HARRIS COUNTY OSSF PLAN REVIEW CONSIDERATIONS

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HARRIS COUNTY OSSF PLAN REVIEW CONSIDERATIONS

• Raymond Beckford
• OSSF Plan Reviewer

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HARRIS COUNTYS MISSION STATEMENT

• Our mission is to serve the constituents of
  Harris County by ensuring developments in the
  unincorporated areas will not pose a threat to
  the safety and welfare of the public as
  prescribed by Commissioners Court. We will
  accomplish this by providing expedient and
  professional service while enforcing all
  applicable Harris County regulations.

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THE APPLICATION FOR AN OSSF PERMIT

• OSSF Permits Costs
• Residential - 260.00
• Commercial - 410.00
• Must be signed by the property owner

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Affidavit to the Public

• Harris County will file the affidavit for the
  property owner with the County Clerks Office.
• Filing Fee 16.00 (Cash or Money Order made
  payable to Harris County)

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Acknowledgment of Testing Requirements for an
OSSF

• Must be signed by the property owner

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PLATTING

• In Brief

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TEXAS LOCAL GOVERNMENT CODE

• SUBCHAPTER A. SUBDIVISION PLATTING REQUIREMENTS
  IN GENERAL
• 232.001 Plat Required
• (a) The owner of a tract of land located outside
  the limits of a municipality who divides the
  tract into two or more parts to lay out a
  subdivision of the tract, .,must have a plat of
  the subdivision prepared.

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WHEN PLATTING IS REQUIRED SUMMARY

• Tracts less than 10 acres but larger than 5 acres
  if created after September 1, 1999
• Tracts less than 5 acres if created after
• September 1, 1989

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RESIDENTIAL LOT SIZING

• 30 TAC 285.4 (a) (1)
• A. Subdivisions of single family dwellings
  platted or created after the effective date,
  served by a public water supply and using
  individual OSSFs for sewage disposal, shall have
  lots of at least ½ acre.
• B. Subdivisions of single family dwellings
  platted or created after the effective date, not
  served by a public water supply and using
  individual OSSFs, shall have lots at least one
  acre.

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THIS PROPERTY MUST PLAT

• Legal Description
• TR 21A, Block 1, Plaza 290 U/R

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The HCAD tax map

• Shows the property owners tract with the legal
  description and the dimensions of the property.

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Tax Assessor Block Book Map

• Shows the tract in its original configuration.
• To access block book maps
• www.tax.co.harris.tx.us

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The recorded plat
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SITE EVALUATION

• Soil
• Seasonal groundwater elevation
• Topography
• Flood hazard
• Separation requirements (setbacks)

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THE STANDARD SOIL/SITE EVALUATION FORM

• Required per 285.30
• Prepared by
• Registered Site Evaluator
• Professional Engineer
• The site/soil evaluation can be presented in any
  format.
• Must have the same information as on the standard
  site/soil evaluation.

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SOIL EVALUATION

• A minimum of two soil bores required
• Show the soil bores on the site drawing.

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Show the depth of indications of the seasonal
water table, not ground water
Use the texture by feel test to verify the class
of soil

• Remember to sign and seal the report

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Development in the 100-year Flood plain Floodway

• 285.31 (c ) (2) Flood Hazards
• In the100-year flood plain
• how will tank floatation
• be eliminated.
• In the floodway - P.E. only
• System shall not increase
• the height of the flood
• b. Components completely
• buried without adding fill
• c. Alarms, junction boxes,
• compressors must be elevated
• above 100-year flood plain

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PLANNING MATERIAL REVIEW
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THE OSSF SITE PLAN

• Must be drawn to standard engineering scale, i.e.
• 1 10, 20, 60
• NOT 1 70 , 1 150 and NOT architecture
  scale
• Show both existing and proposed development
• Show the easements setback requirements
• Show existing proposed water wells
• Show existing proposed water lines

