Standards

The objective in the development of the Standards section of the Service Levels For Drainage Manual was to provide a working document for use by MSD's Drainage Maintenance Department, Stormwater Department, Design-Construction Department and Customer Response Team so that drainage improvements performed throughout the service area are consistent in terms of appearance, functionality and cost.  This should be considered a supplement to the MSD Design Manual.

MSD must look to reduce the total cost of providing drainage service.  The standards facilitate the consideration of various solution alternatives.  MSD is in a position to minimize total costs to the customer by balancing a design with a lower construction cost against an increase in maintenance.

These standards are not intended to be rigid approaches to developing drainage solutions, but rather are intended to show appropriate options for various situations and where applicable to provide preferences for the available options.  Further, as additional situations are identified for which a standard is desirable or where additional approaches are identified for a particular drainage need, they should be included in order that this goal of achieving consistency in MSD drainage improvements can be met.

Catch Basins:   Based on site specific conditions, stormwater catch basins may be constructed of the following types:

• Polyethylene in-line basins (for use in yards or non-paved areas)
• Brick (for retro-fit situations)
• Poured in place
• Pre-cast concrete

Driveway Apron Restoration:   The following are general standards to be used in the restoration of driveway aprons as a part of a drainage improvement project.  These are not rigid requirements, rather specific field conditions may justify a variance from these standards:

1. Driveway aprons reconstructed as result of pipe installation shall be restored with the same type of material (concrete, asphalt or gravel) that existed prior to construction.  An exception to this standard exists where a cost savings can be achieved by installing a concrete apron rather than asphalt or gravel apron as may have been the original type of material.
2. Asphalt and gravel driveway aprons shall only be disturbed and restored to the limits of the pipe trench.
3. Concrete driveway aprons shall be sawcut to provide for pipe trench and upon completion there shall be no less than 4 feet between joints.
4. Concrete driveway aprons shall be restored to a 6-inch thickness and reinforced with polypropylene fibers (a 4-inch DGA bedding may be required if unstable soil conditions exist).
5. Asphalt driveway aprons shall be restored with 4-inch DGA bedding and 2 inches of asphalt.
6. All driveway aprons are to be reconstructed to original dimensions.
7. Driveway pipes shall extend a minimum of 3 feet on each side beyond the edge of reconstructed drive in order to provide a shoulder.   Ground cover shall be placed above the pipe and shall be restored in accordance with MSD's standard for ground restoration.
8. No headwalls/end treatments on driveway pipes.   (Note: Steep ditch grades and/or pipe types may necessitate the use of headwall/end treatments on driveway aprons/pipes).
9. Trench drains across driveway aprons and swale driveway apron installation should only be installed if no other options exist.
10. In areas where standing water is the major problem being addressed by the proposed project (generally in existing developed areas), and where the size of the driveway culverts will not create new, or worsen existing flooding problems, MSD's Design Criteria for sizing pipes may be waived.  Although 12-inch diameter pipe is generally the preferred minimum, pipes as small as 6-inch diameter may be used where pipe cover and/or ditch depth becomes a problem.   Utilizing smaller sizes is generally the preferred alternative to installation of trench drains or swale driveways.  Use of multiple pipes (of any pipe size) is strongly discouraged because of the potential for debris to collect between the pipe openings.
11. On concrete driveway aprons, where repaving of the street is anticipated in the near future, the concrete entrance is to be formed 3/4 inches higher than the abutting street pavement.

Erosion Control:  In addressing erosion problems, MSD's objective is to control erosion using a method which will enhance natural habitat conditions, encourage biodiversity, and assist in water quality improvement.

The following is a list of appropriate corrective measures for erosion control.  This list is not intended to be all inclusive.  Additional measures which are consistent with the Service Levels For Drainage and with the MSD Design Manual may also be considered:

• Geotextile fabric
• Seed and straw mat
• Sod
• Soil bioengineering methods (such as live staking, live fascines, joint plantings, brush layering, etc.)
• Concrete
• Grouted rip rap
• Gabion baskets
• Rip Rap

The "soft" engineering approaches identified in the first four items listed above are preferred to the remaining approaches listed, and should be applied whenever appropriate.

Where the erosion is to a natural channel, the appropriate solution consists of a bioengineering approach with concern for the entire portion of the channel effected by the erosion.

Where the erosion is to an improved channel, the appropriate solution will be dependent upon the erosion condition, and the type of improvement currently existing within the channel.  For example, where the erosion is to areas adjacent to a concrete portion of a channel, then the use of a concrete or rip rap approach may be appropriate.

In accordance with the Jefferson County and MSD Memorandum of Understanding, rip rap should not be used on roadside ditches along the County Through-Road System.

Appropriate uses for rip rap:

• Where there is spot erosion at a pipe outlet or where a side channel discharges into a main channel.
• As a "toe" along the banks of a channel, with a bioengineering approach for restoration and bank stabilization above the rip rap.
• In channel beds where there are dry weather flow conditions and where high velocity conditions exist.
• As a temporary solution where erosion threatens an existing facility.
• For any case where there is erosion outside of an easement and there is no other immediate solution.

Fences:  Where MSD removes and re-installs fences, MSD will re-install the fence at the easement or right-of-way line.

Where properties were sharing a fence, two fences will be re-installed, one on each side of the easement.  The fence will not be re-installed such that it crosses an easement, other than at the farthest two ends of an easement.  As an exception to this standard, in situations where MSD removes only a portion of the fences existing within an easement in order to perform maintenance work on a piped system, MSD may replace the fences to their original location.

MSD allows a fence to be placed within an easement where the easement remaining outside the fence is sufficiently large to provide access and to allow for maintenance of the facility.  In these situations, the property owner remains responsible for the fence and any damage to it.

Fences will be replaced in like kind and with new materials, unless the original materials are essentially new, in which case, the original materials will be used.

Where there is a fence shared by two properties, each property may have a fence placed on its side of the easement line even if a property is not otherwise enclosed by existing fence.

Where a drainage facility exists with fences along the easement lines, MSD may install access gates from each property along the easement where MSD requests the homeowners to routinely maintain the portion of the easement within their property.

All fences re-located or installed by MSD become the property of the customer.  MSD does not provide maintenance or repair to these fences following the expiration of their warranty period.

Standards continued