Design solutions

The purpose of the designed water intake is the reserve water supply of the city in emergency situations of peacetime and for a special period. The operation of borehole water intakes in the normal mode includes their regular pumping. The frequency of pumping pumping equipment is taken 1 time in 3 months. The duration of pumping is 1 day. In accordance with the design assignment, all water intakes are provided with dispensing units for refueling tankers. As water-lifting equipment for supplying water to consumers, electric pumping downhole units of the brand ETsV 10 - 120 - 60 are installed. The equipment is supplied with: a control and protection station of the SUZ - 100 (30 - 100A) type, VU, NU, ZSH sensors, USK level sensor -TE-2-100, which fully provide control over the operation of equipment and levels. Signals about the emergency shutdown of pumping equipment and the achievement of the emergency minimum level in the wells are displayed on the control panel located at the pumping station of the 1st lift of the FAC. For signal transmission, the project provides for laying a control cable KVBbShv10x1,5mm2 from each pumping station on the well. The laying of the control cable is given in the subsection "Power supply system". Turning on and off the pumping equipment of the designed well water intakes, switching to backup power supply is provided in manual mode.

Overview

The water supply station is located on the left-bank above-floodplain terrace of the river within the territory. The explored area of ​​the subsoil, approved in the status of a groundwater deposit, is identified within the buried valley of the left tributary of the river, which contains a complex of aquiferous highly permeable intermorainic sand-gravel-pebble deposits. The development of the groundwater reserves of the deposit is planned to be carried out during the implementation of the measures of the “Target Program for the Organization of Reserve Water Supply of the City in Emergency Situations of Peacetime and for a Special Period. The design water intake scheme is a group of five production wells (taking into account the existing well) located within the ICBC area. Four wells are working, one is reserve. The daily flow rate of each of the wells is 3600 m3/day, while the total flow rate of the design water intake will be 14400 mXNUMX/day. This project provides for the drilling of four exploration and production wells on the territory of the waterworks. Based on the purpose of the designed water intakes, the duration of the emergency period and the quality of groundwater are regulated by the “Instruction for the preparation and operation of drinking water supply systems in emergency situations” M, 1991 (hereinafter referred to as the “Instruction”). The total period of operation in emergency situations is up to 2 years (taking into account occasional connections for 25 years), the frequency of emergency situations is assumed to be 1 time per month. The project was drawn up in accordance with the basic requirements of the "Instructions for the preparation of projects and estimates for geological exploration", M., 1993 (Appendix to the order of Roskomnedra dated November 22.11.93, 108 No. XNUMX).

Source of water supply

The geological section of the groundwater deposit area is represented by rocks of the sedimentary cover of the Vendian, Lower Cambrian and Quaternary age. The Vendian system in the Kotlin horizon is formed by a sequence of siltstones and sandstones with interlayers of clays (Nizhnekotlinskaya suite) and dense clays with sandstone interlayers (Verkhnekotlinskaya suite) with a total thickness of about 200 m. The Lower Cambrian deposits are represented by the Lomonosov and Lontov horizons. The Lomonosov horizon lies at a depth of 95-100 m, is composed of sandstones, sometimes sands, with clay interlayers with a total thickness of 10 ... 15 m. The Lontovskiy horizon is a homogeneous stratum of montmorillonite clays of a characteristic bluish color (blue clays) with a thickness of 60...70 m. Quaternary deposits are represented by sediments of glacial, interglacial and postglacial complexes, which are not consistent in terms of lithology and thickness, mostly 30–50 m thick. In areas of buried valleys that cut through the thickness of the Lower Cambrian deposits, the thickness increases to 100 m or more. In the full section of Quaternary deposits, the following formations are distinguished: Dnieper moraine ( g II dn ) - boulder loam with a total thickness of not more than 2 ... 3 m; moraine is distributed locally in the thalwegs of ancient valleys, represented by glacial Dnieper-Moscow formations (fll dn-ms - predominantly fluvio-glacial sands of various grain sizes (sometimes with gravel-pebble material), filling the ancient buried valley. The thickness of the deposits varies from a few meters (in the sides of the valley) to 30 ... 35 m ( in the thalweg part). Moscow moraine ( g II ms) - boulder loam and sandy loam with a thickness 2... 10 m. In some areas, the moraine is eroded. Mikulin deposits (t III mk) - clays, loams, distributed locally, in areas of erosion of the Moscow moraine, they lie directly on the Dnieper-Moscow sediments. The thickness of the Mikulinsky deposits in the area of ​​the deposit is mainly 2...7 m. Moscow-Valdai deposits (flg,l P-Sh ms-vd) - sands of various grain sizes with lenses of clay deposits with a total thickness of 15 ... 30 m. Luga moraine (g III vdlz) - boulder loam, 5 ... 15 m thick. A complex of supra-moraine deposits: (lg ШЪ, IIV) - ribbon clays, loams, sands with a thickness of 7 ... 15 m. 

