Offering Engineer Consultants for the Greater Dallas and Tarrant Counties
Advantage Drainage offers consulting engineer services through two respective companies in the Dallas Fort Worth Metroplex who can create a well-documented engineering plan to meet any project's needs. We offer State Licensed Engineers to design your complete drainage system.
Each project has its own particular set of design parameters. An elementary solution that solves one drainage problem might not be applicable to another project.
When warranted, our contract consulting civil engineer will analyze the site for volume of runoff and design a discharge system accordingly. Most projects are designed in accordance with the guidelines contained in the "Storm Water Management Design Manual" incorporating the City of Fort Worth Local Criteria Section and the North Central Texas Council of Governments (NCTCOG) integrated Storm Water Management (iSWM) Design Manual for Site Development. These standards were first promulgated in 2006, and are commonly referred to as I-SWIM Standards.
There are a number of factors to consider in the design of a drainage system. Among them are:
The lack of a positive outfall that drains by gravity alone might dictate the installation of a pump.
Consideration is given to the degree of porosity of the site. Projects that are heavily impervious will be designed for larger volumes of discharge that those with more pervious area.
Steeper sites drain faster that flat sites. Steeper sites generally require fewer intakes, while flatter sites require more intakes.
Frequency of Return.
A storm event with a short but intense duration will generate more runoff than a longer but milder storm. All habitable areas should be protected from the inundation expected of a 100-year storm. Other areas can be protected from the same storm, or a storm of lesser duration, depending on the owner’s wishes.
The condition of the receiving body (gutter, inlet, pond, open pervious area, etc.) affects design considerations. A basic principal is to not overload the downstream areas.
Type and Size of Discharge.
Whether using a closed system or an open flume, the choice of material (concrete, smooth or corrugated metal, HDPE) affects certain design parameters. Where a perforated pipe in a gravel trench might work in one instance, groundwater levels or the moisture content of the soil might dictate a solid pipe in another.
During some 45 years in civil engineering and construction, I am still amazed to find that one of the most common breakdowns in construction coordination among the project team members is the design of the local drainage around a building or residence. Drainage issues often are overlooked during the design and construction phase because all of the project team members consider site drainage someone else’s responsibility, or no one thought of it.
Drainage refers primarily to surface water control or storm water control. All waterproofing systems of homes/buildings must be complimented by good drainage practices to preserve property and life. The dynamics of water are powerful and continually active. When water freezes, it expands, causing heave, cracks and crushing of anything next to it. When ice melts it travels along the voids the ice created, traveling far, wide and deep - following the path of least resistance to the lowest point.
Adequate drainage within 5 to 25 feet of the structure is critical for proper performance of the foundation. This is normally accomplished in the landscaping or grading of the lot by a separate contractor after construction, so rain water, hopefully, is directed away from the dwelling. But it is best done before and during construction with final 'tweeking' after construction iscompleted.
Obviously, the owner of the land is the one with the most concern, so it is normally his design team's responsibility to determine exactly where on the lot the structure will be built. What is the soil type present? How deep are the various stratas?
Is this on a gentle sloping lot or a steep one? Where will rainwater go? These questions are commonly answered during the initial design phase. A geotechnical soil report of borings on the lot provide a great deal of information needed by the design team. If the information is not there, you should expect future problems.
In the natural condition, about 60% of the water infiltrated at the surface is used by plants/shrubs/trees, or evaporated at the surface. The remaining 40% of water makes it to the subgrade soils which can affect any clay present. Site hydrology is an extremely complex interaction between rainfall, topography, soils, plants and local geology. This process also is extremely variable from season to season. As soon as you remove the first blade of vegetation or move the first spade of soil on a new site, the complex site hydrologic balance is altered forever.
In all types of construction, the uncontrolled entry of water into the building envelope or crawl space can result in the deterioration of elements within the building envelope. [‘envelope’ is an encapsulating covering such as an outer shell or membrane - in simple terms, it consists of the roof, the above-grade wall system, and the wall system below grade, which provides protection from moisture, air, and temperature ingress and egress]. Allowing water to be directed toward the foundation of a structure is simply a poor practice, but often can be remedied by a good drainage specialist.
We commonly find a poorly designed drainage ditch is causing ongoing soil erosion, lack of a swale is allowing surface water flow towards the building or residence, scouring from adjacent stream bed is undercutting the soil next to the building, or the landscape contractor placed sprinkler risers too close to the foundation, and the list goes on and on. Today wehave many new techniques and materials that help mitigate these defects. Because traditional methods or materials used in the past did not always stem the tide of washouts, broken concrete, collapsed retaining walls and water in the crawl spaces, new things asa biotechnical erosion control transition mat, fully plantable concrete block units for landscaping, channel and area drains, or ADS polyethylene tubing are now incorporated as part of a drainage specialists 'tools' in commercial, industrial and residential applications to resolve drainage defects.
When it comes to storm-water management, most reliable, effective drainage specialists adhere to what is called 'best management practices' (BMPs). By evaluating the situation of a particular site and its storm-water runoff, he can design a system which follows BMPs to reduce the quantity of water flow and improve the overall stability of a structure. In some cases, the drainage concerns or defects are very often mitigated or reduced so a manageable amount is diverted away and mold, movement, or physical/visual damage is no longer a concern. Many drainage problems are not simple to solve, and that is where a good drainage specialist comes in!