Presentation on theme: "Groundwater Flow Problems in Colorado Springs"— Presentation transcript:
1 Groundwater Flow Problems in Colorado Springs 1Groundwater Flow Problems in Colorado Springs(… or, it’s why they call it “the Springs”)TALKING POINTS:The purpose of this presentation is to provide information on a little-known problem associated with development and home-building in our city.A proposal for addressing this problem will also be presented.The problem is shallow groundwater. This is not about the deep groundwater that provides water supply in some communities.Shallow groundwater results from stormwater or irrigation water percolating into the ground, and becoming “perched” in the upper 10’-20’ of the earth’s surface.This is why basements have to be waterproofed, and why foundation drains and provisions for sump pumps are required in today’s building codes.
2 Presentation Outline Background on Groundwater Underdrains Problems – Underdrain System FailuresProposed SolutionUnderdrains vs. Sump Pumps?Implications of Proposed SolutionConclusion & RecommendationsHere is the outline for this presentation.I first need to provide some background on groundwater underdrains, because many people may not be familiar with this term.I then need to explain the problems that can occur with these systems, and I’ll provide some recent examples.We have developed a proposed solution which involves a partnership among the HBA, City Engineering and Colorado Springs Utilities.This partnership is the result of direction given back in 2006 from then Assistant City Manager Greg Nyhoff, CSU Deputy Director Bruce McCormick, and then HBA President Kent Petrie.I will need to draw a distinction between Underdrains, which are all gravity flow systems, and sump pumps, which is the other way of dealing with groundwater around basements and foundations.There are some liability implications of the solution being proposed, so we need to be clear about that.And I’ll finish with the recommendations from the technical team that has been working on this for the past 2+ years (off and on).
3 Groundwater Underdrains – Technical Team 3Groundwater Underdrains – Technical TeamCity Engr HBA CSUCam McNair Bobby Ingels Brent SchubloomSteve Kuehster Bob Branson Charlie MorganBrian Huth Marla Novak Mike WeberTom Repp Marc Whorton Peter BondThese are some of the people from each organization who have contributed to this effort.We didn’t adopt the obvious acronym for our team name (GUT Team), but maybe we should have.Where this is going will require some courage or guts, and it has also required a good bit of determination just to get to this point – so maybe we will begin calling ourselves the GUT Team now.
4 Groundwater Conveyance 4Groundwater ConveyanceGroundwater can be conveyed through an underground pipe network called an “Underdrain” system.Protects foundations and basements from flooding.Used in Colorado Springs since the 1960’s – 1970’s.“Underdrains” have been used for many years to de-water trenches in order to facilitate the installation of sanitary sewer mains.Back in the 60’s or 70’s (we’re not exactly sure when), some smart builders got the idea of connecting the foundation drains that are required around basements to these Underdrains in the sanitary sewer trenches.This has now become a common practice, and it is estimated that there are 400 miles or more of these underdrain mains located in City rights-of-way.Let’s look at a schematic picture that shows this . . .
5 5This picture shows how the foundation drain around the basement of the house is connected to the Underdrain main line under the street.It also shows the sanitary sewer service line and the other utility mains in the street.These service lines on the private property are the responsibility of the property owner to maintain or repair.The utility mains in the public rights-of-way are the responsibility of the City, CSU or other utility company to maintain . . .. . . EXCEPT for the Underdrain mains. The City and CSU have never accepted ownership or maintenance responsibility for these Underdrain mains. And that is part of the problem that we feel is necessary to address now.
6 Background – What are Underdrains? 6Background – What are Underdrains?SANITARY SEWERUNDERDRAINHere is a photo of an Underdrain main and a sanitary sewer main being installed in a new subdivision, within the City right-of-way. The photographer was standing at ground level and looking down into the trench where these pipe systems were being installed.These are the deepest utilities in the street, typically 8’ – 12’ deep or more, depending on the topography.These are gravity flow systems, usually PVC plastic pipes.Notice that the Groundwater Underdrain is a perforated pipe, slightly smaller in diameter than the sanitary sewer main.Notice the granular bedding material and filter fabric around these pipes. This allows groundwater to flow into the Underdrain, and to be carried to an outfall in the storm drainage system.
7 7What are the issues?Underdrain failures can cause public health problemsNo claims to OwnershipLiability to Fund RepairsInadequate Standards for installationNo MaintenanceThe next slide will give some examples of recent Underdrain failures that caused flooded basements or other public health and safety problems.Reported failures number 3 to 4 per year right now. This can be expected to increase as the systems age.Right now, Underdrain mains in City rights-of-way are not accepted for ownership or maintenance by CSU or the City.When problems do occur, the finger-pointing begins among builder, developer, CSU and the City. The home owner is stuck in the middle. No one wants to claim ownership or to accept the liability for funding repairs.Like any other utility system, Groundwater Underdrains need to have consistent standards for installation, some kind of inspection program to assure compliance, and then a program for maintenance and repair.
