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HomeMy WebLinkAbout1993-07-13 - AGENDA REPORTS - GROUNDWATER RPT (2)ADDENDUM TO AGENDA REPORT City Manager ApprovaAY: Item to be presented Anthony J. Nlsich e ki NEW BUSINESS DATE: July 13, 1993 SUBJECT: FOUR OAKS AND LANGSIDE AREA GROUNDWATER REPORT DEPARTMENT: Community Development BACKGROUND Since the submittal of the original Council Report, Staff has continued to work with our Consultant and the affected residents to refine Issues and goals regarding the drainage problems In the Four Oaks/Langside areas. The purpose of this addendum Is to clarify the Staff recommendations and request direction to continue researching methods of financing Improvements. As a result of continued discussions with the consultant, BCI Geonetics, and members of the. neighborhood, staff has focused It's recommendation on the construction of two wells In the Four Oaks area. It Is proposed that the wells be driven In strategic locations in existing street right-of- way and that temporary pumps and piping system be rented on an "as -needed" basis. The estimated cost for this work is approximately $92,000 plus $5,300/month for rental fees. This would eliminate maintenance expenses when the system is not In use and eliminate the need for an expensive underground piping system. A similar approach In the Langside area Is recommended at a cost of approximately $220,000 plus $7,000/month In rental fees. Details are contained within the staff report. Several alternatives regarding the financing of the work Involved have been discussed. Options Include the City financing the required Improvements or a combination of City/Private funding in the form of a Financing District. In either event costs would likely be fronted by the "Contingency Fund which could be reimbursed over a period of time by the "District". At this time Staff is continuing to work with FEMA in hopes of securing financial assistance In the Four Oaks/Langside area. In addition to the preventative measures described above, the City is required to repair the damaged streets in the area. The estimate at this time Is approximately $400,000. We are presently performing tests to determine the extent of repair needed and recommendations will be forthcoming. Federal assistance In this regard looks favorable however, it is not a certainty and Contingency Funds will be required to perform the work with possible reimbursement at a later date. In an effort to expedite the process staff Is requesting Council direction to investigate the possible financing alternatives. APPROVED Agada Item: Staff recommends that the City Council: 1. Receive presentation and file report; and 2. Authorize the City Manager to enter into an agreement with B.C.I. Geonetics to perforin the ground water analysis and provide project design in the amount of $23,445. 3. Authorize the transfer of funds from the Contingency Account, 01-4101-290, to the Four Oaks Account, 25-96084.227. 4. Direct staff to further Investigate and pursue preliminary design of short term solutions and return to Council with financial alternatives to funding proposed repairs. �o��neaa,w.w NEW BUSINESS DATE: SUBJECT: DEPARTMENT: BACKGROUND AGENDA REPORT i City Manager Approval / Item to be presented by. %/ 1##Anthony J. NisicFu July 13, 1993 FOUR OAKS AND LANGSIDE AREA GROUNDWATER REPORT Community Development The prolonged and Intensive rainy season experienced this past winter resulted in ground saturation throughout the Southern California area. Historical data Indicates that high rainfall Intensity over a long period of time causes the water table to rise significantly due to the! re- charge" of ground water supplies. "Recharge" can be affected by rain falling at considerable distances from a point where high water may manifest itself. The result can be seen in springs, artesian wells, and as In the case of the Four Oaks area, a water table higher than the ground surface. The City has retained the services of B.C.I. Geonetics, a geological firm specializing in groundwater to assist in the assessment of the problems. The Initial work consisted of Investigating the causes of the problem and Identifying potential solutions. The second phase of the study Is to provide possible design alternatives and cost estimates. City Staff and our consultant have worked very closely over the past several months researching State, County and Water Agency records as well as geological and topographic Information In our files and have found that the high ground water situation in the Four Oaks area and Langside area are caused by different circumstances. The high water table In the Four Oaks neighborhood is due to the fact that it is a low spot in the topography of the surrounding area. In essence, the area Is bowl -shaped and whenever there are periods of sustained rainfall the ground water surface rises and Intersects the surface of the ground. The circumstances surrounding the Langside area are somewhat different, In that the homes along the river side of this street were built on ground that had been excavated to construct the levy along the river. This work resulted In the lowering of the ground level where the homes were built. The river bottom Is highly permeable gravel and cobble material which transmits water easily. When the level of the river rises significantly the water pressure Increases on the river side which forces water to migrate under the levy. Water then rises to the surface on the street side of the levy which Is actually lower than the water surface in the river. City Staff has Instituted dally and weekly hand and power sweeping of the algae that has grown on the sidewalks, driveways and streets in the areas as a result of the constant presence of water. Traffic loads an the streets have been restricted to passenger vehicles in an effort to minimize damage to the road system. Staff has worked with the refuse haulers and residents In the area to accommodate trash pick-up in smaller vehicles. Some of the streets are damaged and in need of repair and staff has worked continually since April 27 with representatives of FEMA, (Federal Emergency Management Agency), and State DES, (Office of Emergency Services), Inspectors In an 747 Agenda Item: rpy 4 „T. AGENDA - FOUR OAKS July 13, 1993 - Page 2 attempt to secure funding to mitigate some of the damage. This project was submitted to the Federal Disaster Assistance Program on April 30, 1993. Since that time staff has accompanied FEMA and OES damage surveys teams as they monitor conditions in the area on a regular basis. The Damage Survey Report, (DSR), is currently awaiting the results of geotechnical Investigation. Disaster assistance has been secured for the emergency and protective measures