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HomeMy WebLinkAboutRESOLUTIONS - 04182017 - 2017/121 ENGINEER’S REPORT FOR ANNEXATION #5 TO CONTRA COSTA FLOOD CONTROL AND WATER CONSERVATION DISTRICT DRAINAGE AREA 67A PREPARED BY THE STAFF OF THE CONTRA COSTA COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT 255 GLACIER DRIVE MARTINEZ, CA 94553 March 2017 1. RECOMMENDATION: It is recommended that the Board of Supervisors authorize Annexation Number 5 to Drainage Area 67A and that the benefit assessments pursuant to the Benefit Assessment Act of 1982, Government Code Sections 54703 through 54720, inclusive, be adopted for the area to be annexed. 2. DRAINAGE AREA LOCATION: Flood Control and Water Conservation District (District) Drainage Area 67A, formed on June 23, 1987, per Board of Supervisors Resolution No. 87/391 consists of a portion of the Tice Creek watershed in the vicinity of Walnut Creek. The specific location of the areas to be annexed are described in Exhibit A and shown in other exhibits on file for Minor Subdivision 802-08 in the Flood Control Engineering division of the Public Works Department. 3. ANNEXATION AREA: The proposed annexation consists of three lots within Minor Subdivision 802-08 that contain approximately 3.4 acres. The lots are 50,142, 48,237, and 49,000 sq. ft., respectively. 4. REASON FOR ANNEXATION: Tice Creek has a long history of flooding and inundation. The stormwater runoff from additional development within the watershed will compound the flooding problem. The Rossmoor detention basin, located near Tice Valley Road at Rossmoor Parkway, limits the stormwater flow reaching Tice Creek. The benefit received by reduction of flow to Tice Creek reduces the impact of the increase in stormwater created by additional development in the watershed, whether upstream or downstream of this detention basin. Therefore, all developments within the Tice Creek watershed benefit to a large degree by the existence of the Rossmoor detention basin. Like all man-made facilities, the detention basin requires annual maintenance to ensure that it operates as designed. It is, therefore, equitable in the opinion of the District that all properties benefitting by the existence of the detention basin pay a fair share toward its annual maintenance. Therefore, District staff recommends that subdivisions and other developments that will increase the stormwater flow to Tice Creek channel be annexed to Drainage Area 67A and have the benefit assessment levied. The annexation to Drainage Area 67A provides a legal entity under which the benefit assessment for maintenance of the detention basin and storm drains can be levied, after a vote has been taken. 5. FACILITIES TO BE MAINTAINED: Monies collected will be used for the maintenance of the detention basin and operation of the Drainage Area. Maintenance will include, among other things, silt removal, bank repair, landscaping, irrigation water, and weed removal. 6. ESTIMATE OF ANNUAL COSTS: The surface area of the detention basin to be maintained is approximately 5.3 acres in size. The estimated fiscal year 2017-18 maintenance budget for this basin is approximately $81,000. A breakdown of these costs is as follows: A. Trash rack and fence maintenance $9,000.00 B. Sediment removal $28,000.00 C. Vegetation management $32,000.00 D. Inspection and investigation $12,000.00 Estimated Total Annual Costs $81,000.00 7. ANNUAL BENEFIT ASSESSMENT: The Annual Benefit Assessment to be assigned to each of the parcels of the area to be annexed should be based upon its prorated share of the stormwater runoff. Its proportional share is determined by the amount of impervious area to be created on each parcel. Attached is Table A, which is a summary of the three parcels to be annexed to Drainage Area 67A. Table A also indicates the impervious area to be created by each parcel of land. The table indicates that the parcels to be created will generate a total of an additional 24.12 impervious area units (IAU). Each IAU is 1,000 sq. ft. of impervious area. 8. BENEFIT ASSESSMENT IMPLEMENTATION: The annexation to Drainage Area 67A provides funding for the maintenance of the detention basin and associated drainage structures. The annexation also provides that a levy be authorized by a vote of the various properties involved in the annexation. Staff recommends that: 1) all new parcels be assessed in the fiscal year following the filing of the parcel/final map; 2) all existing parcels of land containing impervious areas be assessed in the fiscal year following the filing of the final map; and, 3) that a vote of the property owners involved in the annexation be held to allow a maximum benefit assessment of $93.52 per IAU to be adopted, such maximum to be utilized in case of a need for emergency repairs to the basin and subject to annual adjustment to account for inflation (per Caltrans’ published “Price Index for Selected California Construction Items” or equivalent). TJ:cw G:\fldctl\CurDev\DA Annexations\DA 67A - MS 802-08\Annexation #5 Engineer's Report.doc 3/28/17 Table A Drainage Area 67A Annexation Number 5 (1) Parcel Designation (2) Parcel Size (square feet) (3) Number of IAU per Parcel* (4) FY 17-18 Maintenance Cost Per IAU** (5) FY 16-17 Assessment (Col. 3 x Col. 4) (6) Maximum Assessment*** (Col. 3 x $93.52) Lot B MS 802-08 50,142 7.71 $24.12 $185.97 $721.04 Lot C MS 802-08 48,237 7.71 $24.12 $185.97 $721.04 Lot D MS 802-08 49,000 7.71 $24.12 $185.97 $721.04 Total 23.13 Current DA 67A IAU 3335.69 New DA 67A IAU 3358.82 Notes: * Source: Average Impervious Surface Amounts, Report on Impervious Surface Drainage Fee Ordinance, January 5, 1982, Table 8. ** Maintenance Cost per IAU = Total Maintenance Cost of $81,000 / Total number of IAU’s. *** Maximum Assessment determined by adjusting the maximum assessment approved in DA 67A formation document ($50) by Caltrans “Price Index for Selected California Construction Items” to current year, resulting in $93.52. Maximum assessment value is updated annually.