8 Recent Underdrain Failures 8Recent Underdrain Failures6400 block, Summer Grace Street1300 block, West Costilla StreetPhil Long Expo Center2500 block, Integrity Court6800 block, Grand Prairie Driveetc.Costs to repair average $10K - $50K eachHere are some recent areas where Groundwater Underdrain failures have come to light, causing basement flooding in private property or other problems in public rights-of-way.Each time a street has to be excavated to repair the deepest utility line in the street, the costs of repairs can be expected to exceed $10,000. Street cut fees alone can cost this much. If the location of the failure is difficult to pinpoint, then multiple street cuts may be necessary to isolate and fix the problem.
9 Underdrain Failures 9 STORMWATER OUTFALL INTO SAND CREEK PLUGGED UNDERDRAIN MAINSUMP PIT OUTFALLSThis is a summary of the situation that occurred at 6488 Summer Grace Street, where a plugged Groundwater Underdrain caused the basement to flood.CSU spent ~$30,000 on investigations and pumping of sanitary sewage while the problem was isolated.The temporary solution was to disconnect the house from the underdrain main.The permanent solution will be to unplug the underdrain main. Pulte Homes is preparing to do that, but does not want to accept liability for other problems in that area.This development was done by a separate developer and multiple home builders.SANITARY MAINCRAWL SPACEBASEMENTCRAWL SPACE
10 10What are the Solutions?Proposal = Partnership among HBA, CSU and City EngineeringIn 2006, primarily in response to the Underdrain failure on Grand Prairie Drive, the HBA approached the City and CSU requesting a joint approach to this nagging problem.
11 11ProposalCity Takes Ownership of Underdrain Main lines serving single-family residential homes and nonresidential that opt in to connect to public UD mainsHBA - As representatives of the building industry, has agreed that developers & builders are willing to pay reasonable fees/costs for a long term solution to the UD problem.CSU - reviews designs, inspects installations, and makes repairs when necessarySWENT - manages funds, maps systems, coordinates CSU repairs, coordinates with State (CDPHE)HBA offered to pay a reasonable fee on building permits if the City/CSU would accept ownership of the Groundwater Underdrains in City rights-of-way and use the fees collected to fix these problems as they occur.Overall goal was to assure a quality installation with clear long term ownership that would be reasonably accessible for inspection, cleaning and failure investigation and that is expected to last decades with little or no preventive maintenanceFor the last 2+ years, off and on, the task force representing these 3 agencies has been working on the technical standards, City Code changes, and fee estimates that would be needed to make this proposal a reality.The Stormwater Enterprise, one of the major sub-units within City Engineering, has become a primary player in this effort since the shallow groundwater we are attempting to better manage eventually discharges into the stormwater system.SWENT is required to regulate and monitor discharges into the stormwater system anyway, and SWENT is also a logical repository for the funds collected from the Groundwater Underdrain fees paid by home builders.
12 12What would the City Own?This schematic plan indicates the approximate, typical locations of Sanitary Sewers, Storm Sewers, and Groundwater Underdrains.The City would take ownership of the Underdrain main lines in City rights-of-way and public easements, while property owners would continue to own and be responsible for the service lines on their property.This would make the ownership and maintenance responsibilities for Groundwater systems be the same as for Sanitary Sewer systems.The Stormwater Enterprise has a stake in this because the Groundwater systems discharge into Stormwater systems.Water quality can be a concern because of the possibility for cross-connections between sanitary sewer and groundwater underdrain lines.
13 13What would the City Own?This is a cross-section view of a typical street that shows the relative locations of utilities, including Groundwater Underdrains.Again, the City would own the Underdrain mains while the property owners would continue to own their service lines.This also shows again that the Groundwater Underdrain is typically the deepest utility in the street, which also makes it the most difficult and expensive to repair.