including the BCI study. A decision remains to be made by FEMA regarding the scope of work eligible for assistance, however, It Is our expectation that financial disaster assistance will be available for street repair. The well system Is expected to be submitted as a hazard mitigation project. Staff has also worked closely with homeowners to advise them of the Federal and State assistance that may be available to them. This effort continues and Is likely to continue for some time. Staff effort In this area Including Public Works, Engineering and Emergency Services has exceeded $14,000 and an additional expense of approximately $7,000 in contractual services consisting of sweeping, testing and analysis. We are hoping to recover a majority of these costs from FEMA but this will not be determined for some time as the process Is very slow. ANALYSIS Staff and BCI have looked at several alternatives to mediating the problem. In the Four Oaks area we have looked at existing wells, new wells, de -watering systems and a subsurface drainage system. In the Langside area a system of wells and/or an Interceptor drain along the base of the levy has been reviewed. In Four Oaks, the existing wells on the west edge of the problem area adjacent to the river were determined to be undesirable due to the fact that they are privately owned by an individual who Is out of the Country and staff has not been able to contact him. Additionally, these wells have not been operated In excess of twelve years and their condition at time of abandonment Is unknown. State law also requires abandoned wells to be capped in a proper manner. The effort to restore these wells maybe prohibitive and as they are on the fringe of the affected area the benefit would not be as great as a well located centrally to the depressed area. Subsurface drains by design function In an area generally close to the surface. This treatment could be Installed to protect the streets but would do little to Improve the general area. This system would require significant cost and Inconvenience to construct, and due to the already low elevation of the area may require collection into a wet well where water would then be pumped out of the sump Into the river down stream: Staff believes this to be an unfavorable alternative. The analysis has focussed on a two well system approximately one hundred feet In depth centrally located In the basin or a series of well points, (small diameter pipes), driven strategically throughout the area. Each well point would be connected to a small pump. This amounts to a "dewatering” operation often used In construction but on a larger scale. This option has been discounted due to the complexity and extreme high cost for construction and maintenance of the system required to produce the effect needed to Improve such a large area. The wells could be placed In vaults located in the street, the wells would then pump the water through a piping system to the river at a point down stream. The cost for the two wells Is approximately $92,000. In additlon a piping system and pumps are required. The pumps needed to produce the high volume output would cost approximately $25,000 each. It would probably not be prudent to purchase such a pump and leave It Idle for possibly years at a time. The costs for a rental agreement whereby the pumps would only be installed for the period of time when they are needed thereby reducing maintenance demands and construction costs would be approximately $2,000/each/month. The same approach could be applied to the piping system. Temporary Irrigation pipe could be rented for approximately $1,100/month. This approach would save the cost and Inconvenience of installing a permanent 1 AGENDA - FOUR OAKS July 13, 1993 - Page 3 pipe in ground which could cost approximately $120,000. For comparison purposes a permanent system would cost approximately $262,000 exclusive of any right-of-way costs, and that for an "as needed" system would be $92,000 plus $5,300/month of operation. In addition to construction, consideration must be given for the continued maintenance and operation of the system. The pumps require periodic exercise to maintain their operation as they could go several years at a time without being needed. Staff believes the well approach Is the most effective way of dealing with the long term problem In the Four Oaks Area. The approach to the long range solution In the Langside area Is significantly different due to the dynamics of circumstances creating the problem. A series of three wells approximately 50 feet deep along the levy in the affected area or a system of drains, or combination of both, may be required to intercept the water flowing from the river before it can reach the homes west of the levy. Staff believes that while an Interceptor drain is more expensive, it is likewise more effective in dealing with the problem. Either approach requires access to the rear of the properties adjacent to the levy for construction and maintenance. The approximate cost fora drainage intercept system Is $120,000 and that for a series of three wells is approximately $100,000. In addition, the same concept of additional costs for pumps and a piping system described above also applies here. At this time staff believes a combination of wells and drains is required, a specialist in this field Is reviewing the situation.- The cost.for a combination system would be approximately $415,000 for a permanent system and $220,000 plus $7,000 for rental costs. Financing of the improvements could be accomplished by the formation of a Drainage Benefit Assessment District similar to those in the Shangri-La area or some other method. Staff is also working with FEMA In an attempt to secure funding for Improvements however, It Is premature at this time to speculate on the potential for success in this area. Further analysis is required to determine the best approach to financing the Improvements.. Staff will return to Council for direction and authorization to proceed when more detailed Information Is available. Staff has proceeded with the agreement with B.C.I. Geonetics due to the urgency of the situation and is now requesting formal approval. Funding for this agreement is coming from Contingency Account, FEMA has agreed to pay for a portion of the study and staff continues to work with FEMA in an attempt to acquire additional funding. Staff recommends that the City Council: Receive presentation and file report; and 2. Authorize the City Manager to enter Into an agreement with B.C.I. Geonetics to perform the ground water analysis and provide project design in the amount of $23,445. - 3. Authorize the transfer of funds from the Contingency Account, 01-4101-290, to the Four Oaks Account, 25-96084-227. w� u.mRs.eb