Pheasant Farms Special Forum

Saturday, August 29^th

Simpson Garden Park

Belleville Ditch Drainage Area

Belleville Ditch Drainage Area

• All drainage systems that are connected to the Belleville Ditch are controlled by the water elevation in the ditch
• Key factor to reduce flooding potential is to keep ditch open, clean, sediment free, limit vegetated growth
• Ditch maintenance is handled by Wood County, last ditch cleaning in 2011
• City is monitoring ditch for future cleaning
• IMPORTANT: Keep litter and debris out of ditch

Drainage Systems

Drainage Systems

• Developments north of Poe Rd
• 16 independent systems
• Six ponds
• Three Gravity
• Two that are pumped
• One that is pumped and has a gravity outlet
• Ten direct connections to the Belleville Ditch
• All 16 systems will react differently, with different mechanisms causing flooding.

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Design Criteria

• The design criteria used in BG is similar to design criteria used in most of NW Ohio
• Ohio EPA has additional storm water requirements on new developments to reduce pollutants leaving a site
• Two separate, but related components to consider
• Drainage system or piping network
• Pond sizing

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How are drainage systems designed? Drainage System

• Storm sewer network is designed to carry flow from a 5yr storm, with a 10yr storm not surcharging the curb inlets
• Flows from subwatersheds are summed and compared against capacity of storm sewer
• Storm sewer piping should be dry during periods of no rain
• By design, streets and areas around catch basins may flood during rain events exceeding a 10yr storm

How are drainage systems designed? Drainage System

How are drainage systems designed? Pond Sizing

• Retention ponds can be “wet” or “dry”. They work the same.
• Pond volume design is based upon storing a 25yr storm, while releasing a 2yr storm.
• This is done by comparing the amount of water coming into the pond against the amount of water being released by the outlet (pipe or pump)
• If the outlet is block by debris or a high ditch condition, the pond will fill higher and drain slower

How are drainage systems designed? Pond Sizing

• Sample Calculation Sheet for pond sizing

Let’s talk about these 2yr, 5yr, 25yr, 100yr storms

• A 2yr storm is not guaranteed to happen once every 2 years, nor is a 100yr storm guaranteed to happen once every 100 years.
• The storm intervals (1, 2, 5, 25, etc) are based upon statistical analysis of many years of rainfall data through a process called frequency analysis and are referred to as “recurrence intervals” by hydrologists.

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Let’s talk about these 2yr, 5yr, 25yr, 100yr storms

• So all of that means that these storm events are based upon probabilities of them occurring.

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Let’s talk about these 2yr, 5yr, 25yr, 100yr storms

• As an example, over the course of 1 million years a 100yr storm would be expected to occur 10,000 times. When those 10,000 occurrences happen does not matter to the process of establishing the probability.

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Let’s talk about these 2yr, 5yr, 25yr, 100yr storms

1yr, 24-hr Event: 1.99 Inches

10yr, 2-hr Event: 2.08 Inches

100yr, 30-min Event: 1.99 Inches

200yr, 24-hr Event: 5.92 Inches

June 27^th, 2015 24-hr, 5.80 Inches

Gravity Systems, Pumps, Recurrence Intervals, Subwatersheds….I thought you were here to help me

• Key points from all of this engineering talk so far
• The water elevation in Belleville Ditch affects the operation of the drainage systems
• Pipes are sized to carry a 5yr flow, with a 10yr flow not coming up out of curb inlets
• Piping should completely drain between storm events
• Street flooding may occur during large rain events

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Pheasant Farms Drainage Concerns

• While we cannot avoid street flooding, we can do some things to minimize, and in many cases, eliminate basement flooding
• Just a quick overview of the Pheasant Farms drainage system and then we will talk about solutions

Pheasant Farms Drainage System

Pheasant Farms – Manitoba Pond System

• Originally designed as a dry pond, then converted to a wet pond
• As a result the storm sewer system and stone backfill is always submerged
• Water elevation in pond controls depth of water in piping and stone
• City is committed to “drying out” the storm sewer system, while keeping a wet pond

Basement Flooding Modes of Entry

Basement Flooding

• There are many modes of entry for water into a basement and each home could be at risk for one or more of the following conditions
• Downspouts connected to foundation/perimeter drain
• Poorly sloped grade at house foundation
• Backup of water within the service laterals (sanitary or storm)
• Backup of water in service lateral trench bedding stone (sanitary, storm or water)

Downspouts Connected To Foundation Drain

• This practice delivers all of the rainwater from the roof of your home to your sump crock, which is within the basement
• Easy fix, disconnect downspouts and direct them away from your foundation, but not onto your neighbor’s property

Poorly Graded Yard

• Possible source due to original construction.
• Concrete patio or sidewalk may settle near house
• The ground around your foundations should slope away from your house

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Water Backing Up Within Service Laterals

• Not a likely source
• If backups are occurring, installation of a check valve can prevent future flooding

Water Backing Up In Service Lateral Bedding Stone

• More probable occurrence
• City is working on solution to dry out the drainage system between storms
• Homeowners can install bentonite water stop to prevent the migration of water to foundation walls (we will talk about this further in a moment)

Bentonite Water Stop

• These can be installed by your local plumber
• Costs range depending upon complexity, but expect to pay $1,500 to $2,500 per water stop
• Real world cases where this repair has stopped consistently running sump pumps

Where to Install Water Stop

Dig up service lateral, remove stone bedding, install bentonite

Water Stop Financing Option

• The city has a financing program to help spread out the cost
• Customer submits two quotes for performing the work
• Customer enters into an agreement with the Utilities Department for financing the work
• Term of financing is a period up to 10 years
• Interest Rate will be charged at Prime Rate plus 1.75%
• Monthly payment will be included on the customer’s utility bill
• City will issue payment directly to the contractor upon submittal of an invoice

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Summary

• Efficiency of Belleville Ditch is key to reducing the number and severity of flooding events
• There are 16 separate drainage systems in the Pheasant Farms/Quail Hollow area that each react differently to rain events
• Drainage systems and ponds are designed for specific storm events, so larger events may cause flooding
• Basement flooding can be caused by many factors and may require multiple solutions

What Can the City Do to Help?

• Monitor Belleville Ditch condition and work with Wood County to clean ditch when needed
• Drain the submerged drainage system, while keeping the wet pond
• Offer financing program to spread out the cost of installing water stops
• Coordinate stream cleanup activities for residents or HOA volunteers

What Can You Do to Help?

• Keep liter, trash, debris out of the drainage system, pond and ditch
• Disconnect down spouts
• Check grading around your house
• Install check dams if necessary
• Install water stops if necessary