14 What will it cost? ALL ARE ONE TIME FEES 14Developer- CSU plan review and inspection fee=$23 per SF Residential lot (≤ triplex).$92 per Non-Residential lot (with GU main).CCTV inspections on T&M basis.Builder - City Underdrain maintenance fee=$60 per SF building permit.Non-Residential plus the mandatory State permit:(if connected) < 2 acres $ 602-5 acres $1205-10 acres $180> 10 acres $300Estimated fees are shown here.The $23 CSU portion will be collected when water & wastewater fees are paid, and this will cover CSU expenses associated with plan reviews and field inspections during installations. CCTV inspections will be charged on a Time + Materials basis.The $60 City portion will be collected with the building permit, and is intended to produce a Groundwater Underdrain maintenance fund adequate to pay for an assumed 3 failures per year, plus a nominal amount for City inspections and asset management.The reserve fund is designed to be built up to a level sufficient to cover 3 major failures in 1 year - but only 3 to 4 major failures in a decade. The fee amount may need to be re-evaluated in the future if this proves to be too high or too low.For non-residential properties (> triplex), underdrain main extensions and connections are not typical, but if they occur, the proposed fees are $92 for CSU and $60 - $300 for the City, depending on the size of the site.There are also State permits required for non-residential properties that have subterranean dewatering systems.Non-residential properties that discharge groundwater directly into a stormwater system (rather than into a groundwater underdrain system) would also need a revocable permit from the City, but would not be subject to these fees.Detailed information on the assumptions and the financial model are available on our web site.
15 What about basement/crawlspace Sump Pumps? 15What about basement/crawlspace Sump Pumps?A problem with Sump Pumps is that they discharge to the lawn, and can cause water to flow across the sidewalk and curb, and then into the street.This causes icing in winter, green slimy algae in summer, and premature street deterioration.
16 16Current building codes require that provisions be made for sump pumps in basements and crawl spaces.
17 17Sump PumpsGround water volumes can be so over-whelming such that a pump cannot keep up with the groundwater infiltrationResulting in floodingHere is another potential problem with sump pumps.During rainy seasons, the capacity of a sump pump can be overwhelmed and basement flooding can occur anyway.An underdrain system is gravity flow, so no pumping would be necessary.However, it may make sense to continue to provide the sump pit, piping and wiring for sump pumps as a back-up in case the underdrain system should become clogged.
18 18Sump PumpsGroundwater Underdrain fees are intended to be used to repair and maintain Underdrain systems only.Not for sump pumps or discharges from sump pumps.Groundwater Underdrains cannot be retrofitted in areas that were not originally built with them – cost prohibitive.City Street Division uses “French Drains” (shallower collection systems) for sump pump discharge problems.It should be made clear that the proposed Groundwater Underdrain fees are not intended to be used to deal with sump pump discharge problems.The sump pumps themselves and their associated piping and wiring are the property owners’ responsibility to maintain and repair, just as the foundation drains and underdrain service lines are.Retrofitting underdrain systems in neighborhoods that were not originally built with them would be cost prohibitive, and this is certainly not the purpose of the proposed GU fees.Also, dealing with the consequences of sump pump discharge problems onto our street system is not the intent of these proposed fees. Normally these kinds of problems are handled by the Street Division via “French Drains” when street reconstruction is due.18
19 Implications with Implementing the Proposal 19Implications with Implementing the ProposalFinancialLiability/RiskNull AlternativeThis proposal is not without some risk, but we think it is manageable.From the financial standpoint, an unusually rainy year early in the program could cause more underdrain failures than anticipated and wipe out the Underdrain Fund. If this happens, the City and CSU would have to make up the difference, and the HBA may have to accept higher fees to repay the loan and rebuild the fund.Taking ownership of the Underdrain mains would carry some liability concerns, although this would be no different than the liabilities associated with other utilities and stormwater facilities in City rights-of-way. It could be argued that the City has assumed some liability now anyway by allowing these systems to be installed in public rights-of-way and easements, even though the City expressly denies (via plat notes and development plan notes) accepting ownership or liability.Doing nothing, or the “Null Alternative”, simply perpetuates the current practices. As GU systems age, deteriorate or fail for other reasons, each one will become a source of conflict between the City and the development community, and the homeowner will be stuck in the middle.
20 Conclusions & Recommendations 20Conclusions & RecommendationsCity/CSU/HBA – PARTNERSHIP RECOMMENDS:City Takes OwnershipDEVELOPERS and BUILDERS agree to pay reasonable fees to CSU and City (SWENT)SWENT manages the money and the overall programCSU performs duties of plan reviewer, inspector, and repair contractorSo this is what the GUT Team recommends
21 For More Information: Details available on web - www.SpringsGov.com/ 21For More Information:Details available on web -Technical StandardsCity Code ChangesFeesRate CaseGroundwaterUnderdrainsWe have developed a lot of information on this subject, and it is posted on the website shown here.Included are the proposed Technical Standards for future installations, City Code changes necessary to implement this proposal, the proposed fees and CSU rate case, as well as other background information.At present, this information is in draft form, as this is a work in progress.
22 Questions 22 Thank you for your attention to this presentation. The GUT Team and I will be glad to try to address any questions or concerns you may have.