• 0.5% absolute minimum for draining water
• 1% Workable minimum for grading paving material. Useful as a drainage pitch on tops of walls and step treads. OK for a cross slope.
• 2% Generally recommended gradient for most surfaces
• 3% Gradient at which slope becomes obvious to the human eye. Maximum gradient for road intersections.
• 5% Maximum slope allowed for universal access without ramp
• 8.33% Maximum longitudinal gradient allowed for accessible ramps
• 10% Acceptable for pathways which do not have to meet ADA requirements
• 33% Recommended maximum gradients for lawns maintained with gang mowers
• 50% maximum gradient for cut or fill slopes. At or flatter than angle of repose for most common soils.

• With buildings, keep the finish floor elevation at least six inches above finsih grade at the outside preimeter of building
• Swale side slopes should generally be no steeper than 3:1
• Centerline of swale located ten feet from the building
• H.P.S. is six inches below finish grade outside of building
• Swale longitudinal slopes are ideally 2%
• Avoid grading within dripline of trees

1. Foundation Drain
2. Drain line from rainwater leaders
3. Roof gutter
4. Solid pipe to city catch basin
5. Catch basin in street
6. Drain inlet
7. Trench drain
8. Cistern for rainwater capture
9. Connection of roof drain to foundation drain

Q = CIA

• Q is peak discharge in cfs
• C is the composite runoff coefficient of the watershed
• I is the rainfall intensity for the design storm chosen in inches per hour
• A is the watershed area in Acres

• Pipes 2" or 3" smallest
• 4" - 12" made in 2" increments
• 12" to 24" made in 3" increments
• 24" and above made in 6" increments

1. Water should not drain towards buildings
2. Concentrated runoff should not be directed across property lines
3. Use swales to divert water from structures or areas to be protected
4. 12" minimum cover over any drain pipe
5. Avoid setting underground pipes excessively deep
6. Drop invert of downstream pipe at least 0.1 ft below the invert of the lowest upstream pipe
7. Sanitary sewers need to be located below water or storm drainge pipes

1. Slab on Grade
2. Pier and Grade Beam
3. Spread or Strip Footings with Crawwl Spaces
4. Spread fFootings with Basements
5. Pole Foundations

Slab on grade.

Consists of reinforced concrete slab several inches thick placed over a vapor barier, over one inch thick sand layer, sand several inches of compacted granular fill. Not appropriate for sites with moderate slopes.

42 inches

measured vertically from the leading edge of the stair tread or adjacent walking surface

Maximum rise for ramp

Maximum run  for ramp

2.5' rise

30' run

At least twice as wide as ramp run leading to it

Landing length shall be a min of 5' clear

Riser height range

Tread depth range

Riser: 4" - 7" height

Tread: 12" - 18" depth 

Contour Offset = 

Cross Slope X Width

Longitudinal Slope

1. A monitoring and maintenacne plan
2. A contingency plan - executed when monitoring indicates that the mitigations are failing to meet performance standards
3. A guarantee that the work will be performed as planned and approved. 

1. Peak flows increase due to increased runoff
2. Volume of runoff increases due to increased runoff
3. Time to peak decreases due to smoother watershed surfaces
4. Channel erosion increases
5. Flood high water levels and frequency of flooding increase
6. Channel flows become more erratic, with adverse impacts on habitat

• Increased channel erosion - the channel tries to widen and deepen itself in order to accommodate additional runoff. This requires armoring the banks and bottom of channel to protect adjacent structures.
• Increased flood levels and frequency of flooding
• More erratic flows: higher floods and lower baseflow (less water able to recharge water table due to less pervious surfaces in watershad)
• Nutrient loading may cause algae blooms, kill organisms etc.

Detention Pond: No volume control, peak discharge control only. 

Retention Pond: Both volume and peak discharge control. Must attempt to get water to infiltrate into the ground. More storage usually necessary and for a longer duration than detention system.

• Retention ponds
• French drains: Gravel filled trenches
• Leaching catch basins
• Drain fields: Like a septic tank, perforated pipes in gravel filled ditches.
• Porous paving

1. Growing Medium
2. Filter Membrane
3. Drainage layer
4. Root barrier
5. Protection Board
6. Insulation
7. Waterproofing Membrane
8. Roof of Building