ADU Stormwater Management: Safe and Sustainable Construction Project

Accessory dwelling units development is not only a fascinating process of thinking through the interior or the selection of decorative elements, but also many other less creative, but no less important nuances. One of these construction aspects has a direct relation to our environment and the natural elements, namely, the stormwater mitigation system organization.

In this review, we will pay close attention to why it is so crucial to manage stormwater, what is the average cost of this component of ADU development, as well as what are the main criteria of stormwater management in your city.

Stormwater Management: Core Info

To begin with, it makes sense to determine what stormwater is. Stormwater is water that appears as a result of heavy rainfall, and that settles on the impervious surfaces of your primary residence or accessory dwelling unit. To avoid misunderstandings, we will explain that impervious surfaces are surfaces that are 99% likely not to let water through, e.g., a roof, a tile path, asphalt, concrete structures, etc. As a result, after accumulation in impervious areas, rainwater spreads over the ground, which will inevitably lead to adverse environmental consequences, in particular, soil erosion.

However, unlike earthquakes or tsunamis, this process is entirely manageable. For this reason, in almost every city in Sacramento, California, the local building department requires the stormwater runoff supply system organization from property owners. The installed structure allows it to accumulate stormwater in one place and then be evenly distributed into the soil without any harm.

Stormwater Drains for ADUs: Required or Not?

The vast majority of accessory dwelling units belong to the category of projects with a small room area, therefore, there are no strict requirements for the organization of a stormwater runoff system in relation to ADUs.

However, we identify three reasons why you may definitely need it:

• Regardless of the amount of precipitation in the location of your residence, the creation of a stormwater drain system is the responsibility of every property owner from a moral and ethical point of view. No department can oblige a person to take care of the environment everywhere. However, it is in the power of every landlord to ensure the environmental friendliness of the accessory dwelling unit construction on the premises of the site.
• The appearance of any impervious improvements on your parcel automatically means an increased risk of soil erosion during precipitation in the absence of a stormwater management system. Therefore, if you are planning to lay out a tiled path or build a parking lot next to the new ADU, then consider the creation of a storm drain, which you can also tie to the main house system.
• Units with a large area, in particular, detached ADUs, are a separate subject for discussion. In some cases, when the area of the ADU exceeds a certain threshold and the status of the building changes, the authorities may necessarily require the organization of a stormwater drainage system and in this case, a single sewer is not the solution.

Please note, the rules for the building of the accessory dwelling unit and all adjacent structures and connections vary from city to city. For this reason, to verify the necessity of storm drains creation on your site, we recommend you to consult with a specialist in the field of building laws/requirements.

All About Stormwater Drains Costs

The final estimate for the new accessory dwelling unit necessarily includes items such as design, security, plumbing, or electrical service. If you want to create an environmentally friendly and cost-effective project, then there is a place on this list for a stormwater management system.

The type of stormwater runoff has a primary impact on the final cost:

• Open and close stormwater drains

When planning the appearance of the ADU project on your site, choosing open or closed stormwater drains is the easiest and cheapest since these are the most common systems. Open stormwater drains have a higher price tag than closed ones because they require more extensive landscaping; however, cleaning them is incomparably easier than caring for closed drains, which takes several hours. Nevertheless, the undoubted advantage is that you can connect both of these systems with a primary residence, which will reduce overall costs.

• Stormwater basins

Recently, stormwater basins (installation costs from $5,000 to $10,000) have been gaining popularity, and there are several reasons for this. Firstly, the basin can accommodate a large amount of water, and this is a guarantee of your protection from flooding. Secondly, a basin ensures uniform absorption of water into the soil, unlike drain pipes, which typically spread large flows that can destroy the soil. Finally, the created stormwater basin opens up new possibilities for transforming the landscape of your site.

• Slot stormwater drains

Slot drains are an advanced technology in the world of stormwater management. Specialists install them next to the impervious improvements at a distance of one meter from each other. This is a very aesthetic solution, as slot drains do not attract much attention. However, the main subject of doubt is that slot drains cannot withstand an abnormally large amount of water, so if your accessory dwelling unit is in the city with an increased risk of heavy rainfall, then it makes sense to opt for one of the above options.

Stormwater System & Construction Requirements

As we mentioned earlier, the construction of a storm drain system is not a prerequisite for the implementation of an ADU project. However, we also want to emphasize once again that this condition is entirely in the hands of the local construction department. For example, in some cases, when a homeowner builds an ADU with an area of more than 500 sq. ft., he should equip a stormwater management system. Moreover, if the system has a basin configuration, then the authorities have the right to check it for operability and cleanliness, which is especially relevant for basins since harmful microorganisms will start living here if no one cleans it.

This example serves as evidence that it will never be superfluous to contact construction industry professionals who will help you pick the best strategy for the stormwater management system organization. Specialists will not only settle all legal issues but also ensure the reliability of the system, which will serve you for many years. Finally, only masters can integrate the stormwater management system into a single ecosystem of your site in such a way that it will fulfill not only a functional but also an aesthetic mission.

Frequently Asked Questions — FAQ

What are the three reasons for the need for a stormwater management system?

The answer to this question is more straightforward than cooking pasta. Firstly, installed stormwater drains preserve the integrity of the soil. Secondly, this system has a beneficial effect on the environment and, thirdly, the stormwater supply management system will prevent the erosion of plant roots, the destruction of flower beds and lawn.

For which types of ADU does the property owner need to install a stormwater management system?

Regardless of the type of accessory dwelling unit, we recommend considering the option of stormwater management system development. The only difference is that, for example, in the case of detached ADUs, homeowners will have to make separate connections; while being the owner of an attached unit, you can contact the system with the main house.

What is the average price for a stormwater management development system in Sacramento, California?

The answer to this question depends on the configuration of the stormwater management system you choose. Since customers prefer different projects, we will list the main ones, namely the installation of stormwater basin costs in the range of $5,000-$10,000, while slot stormwater drains will cost much cheaper.

Which specialists work with stormwater management development?

Typically, the stormwater management system installation process is the prerogative of landscape design specialists. These craftsmen work according to permitted standards, have all the required practical and creative skills, select the system configuration for the needs of the applicant, contact the stormwater system of the new ADU with the main residence, or vice versa, and create an independent and accessible stormwater basin.