Hydogeological conditions

In the hydrogeological section of the territory under consideration, the following main aquifers and complexes are distinguished: groundwater horizon; intermoraine complex (as part of the upper and lower intermoraine horizons); Lomonosov horizon; GThe groundwater horizon has a sporadic distribution and is confined mainly to modern deposits, as well as to thin sandy interlayers in banded clays and loams of Upper Quaternary deposits (g, lg Wb). The groundwater table lies at a predominant depth of 0.. .0,5 m. Groundwater is fed by atmospheric precipitation; The intermorainic aquifer complex is confined to the ancient buried valleys, stretching mainly in the latitudinal direction, and is represented by the upper and lower intermorainic horizons, hydraulically interconnected due to the absence of a sustained separating clay layer. The upper intermorainic aquifer (f lg, l П-Ш ms - vd) within the territory under consideration lies at depths of 15...35 m directly under the Luga moraine, underlain by clay formations of the Moscow moraine. The water-bearing rocks are mainly represented by fine- and medium-grained sands, with gravel-pebble inclusions noted at the base of the aquifer. The water content of the upper intermoraine horizon is characterized by specific well flow rates of 2,2.. .2,8 l/s. The lower intermoranic aquifer (f II dn-ms) lies at depths of 60...85 m under the deposits of the Moscow moraine or directly under the upper intermoranic horizon, underlain by boulder loams of the Dnieper moraine or Lower Cambrian clays. Water-bearing rocks are represented by sands of various granularity, with a thickness from a few meters near the boundaries of the horizon to 30 ... 35 m in the thalweg part of ancient valleys. The water content of the horizon at the site is characterized by specific well flow rates up to 3,9 l/s. The Lomonosov aquifer (C\ 1m) lies at a depth of 80 ... 90 m, is represented by sandstones, sometimes sands, with interlayers of clays with a thickness of 10.. 15 m. The water content of the horizon is very low, the specific flow rates of wells usually do not exceed hundredths of a liter per second. Within the territory under consideration, the Lomonosov horizon is of no practical importance for use due to its very low water abundance.

Methodology and scope of work. Main design parameters of exploration and production wells

In accordance with the terms of reference, at the site of the projected water intake on the territory of the waterworks, it is planned to drill four exploration and production wells to the lower intermorainic horizon. Drilling method - shock-rope. Well depth - 85,0 m. Static level - 10,0 m. Specific flow rate - 3,9 l/s. Operational flow rate - 150 m / hour. (3600 m / day). Estimated dynamic water level in the well -25,0 m. PThe project provides for the implementation of field and cameral work. Field work includes: drilling of 4 exploration wells; hydrogeological works; equipment of wells with water-lifting equipment; carrying out topographic and geodetic works. Drilling of wells will be carried out by percussion-rope method using UKS-22M rigs with soil sampling. The initial drilling diameter is 600 mm, the final one - at a design depth of 85,0 m - 300 mm. Drilling is in progress: from 0,0 to 17,0 meters with a tip D = 600 mm; from 17,0 to 35,0 meters with a tip D = 500 mm; from 35,0 to 60,0 meters with a tip D = 400 mm. from 60,0 to 85,0 meters with a tip D = 300 mm. Soil sampling interval is 3 m, but not less than 1 sample from each layer. Drilling wells is accompanied by observations of the lithological composition and thickness of passable rocks, the position of the water level during gelling. 

Well design

In accordance with the design geological section, the following well design was adopted: The 1st casing string d = 24" (surface conductor) is hauled to a depth of 17 m. The wellhead is dug in with a pit with dimensions in terms of 1 x 1 m and a depth of 1 m and filled with cement mortar. Waiting for cement hardening (WSC) - 3 days. The 2nd casing string d=20" is hauled to a depth of 35 m, followed by annular grouting of the pipe strings in the range of 17,0-0,0 m and the exit of the cement slurry at the wellhead. WOC - 3 days. 3rd - the working string of casing pipes d=16" is hauled to a depth of 60 m, followed by annular grouting of the strings in the range of 35,0-0,0 m and the exit of the cement slurry at the wellhead. OZTs - 3 days. 4th - a working string of casing pipes d = 12" is hauled to a depth of 85m. 5th - filter column d = 8", installed "sunk" on the stuffing box in the depth range of 60-85 m. The filter with a diameter of 8" mm with a total length of 25 m. The above-filter blind part is 5 m long. The installation interval of the working part of the filter is determined in accordance with the design geological section and is 65 ... 85 m. The working part of the filter is a pipe D8", perforated with round holes in staggered, with a duty cycle of 35%, wrapped with stainless steel wire. After installing the filter, the pipe string d = 12 "is raised to a depth of 65 m with simultaneous gravel backfilling of the filter string in the interval 85.. .60 m. Further geophysical studies of the well are carried out: gamma-ray logging, caliper logging and temperature logging. Depth, well design and filter type are adjusted during the drilling process in accordance with the actual geological section and hydrogeological parameters of the production aquifer. Upon completion of the installation of the filter column in order to clean the wellbore from particles of cuttings, the well is pumped.