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System Flow Diagram
750 Gallons
500 Gallons
chlorinator
500 Gallons
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10/10 Requirements
In watersheds impaired for bacteria on the EPA
303(d) list, all OSSFs must use secondary
treatment meeting a 30-day avg. CBOD of 10 mg/L
TSS of 10mg/L Most ATUs installed in Harris
County must be listed on our approved list of
ATUs meeting the 10/10 requirement Septic tanks
installed in Harris County must be listed on our
approved septic tank list
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Surface Spray Irrigation

• 0.041 gal/sf/day isotherm goes through Hwy
  6/Telge Rd.
• Nothing within 10 feet of a sprinkler nozzle
• Specify the sprinkler nozzle criteria- max. inlet
  pressure of 40 psi, gpm, low angle 15 or less in
  trajectory
• Provide a landscape plan- what type of grass or
  other vegetation will be planted
• Provide the spray schedule
• Reduced spray area if designed by report prepared
  by
• Clifford Fedler, Ph.D., PE, Evaluation of
  Surface Application Rates for Texas OSSF Systems

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Drip Irrigation

• Correct application rate, length of drip tube
  needed
• Size the pump, supply and return lines
• Provide dosing calculations how many doses per
  day
• Specify the filtering device must filter down
  to 100 microns
• State or show how deep the drip tube is to be
  installed
• Show detailed diagram for mound i.e. how high
  wide is the mound, how deep are the emitters into
  mound. Specify class of soil cubic yards of
  fill needed.
• Fill permit is required for mounds.

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Hydraulic Detention Time (HDT) The amount of time
it takes wastewater to travel through a component
in the treatment system HDT Tank Volume
avg. flow Longer HDT allows for
cleaner effluent Significant in the pretreatment
tank
500 gallon Pretreatment Tank (min.)
Source Analyzing Wastewater Treatment Systems,
B. Lesikar, Ph.D., PE et.al
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ATU sized by the number of bedrooms (150 gallons
per bedroom)
A four bedroom house would need a 600 gallon ATU
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Our Requirement for Pump Tanks

Pump tanks shall be equipped such that when
pumping a portion of the effluent is returned
below the static water level to insure scour of
the pump tank bottom
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RESIDENTIAL DESIGN PARAMETERS

• Hydraulic Loading
• Average flows
• Correct calculations
• Component sizing
• Proper setting of
• components controls
• Dose volume
• Pump rates

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COMMERCIAL DESIGN PARAMETERS

• Hydraulic Loading
• Organic Loading
• Peak Average Flows
• Number of People
• Days of Operation
• Hours of Operation
• Correct Calculations
• Component Sizing
• Proper setting of components controls

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FLOW EQUALIZATION (SURGE) TANKS

• Compensates for peak flows
• Should be a part of the OSSF for restaurants,
  schools, churches, office/warehouses
• Often undersized
• Control panel should be able to track high water
  alarm events, dosing events, pump operation time

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Grease Trap Sizing
F O G
Use both EPA and Uniform Plumbing Code
methods. Use the larger of the two sizes.
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PROVIDE REFERENCES

• Texas Commission on Environmental Quality Chapter
  285 Table III
• Goldstein, S. and W. Moberg, 1973. Wastewater
  Treatment Systems for Rural Communities
• US Environmental Protection Agency (EPA) Design
  Manual Onsite Wastewater Treatment, 1980
• B. Lesikar, W. Stuth, Sr., et al., 2008. Texas
  AgriLife Extension Service. Analyzing Wastewater
  Treatment Systems-Serving Residential and
  Commercial Facilities for High Strength and
  Hydraulic Loading.

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COMMON DESIGN DEFICIENCES

• Surveys not submitted
• Site plan not to scale
• Site plan dimensions dont match property
  dimensions
• Buoyancy calculations
• Undersized components disposal fields
• BOD calculations
• Reference source for hydraulic and organic loading

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A Few Things To Consider

• Consider flow equalization for two or more homes
  on one system
• Consider expansion during the design phase
• Include flow monitoring devices - water meters,
• elapse time meters, cycle counters
• Commercial effluent filters will help lower BOD

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QUESTIONS
Ray Beckford 713-956-3047
raymond.beckford_at_hcpid.org