Transcript OSSF Presentation - Eng.hctx.net

Raymond Beckford
OSSF Plan Reviewer
HARRIS COUNTY’S 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.
THE
APPLICATION
FOR AN OSSF
PERMIT
OSSF Permits Costs:
Residential - $260.00
Commercial - $410.00
Must be signed by the
property owner
Affidavit to
the Public
Harris County will
file the affidavit
for the property
owner with the
County Clerk’s
Office.
Filing Fee $16.00
(Cash or Money
Order made
payable to Harris
County)
Acknowledgment
of Testing
Requirements for
an OSSF
Must be
signed by the
property
owner
In Brief
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.
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
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.
THIS
PROPERTY
MUST PLAT
 Legal Description:
TR 21A, Block 1, Plaza 290 U/R
The HCAD tax map
Shows the
property owner’s
tract with the
legal description
and the
dimensions of the
property.
Tax Assessor Block
Book Map
Shows the tract in its original
configuration.
To access block book maps:
www.tax.co.harris.tx.us
The recorded plat
SITE EVALUATION
Soil
Seasonal groundwater elevation
Topography
Flood hazard
Separation requirements (setbacks)
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.
SOIL EVALUATION
•A minimum of two soil
bores required
•Show the soil bores on
the site drawing.
Use the texture by feel
test to verify
the class of soil
Show the depth of
indications of the
“seasonal” water table,
not ground water
Remember to sign
and seal the report
Development in the 100-year
Flood plain & Floodway
Subject:
§285.31 (c ) (2) Flood Hazards
• In the100-year flood plain
how will tank floatation
be eliminated.
• In the floodway - P.E. only
a. 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
Date:
Certification for a proposed spray irrigation system installed in the regulated
flood-way located at __________________________________________
Per the requirements of 30 TAC 285; specifically §285.31(c)(2), a professional engineer must
demonstrate that the proposed system will not increase the height of the flood. Per the Rule, the
proposed system is a surface application system and the proposed components that will be above
the existing surface grade (e.g.: access risers and control panel(s)) are exempted by the Rule.
The installer must perform a competent installation in accordance with the Rule and ; after
settling around the tank battery and spray area piping installation, have no fill above the existing
grade.
The pertinent Rule follows:
§285.31(c) Surface drainage criteria.
(2) Flood hazard. Any potential OSSF site within a 100-year floodplain is subject to
special planning requirements. The OSSF shall be located so that a flood will not damage
the OSSF during a flood event, resulting in contamination of the environment. Planning
materials shall indicate how tank flotation is eliminated. Additionally, if the site is within
the regulated floodway, a professional engineer shall demonstrate that:
(A) the system shall not increase the height of the flood;
(B) all components, with the exception of risers, chlorinators, cleanouts,
sprinklers, and inspection ports, shall be completely buried without adding fill;
and
(C) non-buried components (e.g. alarms, junction boxes, and compressors) shall
be elevated above the 100-year flood elevation.
If there are any questions, please contact me immediately.
Signature and seal of Professional Engineer
PLANNING MATERIAL REVIEW
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
System Flow Diagram
750 Gallons
500 Gallons
500 Gallons
chlorinator
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
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
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.
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
ATU sized by the number of bedrooms
(150 gallons per bedroom)
A four bedroom
house would need a
600 gallon ATU
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
RESIDENTIAL DESIGN
PARAMETERS
 Hydraulic Loading
 Average flows
 Correct calculations
 Component sizing
 Proper setting of
 components & controls
Dose volume
Pump rates
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
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
Grease Trap Sizing
Use both EPA and Uniform
Plumbing Code methods.
Use the larger of the two
sizes.
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.
COMMON DESIGN
DEFICIENCES
 Surveys not submitted
 Site plan not to scale
 Site plan dimensions don’t match property
dimensions
 Buoyancy calculations
 Undersized components & disposal fields
 BOD calculations
 Reference source for hydraulic and organic
loading
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
QUESTIONS
Ray Beckford
713-956-3047
[email protected]