Portland Land Use Code

Citation: Portland Land Use Code
Parent Document: Portland Land Use Code
Jurisdiction: Portland (municipal)
Original Source: https://www.portlandmaine.gov/asset/a5dcd1dc-4117-40b3-b3da-74a56919e14b ↗

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TABLE 11-B: DRAINAGE SPACING edge of a wetland. Surface drainage which is
Grade (%) Spacing directed to an unscarified buffer strip shall be
0-2 250 ft. diffused or spread out to promote infiltration
3-5 200-135 ft. of the runoff and to minimize channelized flow
6-10 100-80 ft. of the drainage through the buffer strip.
11-15 80-60 ft. G. Ditch relief (cross drainage) culverts, drainage
16-20 60-45 ft. dips, and water turnout shall be installed in a
21+ 40 ft. manner effective in directing drainage onto
unscarified buffer strips before the flow gains
to permitted uses within the district. A road or sufficient volume or head to erode the road,
driveway may also be approved by the review driveway, or ditch. To accomplish this, the
authority in a Resource Protection subdistrict, following shall apply:
upon a finding that no reasonable alternative 1. Ditch relief culverts, drainage dips, and
route or location is available outside the associated water turnouts shall be spaced
district. When a roadway or driveway is along the road or driveway at intervals no
permitted in a Resource Protection subdistrict, greater than indicated in Table 11-B.
the road and/or driveway shall be setback as far 2. Drainage dips may be used in place of ditch
as practicable from the normal high-water line relief culverts only where the grade is 10%
of a water body, tributary stream, or upland or less.
edge of wetland. 3. On sections having slopes greater than ten
D. Road and driveways banks shall be no steeper 10%, ditch relief culverts shall be placed at
than slope of two horizontal to one vertical and approximately a 30 degree angle
shall be graded and stabilized in accordance downslope from a line perpendicular to
with the provisions for erosion and the centerline of the road or driveway.
sedimentation control contained in Subsection 4. Ditch relief culverts shall be sufficiently
11.4.4. sized and properly installed in order to
E. Road and driveway grades shall be no greater allow for effective functioning, and their
than 10% except segments of less than 200 inlet and outlet ends shall be stabilized
feet. with appropriate materials.
F. In order to prevent road and driveway surface 5. Ditches, culverts, bridges, dips, water
drainage from directly entering water bodies, turnouts, and other storm water runoff
tributary streams, or wetlands, roads and control installations associated with roads
driveways shall be designed, constructed, and and driveways shall be maintained on a
maintained to empty onto an unscarified buffer regular basis to assure effective
strip at least 50 feet plus two times the average functioning.
slope in width between the outflow point of the
ditch or culvert and the normal high-water line
of a water body, tributary stream, or upland CITY OF PORTLAND LAND USE CODE | 11-15 SHORELAND OVERLAY ZONE

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