:
ROAD GRADE Percent | SPACING feet |
1-2 | 1,000 |
3-5 | 800-500 |
6-10 | 400-200 |
11-15 | 180-130 |
16-20 | 125-120 |
f. Cross drainage culverts should be sufficiently sized and properly installed in order to allow for drainage of storm or spring water runoff.01-672 C.M.R. ch. 15, § 04